UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Validation of oscillometric blood pressure measuring devices : a case study of the BpTRUtm Mattu, Gurdial Singh 2003

You don't seem to have a PDF reader installed, try download the pdf

Item Metadata

Download

Media
ubc_2003-0417.pdf [ 3.3MB ]
Metadata
JSON: 1.0091081.json
JSON-LD: 1.0091081+ld.json
RDF/XML (Pretty): 1.0091081.xml
RDF/JSON: 1.0091081+rdf.json
Turtle: 1.0091081+rdf-turtle.txt
N-Triples: 1.0091081+rdf-ntriples.txt
Original Record: 1.0091081 +original-record.json
Full Text
1.0091081.txt
Citation
1.0091081.ris

Full Text

VALIDATION OF O S C I L L O M E T R Y BLOOD PRESSURE MEASURING DEVICES; A CASE STUDY OF THE B p T R U ™ by DR. GURDIAL SINGH MATTU M B . B C h . , T h e University of W a l e s C o l l e g e of M e d i c i n e , 1 9 9 3 C . C . F . P . , T h e University of British C o l u m b i a , 1 9 9 9  A T H E S I S S U B M I T T E D IN P A R T I A L F U L F I L M E N T O F THE REQUIREMENTS FOR THE DEGREE OF M A S T E R S IN S C I E N C E in THE FACULTY OF GRADUATE STUDIES ( D e p a r t m e n t of P h a r m a c o l o g y a n d T h e r a p e u t i c s ; F a c u l t y of M e d i c i n e ) W e a c c e p t this thesis a s c o n f o r m i n g to t h e required s t a n d a r d  THE UNIVERSITY OF BRITISH COLUMBIA July 2 0 0 3 © Gurdial S i n g h M a t t u , 2 0 0 3  In p r e s e n t i n g this t h e s i s in partial fulfilment of t h e r e q u i r e m e n t s for a n a d v a n c e d d e g r e e at t h e University of British C o l u m b i a , I a g r e e that t h e Library shall m a k e it freely available for r e f e r e n c e a n d study. I further a g r e e that p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of this thesis for s c h o l a r l y p u r p o s e s m a y be g r a n t e d by t h e h e a d of m y d e p a r t m e n t or by his or her r e p r e s e n t a t i v e s . It is u n d e r s t o o d that c o p y i n g or p u b l i c a t i o n of this thesis for financial g a i n shall not be a l l o w e d w i t h o u t m y written p e r m i s s i o n .  D e p a r t m e n t of P h a r m a c o l o g y a n d T h e r a p e u t i c s F a c u l t y of M e d i c i n e T h e University of British C o l u m b i a Vancouver, Canada  Date  /  ' -faHr £oo3  t  ABSTRACT  Hypertension is one of the most common reasons why North Americans visit a physician's office and its measurement technique has been reasonably standard since the earliest accepted description of an indirect method of measuring blood pressure by Riva Rocci in 1896. traditional sphygmomanometer in 1905.  Korotkoff later modified the  However, since then the mercury sphygmomanometer has  become not only the gold standard, but also an essential diagnostic tool in everyday medical care.  Recently however, there has been growing concern over the accuracy of the measurements obtained and the potential biohazard with standard mercury sphygmomanometers. Many cities and countries in Europe and North America, are in the process of phasing them out. Newer instruments such as the auscultatory aneroid, and the automated electronic devices of which the majority are of the oscillometric type, are beginning to appear. All new devices have the option of undergoing a validation process to assess the accuracy according to the relevant governing bodies.  The BpTRU™ is an automated oscillometric electronic blood pressure device developed by VSM Medtech Ltd of Vancouver. Connected in parallel by means of a T-tube, to the current gold standard mercury sphygmomanometer, allowed blood pressures to be measured simultaneously. Two observers blinded from each other and the device, recorded blood pressures individually.  The mean observer  average was compared to the device mean blood pressures for agreement. This was done according to the American National Standard for Electronic or Automated Sphygmomanometers-1992 and the British Hypertension Society protocol-1993.  The validation process was initially conducted in adults and agreement was within the above standards. However the device tended to underestimate at higher systolic blood pressures, so the algorithm was modified and the device re-validated using embedded raw data.  After running the validation study in  children, which again satisfied the above criteria, the raw data was combined in a final study.  The BpTRU™ is the only automated blood pressure measuring device that has been  independently  validated and has attained a high level of accuracy over this broad age and blood pressure range.  ii  TABLE OF CONTENTS  Declared Authorization Abstract  ii  T a b l e of C o n t e n t s  111  Acknowledgements  v  CHAPTER I  O v e r a l l Introduction Objectives  C H A P T E R II  C o m p a r i s o n of the oscillometric blood p r e s s u r e m o n i t o r ( B P M - 1 0 0 t a ) w i t h t h e auscultatory mercury sphygmomanometer  C H A P T E R III  C H A P T E R IV  1 5  B e  6  Abstract Introduction Methods Results Discussion Tables Figures References  7 8 10 14 17 20 22 24  V a l i d a t i o n of a n e w a l g o r i t h m for t h e B P M - 1 0 0 e l e c t r o n i c o s c i l l o m e t r i c office blood pressure monitor  26  Abstract Introduction Methods Results Discussion Tables Figures References  27 29 30 32 34 36 38 40  C o m p a r i s o n of t h e a u t o m a t e d n o n - i n v a s i v e o s c i l l o m e t r i c blood p r e s s u r e m o n i t o r ( B p T R U ™ ) with t h e a u s c u l t a t o r y m e r c u r y s p h y g m o m a n o m e t e r in t h e paediatric population  41  Abstract Introduction Methods Results Discussion Tables Figures References  42 43 45 51 55 57 59 61  iii  CHAPTER V  A c c u r a c y of t h e B p T R U ™ , a n a u t o m a t e d e l e c t r o n i c b l o o d p r e s s u r e d e v i c e  62  Abstract Introduction Methods Results Discussion Tables Figures References  63 64 66 68 71 74 77 79  C H A P T E R VI  Overall D i s c u s s i o n  81  C H A P T E R VII  Conclusions  87  C H A P T E R VIII  References  90  iv  ACKNOWLEDGEMENTS  M a n y t h a n k s to Dr. J a m e s M. W r i g h t for providing inspiration a n d s u p p o r t to e n a b l e t h e c o m p l e t i o n of this Masters thesis.  A special t h a n k you to m y s u p p o r t i v e a n d u n d e r s t a n d i n g f a m i l y , especially P a r v e e n a n d C h a r a n M a t t u  CHAPTER I  OVERALL INTRODUCTION  M e a s u r e m e n t of blood p r e s s u r e accurately is crucial; as b a s e d o n t h e s e m e a s u r e m e n t s , patients are labelled a n d n o n - d r u g a n d d r u g t h e r a p i e s r e c o m m e n d e d [1][2]. It is t h e r e f o r e e s s e n t i a l that the m e t h o d of measuring  blood p r e s s u r e  is a c c u r a t e a n d r e p r o d u c i b l e .  T h e c u r r e n t s t a n d a r d for blood  m e a s u r e m e n t is t h e a u s c u l t a t o r y m e t h o d using the m e r c u r y s p h y g m o m a n o m e t e r . p r e s s u r e s to r e p l a c e that s t a n d a r d with other m e t h o d s .  pressure  H o w e v e r , there are  O n e of the c o n c e r n s is a b o u t m e r c u r y poisoning.  A s a result of this m a n y S t a t e s in the U S , other cities in North A m e r i c a a n d s o m e E u r o p e a n countries have  banned  or  are  preparing  s p h y g m o m a n o m e t e r s [3][4]. the  100-year-old  to  ban  mercury  in  both  thermometers  and  blood  pressure  It is predicted by s o m e that it is only a m a t t e r of t i m e before alternatives to  mercury sphygmomanometer  are required  [5].  Another  pressure on the  s p h y g m o m a n o m e t e r is that it is subject to u n a c c e p t a b l e inter a n d i n t r a - o b s e r v e r variability.  mercury T h i s is a  setting in w h i c h a c o m p u t e r , w h i c h u s e s a r e p r o d u c i b l e a n d repetitive m e t h o d h a s o b v i o u s a d v a n t a g e s . A n o t h e r p r e s s u r e on t h e m e r c u r y s p h y g m o m a n o m e t e r c o m e s f r o m t h e r e q u i r e m e n t s of clinical trials. Despite  these  procedure.  requirements,  bias  can  be  demonstrated  to  commonly  occur  during  the  selection  In t h e clinical trial setting it is critical to m i n i m i z e bias at all s t a g e s of t h e trial.  During a  s y s t e m a t i c r e v i e w of a large n u m b e r of trials it w a s f o u n d that diastolic blood p r e s s u r e variability at baseline w a s substantially less t h a n systolic variability at b a s e l i n e a n d substantially less t h a n diastolic variability at the e n d of the s t u d y [6]. T h e m o s t likely e x p l a n a t i o n for this d e c r e a s e d variability at baseline is that m a n y s u b j e c t s m u s t have had a diastolic blood p r e s s u r e e q u a l to or j u s t a b o v e the entry criteria. T h i s reflects o b s e r v e r bias in order to e n h a n c e r e c r u i t m e n t of patients into t h e study.  T h e use of an  objective blood p r e s s u r e m e a s u r i n g d e v i c e to identify patients at b a s e l i n e w o u l d p r e v e n t this bias.  A n o t h e r r e a s o n for d e v e l o p i n g n e w blood p r e s s u r e m e a s u r i n g d e v i c e s a r e t h e practicalities of m o s t physician's offices or clinics, t h e place w h e r e m o s t of our blood p r e s s u r e m e a s u r e m e n t s t a k e place.  Most  physicians d o not h a v e t h e t i m e , k n o w l e d g e or skill to carefully m e a s u r e blood p r e s s u r e in the s a m e m a n n e r that t h e y w e r e m e a s u r e d in the clinical trials [7].  T h u s if t h e y c a n n o t r e p r o d u c e the setting that  the e v i d e n c e is b a s e d u p o n they c a n n o t m a k e d e c i s i o n s for their patients b a s e d on t h e best available evidence.  A m e t h o d that w o u l d r e p l a c e the m e r c u r y s p h y g m o m a n o m e t e r m u s t deal with the practical  t i m e c o n s t r a i n t s in a physician's office a n d m i m i c the blood p r e s s u r e m e a s u r e m e n t s a c h i e v e d in a clinical trial setting as m u c h as possible.  2  M o s t of t h e n e w m e t h o d s for m e a s u r i n g blood p r e s s u r e at t h e p r e s e n t t i m e u s e t h e technique. pressure.  oscillometric  T h i s m e t h o d refers to t h e m e a s u r e m e n t of t h e oscillations, c a u s e d by t h e arterial pulse T h e s e oscillations are t h e result of the cuff c a u s i n g t h e o c c l u s i o n of the a r t e r y (usually the  brachial), that it overlies.  T h e m e t h o d d o e s not u s e s o u n d s o m i c r o p h o n e s a r e not n e e d e d a n d external  n o i s e is not a p r o b l e m .  H o w e v e r , t h e m e t h o d is sensitive to patient m o v e m e n t .  T h e cuff, w r a p p e d  a r o u n d t h e patient's u p p e r a r m is a u t o m a t i c a l l y inflated with air to o c c l u d e t h e brachial pulse.  On  deflation, p r e s s u r e d a t a is r e c o r d e d by the d e v i c e in w a v e f o r m (as s h o w n in f i g u r e 1).  Fig 1 : p u l s e w a v e f o r m a g a i n s t t i m e  T h e m a x i m u m a m p l i t u d e of the p u l s e w a v e is t a k e n a s t h e m e a n arterial p r e s s u r e ( M A P ) a n d the systolic a n d diastolic blood p r e s s u r e s are c a l c u l a t e d f r o m this plus t h e pattern of t h e w a v e f o r m s .  T h e software  a l g o r i t h m s u s e d by t h e m a n y m a n u f a c t u r e r s of blood p r e s s u r e m e a s u r i n g d e v i c e s a r e proprietary a n d t h e r e f o r e not p u b l i s h e d i n f o r m a t i o n .  W h e n a local c o m p a n y , V S M M e d T e c h L t d . of V a n c o u v e r , C a n a d a a p p r o a c h e d T h e U B C High Blood P r e s s u r e Clinic w i t h a n e w a n d novel a p p r o a c h to m e a s u r i n g a n d r e c o r d i n g blood p r e s s u r e in the office, it w a s o f c o n s i d e r a b l e interest to m e .  I w a s i n t e r e s t e d in l e a r n i n g h o w s u c h n e w d e v i c e s w e r e validated  a n d w a s t h e r e f o r e e n t h u s i a s t i c to be involved in the d e s i g n , m o d i f i c a t i o n , e x e c u t i o n a n d analysis of clinical trials for that p u r p o s e .  T h i s involved learning the r i g o r o u s u n i f o r m criteria a s set by the A m e r i c a n  National S t a n d a r d for Electronic or A u t o m a t e d S p h y g m o m a n o m e t e r s , A N S I / A A M I S P 1 0 - 1 9 9 2 a n d the British H y p e r t e n s i o n S o c i e t y protocol, the s t a n d a r d setting b o d i e s for t h e s e t y p e s of d e v i c e s [8,9]. T h e p r o c e s s of participation in 2 clinical validation trials of t h e B p T R U ™ , m a n u f a c t u r e d by V S M M e d t e c h Limited plus re-validation u s i n g s t o r e d electronic d a t a p e r m i t t e d m e to learn a lot a b o u t the validation p r o c e s s a n d s t a n d a r d s . A s a result of this learning p r o c e s s I h a v e b e e n a b l e to m a k e r e c o m m e n d a t i o n s  3  as to h o w t h e validation p r o c e s s a n d s t a n d a r d s c a n be i m p r o v e d a n d h o w t h e B p T R U ™ s h o u l d be further t e s t e d in t h e f u t u r e .  T h e results of this thesis are d e s c r i b e d in f o u r c h a p t e r s . s u m m a r i z e s the validation trial in adults [10].  C h a p t e r t w o r e p r e s e n t s a p u b l i s h e d paper that  C h a p t e r three d e s c r i b e s h o w t h e c o m p u t e r algorithm w a s  m o d i f i e d using s t o r e d electronic d a t a f r o m t h e trial outlined in C h a p t e r t w o [11].  C h a p t e r f o u r d e s c r i b e s a s e c o n d trial to d e t e r m i n e t h e a c c u r a c y o f t h e d e v i c e in c h i l d r e n ( a g e r a n g e 3 to 18 y e a r s ) .  T h e C h a p t e r is r e a d y to be s u b m i t t e d for publication.  Finally, to s u m m a r i z e t h e overall  a c c u r a c y of the B p T R U ™ the r a w d a t a for e a c h subject in t h e adult a n d paediatric trials w a s c o m b i n e d a n d p r e s e n t e d in C h a p t e r five. T h i s s t u d y is also n o w r e a d y to be s u b m i t t e d for publication.  C h a p t e r six r e p r e s e n t s the overall d i s c u s s i o n . It includes r e c o m m e n d a t i o n s to t h e regulatory b o d i e s as to h o w to i m p r o v e t h e validation p r o c e s s a n d r e c o m m e n d a t i o n s to t h e c o m p a n y that m a k e s the B p T R U ™ as to f u t u r e trials to f u r t h e r d e m o n s t r a t e the u s e f u l n e s s of the device.  4  Objectives: •  T o compare the B p T R U ™  oscillometric  blood p r e s s u r e - m e a s u r i n g  device with the auscultatory  m e r c u r y s p h y g m o m a n o m e t e r in adults. •  To  compare  the  blood  pressure  device  against  the  standard  auscultatory  mercury  s p h y g m o m a n o m e t e r in t h e paediatric p o p u l a t i o n . •  T o c o m b i n e t h e adult a n d paediatric d a t a in t h e f o r m of a n individual d a t a m e t a - a n a l y s i s , to a s s e s s t h e overall a c c u r a c y of t h e d e v i c e .  •  T o critique t h e r e g u l a t o r y r e q u i r e m e n t s f o r blood p r e s s u r e - m e a s u r i n g d e v i c e s a n d m a k e s u g g e s t i o n s for i m p r o v e m e n t .  •  T o r e c o m m e n d a n d d e v e l o p n e w clinical trials t o d e m o n s t r a t e t h e u s e f u l n e s s in t h e p r i m a r y c a r e setting.  5  CHAPTER II  COMPARISION of the OSCILLOMETRIC BLOOD PRESSURE MONITOR (BPM-100 THE AUSCULATORY MERCURY SPHYGMOMANOMETER  Beta  ) WITH  Gurdial S. M a t t u , M B B C h , C C F P , T h o m a s L. Perry, Jr. M D , F R C P ( C ) J a m e s M W r i g h t , M D , P h D , F R C P ( C ) , D e p a r t m e n t of P h a r m a c o l o g y & T h e r a p e u t i c s a n d D e p a r t m e n t of M e d i c i n e , University of British C o l u m b i a , V a n c o u v e r , B C , C a n a d a . a  3 0  a b  3  "Corresponding Author: J a m e s M. W r i g h t , M D , P h D , F R C P ( C ) , D e p a r t m e n t of P h a r m a c o l o g y & T h e r a p e u t i c s a n d D e p a r t m e n t of M e d i c i n e , T h e University of British C o l u m b i a , 2 1 7 6 Health S c i e n c e s Mall, V a n c o u v e r , B C , C a n a d a , V 6 T 1Z3, t e l e p h o n e : ( 6 0 4 ) 8 2 2 - 4 2 7 0 , f a x : ( 6 0 4 ) 8 2 2 - 0 7 0 1 , e m a i l : jmwright@interchange.ubc.ca 3  b  S o u r c e of F u n d i n g : V S M - M e d T e c h Short Title:  V a l i d a t i o n of t h e B P M - 1 0 0 t a monitor. Be  6  ABSTRACT Background: T o c o m p a r e directly t h e a c c u r a c y of t h e B P M - 1 0 0 t a m o n i t o r ( a n a u t o m a t e d o s c i l l o m e t r i c b l o o d p r e s s u r e B e  device) with standard auscultatory mercury sphygmomanometry.  Design: T h e B P M - 1 0 0 t a w a s c o n n e c t e d in parallel v i a a T - t u b e to a m e r c u r y s p h y g m o m a n o m e t e r . T h e B P M B e  1 0 0 t a a n d t w o t r a i n e d o b s e r v e r s (blinded f r o m e a c h other, a n d t h e B P M - 1 0 0 t a ) m e a s u r e d t h e sitting Be  B e  blood p r e s s u r e s ( B P ) s i m u l t a n e o u s l y .  Methods: M e a n s , s t a n d a r d d e v i a t i o n a n d r a n g e w e r e c a l c u l a t e d f o r all d e m o g r a p h i c d a t a : a g e , a r m size, heart rate and BP. Agreement between the B P M - 1 0 0  B e t a  and the mean of 2 observers (reference) w a s determined  a n d e x p r e s s e d a s t h e m e a n ± S D , plus t h e % of d i f f e r e n c e s w i t h i n 5, 10 a n d 15 m m H g .  Results: O f 9 2 r e c r u i t e d s u b j e c t s , 8 5 ( 9 2 . 4 % ) m e t t h e inclusion criteria, a n d 3 9 1 s e t s of sitting B P a n d heart rate m e a s u r e m e n t s w e r e available for analysis.  T h e mean difference between the B P M - 1 0 0 t B e  a  monitor and  t h e r e f e r e n c e w a s - 0 . 6 2 ± 6.96 m m H g for systolic B P , - 1 . 4 8 ± 4 . 8 0 m m H g f o r diastolic B P a n d 0.14 ± 1.86 b p m f o r heart rate. T h e o n l y limitation of t h e d e v i c e w a s a t e n d e n c y f o r t h e d e v i c e to u n d e r e s t i m a t e higher systolic b l o o d p r e s s u r e s . T h i s limitation h a s b e e n a d d r e s s e d by a m i n o r c h a n g e in t h e a l g o r i t h m ( s e e f o l l o w i n g c o m p a n i o n p u b l i c a t i o n ) . [8]  Conclusion: The BPM-100  B e t  a is a n a c c u r a t e B P m o n i t o r f o r t h e office s e t t i n g , w h i c h m e e t s all r e q u i r e m e n t s of t h e  A s s o c i a t i o n f o r t h e A d v a n c e m e n t o f M e d i c a l I n s t r u m e n t a t i o n a n d a c h i e v e s a n " A " g r a d e a c c o r d i n g to t h e British H y p e r t e n s i o n S o c i e t y s t a n d a r d .  Key Words:  b l o o d p r e s s u r e , m e a s u r e m e n t , monitor, o s c i l l o m e t r i c , v a l i d a t i o n , a u t o m a t i c .  7  INTRODUCTION  Sir G e o r g e P i c k e r i n g d e s c r i b e d blood p r e s s u r e a s a d y n a m i c p r o c e s s , s u c h that a single blood p r e s s u r e r e a d i n g in t h e physician's office is like w a t c h i n g a single f r a m e of a m o v i e [1]. T o p r a c t i c e rational evidence-based  medicine  when  managing  elevated  blood  pressure,  one  should  document  blood  p r e s s u r e s in a m a n n e r at least as g o o d a s that e m p l o y e d in t h e large r a n d o m i z e d c o n t r o l l e d trials ( R C T s ) . T h e latter g e n e r a l l y r e q u i r e that t h e patient rest c o m f o r t a b l y for at least 5 m i n u t e s b e f o r e a t e c h n i c i a n or n u r s e m e a s u r e s t h e b l o o d p r e s s u r e r e p e a t e d l y (at least 3 t i m e s ) f o l l o w i n g a p p r o v e d s t a n d a r d s . [ 2 ]  This  m a y b e a c h i e v a b l e in s o m e specialty clinics, but is s e l d o m f o l l o w e d in t h e f a m i l y p h y s i c i a n s e t t i n g , w h e r e m o s t patients w i t h high b l o o d p r e s s u r e a r e m a n a g e d .  It is a practical reality that a c c u r a t e r e p r o d u c i b l e d o c u m e n t a t i o n of r e s t i n g b l o o d p r e s s u r e is difficult f o r t h e a v e r a g e o u t p a t i e n t p h y s i c i a n or n u r s e to a c h i e v e . C o m m o n e r r o r s in b l o o d p r e s s u r e r e a d i n g s include: insufficient or n o t i m e f o r t h e patient to rest, u n s u p p o r t e d a r m , u n s u p p o r t e d b a c k , a r m not at heart level, talking at t h e t i m e of t h e m e a s u r e m e n t , distracting b a c k g r o u n d noise, i n a p p r o p r i a t e c u f f a n d bladder size, failure to r e c o r d m e a s u r e m e n t i m m e d i a t e l y , r o u n d i n g of n u m b e r s to n e a r e s t 5 or 10 instead of to 2 m m H g , t o o rapid d e f l a t i o n of c u f f p r e s s u r e , a n d u s i n g a n o n - c a l i b r a t e d i n s t r u m e n t [3].  A n y m e t h o d that m i g h t i m p r o v e blood p r e s s u r e m e a s u r e m e n t  m u s t satisfy e c o n o m i c a n d  practical  realities of o f f i c e p r a c t i c e . It m u s t g e n e r a t e m e a s u r e m e n t s that a r e a n a c c u r a t e reflection of t h e p r e s e n t s t a n d a r d ( a u s c u l t a t o r y m e a s u r e m e n t s with a m e r c u r y s p h y g m o m a n o m e t e r ) f r o m a t e c h n i q u e that is e q u a l to or better t h a n u s u a l p r a c t i c e . In addition it s h o u l d r e d u c e or not a d d to p h y s i c i a n / n u r s e effort a n d t i m e .  T h e B P M - 1 0 0 t a . p r o d u c e d by V S M M e d T e c h L t d . of V a n c o u v e r , C a n a d a , is a n a u t o m a t e d , n o n - i n v a s i v e B e  b l o o d p r e s s u r e m o n i t o r d e s i g n e d to g e n e r a t e r e p e a t e d m e a s u r e s of t h e b l o o d p r e s s u r e a n d pulse rate of patients w i t h o u t requiring t h e p r e s e n c e of a physician or n u r s e . T h e d e v i c e u s e s s t a n d a r d blood p r e s s u r e c u f f s to m e a s u r e t h e blood p r e s s u r e in t h e u p p e r a r m u s i n g t h e o s c i l l o m e t r i c t e c h n i q u e . T h e p u r p o s e of this s t u d y w a s to directly c o m p a r e t h e a c c u r a c y of t h e B P M - 1 0 0 t a m o n i t o r w i t h s t a n d a r d a u s c u l t a t o r y B e  m e a s u r e m e n t s using a mercury s p h y g m o m a n o m e t e r  8  in a c c o r d a n c e w i t h g u i d e l i n e s p r o v i d e d by t h e  A s s o c i a t i o n for the A d v a n c e m e n t of M e d i c a l I n s t r u m e n t a t i o n ( A A M I ) S P 1 0 : 1 9 9 2 , t h e s t a n d a r d setting b o d y for both t h e s e d e v i c e s . [ 4 ]  9  METHODS  Subject Enrolment S u b j e c t s w e r e recruited using public notices in a University s e t t i n g , t h r o u g h t h e Blood P r e s s u r e Clinic at t h e University o f British C o l u m b i a , a n d t h r o u g h f a m i l y physician p r a c t i c e s a s s o c i a t e d with t h e University. S c r e e n i n g w a s d e s i g n e d t o enrol at least 8 5 s u b j e c t s with a m i n i m u m o f 3 a c c e p t a b l e pairs of blood p r e s s u r e m e a s u r e m e n t s a n d m e e t i n g t h e required target p o p u l a t i o n o b j e c t i v e s d e f i n e d below.  Ethical Approval Ethical a p p r o v a l of t h e s t u d y a n d c o n s e n t f o r m w a s o b t a i n e d f r o m t h e Clinical S c r e e n i n g C o m m i t t e e f o r H u m a n E x p e r i m e n t a t i o n o f t h e University of British C o l u m b i a prior t o initiation o f a n y o f t h e s t u d y procedures.  Inclusion criteria All s u b j e c t s h a d t o b e h e m o d y n a m i c a l l y stable a n d at least 18 y e a r s o l d . S u b j e c t s w i t h r h y t h m irregularities s u c h a s atrial fibrillation or with a n a u s c u l t a t o r y g a p w e r e eligible. All s u b j e c t s s i g n e d t h e c o n s e n t f o r m prior to e n r o l m e n t . T o be included s c r e e n i n g m e a s u r e m e n t criteria h a d to be m e t , a n d a m i n i m u m of 3 valid pairs of m e a s u r e m e n t s o b t a i n e d .  Exclusion criteria S u b j e c t s w i t h u n s t a b l e , a c c e l e r a t e d o r m a l i g n a n t h y p e r t e n s i o n w e r e e x c l u d e d , a s w e r e patients with s e v e r e peripheral v a s c u l a r d i s e a s e o r o t h e r existing c o n d i t i o n that t h e i n v e s t i g a t o r s felt w o u l d not allow f o r safe  or  accurate  non-invasive  blood  pressure  measurements.  There  were  also  pre-specified  m e a s u r e m e n t e x c l u s i o n criteria f o r both s u b j e c t s a n d individual m e a s u r e m e n t s : 1) S u b j e c t s in w h o m t h e i n t e r - o b s e r v e r a g r e e m e n t w a s g r e a t e r t h a n 10 m m H g in either t h e systolic o r diastolic blood p r e s s u r e m e a s u r e m e n t s at s c r e e n i n g .  2 ) S u b j e c t s w h o h a d less t h a n 3 valid pairs o f r e a d i n g s . 3 ) S u b j e c t s w h o  had s u c h w e a k K o r o t k o f f s o u n d s , that either of t h e o b s e r v e r s d e e m e d a c c e p t a b l e a u s c u l t a t i o n i m p o s s i b l e . 4 ) A n y m e a s u r e m e n t in w h i c h t h e inter-observer a g r e e m e n t w a s g r e a t e r t h a n 10 m m H g f o r either t h e systolic or diastolic r e a d i n g . 5 ) A n y m e a s u r e m e n t in w h i c h t h e B P M - 1 0 0 error.  10  B e t  a did not r e c o r d or r e c o r d e d a n  Target population objectives: 1) A n e q u a l n u m b e r of m a l e s a n d f e m a l e s u b j e c t s . 2) R a n g e of a r m sizes ( m e a s u r e d at m i d - b i c e p s ) . •  A t least 1 0 % g r e a t e r t h a n 35 c m c i r c u m f e r e n c e (large a r m c u f f ) .  •  A t least 1 0 % less t h a n 2 5 c m c i r c u m f e r e n c e ( s m a l l a r m c u f f ) .  3) R a n g e of systolic b l o o d p r e s s u r e s ( m e a n of 2 o b s e r v e r s ) . •  At least 1 0 % g r e a t e r 180 m m H g systolic.  •  A t least 1 0 % less t h a n 100 m m H g systolic.  4 ) R a n g e of diastolic b l o o d p r e s s u r e s ( m e a n of 2 o b s e r v e r s ) . •  A t least 1 0 % g r e a t e r 100 m m H g diastolic.  •  A t least 1 0 % less t h a n 6 0 m m H g diastolic.  Study design  S u b j e c t s w e r e recruited d u r i n g S e p t e m b e r a n d O c t o b e r 1 9 9 9 . All s u b j e c t s p r o v i d e d s i g n e d  informed  c o n s e n t prior to e n r o l m e n t . A s i g n e d c o p y of t h e c o n s e n t f o r m w a s p r o v i d e d to e a c h s u b j e c t . All s u b j e c t s w e r e e n t e r e d into t h e s u b j e c t log a n d a s s i g n e d a s u b j e c t c o d e . B a s i c d e m o g r a p h i c d a t a w e r e collected o n e a c h s u b j e c t e n r o l l e d into t h e trial including a g e , sex, p r e - e x i s t i n g h e a l t h c o n d i t i o n s a n d m e d i c a t i o n s , a n d a r m c i r c u m f e r e n c e s ( m e a s u r e d at m i d - b i c e p s o n t h e a r m of blood p r e s s u r e r e c o r d i n g s ) .  S u b j e c t s w e r e t h e n s e a t e d in a quiet but well illuminated r o o m o n a c h a i r w i t h c o m f o r t a b l e b a c k s u p p o r t . T h e a r m f r o m w h i c h b l o o d p r e s s u r e m e a s u r e m e n t s w e r e r e c o r d e d w a s p l a c e d in a c o m f o r t a b l e position o n a n a d j u s t a b l e t a b l e at h e a r t level. T h e a p p r o p r i a t e - s i z e d c u f f ( b a s e d o n c u f f m a r k i n g s ) w a s s e l e c t e d f r o m f o u r sizes p r o v i d e d with t h e B P M - 1 0 0 t a a n d a p p l i e d to t h e s u b j e c t ' s b a r e u p p e r a r m with t h e B e  indicator o v e r t h e brachial artery.  T h e B P M - 1 0 0 t a w a s c o n n e c t e d in parallel w i t h a m e r c u r y s p h y g m o m a n o m e t e r b y m e a n s of a T - t u b e B e  w i t h a r m s of e q u a l l e n g t h . A T r i m l i n e p r e c i s i o n m e r c u r y s p h y g m o m a n o m e t e r ( r a n g e 0 to 3 0 0 m m H g ,  11  g r a d a t i o n s o f 1 m m H g , a c c u r a c y ± 0.5 m m H g ) w a s u s e d a s t h e s t a n d a r d s p h y g m o m a n o m e t e r to p r o v i d e the auscultatory reference readings.  A heart rate m o n i t o r , t h e N o n i n f i n g e r p u l s e o x i m e t e r , w a s c o n n e c t e d to t h e s u b j e c t ' s o t h e r a r m or a l t e r n a t e b o d y location a s a p p r o p r i a t e ; this d e v i c e h a s a r a n g e o f 18 to 3 0 0 b e a t s per m i n u t e a n d a c c u r a c y of ± 3 % .  O n e of t h e t w o o b s e r v e r s  located the diaphragm  o f t h e s t e t h o s c o p e o v e r t h e brachial artery  and  d e t e r m i n e d o p t i m a l position for a d e q u a t e a u s c u l t a t i o n . A u s c u l t a t i o n f o r b l o o d p r e s s u r e s w a s p e r f o r m e d with a dual-headed teaching stethoscope. T h e observers w e r e seated on adjustable seats opposite the s u b j e c t s o that t h e y c o u l d r e a d t h e s t a n d a r d m e r c u r y s p h y g m o m a n o m e t e r w i t h o u t i n t r o d u c i n g parallax e r r o r s . A n i n t e r p o s e d c u r t a i n blinded o b s e r v e r s f r o m e a c h o t h e r . T h e t w o o b s e r v e r s w e r e e x p e r i e n c e d r e g i s t e r e d n u r s e s w h o s e b l o o d p r e s s u r e r e c o r d i n g skills w e r e c o n f i r m e d by t h e i n v e s t i g a t o r s prior to a n y trial s u b j e c t e n r o l m e n t .  T h e B P M - 1 0 0 t a d e v i c e a u t o m a t i c a l l y inflates a n d d e f l a t e s t h e cuff, a n d t h e n u s e s t h e o s c i l l o m e t r i c B e  t e c h n i q u e to c a l c u l a t e systolic a n d diastolic blood p r e s s u r e . In this t e c h n i q u e , t h e m e a n arterial p r e s s u r e ( M A P ) is m e a s u r e d directly f r o m t h e c u f f p r e s s u r e d u r i n g d e f l a t i o n , a n d t h e systolic a n d diastolic B P points a r e c a l c u l a t e d a s ratios o f t h e M A P p u l s e a m p l i t u d e . T h e B P M - 1 0 0 t a a u t o m a t i c a l l y inflates t h e B e  c u f f after initiation to p r e s e t p r e s s u r e s , a n d a u t o m a t i c a l l y a d j u s t s to h i g h e r p r e s s u r e s if n e c e s s a r y to e n s u r e c o m p l e t e c a p t u r e of t h e p u l s e w a v e s . T h e c u f f s l o w l y d e f l a t e s a u t o m a t i c a l l y at a rate of 4 m m H g / s e c o n d in a t r u e linear f a s h i o n .  The BPM-100 BPM-100  B e t  B e t a  w a s s e t to cycle e v e r y 2 m i n u t e s a n d t h e o b s e r v e r s ( b l i n d e d f r o m e a c h other, a n d t h e  a ) s i m u l t a n e o u s l y visually r e c o r d e d t h e systolic a n d diastolic b l o o d p r e s s u r e s by listening to  the Korotkoff sounds and watching the standard mercury sphygmomanometer. Korotkoff sound phase I (the b e g i n n i n g of t h e c o m p r e s s i o n s o u n d ) w a s t a k e n a s t h e systolic b l o o d p r e s s u r e ; a n d p h a s e V (the point o f c o m p l e t e  disappearance  of t h e s o u n d ) w a s t a k e n a s t h e diastolic  blood pressure.  These  m e a s u r e m e n t s w e r e i n d e p e n d e n t l y r e c o r d e d by e a c h of t h e o b s e r v e r s . T h e B P M - 1 0 0 t a r e a d i n g s a n d B e  12  pulse rate w e r e r e c o r d e d by o n e of us ( G S M ) i n d e p e n d e n t l y a n d b l i n d e d f r o m t h e t w o o b s e r v e r s . A total of six m e a s u r e m e n t s w e r e r e c o r d e d  by this m e t h o d .  T h e first m e a s u r e m e n t w a s c o n s i d e r e d  the  s c r e e n i n g m e a s u r e m e n t a n d w a s not u s e d f u r t h e r in t h e v a l i d a t i o n s t u d y ( t h e first r e a d i n g w a s u s e d to establish observer agreement and satisfactory auscultation technique).  O n e of u s ( G S M ) also r e c o r d e d t h e heart rate r e f e r e n c e v a l u e via t h e s t a n d a r d N o n i n finger  pulse  o x i m e t e r at a p p r o x i m a t e l y t h e m i d - p o i n t of a u t o m a t i c d e f l a t i o n , w i t h o u t k n o w l e d g e of t h e B P M - 1 0 0 t a B e  estimate.  A f t e r six m e a s u r e m e n t s w h e n all r e a d i n g s a n d r e c o r d i n g s w e r e p r o p e r l y d o c u m e n t e d t h e cuff  w a s r e m o v e d f r o m t h e s u b j e c t s ' a r m , a n d t h e s u b j e c t w a s a l l o w e d to l e a v e .  Data Analysis M e a n , s t a n d a r d d e v i a t i o n a n d r a n g e w e r e c a l c u l a t e d f o r all t h e d e m o g r a p h i c d a t a : a g e , a r m size, heart rate a n d b l o o d p r e s s u r e s . T h e first blood p r e s s u r e m e a s u r e m e n t w a s a s c r e e n i n g m e a s u r e m e n t only a n d w a s not u s e d in t h e a n a l y s i s . E a c h s u b s e q u e n t m e a s u r e m e n t w a s r e v i e w e d f o r t h e e x c l u s i o n criteria outlined a b o v e f o r both t h e B P M - 1 0 0 t a a n d t h e o b s e r v e r s . B e  For e a c h i n c l u d e d systolic a n d diastolic b l o o d p r e s s u r e m e a s u r e m e n t t h e m e a n of t h e 2 o b s e r v e r v a l u e s w a s calculated and defined as the reference standard.  Differences between the 2 observers were  expressed as the m e a n difference ± standard deviation, and as the % < 5 m m H g .  Differences between  t h e B P M - 1 0 0 t a a n d t h e r e f e r e n c e s t a n d a r d w e r e a l s o d e t e r m i n e d f o r e a c h systolic a n d diastolic blood B e  p r e s s u r e m e a s u r e m e n t a n d e x p r e s s e d as t h e m e a n d i f f e r e n c e ± s t a n d a r d d e v i a t i o n a c c o r d i n g to t h e A A M I s t a n d a r d [4], a s well a s t h e % of i n t e r - t e c h n i q u e d i f f e r e n c e s w i t h i n 5 m m H g , 10 m m H g a n d 15 m m H g a c c o r d i n g to t h e B H S s t a n d a r d [5].  Inter-technique differences between the B P M - 1 0 0  B e t a  heart  rates a n d t h e r e f e r e n c e heart rates o b t a i n e d f r o m t h e N o n i n p u l s e o x i m e t e r w e r e a l s o c a l c u l a t e d similarly. T o a s s e s s h o w t h e d i f f e r e n c e s related to t h e a b s o l u t e blood p r e s s u r e v a l u e t h e B P M - 1 0 0 m i n u s r e f e r e n c e s t a n d a r d d i f f e r e n c e w a s plotted a g a i n s t t h e a v e r a g e of t h e 2 B P v a l u e s u s i n g a B l a n d A l t m a n display for both systolic a n d diastolic B P [6].  13  RESULTS  Enrolled subjects O f t h e 9 2 s u b j e c t s e n r o l l e d , 85 ( 9 2 . 4 % ) w e r e i n c l u d e d a n d 7 ( 7 . 6 % ) w e r e e x c l u d e d . R e a s o n s  for  e x c l u s i o n a r e detailed b e l o w . P r e - e x i s t i n g m e d i c a l c o n d i t i o n s of e n r o l l e d s u b j e c t s i n c l u d e d s o m e with h y p e r t e n s i o n , renal d i s e a s e (including s u b j e c t s o n dialysis), obesity, s t r o k e , a n g i n a a n d C r o h n ' s d i s e a s e . S u b j e c t s w e r e a l s o t a k i n g v a r i o u s a n t i - h y p e r t e n s i v e a n d o t h e r m e d i c a t i o n s . N o a d v e r s e side effects w e r e r e p o r t e d d u r i n g or f o r up to 30 d a y s after t h e trial. T h r e e individuals w h o h a d e l e v a t e d b l o o d p r e s s u r e s a n d p o s s i b l y u n r e c o g n i z e d h y p e r t e n s i o n w e r e a d v i s e d to f o l l o w u p w i t h their r e g u l a r p h y s i c i a n .  Excluded Subjects T h e first 3 of t h e 9 2 v o l u n t e e r s w e r e e x c l u d e d b e c a u s e of t h e inability to o b t a i n at least 3 s a t i s f a c t o r y sets of B P r e a d i n g s .  T h i s w a s f o u n d to be d u e to a t e c h n i c a l p r o b l e m w i t h t h e B P M - 1 0 0 t a m o n i t o r deflation B e  m e c h a n i s m , w h i c h w a s rectified prior to a n y f u r t h e r s u b j e c t s b e i n g s t u d i e d . T w o s u b j e c t s w e r e e x c l u d e d b e c a u s e of a s c r e e n i n g B P i n t e r - o b s e r v e r d i f f e r e n c e of g r e a t e r t h a n 10 m m H g , a n d 2 b e c a u s e of inability to r e c o r d a c c u r a t e l y t h e diastolic blood p r e s s u r e s .  Target population and demographic data All t a r g e t p o p u l a t i o n o b j e c t i v e s w e r e m e t .  O f t h e 85 i n c l u d e d s u b j e c t s 4 4 ( 5 1 . 8 % ) w e r e m a l e . T h e m e a n  a g e w a s 4 3 . 1 ± 15.6 y e a r s ( r a n g e of 18 - 8 3 y e a r s ) .  There were  10 s u b j e c t s ( 1 1 . 8 % ) with  arm  c i r c u m f e r e n c e e x c e e d i n g 35 c m , a n d 9 s u b j e c t s ( 1 0 . 6 % ) s u b j e c t s w i t h a r m c i r c u m f e r e n c e less t h a n 25 cm.  Included blood pressure measurements Included d a t a totalled 3 9 1 s e t s of s i m u l t a n e o u s l y r e c o r d e d m e a s u r e m e n t s . In 4 1 ( 1 0 . 5 % ) systolic B P e x c e e d e d 180 m m H g , a n d in 53 ( 1 3 . 6 % ) systolic w a s less t h a n 100 m m H g . e x c e e d e d 100 m m H g , a n d in 54 ( 1 3 . 8 % ) diastolic w a s less t h a n 6 0 m m H g .  14  In 4 3 ( 1 1 . 0 % ) diastolic B P  Excluded  blood  pressure  measurements  Thirty-four ( 8 . 0 % ) systolic a n d diastolic B P m e a s u r e m e n t s w e r e e x c l u d e d . F o u r ( 0 . 9 % ) w e r e d u e t o a B P M - 1 0 0 t a t e c h n i c a l error; t h e B P M - 1 0 0 t a either r e c o r d e d a n error o r d i d n o t d i s p l a y t h e r e a d i n g . B e  were  B e  excluded  because  one  observer  forgot  the  number  before  recording  the  Four  mercury  s p h y g m o m a n o m e t e r r e a d i n g . T w e n t y - o n e w e r e e x c l u d e d b e c a u s e o n e o f t h e o b s e r v e r s d i d not feel that a s a t i s f a c t o r y a u s c u l t a t i o n c o u l d b e o b t a i n e d ( 1 5 systolic, 6 diastolic).  Five ( 1 . 3 % ) w e r e  excluded  b e c a u s e t h e o b s e r v e r s d i d n o t a g r e e within 10 m m H g f o r t h e systolic or diastolic B P .  Sphygmomanometer  readings  M e a n d i f f e r e n c e b e t w e e n t h e o b s e r v e r s ( o b s e r v e r 1 - o b s e r v e r 2 ) f o r t h e 3 9 1 systolic m e a s u r e m e n t s w a s - 0 . 6 4 ± 1.94 m m H g .  T h e majority of t h e d i f f e r e n c e s , 9 7 . 7 % , w e r e < 5 m m H g .  the protocol p r e s c r i b e d e x c l u s i o n of d i f f e r e n c e s e x c e e d i n g 10 m m H g . o b s e r v e r s f o r diastolic B P w a s - 1 . 0 8 + 2 . 4 6 m m H g .  All w e r e < 10 m m H g a s  Mean difference between the 2  M o s t ( 9 5 . 7 % ) w e r e < 5 m m H g a n d all w e r e < 10  mmHg.  Range  and distribution  of reference  standard  measurements  T h e m e a n systolic B P f o r t h e 3 9 1 systolic r e f e r e n c e s t a n d a r d m e a s u r e m e n t s  ( a v e r a g e of t h e t w o  o b s e r v e r s ) w a s 128.7 ± 3 0 . 7 m m H g ( r a n g e 81.5 to 2 2 3 . 5 m m H g ) . T h e m e a n r e f e r e n c e s t a n d a r d diastolic B P w a s 7 7 . 4 ± 1 6 . 7 m m H g ( r a n g e 4 5 . 5 t o 120.5 m m H g ) .  M e a n heart rate u s i n g t h e N o n i n f i n g e r pulse  o x i m e t e r w a s 7 0 . 2 + 12.3 beats p e r m i n u t e ( r a n g e 4 2 to 1 0 4 b e a t s p e r m i n u t e ) .  Accuracy  of BPM-100  Beta  as compared  with  The m e a n difference between the B P M - 1 0 0 (BPM-100  B e t a  the reference  B e t a  standard  measurements  a n d t h e r e f e r e n c e s t a n d a r d systolic a n d diastolic B P  - r e f e r e n c e ) is well within t h e A A M I s t a n d a r d [4] a n d is s h o w n in T a b l e 1 . T a b l e 2 s h o w s t h e  p r o p o r t i o n of systolic a n d diastolic d i f f e r e n c e s within 5, 10, a n d 15 m m H g a n d h o w this c o n f o r m s to t h e BHS standard [5]. T h e B P M - 1 0 0 d e v i c e is d e s i g n e d t o d e t e r m i n e t h e a v e r a g e o f u p t o f i v e b l o o d p r e s s u r e r e a d i n g s in individual s u b j e c t s .  W e therefore calculated the subject m e a n B P M - 1 0 0  B e t a  minus the subject  mean  r e f e r e n c e s t a n d a r d systolic a n d diastolic B P m e a s u r e m e n t s a s a m e a s u r e o f a c c u r a c y in t h e practical  15  clinical s e t t i n g .  T h i s g a v e a slightly different m e a n d i f f e r e n c e a n d a l o w e r s t a n d a r d d e v i a t i o n for t h e 85  s u b j e c t s a s s h o w n in T a b l e 1. It w a s also a s s o c i a t e d w i t h a slight i m p r o v e m e n t in t h e p r o p o r t i o n of systolic a n d diastolic d i f f e r e n c e s within 5, 10 a n d 15 m m H g ( T a b l e 2 ) . In Fig 1 t h e B l a n d A l t m a n d i s p l a y of m e a s u r e m e n t s f o r systolic B P s h o w s t h e d i f f e r e n c e of e a c h B P M 1 0 0 t a a n d r e f e r e n c e s t a n d a r d systolic B P plotted a g a i n s t t h e a v e r a g e of t h e B P M - 1 0 0 t a a n d t h e Be  B e  r e f e r e n c e s t a n d a r d systolic B P .  T h i s f i g u r e d e m o n s t r a t e s that t h e B P M - 1 0 0  t h e systolic B P ( n e g a t i v e v a l u e s ) for systolic m e a s u r e m e n t s > 1 5 0 m m H g .  B e t  a t e n d s to u n d e r e s t i m a t e  In Fig 2 t h e B l a n d A l t m a n  d i s p l a y of m e a s u r e m e n t s f o r diastolic blood p r e s s u r e s h o w s t h e d i f f e r e n c e of e a c h r e f e r e n c e a n d B P M diastolic b l o o d p r e s s u r e plotted a g a i n s t t h e a v e r a g e of t h e B P M - 1 0 0 blood pressure.  B e t a  a n d r e f e r e n c e s t a n d a r d diastolic  In this c a s e t h e d i f f e r e n c e s a r e c l u s t e r e d a r o u n d a d i f f e r e n c e of 0 o v e r t h e w h o l e r a n g e  of p r e s s u r e s . T h e m e a n d i f f e r e n c e of t h e B P M - 1 0 0 t a n d t h e r e f e r e n c e heart rate w a s 0.14 ± 1.86 b e a t s per m i n u t e . B e  a  16  DISCUSSION  T h e m o s t c o m m o n r e a s o n f o r patient office visits to a p h y s i c i a n in C a n a d a a n d t h e U n i t e d S t a t e s is hypertension.[6]  For d i a g n o s i s a n d t r e a t m e n t t o be c o n s i s t e n t , it is i m p o r t a n t that b l o o d  m e a s u r e m e n t s in t h e p h y s i c i a n ' s office b e a s s t a n d a r d i z e d a n d a c c u r a t e a s p o s s i b l e .  pressure  A n accurate,  c o n v e n i e n t a n d a f f o r d a b l e a u t o m a t i c blood p r e s s u r e m e a s u r i n g d e v i c e w o u l d i m p r o v e c o n s i s t e n c y a n d a c c u r a c y of m e a s u r e m e n t s in different p r a c t i c e s e t t i n g s .  T h e A s s o c i a t i o n f o r t h e A d v a n c e m e n t o f M e d i c a l I n s t r u m e n t a t i o n ( A A M I ) , is t h e s t a n d a r d setting b o d y for blood p r e s s u r e m e a s u r e m e n t d e v i c e s . Its guidelines require that t h e m e a n d i f f e r e n c e of b l o o d p r e s s u r e m e a s u r e m e n t s b e t w e e n a n e w d e v i c e a n d t h e m e r c u r y s t a n d a r d m u s t b e w i t h i n ± 5 m m H g with a s t a n d a r d d e v i a t i o n of < 8 m m H g . standard.  It c a n be s e e n that in this s t u d y t h e B P M - 1 0 0 t a m o n i t o r easily m e t this B e  It c a n a l s o b e s e e n that t h e m e a n d i f f e r e n c e b e t w e e n t h e B P M - 1 0 0 B e t a a n d t h e r e f e r e n c e  m e a s u r e m e n t s w a s similar t o that for t h e i n t e r - o b s e r v e r m e a s u r e m e n t s .  T h e s t a n d a r d deviation o f t h e  d i f f e r e n c e b e t w e e n t h e B P M - 1 0 0 t a m e a s u r e m e n t s a n d t h e r e f e r e n c e s t a n d a r d e x c e e d e d that of t h e B e  i n t e r - o b s e r v e r m e a s u r e m e n t s , but w a s well within t h e A A M I r e q u i r e m e n t o f a s t a n d a r d deviation of less than 8 m m H g .  T h e l o w variability o f t h e i n t e r - o b s e r v e r m e a s u r e m e n t s in t h i s s t u d y is n o t a n a c c u r a t e  reflection o f this m e a s u r e , a s t h e protocol d i c t a t e d that i n t e r - o b s e r v e r d i f f e r e n c e s e x c e e d i n g 10 m m H g be e x c l u d e d ( N = 5 in this s t u d y ) .  T h e m a j o r potential limitation of t h e B P M - 1 0 0 t a d e t e c t e d in this s t u d y is t h e u n d e r e s t i m a t i o n of systolic B e  m e a s u r e m e n t s > 150 m m H g a s d e m o n s t r a t e d by t h e B l a n d A l t m a n d i s p l a y (Fig 1). It is k n o w n that t h e o s c i l l o m e t r i c t e c h n i q u e , w h e n c o m p a r e d with s t a n d a r d a u s c u l t a t o r y m e t h o d s t e n d s t o b o t h u n d e r e s t i m a t e systolic B P a n d to yield high s t a n d a r d d e v i a t i o n s f o r higher systolic p r e s s u r e s . [ 7 ] potential limitation t h e m a n u f a c t u r e r  undertook a further developmental  study using the stored raw  e l e c t r o n i c d a t a a n d t h e a u s c u l t a t e d b l o o d p r e s s u r e d a t a o b t a i n e d d u r i n g this s t u d y . result of this s u b s e q u e n t s t u d y a r e p r e s e n t e d in t h e f o l l o w i n g c o m p a n i o n p a p e r [8].  17  A s a result of this  T h e methods and  A n o t h e r potential limitation is t h e relatively high variability of t h e d i f f e r e n c e s b e t w e e n t h e B P M d e v i c e a n d t h e r e f e r e n c e s t a n d a r d individual m e a s u r e m e n t s . H o w e v e r , t h e r e f e r e n c e s t a n d a r d is a n indirect e s t i m a t e of t h e true intra-arterial p r e s s u r e a n d s t u d i e s c o m p a r i n g a u s c u l t a t i o n a n d intra-arterial p r e s s u r e s a r e a s s o c i a t e d with a higher d e g r e e of variability t h a n that s e e n h e r e . [ 9 - 1 2 ]  In o t h e r w o r d s w h e n a large  d i f f e r e n c e b e t w e e n 2 m e a s u r e m e n t s is s e e n o n e c a n n o t be c e r t a i n w h i c h of t h e m e a s u r e m e n t s is t h e best e s t i m a t e of intra-arterial b l o o d p r e s s u r e .  T h e B P M - 1 0 0 t a u s e s t h e o s c i l l o m e t r i c m e t h o d , w h i c h is t h e o n e u s e d by m o s t a m b u l a t o r y a n d h o m e B e  blood pressure measuring devices. d i s c a r d t h e first.  The BPM-100  B e t a  is d e s i g n e d to m e a s u r e 6 b l o o d p r e s s u r e s a n d  T h e first is d i s c a r d e d , a s it is n o r m a l l y d o n e w i t h t h e p h y s i c i a n or n u r s e p r e s e n t in t h e  r o o m w i t h t h e patient.  T h e d e v i c e is d e s i g n e d to m e a s u r e a n d s a v e t h e last 5 m e a s u r e m e n t s plus t h e  a v e r a g e of t h e s e 5 m e a s u r e m e n t s a u t o m a t i c a l l y w h i l e t h e p h y s i c i a n / n u r s e is i n v o l v e d in o t h e r activities. T h e m e a n B P a s well a s t h e individual m e a s u r e m e n t s c a n be r e c o r d e d in t h e p a t i e n t ' s c h a r t .  T h e m e a n B P is t h e b e s t e s t i m a t e of t h e r e s t i n g p r e s s u r e of t h e p a t i e n t f o r t h a t visit. some  value  in c a l c u l a t i n g t h e d i f f e r e n c e s  m e a s u r e d by t h e B P M - 1 0 0  B e t  between  the m e a n  T h e r e is t h e r e f o r e  v a l u e s f o r all individual  A s c a n be s e e n in T a b l e 1 a n d 2 this a n a l y s i s is a s s o c i a t e d with  either n o c h a n g e o r a n i m p r o v e m e n t in t h e p e r f o r m a n c e o f t h e B P M - 1 0 0  B e t a  monitor.  T h e i m p o r t a n c e of m e a s u r i n g b l o o d p r e s s u r e p r o p e r l y c a n n o t b e u n d e r e s t i m a t e d . [ 1 1 - 1 3 ] in  patients  as  a a n d by a u s c u l t a t i o n . T h i s d a t a p r o b a b l y better reflects t h e clinical reliability  of this m o n i t o r in a p r a c t i c e s e t t i n g .  hypertension  subjects  who  are  truly  normotensive  and  vice  versa  has  potential  Diagnosing far  reaching  c o n s e q u e n c e s f o r t h e patient i n v o l v e d . B l o o d p r e s s u r e m e a s u r e m e n t s t h e r e f o r e s h o u l d not o n l y b e a c c u r a t e a n d c o n s i s t e n t but r e p r o d u c i b l e [ 1 3 , 1 4 ] . 100  B e t  O u r s t u d y s u g g e s t s this is p o s s i b l e u s i n g t h e B P M -  a monitor.  L a n g l o i s [3], d e s c r i b e s c o m m o n e r r o r s in m e a s u r i n g a n d r e c o r d i n g b l o o d p r e s s u r e m e a s u r e m e n t s . U s i n g a well v a l i d a t e d a u t o m a t i c b l o o d p r e s s u r e m o n i t o r c o u l d rectify m a n y of t h e s e e r r o r s .  'No waiting times'  c a n be p r e v e n t e d by setting t h e t i m e b e t w e e n m e a s u r e m e n t s f r o m 1 to 5 m i n u t e s (cycle t i m e ) , d e p e n d i n g  18  o n h o w long t h e patient h a s b e e n s e a t e d at rest. the m e a n  blood  S i n c e t h e first m e a s u r e m e n t is not u s e d in calculating  p r e s s u r e , it gives t i m e f o r patients to relax a n d g e t a c c u s t o m e d  to t h e  'Distracting noise or t a l k i n g ' is not a n issue b e c a u s e p a t i e n t s c a n b e left a l o n e in a quiet r o o m .  method.  'Rounding  off n u m b e r s ' is a v o i d e d b e c a u s e t h e B P M - 1 0 0 t a m o n i t o r r e c o r d s m e a s u r e m e n t s to t h e n e a r e s t 1 m m H g B e  without  any  bias.  'Fast  deflation'  is  not  a  factor  because  deflation  is  uniform  and  preset  at  4  mmHg/second.  A s m a r a n d Z a n c h e t t i state "as w e a p p r o a c h t h e e n d of t h e 2 0 n e w e r a in b l o o d p r e s s u r e m e a s u r e m e n t . " [ 1 5 ]  t h  c e n t u r y , w e a r e a s s i s t i n g t h e birth of a  By utilizing a g o o d a u t o m a t i c B P m o n i t o r , o n e  can  e l i m i n a t e t h e " h u m a n error" a s s o c i a t e d with both m e r c u r y a n d a n e r o i d d e v i c e s , w h i l e p e r f o r m i n g multiple, a c c u r a t e B P r e a d i n g s w h i c h a r e in a c c o r d a n c e w i t h c u r r e n t clinical g u i d e l i n e s .  In c o n c l u s i o n , this s t u d y d e m o n s t r a t e s that t h e B P M - 1 0 0 t a o s c i l l o m e t r i c d e v i c e p r o v i d e s a n a c c u r a t e B e  m e a s u r e of b l o o d p r e s s u r e that c l o s e l y a p p r o x i m a t e s that a c h i e v e d by t h e indirect a u s c u l t a t o r y m e t h o d using a mercury s p h y g m o m a n o m e t e r . new devices.  T h i s validation s t u d y satisfies t h e A A M I a n d B H S s t a n d a r d s f o r  W e b e l i e v e that t h e B P M - 1 0 0 t B e  a  offers practical potential a d v a n t a g e s to i m p r o v e t h e  a c c u r a c y , reproducibility a n d e f f i c i e n c y of b l o o d p r e s s u r e m e a s u r e m e n t by p h y s i c i a n s or n u r s e s .  19  x>  o  c  o o oo | oo  "i-S E JS 0 E <n  CM CN  V  13  _l  O  I-  < Q  0  p  CO 0 - 1 0 S: p c 0 £  +1  = st £  21  xi  c  •  ,  xi  co •o c  1 - | .2 0 U3  E E  co  o CD cd | CD cd v  CO CN CO  X I •—  CO c  o 0  cH c o 0- -Xi E  H  x>  E  p  I in  CM CD  CO CD  +1  E  0  "55  co  _c  o o  CO  IK z:  Q_ CO  0  o c 0 0  0  IK  0  0 Q.  oo  CN  o o  CO  CL CO  CD  CO  E o c co >  XI  < 0  I  o o  0 0  CD c  CO 0  E  o 0  0  15 o XI 0  o o  o c co  c 0  '¥ lw  c  g 'o o  W  <  o  co VI  CN  CD  CN  co  co  Fig 1  B l a n d - A l t m a n D i s p l a y of S y s t o l i c M e a s u r e m e n t s , All C u f f s , 391  50  75  100  125  measurements  150  175  200  Mean of BPM and Obs Avg (mmHg)  B l a n d - A l t m a n display of all systolic m e a s u r e m e n t s for all cuffs ( n = 3 9 1 ) . B P M , B P M - 1 0 0 t a monitor; O b s A v g , o b s e r v e r a v e r a g e . B e  22  225  250  Fig 2  Bland-Altman Display of Diastolic M e a s u r e m e n t s , All C u f f s , 391  measurements  20  T3 C  15  ^  i i  OOo  10  mean  +2SD  5  m E O o) 0) > o <  (/)  0  O C D  - 5 -I -10  mean  -2SD  -15 - 2 0 -I -25 20  40  60  80  100  Mean of BPM and Obs Avg (mmHg)  B l a n d - A l t m a n d i s p l a y of all diastolic m e a s u r e m e n t s f o r all c u f f s (n = 3 9 1 ) . B P M , B P M - 1 0 0 t a monitor; Obs Avg, observer average. B e  23  120  140  References 1.  P i c k e r i n g G. Hypertension: causes, consequences and management. 2 Edition. Churchill L i v i n g s t o n e . E d i n b u r g h a n d L o n d o n , 1 9 7 4 . n d  2.  Systolic H y p e r t e n s i o n in the Elderly P r o g r a m . P r e v e n t i o n of s t r o k e by a n t i - h y p e r t e n s i v e d r u g t r e a t m e n t in older p e r s o n s w i t h isolated systolic h y p e r t e n s i o n . Final results of t h e Systolic H y p e r t e n s i o n in t h e Elderly P r o g r a m . T h e J o u r n a l of the A m e r i c a n M e d i c a l A s s o c i a t i o n 1 9 9 1 ; 2 6 5 : 3 2 5 5 - 3 2 6 4 .  3.  Langlois S. Measuring blood pressure: H o w competent are w e ? P e r s p e c t i v e s in C a r d i o l o g y 1 9 9 9 ; 2 9 - 3 9 .  4.  A m e r i c a n National S t a n d a r d for Electronic or A u t o m a t e d S p h y g m o m a n o m e t e r s : A N S I / A A M I S P 1 0 . A r l i n g t o n , V A : A s s o c i a t i o n for the A d v a n c e m e n t of M e d i c a l I n s t r u m e n t a t i o n . 1 9 9 2 .  5.  O ' B r i e n E, Petrie J , Littler W , et a l . T h e British H y p e r t e n s i o n S o c i e t y protocol for t h e e v a l u a t i o n of blood p r e s s u r e m e a s u r i n g d e v i c e s . J o u r n a l of H y p e r t e n s i o n 1 9 9 3 ; 11 (suppl 2 ) : S 4 3 - S 6 2 .  6.  Bland J M , A l t m a n D G . Statistical m e t h o d s for a s s e s s i n g a g r e e m e n t b e t w e e n t w o m e t h o d s of clinical m e a s u r e m e n t . Lancet 1 9 8 6 ; 1 : 3 0 7 - 3 1 0 .  7.  Woodwell DA. National a m b u l a t o r y m e d i c a l c a r e survey: 1995 s u m m a r y . A d v a n c e D a t a 1 9 9 7 ; 2 9 5 : 1-25.  8.  O ' B r i e n E, A t k i n s N, M e e F, O ' M a l l e y K: E v a l u a t i o n of blood p r e s s u r e m e a s u r i n g d e v i c e s . Clinical & E x p e r i m e n t a l H y p e r t e n s i o n 1 9 9 3 ; 15: 1 0 8 7 - 1 0 9 7 .  9.  W r i g h t J M , M a t t u G S , Perry T L Jr, Gelfer M, et a l . V a l i d a t i o n of a n e w a l g o r i t h m for t h e B P M - 1 0 0 electronic o s c i l l o m e t r i c office blood p r e s s u r e monitor. Blood P r e s s u r e M o n i t o r i n g 2 0 0 1 ; 6: 1 6 1 - 1 6 5 .  10. Berliner K, Fujiy H, L e e D H , Yildiz M, G a m i e r B. Blood p r e s s u r e m e a s u r e m e n t s in o b e s e p e r s o n s : C o m p a r i s o n measurements. A m e r i c a n J o u r n a l of C a r d i o l o g y 1 9 6 1 ; July: 1 0 - 1 7 .  of intra-arterial  and  auscultatory  11. S p e n c e J D , Sibbald W J , Cape RD. Direct, indirect a n d m e a n blood p r e s s u r e s in h y p e r t e n s i v e p a t i e n t s : T h e p r o b l e m of cuff artefact d u e to arterial wall stiffness a n d a partial s o l u t i o n . Clinical & Investigative M e d i c i n e 1 9 7 9 ; 2 : 1 6 5 - 1 7 3 . 12. C a m p b e l l N R . H y p e r t e n s i o n m a n a g e m e n t in clinical practice. C a n a d i a n J o u r n a l of C a r d i o l o g y 2 0 0 0 ; 16: 5 7 4 - 5 7 6 . 13. C a r e w M et al. H y p e r t e n s i o n in C a n a d a . C a n a d i a n F a m i l y Physician 1 9 9 9 ; 4 5 : 1 7 5 6 - 1 7 5 8 . 14. H a n d a S P . M e a s u r i n g blood p r e s s u r e properly. P e r s p e c t i v e s in C a r d i o l o g y 1 9 9 9 ; 1-2.  24  15. C a m p b e l l N R , M c K a y D W . A c c u r a t e blood p r e s s u r e m e a s u r e m e n t : W h y d o e s it m a t t e r ? Canadian Medical Association Journal 1999; 1 6 1 : 277-278. 16. A s m a r R, Z a n c h e t t i A. G u i d e l i n e s for t h e u s e of self-blood p r e s s u r e m o n i t o r i n g : A s u m m a r y report of t h e first international consensus conference. J o u r n a l of H y p e r t e n s i o n 2 0 0 0 , 18: 4 9 3 - 5 0 8 .  25  CHAPTER III  Validation  of a New Algorithm  for the BPM-100 Electronic Monitor  Oscillometric  Office  Blood  Pressure  J a m e s M . W r i g h t * , M D P h D F R C P ( C ) , Gurdial S. M a t t i / , M B B C h C C F P , T h o m a s L. P e r r y Jr. M D F R C P ( C ) , M a r k E. G e l f e r , M D , Kevin D. S t r a n g e , M A S c , A n t o n Z o r n ° , Dipl T c h , Y u n q u a n C h e n P h D ab  a b  0  0  0  D e p a r t m e n t of P h a r m a c o l o g y & T h e r a p e u t i c s a n d D e p a r t m e n t of M e d i c i n e , University of British Columbia, V S M M e d T e c h Ltd., V a n c o u v e r , B C , C a n a d a 3  b  0  ^Corresponding Author: J a m e s M. W r i g h t , M D , P h D , F R C P ( C ) , D e p a r t m e n t of P h a r m a c o l o g y & T h e r a p e u t i c s a n d D e p a r t m e n t of M e d i c i n e , T h e University of British C o l u m b i a , 2 1 7 6 H e a l t h S c i e n c e s Mall, V a n c o u v e r , B C , C a n a d a , V 6 T 1Z3, t e l e p h o n e : ( 6 0 4 ) 8 2 2 - 4 2 7 0 , f a x : ( 6 0 4 ) 8 2 2 - 0 7 0 1 , e m a i l : jmwright@interchange.ubc.ca 3  0  S o u r c e of F u n d i n g : V S M - M e d T e c h Short Title:  B P M - 1 0 0 a l g o r i t h m validation.  26  ABSTRACT  Background: T o test t h e a c c u r a c y of a n e w a l g o r i t h m f o r t h e B P M - 1 0 0 , a n a u t o m a t e d o s c i l l o m e t r i c b l o o d p r e s s u r e ( B P ) m o n i t o r , u s i n g s t o r e d d a t a f r o m a n i n d e p e n d e n t l y c o n d u c t e d v a l i d a t i o n trial c o m p a r i n g t h e B P M - 1 0 0  B e t  a  with a m e r c u r y s p h y g m o m a n o m e t e r .  Design: R a w pulse w a v e a n d cuff p r e s s u r e d a t a w e r e s t o r e d electronically u s i n g e m b e d d e d s o f t w a r e in t h e B P M 1 0 0 t a , d u r i n g t h e validation trial. T h e 3 9 1 s e t s of m e a s u r e m e n t s w e r e s e p a r a t e d o b j e c t i v e l y into t w o Be  s u b s e t s . A s u b s e t of 136 m e a s u r e m e n t s w a s u s e d to d e v e l o p a n e w a l g o r i t h m to e n h a n c e t h e a c c u r a c y of t h e d e v i c e w h e n r e a d i n g higher systolic p r e s s u r e s . T h e larger s u b s e t of 2 5 5 m e a s u r e m e n t s (3 r e a d i n g s f o r 85 s u b j e c t s ) w a s u s e d a s test d a t a to validate t h e a c c u r a c y of t h e n e w a l g o r i t h m .  Methods: Differences between the new algorithm  B P M - 1 0 0 a n d t h e r e f e r e n c e ( m e a n of t w o o b s e r v e r s )  were  d e t e r m i n e d a n d e x p r e s s e d a s t h e m e a n d i f f e r e n c e + S D , plus t h e % of m e a s u r e m e n t s within 5 m m H g , 10 m m H g , a n d 15 m m H g .  Results: T h e m e a n d i f f e r e n c e b e t w e e n t h e B P M - 1 0 0 a n d r e f e r e n c e systolic B P w a s - 0 . 1 6 ± 5.13 m m H g , with 7 3 . 7 % < 5 m m H g , 9 4 . 9 % < 10 m m H g a n d 9 8 . 8 % < 15 m m H g . T h e m e a n d i f f e r e n c e b e t w e e n t h e B P M 100 a n d r e f e r e n c e diastolic B P w a s - 1 . 4 1 ± 4 . 6 7 m m H g , with 7 8 . 4 % < 5 m m H g , 9 2 . 5 % < 10 m m H g , a n d 9 9 . 2 % < 15 m m H g . T h e s e d a t a i m p r o v e u p o n that of t h e B P M - 1 0 0 "A" g r a d e B H S p r o t o c o l .  27  B e t a  and pass the AAMI standard, and  Conclusion: This  s t u d y illustrates a n e w  m e t h o d for d e v e l o p i n g  and testing  a change  in a n a l g o r i t h m  for  an  o s c i l l o m e t r i c B P m o n i t o r utilizing c o l l e c t e d a n d s t o r e d electronic d a t a a n d d e m o n s t r a t e s that the n e w algorithm meets the A A M I standard and BHS protocol.  Key Words:  blood p r e s s u r e , m e a s u r e m e n t , monitor, a l g o r i t h m , o s c i l l o m e t r i c  28  INTRODUCTION  T h e u s e of electronic blood p r e s s u r e m e a s u r i n g i n s t r u m e n t s in d i a g n o s i n g h y p e r t e n s i o n a n d m o n i t o r i n g blood p r e s s u r e ( B P ) h a s i n c r e a s e d d r a m a t i c a l l y o v e r t h e past s e v e r a l y e a r s . T h e r e h a v e b e e n  many  articles w r i t t e n s u p p o r t i n g t h e u s e o f s u c h d e v i c e s , especially in t h e h o m e setting (self) [1] a n d f o r a m b u l a t o r y u s e ( 2 4 h o u r ) [2]. M o s t of t h e s e d e v i c e s u s e t h e o s c i l l o m e t r i c t e c h n i q u e , w h i c h m e a s u r e s t h e m e a n arterial B P directly f r o m cuff p r e s s u r e , t h e n c a l c u l a t e s t h e systolic a n d diastolic B P ' s a c c o r d i n g to a n a l g o r i t h m that is u n i q u e t o e a c h d e v i c e or m a n u f a c t u r e r . T h e s e i n s t r u m e n t s c a n be validated by testing t h e m a g a i n s t a u s c u l t a t o r y m e a s u r e m e n t u s i n g a m e r c u r y s p h y g m o m a n o m e t e r , a c c o r d i n g to e s t a b l i s h e d p r o t o c o l s set b y either t h e A s s o c i a t i o n f o r t h e A d v a n c e m e n t o f M e d i c a l I n s t r u m e n t a t i o n ( A A M I ) [3] o r t h e British H y p e r t e n s i o n S o c i e t y ( B H S ) [4]. It is k n o w n that m o s t o s c i l l o m e t r i c m o n i t o r s , t h o u g h a c c u r a t e , tend to u n d e r e s t i m a t e a n d give a higher s t a n d a r d of d e v i a t i o n f o r higher systolic p r e s s u r e s w h e n c o m p a r e d w i t h s t a n d a r d a u s c u l t a t o r y m e t h o d s [5].  T h e B P M - 1 0 0 is a n o s c i l l o m e t r i c blood p r e s s u r e m e a s u r i n g i n s t r u m e n t that h a s b e e n d e v e l o p e d a n d m a n u f a c t u r e d b y V S M M e d T e c h L t d . o f V a n c o u v e r , C a n a d a . T h i s d e v i c e w a s d e s i g n e d specifically for t h e p r i m a r y c a r e setting, t o aid t h e clinician in d i a g n o s i n g h y p e r t e n s i o n a n d in m o n i t o r i n g t h e patient's c o u r s e . It w a s t e s t e d in a n i n d e p e n d e n t l y c o n d u c t e d validation s t u d y a c c o r d i n g t o t h e A A M I s t a n d a r d ; t h e details of this s t u d y a r e r e p o r t e d s e p a r a t e l y in t h e p r e v i o u s article [6]. T h e d e v i c e p e r f o r m e d well, p a s s i n g both t h e A A M I s t a n d a r d a n d B H S protocol, but t e n d e d t o u n d e r e s t i m a t e t h e h i g h e r systolic blood p r e s s u r e s a s d e t e c t e d w i t h t h e B l a n d - A l t m a n plot. In this article, w e report a m e t h o d f o r t h e d e v e l o p m e n t a n d testing of a m o d i f i c a t i o n t o t h e a l g o r i t h m f o r e s t i m a t i n g systolic B P using s t o r e d e l e c t r o n i c d a t a .  29  METHODS  S u b j e c t s w e r e recruited a n d t e s t e d at t h e Blood P r e s s u r e Clinic of t h e U n i v e r s i t y of British C o l u m b i a a c c o r d i n g to t h e m e t h o d r e p o r t e d in t h e c o m p a n i o n p a p e r a n d i n c l u d e d ethical a p p r o v a l , explicit inclusion a n d e x c l u s i o n criteria, target p o p u l a t i o n o b j e c t i v e s , s t u d y d e s i g n , d a t a a n a l y s i s a n d results [6].  In t h e original B P M - 1 0 0 t B e  a  clinical trial [6], 8 5 patients w e r e t e s t e d a n d a c c e p t e d f o r statistical a n a l y s i s .  E a c h patient w a s m e a s u r e d a total of six t i m e s . p u r p o s e s , a n d not u s e d f u r t h e r in t h e a n a l y s i s .  T h e first r e a d i n g w a s u s e d f o r s u b j e c t  screening  T h e r e m a i n i n g f i v e r e a d i n g s w e r e f u r t h e r s c r e e n e d for  e x c l u s i o n a c c o r d i n g to p r e - d e t e r m i n e d criteria, resulting in a m i n i m u m of t h r e e a n d m a x i m u m of five readings for each subject.  T h e total n u m b e r of r e a d i n g s i n c l u d e d f o r statistical a n a l y s i s w a s 3 9 1 , 136  r e a d i n g s m o r e t h a n t h e m i n i m u m A A M I r e q u i r e m e n t of 2 5 5 r e a d i n g s (85 s u b j e c t s t i m e s 3 r e a d i n g s for each subject).  D u r i n g t h e original s t u d y , t h e o s c i l l o m e t r i c a l g o r i t h m of t h e B P M - 1 0 0 t a c o l l e c t e d t h e c u f f p r e s s u r e a n d B e  pulse i n f o r m a t i o n f r o m t h e blood p r e s s u r e c u f f d u r i n g deflation a n d c a l c u l a t e d t h e systolic a n d diastolic blood p r e s s u r e s a s well a s t h e p u l s e rate. d a t a collection a n d B P c a l c u l a t i o n s .  T h e e m b e d d e d s o f t w a r e in t h e B P M - 1 0 0 t a p e r f o r m e d t h e B e  After each measurement, the cuff pressure and pulse information  w a s e x p o r t e d to a n o t h e r c o m p u t e r to a r c h i v e t h e r a w d a t a a n d a l l o w f o r a n a l y s i s of t h e a l g o r i t h m .  T h e original B P M - 1 0 0 clinical trial d a t a set of 3 9 1 m e a s u r e m e n t s w a s o b j e c t i v e l y s e p a r a t e d into t w o d a t a s u b s e t s a s d e s c r i b e d b e l o w . T h e first s u b s e t i n c l u d e d a total of 2 5 5 m e a s u r e m e n t s , w h i c h included 3 m e a s u r e m e n t s f r o m e a c h of t h e 85 s u b j e c t s , a n d r e p r e s e n t e d t h e m i n i m u m r e q u i r e m e n t s f o r A A M I criteria.  T h e s e c o n d s u b s e t of 136 m e a s u r e m e n t s w a s a v a i l a b l e to a s s i s t in t h e d e v e l o p m e n t of a  m o d i f i c a t i o n to t h e B P M - 1 0 0  B e t a  a l g o r i t h m . O n c e t h e n e w a l g o r i t h m w a s d e v e l o p e d t h e first s u b s e t of 2 5 5  m e a s u r e m e n t s w a s u s e d to o b j e c t i v e l y e v a l u a t e t h e p e r f o r m a n c e of t h e a l g o r i t h m o n " n e w " d a t a .  T o a v o i d bias t o w a r d s early, m i d d l e or late d a t a points in t h e s e q u e n c e of u p to five m e a s u r e m e n t s c o l l e c t e d f r o m e a c h s u b j e c t in t h e original clinical d a t a [6], t h e first s u b s e t w a s s e l e c t e d u s i n g a rotating  30  selection pointer.  T h e p r o c e d u r e involved s e l e c t i n g t h e first t h r e e a v a i l a b l e m e a s u r e m e n t s f r o m the first  s u b j e c t a n d t h e n t h e s e c o n d , third, a n d f o u r t h m e a s u r e m e n t f r o m t h e s e c o n d s u b j e c t a n d s o o n .  Some  s u b j e c t s h a d o n l y t h r e e or f o u r m e a s u r e m e n t s , a s s o m e w e r e e x c l u d e d in t h e original clinical trial d a t a collection, but t h e pointer s k i p p e d to t h e next available m e a s u r e m e n t until e a c h s u b j e c t had exactly 3 measurements.  W h e n t h e e n d of t h e m e a s u r e m e n t s w a s r e a c h e d f o r a n y s u b j e c t w i t h o u t selecting 3  m e a s u r e m e n t s , t h e selection pointer rotated b a c k to t h e start of t h e m e a s u r e m e n t s for that subject.  T h e s m a l l e r s u b s e t w a s u s e d to d e v e l o p a n e w a l g o r i t h m that g a v e a better e s t i m a t e for higher systolic measurements.  T h i s did not require c h a n g i n g the a l g o r i t h m for t h e diastolic B P .  A f t e r t h e algorithm  m o d i f i c a t i o n w a s s u c c e s s f u l l y d e v e l o p e d u s i n g t h e s m a l l e r d a t a s u b s e t , it w a s t h e n r e a d y for validation. T h e e x t e r n a l a l g o r i t h m w a s f o r m a l l y t e s t e d o n t h e first s u b s e t of 2 5 5 m e a s u r e m e n t s f r o m t h e original clinical trial p o p u l a t i o n (85 s u b j e c t s t i m e s 3 m e a s u r e m e n t s per s u b j e c t ) .  T h e p e r f o r m a n c e results of the  n e w a l g o r i t h m w e r e a n a l y z e d a c c o r d i n g to the A A M I s t a n d a r d for all p o p u l a t i o n , o b s e r v e r , a n d a c c u r a c y requirements.  T h e n e w a l g o r i t h m w a s t h e n i n c o r p o r a t e d into the e m b e d d e d s o f t w a r e to c r e a t e t h e B P M - 1 0 0 .  A n N I B P s i m u l a t o r ( B P P u m p , B i o - T e k I n s t r u m e n t s , Inc., W i n o o s k i , V e r m o n t ) w a s u s e d to  provide  oscillometric input d a t a to t h e B P M - 1 0 0 d e v i c e . T h e B P M - 1 0 0 d i s p l a y e d t h e results a n d e x p o r t e d the cuff p r e s s u r e a n d o s c i l l o m e t r i c d a t a to the P C . T h e n e w a l g o r i t h m d e v e l o p e d a n d t e s t e d in t h e P C n o w u s e d the n e w d a t a f r o m t h e s i m u l a t o r via t h e B P M - 1 0 0 , a n d c a l c u l a t e d a n d d i s p l a y e d t h e results. A r e g r e s s i o n test c o m p a r e d t h e 2 s e t s of d a t a o v e r a w i d e r a n g e of p a r a m e t e r s ( B P 8 0 - 2 2 0 / 5 0 - 1 3 0 m m H g a n d heart rate 50 to 130 b p m ) ; a c c e p t a n c e criteria w e r e that the d i f f e r e n c e b e t w e e n e a c h r e a d i n g m u s t be within +/1 m m H g . T h i s test e n s u r e d that t h e a l g o r i t h m s i m p l e m e n t e d in t h e 2 different s o f t w a r e p l a t f o r m s o p e r a t e d identically a n d v a l i d a t e d the i m p l e m e n t a t i o n of t h e a l g o r i t h m in the e m b e d d e d s o f t w a r e .  31  RESULTS  Enrolled subjects S e e c o m p a n i o n publication f o r details o f e n r o l l e d , included a n d e x c l u d e d s u b j e c t s [6]. All target p o p u l a t i o n o b j e c t i v e s a n d r e q u i r e m e n t s of t h e A A M I protocol w e r e m e t in this study as they included t h e s a m e 85 s u b j e c t s included in t h e c o m p a n i o n study [6].  Included blood pressure measurements The  total  number  of  included  measurements  amounted  to  255. Twenty-seven  blood  pressure  m e a s u r e m e n t s ( 1 0 . 6 % ) h a d a systolic o f g r e a t e r t h a n 180 m m H g , a n d 3 7 m e a s u r e m e n t s ( 1 4 . 5 % ) h a d a systolic o f less t h a n 100 m m H g . T h e r e m a i n i n g 191 systolic m e a s u r e m e n t s ( 7 4 . 9 % ) w e r e b e t w e e n t h e s e e x t r e m e s . T w e n t y - f i v e blood p r e s s u r e m e a s u r e m e n t s ( 9 . 8 % ) h a d a diastolic of g r e a t e r t h a n 100 m m H g , a n d 3 9 m e a s u r e m e n t s ( 1 5 . 3 % ) h a d a diastolic o f less t h a n 6 0 m m H g .  T h e r e m a i n i n g 191 diastolic  measurements (74.9 %) were between these extremes.  Excluded blood pressure measurements For details o f t h e 3 4 e x c l u d e d blood p r e s s u r e m e a s u r e m e n t s s e e c o m p a n i o n s t u d y [6]. In a d d i t i o n , a s e c o n d s u b s e t of 136 m e a s u r e m e n t s u s e d t o d e v e l o p t h e n e w a l g o r i t h m w a s e x c l u d e d a s d e s c r i b e d in t h e m e t h o d s s e c t i o n .  Reference standard measurements (Inter-observer) Overall m e a n d i f f e r e n c e b e t w e e n t h e o b s e r v e r s ( o b s e r v e r 1 - o b s e r v e r 2 ) f o r t h e 2 5 5 systolic blood p r e s s u r e m e a s u r e m e n t s w a s - 0 . 6 5 + 1.99 m m H g , ( r a n g e - 1 0 t o + 9 m m H g ) .  M o s t of t h e systolic  m e a s u r e m e n t d i f f e r e n c e s , 9 8 . 0 % , w e r e within 5 m m H g .  All w e r e within 10 m m H g as a n y o u t s i d e this  r a n g e w e r e e x c l u d e d a s o n e of t h e e x c l u s i o n criteria.  T h e overall m e a n d i f f e r e n c e b e t w e e n t h e 2  o b s e r v e r s f o r diastolic blood p r e s s u r e w a s - 1 . 0 5 ± 2.46 m m H g , ( r a n g e , - 8 m m H g t o + 7 m m H g ) . ( 9 5 . 3 % ) w e r e within 5 m m H g a n d all w e r e within 10 m m H g as d e s c r i b e d a b o v e .  32  Most  Range and distribution  of reference  measurements  T h e overall m e a n systolic blood p r e s s u r e for t h e 2 5 5 systolic blood p r e s s u r e m e a s u r e m e n t s  recorded  ( a v e r a g e of t h e t w o o b s e r v e r s ) w a s 128.5 ± 3 0 . 9 m m H g ( r a n g e 81.5 to 2 2 3 . 5 m m H g ) . T h e overall m e a n diastolic blood p r e s s u r e w a s 7 7 . 3 ± 16.6 m m H g ( r a n g e 4 8 to 119.5 m m H g ) .  T h e m e a n heart rate using  t h e N o n i n f i n g e r p u l s e o x i m e t e r ( O n y x , N o n i n M e d i c a l Inc., P l y m o u t h , M i n n e s o t a ) w a s 70.1 + 12.4 beats per m i n u t e ( r a n g e 4 2 to 104 beats per m i n u t e ) .  Accuracy  of BPM-100 as compared  to the reference  standard  measurements.  T h e overall m e a n d i f f e r e n c e b e t w e e n the r e f e r e n c e s t a n d a r d systolic a n d diastolic blood p r e s s u r e a n d the B P M - 1 0 0 ( r e f e r e n c e - B P M - 1 0 0 ) is well within t h e A A M I s t a n d a r d a n d is s h o w n in T a b l e 1 [3]. T a b l e 2 s h o w s t h e p r o p o r t i o n of systolic a n d diastolic d i f f e r e n c e s within 5, 10, a n d 15 m m H g a n d h o w this c o n f o r m s to t h e B H S p r o t o c o l . [4] T h e B P M - 1 0 0 d e v i c e is d e s i g n e d to d e t e r m i n e t h e a v e r a g e of u p to f i v e b l o o d p r e s s u r e r e a d i n g s in individual s u b j e c t s . W e t h e r e f o r e c o m p a r e d the m e a n of t h e 3 r e f e r e n c e s t a n d a r d systolic blood p r e s s u r e m e a s u r e m e n t s w i t h the m e a n of t h e 3 B P M - 1 0 0 m e a s u r e m e n t s f o r individual s u b j e c t s s o a s to o b s e r v e t h e a c c u r a c y in t h e practical clinical s e t t i n g . T h i s g a v e the s a m e m e a n d i f f e r e n c e a n d a lower s t a n d a r d deviation a s c a n be s e e n in T a b l e 1.  It a l s o led to a n i m p r o v e m e n t in t h e p r o p o r t i o n of systolic a n d  diastolic d i f f e r e n c e s within 5, 10 a n d 15 m m H g a c c o r d i n g to t h e B H S protocol ( T a b l e 2 ) . In Fig 1 t h e B l a n d - A l t m a n display [7] of individual m e a s u r e m e n t s for systolic blood p r e s s u r e (N = 2 5 5 ) s h o w s that t h e d i f f e r e n c e s of t h e r e f e r e n c e s t a n d a r d a n d B P M - 1 0 0 blood p r e s s u r e s a r e c l u s t e r e d a r o u n d 0 o v e r t h e w h o l e r a n g e of systolic r e a d i n g s . In Fig 2 the B l a n d - A l t m a n d i s p l a y of individual m e a s u r e m e n t s for diastolic blood p r e s s u r e (N = 2 5 5 ) s h o w s that the d i f f e r e n c e s of t h e r e f e r e n c e s t a n d a r d a n d B P M - 1 0 0 blood p r e s s u r e s g i v e s t h e s a m e picture a s for t h e 391 m e a s u r e m e n t s in t h e p r e v i o u s p a p e r . [6]  T h e m e a n d i f f e r e n c e b e t w e e n t h e r e f e r e n c e a n d m e a s u r e d heart rate ( m e a s u r e d m i n u s r e f e r e n c e ) w a s 0.16 ± 2 . 0 2 b p m , w i t h a r a n g e o f - 1 6 to +6 b p m .  33  DISCUSSION  T h e B P M - 1 0 0 e l e c t r o n i c office blood p r e s s u r e i n s t r u m e n t w i t h t h e n e w a l g o r i t h m m e e t s t h e protocol a n d s t a n d a r d of t h e A s s o c i a t i o n f o r t h e A d v a n c e m e n t of M e d i c a l I n s t r u m e n t a t i o n f o r a c c u r a c y w h e n c o m p a r e d to traditional m e r c u r y B P m e a s u r e m e n t p e r f o r m e d by trained n u r s e s u s i n g a r e s e a r c h - g r a d e precision m e r c u r y s p h y g m o m a n o m e t e r . A s w e l l , it e a r n e d a n "A" g r a d e f o r b o t h systolic a n d diastolic r e a d i n g s , a c c o r d i n g to t h e British H y p e r t e n s i o n S o c i e t y p r o t o c o l .  It i m p r o v e s o n t h e a c c u r a c y of e s t i m a t i o n of  higher systolic b l o o d p r e s s u r e s a s c o m p a r e d to t h e p r e v i o u s v e r s i o n ( B P M - 1 0 0  B e t  a ) [6]; t h e B P M - 1 0 0 is  t h e o n l y v e r s i o n that is a v a i l a b l e f o r sale in N o r t h A m e r i c a .  T h e m e t h o d s u s e d in this s t u d y d e m o n s t r a t e t h e u n i q u e c h a r a c t e r i s t i c s of u s i n g t h e o s c i l l o m e t r i c m e t h o d for d e t e c t i n g  blood  pressure. The  readings were obtained  and  recorded  using standard  validation  m e t h o d s . H o w e v e r , b e c a u s e t h e o s c i l l o m e t r i c t e c h n i q u e utilizes e l e c t r o n i c a n a l y s i s of t h e pulse w a v e s of e a c h b l o o d p r e s s u r e m e a s u r e m e n t , w e w e r e able to utilize t h e p r e v i o u s l y r e c o r d e d test r e a d i n g s to d e v e l o p a n e w a l g o r i t h m to i m p r o v e u p o n t h e e s t i m a t e of systolic b l o o d p r e s s u r e a n d s u b s e q u e n t l y to validate t h e n e w a l g o r i t h m u s i n g r e c o g n i z e d p r o t o c o l s a n d s t a n d a r d s .  T h e u s e of o s c i l l o m e t r i c d e v i c e s f o r m e a s u r i n g blood p r e s s u r e is rapidly i n c r e a s i n g , a n d O ' B r i e n a n d o t h e r s h a v e w r i t t e n a b o u t t h e n e e d f o r better m e t h o d s to test a n d v a l i d a t e t h e s e d e v i c e s , [8] [9]. T h e y a r e a w a r e that m a n y m a n u f a c t u r e r s c h a n g e t h e a l g o r i t h m in their d e v i c e s a n d d o not a l w a y s report or rev a l i d a t e t h e d e v i c e s b e c a u s e t h e c o s t of re-testing is prohibitive.  P r e s u m a b l y , a s in t h e c a s e of t h e B P M -  100, t h e c h a n g e s in t h e a l g o r i t h m a r e to i m p r o v e t h e a c c u r a c y of t h e d e v i c e . T h e m e t h o d w e d e s c r i b e is o n e w a y in w h i c h c o m p a n i e s c a n v a l i d a t e a n d report t h e s e c h a n g e s , w h i l e s a v i n g t h e t i m e a n d m o n e y a s s o c i a t e d w i t h r e p e a t i n g t h e entire validation p r o c e s s . T h e original clinical d a t a is c o l l e c t e d in t h e p r e s c r i b e d m a n n e r , a n d is r e c o r d e d a n d s t o r e d both m a n u a l l y a n d electronically. T h i s d a t a is t h e n available to "re-test" a n y c h a n g e s in t h e a l g o r i t h m s u s e d to e s t i m a t e t h e systolic a n d diastolic blood pressures.  We  b e l i e v e that t h e m e t h o d p r e s e n t e d c o u l d r e p r e s e n t a p r e c e d e n t f o r i m p r o v i n g t h e efficiency of  validation of c h a n g e s to t h e e m b e d d e d s o f t w a r e of o s c i l l o m e t r i c b l o o d p r e s s u r e m e a s u r i n g d e v i c e s .  34  In  this particular c a s e t h e m e t h o d c r e a t e d a n a l g o r i t h m that i m p r o v e d t h e a c c u r a c y of t h e  BPM-100  o s c i l l o m e t r i c d e v i c e for higher systolic m e a s u r e m e n t s . W h e n this a l g o r i t h m w a s t e s t e d , it readily satisfied t h e A A M I s t a n d a r d a n d B H S "A" p r o t o c o l .  35  x> c CO ^ 3  "o co  O  S _i (O  o  0 X)  E E  I— CO  < Q  CO J)  Q) - 1 -  " c !*= E  XI c .  co x> c  03  55  0  co^^ c ~ E O 5 5 £  _ i </) X) -—  o  co >co  •B o.  CD O CO CD c=  c  CD SCD  o o o c o  X P c  E it E  3  CD  co X> CD  co Q.  E o o o o  Q. CQ CD  c c co o Si  Xl  CD  "5 3  ^ .9-  "5 » c  co  £ "c 0  CD  g£ CO <D  o 0  O  c  co E o x: CD Q.  0  <  0  co  0  £ £ o  "co  o > o— 0  =  03 CO <$ CO  < 0 CO f—  1  _  0  XI  u  E E  I  in  m CD  m I oo VI  oo  O O  CO CD  Oil CN CD CD  oo CO oo in CD CD  Al  03  co  oo Al  O O O o Q.  VI  in co  CO X CQ 0  ^c—'  0- 000  |co o o  o o o o  CL CO  x  1/3 03 O c CD  4—  > ! 0 IDC CC co I co 3 C  CD  o c:  CD k_  DH  c  o o  0.  CQ  -#—<  TO  03 "3, CD 03 X3  o o  Q-  co | 1/3  0  CN 0 -Q CD  eg  -a  CD CD H— H— CD  CD  lo  o o 03  |CQ  c CD 0  E o 0  '¥ IW  g. CO CO CD 03 c >, 0  0 E o 0 1_ o CO CO CD c 0  irten sio  0. 0- CQ  Ti 0  E  dual  m in  CN  0 Q- > >* T3 X .c CO CD 03  —  m  de  IX E E Im  i CO o X CD  Fig 1  Bland-Altman Display of Systolic M e a s u r e m e n t s , All Cuffs, 255 measurements 30 T3 C  re O) X  E E  O a> o  >  ren  Q. CQ  20 mean  10 -  -V  0 -  <  .a o o  ^  +2SD  o  '<gy o -*o-cr-o—  -10 -  mean  0  -2SD  -20 -  a -.30 50  75  100  125  150  175  200  Mean of BPM and Obs Avg (mmHg)  B l a n d - A l t m a n display o f systolic m e a s u r e m e n t s , all cuffs, 2 5 5 m e a s u r e m e n t s . B P M , B P M - 1 0 0 electronic oscillometric monitor; O b s A v g , o b s e r v e r a v e r a g e .  38  225  250  Fig 2  Bland-Altman Display of Diastolic M e a s u r e m e n t s , All Cuffs, 255 m e a s u r e m e n t s 20  c ^ re o)  15  oo  10  i i  5  m E  0  mean +2SD  4 -  O O) o >  o < </) £ .o  jg °  -5 -10  mean -2SD  -15 -20 -25 20  40  60  80  100  120  Mean of BPM and Obs Avg (mmHg)  B l a n d - A l t m a n display o f diastolic m e a s u r e m e n t s , all cuffs, 2 5 5 m e a s u r e m e n t s . B P M , B P M - 1 0 0 electronic oscillometric m o n i t o r ; O b s A v g , o b s e r v e r a v e r a g e .  39  140  REFERENCES 1.  A s m a r R, Z a n c h e t t i A. O n b e h a l f of t h e O r g a n i z i n g C o m m i t t e e : G u i d e l i n e s for t h e u s e of s e l f - b l o o d p r e s s u r e m o n i t o r i n g : a s u m m a r y report of t h e first international c o n s e n s u s c o n f e r e n c e . J o u r n a l of H y p e r t e n s i o n 2 0 0 0 , 18: 4 9 3 - 5 0 8 .  2.  M y e r s M, H a y n e s R, R a b k i n S. C a n a d i a n H y p e r t e n s i o n S o c i e t y G u i d e l i n e s for A m b u l a t o r y B l o o d P r e s s u r e M o n i t o r i n g . A m e r i c a n J o u r n a l of H y p e r t e n s i o n 1999; 12: 1 1 4 9 - 1 1 5 7 .  3.  A m e r i c a n National S t a n d a r d for Electronic or A u t o m a t e d S p h y g m o m a n o m e t e r s : - A N S I / A A M I SP10-1992. A r l i n g t o n , V A : A s s o c i a t i o n for t h e A d v a n c e m e n t of M e d i c a l I n s t r u m e n t a t i o n 1 9 9 3 .  4.  O ' B r i e n E, Petrie J , Littler W , et a l . T h e British H y p e r t e n s i o n S o c i e t y Protocol for t h e E v a l u a t i o n of Blood Devices. J o u r n a l of H y p e r t e n s i o n 1 9 9 3 ; 1 1 ( s u p p l 2 ) : S 4 3 - S 6 2 .  5.  6.  Pressure  Measuring  O ' B r i e n E, A t k i n s N, M e e F, O ' M a l l e y K. E v a l u a t i o n of Blood P r e s s u r e M e a s u r i n g D e v i c e s . Clinical & E x p e r i m e n t a l H y p e r t e n s i o n 1 9 9 3 ; 15(6): 1 0 8 7 - 1 0 9 7 . M a t t u G S , Perry T L Jr, W r i g h t J M . C o m p a r i s o n of the oscillometric blood p r e s s u r e m o n i t o r ( B P M - 1 0 0 t ) w i t h t h e mercury sphygmomanometer. B l o o d P r e s s u r e M o n i t o r i n g 2 0 0 1 ; 6: 1 5 3 - 1 5 9 . B e  a  auscultatory  7.  Bland J M , Altman D G . Statistical m e t h o d s for a s s e s s i n g a g r e e m e n t b e t w e e n t w o m e t h o d s of clinical m e a s u r e m e n t . Lancet 1986; 1:307-310.  8.  O ' B r i e n E, D e G a u d e m a r i s R, B o b r i e G, R o s e i E, V a i s s e B. Devices and Validation. Blood P r e s s u r e M o n i t o r i n g 2 0 0 0 ; 5: 9 3 - 1 0 0 .  9.  O ' B r i e n E, Petrie J , Littler W , et a l . S h o r t report: A n O u t l i n e of the R e v i s e d British H y p e r t e n s i o n S o c i e t y P r o t o c o l for t h e Evaluation of Blood P r e s s u r e M e a s u r i n g D e v i c e s . J o u r n a l of H y p e r t e n s i o n 1 9 9 3 ; 1 1 : 6 7 7 - 6 7 9 .  40  CHAPTER IV  COMPARISON OF THE AUTOMATED NON-INVASIVE OSCILLOMETRIC B L O O D PRESSURE MONITOR ( B p T R U ™ ) WITH THE AUSCULTATORY MERCURY SPHYGMOMANOMETER IN THE PAEDIATRIC POPULATION  Gurdial S. M a t t u , M B B C h , C C F P , Balraj S. H e r a n J a m e s M W r i g h t , M D , P h D , F R C P ( C ) , D e p a r t m e n t of P h a r m a c o l o g y & T h e r a p e u t i c s a n d D e p a r t m e n t o f M e d i c i n e " , U n i v e r s i t y o f British C o l u m b i a , Vancouver, BC, Canada. a  3  a b  3  'Corresponding Author: J a m e s M. W r i g h t , M D , P h D , F R C P ( C ) , D e p a r t m e n t o f P h a r m a c o l o g y & T h e r a p e u t i c s a n d D e p a r t m e n t of M e d i c i n e , T h e University o f British C o l u m b i a , 2 1 7 6 Health S c i e n c e s Mall, V a n c o u v e r , B C , C a n a d a , V 6 T 1 Z 3 , t e l e p h o n e : ( 6 0 4 ) 8 2 2 - 4 2 7 0 , f a x : ( 6 0 4 ) 8 2 2 - 0 7 0 1 , e m a i l : jmwright@interchange.ubc.ca 3  b  Source of Funding: V S M - MedTech Short Title:  V a l i d a t i o n o f t h e B p T R U ™ in P a e d i a t r i c s .  41  ABSTRACT  Background T o c o m p a r e directly t h e a c c u r a c y of t h e B P M - 1 0 0 m o n i t o r (an a u t o m a t e d o s c i l l o m e t r i c blood p r e s s u r e d e v i c e ) with s t a n d a r d a u s c u l t a t o r y m e r c u r y s p h y g m o m a n o m e t r y in a paediatric p o p u l a t i o n .  Design T h e B P M - 1 0 0 w a s c o n n e c t e d in parallel w i t h a s t a n d a r d m e r c u r y s p h y g m o m a n o m e t e r .  T w o observers  m e a s u r e d the blood p r e s s u r e s s i m u l t a n e o u s l y with the B P M - 1 0 0 . T h e o b s e r v e r s a n d t h e B P M - 1 0 0 w e r e all triple-blinded f r o m e a c h other.  Methods For e a c h of t h e d e m o g r a p h i c d a t a - s u b j e c t a g e , s e x a n d a r m sizes, - t h e m e a n , s t a n d a r d deviation ( S D ) and range was calculated. measurements  (observer  T h e d i f f e r e n c e b e t w e e n the m e a n B P M - 1 0 0 a n d the s t a n d a r d average)  was  calculated  with  SD  and  ranges.  The  reference  percentage  of  m e a s u r e m e n t s within 5, 10 a n d 15 m m H g a g r e e m e n t w a s e x p r e s s e d .  Results F r o m the 36 s u b j e c t s recruited a g e d 3-18 y e a r s , 162 pairs of sitting b l o o d p r e s s u r e s w e r e i n c l u d e d .  The  I. difference  between  the  mean  BPM-100  readings  and  the  reference  standard  measurements  (as  V  d e t e r m i n e d by t h e o b s e r v e r s ) w a s 1.45 ± 5.67 m m H g for systolic blood p r e s s u r e s , a n d -3.24 ± 7.39 m m H g for diastolic p r e s s u r e a n d 0.20 ± 2.47 b p m for heart rate.  Conclusion T h e B P M - 1 0 0 is a s a c c u r a t e in m e a s u r i n g blood p r e s s u r e in c h i l d r e n a s it is in t h e adult p o p u l a t i o n .  It  m e e t s all r e q u i r e m e n t s of t h e A s s o c i a t i o n of A d v a n c e m e n t of M e d i c a l I n s t r u m e n t a t i o n a n d a c h i e v e d a g r a d e ' B ' in t h e m o d i f i e d B H S p r o t o c o l .  42  Introduction  Until t h e publication of t h e first T a s k F o r c e R e p o r t o n blood p r e s s u r e control in c h i l d r e n j u s t o v e r 25 years a g o , the m e a s u r e m e n t of blood p r e s s u r e w a s infrequently p e r f o r m e d [1].  C u r r e n t l y t h e A m e r i c a n Heart  A s s o c i a t i o n r e c o m m e n d s all c h i l d r e n h a v e a n n u a l blood p r e s s u r e s r e c o r d e d . A l t h o u g h t h e p r e v a l e n c e of h y p e r t e n s i o n in t h e paediatric p o p u l a t i o n is v e r y low, a c c u r a t e d i a g n o s i s a n d m a n a g e m e n t of it c a n h a v e f a r - r e a c h i n g c o n s e q u e n c e s in the p r e v e n t i o n of e n d - o r g a n d a m a g e .  S i n c e the earliest a c c e p t e d d e s c r i p t i o n of a n indirect m e t h o d of m e a s u r i n g blood p r e s s u r e s d e s c r i b e d by Riva R o c c i in 1 8 9 6 , it h a s b e c o m e increasingly a p p a r e n t that this t e c h n i q u e is highly s u b j e c t i v e .  If not  properly p r a c t i s e d , m e a s u r i n g blood p r e s s u r e w i t h a m e r c u r y s p h y g m o m a n o m e t e r a n d s t e t h o s c o p e c a n be highly i n a c c u r a t e w i t h g r a v e c o n s e q u e n c e s for patients.  In addition it is t i m e - c o n s u m i n g w h e n d o n e  properly a n d t h u s d o e s not fit well into a b u s y physician's s c h e d u l e .  W i t h m e r c u r y being b a n n e d by s e v e r a l E u r o p e a n c o u n t r i e s a n d m a n y U S cities, d u e to the c o n c e r n of m e r c u r y p o i s o n i n g , potentially c a u s i n g learning disabilities, i m p a i r i n g k i d n e y a n d i m m u n e f u n c t i o n , a n d in e x t r e m e c a s e s the loss of sight a n d h e a r i n g . desirable.  A c c u r a t e a u t o m a t i c o s c i l l o m e t r i c d e v i c e s a r e increasingly  T h i s m a y b e the e n d of the era of m e r c u r y s p h y g m o m a n o m e t e r , a n d herald the b e g i n n i n g of  n e w s t a n d a r d of blood p r e s s u r e m e a s u r e m e n t .  T h e B P M - 1 0 0 w a s p r e v i o u s l y validated in a study with 85 adult s u b j e c t s ( a g e d 18 y e a r s a n d older). It m e t t h e A A M I r e q u i r e m e n t s a n d a c h i e v e d a n 'A' g r a d e a c c o r d i n g to t h e B H S p r o t o c o l [2].  It s u b s e q u e n t l y  i m p r o v e d its a l g o r i t h m to c o r r e c t for u n d e r e s t i m a t i o n of higher systolic blood p r e s s u r e s . [3].  T h e p u r p o s e of this s t u d y is to d e t e r m i n e t h e a c c u r a c y a n d reproducibility of t h e a u t o m a t e d n o n - i n v a s i v e oscillometric blood p r e s s u r e monitor, B p T R U ™  ( m o d e l B P M - 1 0 0 ) a s c o m p a r e d to the gold s t a n d a r d  m e r c u r y s p h y g m o m a n o m e t e r in the paediatric p o p u l a t i o n ( a g e s 3 to 18 y e a r s ) . T o a c h i e v e this, t h e study w a s p e r f o r m e d in a c c o r d a n c e w i t h t h e s t a n d a r d guidelines a n d p r o t o c o l s A A M I S P 1 0 - 1 9 9 2 provided by t h e A s s o c i a t i o n for t h e A d v a n c e m e n t of M e d i c a l I n s t r u m e n t a t i o n ( A A M I ) a s well a s t h e recently r e l e a s e d  43  draft A A M I / CDV-1 SP-10 M a n u a l , Electronic or A u t o m a t e d S p h y g m o m a n o m e t e r s ; t h e regulating bodi for validating t h e s e t y p e s of m o n i t o r s .  44  Methods  Ethical Approval Ethical a p p r o v a l of t h e study, the c o n s e n t a n d a s s e n t f o r m s w a s o b t a i n e d f r o m a s o v e r e i g n body, the I n d e p e n d e n t R e v i e w C o n s u l t i n g g r o u p f r o m California prior to initiation of a n y s t u d y p r o c e d u r e s .  Subject enrolment S u b j e c t s w e r e recruited f r o m  notices in P r i m a r y C a r e p r a c t i c e s a n d t h e B.C.'s C h i l d r e n ' s  Hospital,  University of British C o l u m b i a , w h i c h included h y p e r t e n s i o n a n d renal clinics to m e e t s o m e of the hypertensive  criteria  listed  below.  Recruitment  into t h e s t u d y w a s  without  bias.  Screening  was  e s t a b l i s h e d in o r d e r to m e e t t h e target r e q u i r e m e n t s for the s t u d y of 34 s u b j e c t s . A t t h e e n d of the study s u b j e c t s w e r e e n r o l l e d , in o r d e r to m e e t the d e f i c i e n c i e s in t h e target p o p u l a t i o n r e q u i r e m e n t s .  Inclusion criteria i Either a p a r e n t or g u a r d i a n , w h o s i g n e d the c o n s e n t f o r m , a c c o m p a n i e d all s u b j e c t s .  Subjects who were  able, w e r e g i v e n t h e a s s e n t f o r m a n d instructed to r e a d a n d s i g n prior t o a n y s t u d y p r o c e d u r e s being performed. stable.  S u b j e c t s w e r e b e t w e e n t h e a g e s of 3 y e a r s to 18 y e a r s , a n d w e r e all h e m o d y n a m i c a l l y  T o be included in the study, s c r e e n i n g m e a s u r e m e n t criteria to e v a l u a t e o b s e r v e r a g r e e m e n t for  the s u b j e c t h a d to be m e t .  Exclusion criteria P r e - m e a s u r e m e n t s c r e e n i n g criteria a l l o w e d for s u b j e c t s with significant a r r h y t h m i a s or a n y other existing c o n d i t i o n , w h o t h e investigators felt w o u l d not allow for s a f e a n d a c c u r a t e b l o o d p r e s s u r e m e a s u r e m e n t s , to be e x c l u d e d . A s with the s t u d y with adults t h e r e w e r e five p o s t - m e a s u r e m e n t but p r e - s p e c i f i e d e x c l u s i o n criteria for both s u b j e c t s a n d individual m e a s u r e m e n t s [2]:  1.  s u b j e c t s in w h o m t h e first ( s c r e e n i n g ) m e a s u r e m e n t s h a d a n i n t e r - o b s e r v e r a g r e e m e n t for either systolic  or diastolic  blood  pressures  greater  m e a s u r e m e n t criteria d o w n t h e list);  45  than  10 m m H g  (this  precludes  all other  post-  2.  s u b j e c t s w h o h a d less t h a n t h r e e systolic a n d diastolic pairs of r e a d i n g s (this p r e c l u d e s all o t h e r p o s t - m e a s u r e m e n t criteria d o w n the list);  3.  a n y m e a s u r e m e n t s in w h i c h t h e inter-observer a g r e e m e n t f o r either systolic or diastolic  blood  p r e s s u r e s w a s g r e a t e r t h a n 10 m m H g  4.  s u b j e c t s w h o h a d sufficiently w e a k pulses a n d c o n s e q u e n t l y w e a k K o r o t k o f f s o u n d s s u c h that the o b s e r v e r s felt that s a t i s f a c t o r y a u s c u l t a t i o n w a s not p o s s i b l e ;  5.  m e a s u r e m e n t s by t h e B P M - 1 0 0 that did not r e c o r d for t e c h n i c a l r e a s o n s .  Target population objectives 1.  A n e q u a l n u m b e r of m a l e a n d f e m a l e s u b j e c t s .  2.  A r a n g e of a g e s (all a g e d 3 to 18 y e a r s of a g e ) - at least 6 s u b j e c t s a g e d 3 to 5 y e a r s - at least 6 s u b j e c t s a g e d 6 to 8 y e a r s - at least 4 s u b j e c t s a g e d 9 to 11 y e a r s - at least 4 s u b j e c t s a g e d 12 to 14 y e a r s - at least 4 s u b j e c t s a g e d 15 to 18 y e a r s w i t h at least 20 of t h e s e s u b j e c t s being a g e d 3 to 12 y e a r s .  3.  A t least 6 s u b j e c t s previously identified a s h y p e r t e n s i v e by their P r i m a r y C a r e P h y s i c i a n .  4.  A t least 7 s u b j e c t s with a r m sizes ( m e a s u r e d at m i d - b i c e p s w i t h t h e infant cuff) b e t w e e n 13 a n d 1 8 c m c i r c u m f e r e n c e - (infant sized blood p r e s s u r e c u f f ) .  Study design S u b j e c t s w e r e recruited f r o m J u n e to A u g u s t 2 0 0 1 . All s u b j e c t s b e l o w 16 y e a r s of a g e h a d a c c o m p a n y i n g p a r e n t s or g u a r d i a n s a n d w e r e e x p l a i n e d s t u d y p r o c e d u r e s .  C o n s e n t f o r m s ( s i g n e d by p a r e n t s a n d  c h i l d r e n 16 to 18 y e a r s of a g e ) a n d w h e r e applicable a s s e n t f o r m s ( s i g n e d by s u b j e c t s ) w e r e o b t a i n e d prior to a n y s t u d y p r o c e d u r e s .  All w e r e given c o p i e s of t h e s e .  log a n d a s s i g n e d a s u b j e c t c o d e .  T h e y w e r e t h e n e n t e r e d into the subject  D e m o g r a p h i c d a t a including a g e , s e x , height, a r m  46  circumference  ( m e a s u r e d at m i d - b i c e p s ) a n d pre-existing health c o n d i t i o n s a n d c u r r e n t m e d i c a t i o n s w e r e all r e c o r d e d by G S M (investigator).  T h e s u b j e c t s w e r e t h e n s e a t e d in a quiet r o o m , w i t h t h e b a c k well s u p p o r t e d a n d f e e t flat o n the g r o u n d . For t h e s m a l l e r s u b j e c t s a n additional footstool w a s p r o v i d e d to aid t h e a c h i e v e m e n t of this p o s t u r e . A l s o , s u b j e c t s in t h e y o u n g e r a g e r a n g e s w e r e a l l o w e d to b e s e a t e d in t h e laps of their p a r e n t s or g u a r d i a n , but w e r e still s t a n d a r d i s e d by t h e a b o v e criteria. A n a p p r o p r i a t e l y sized cuff ( b a s e d o n t h e a r m size m a r k i n g s o n t h e cuffs p r o v i d e d ) w a s applied to the s u b j e c t ' s left a r m , w h i c h w a s p l a c e d o n a c o m f o r t a b l e s u r f a c e at heart level.  A s in t h e original s t u d y in adults, the B P M - 1 0 0 w a s c o n n e c t e d in parallel w i t h a T r i m l i n e  mercury  s p h y g m o m a n o m e t e r by m e a n s of a T - t u b e to t h e cuff, a n d w a s u s e d to p r o v i d e t h e a u s c u l t a t o r y r e f e r e n c e r e a d i n g s [2].  A N o n i n heart rate m o n i t o r w a s c o n n e c t e d to t h e s u b j e c t ' s right h a n d or o t h e r b o d y part.  T h e T r i m l i n e m e r c u r y s p h y g m o m a n o m e t e r ( T r i m l i n e M e d i c a l P r o d u c t s , B r a n c h b u r g , N e w Jersey, U S A ) has r a n g e of 0 - 3 0 0 m m H g with g r a d a t i o n s of 1 m m H g , a c c u r a c y ± 0 . 5 m m H g .  T h e N o n i n f i n g e r pulse  o x i m e t e r ( O n y x , N o n i n M e d i c a l Inc., P l y m o u t h , M i n n e s o t a , U S A ) h a s a r a n g e of 1 8 - 3 0 0 beats / m i n ( b p m ) w i t h a n a c c u r a c y of ± 3 % .  T h e B P M - 1 0 0 w a s a l s o c o n n e c t e d to a T o s h i b a d a t a collection  laptop  c o m p u t e r , to s t o r e all cuff p r e s s u r e a n d pulse i n f o r m a t i o n f r o m t h e blood p r e s s u r e cuff.  O n e of the o b s e r v e r s p a l p a t e d t h e brachial pulse of the left a r m a n d p l a c e d the d i a p h r a g m of a d u a l h e a d e d t e a c h i n g s t e t h o s c o p e over this point.  T h e o b s e r v e r s w e r e s e a t e d o p p o s i t e the subject o n  a d j u s t a b l e s e a t i n g s o that they w e r e able to r e a d t h e m e r c u r y s p h y g m o m a n o m e t e r at eye-level without introducing parallax e r r o r s . A curtain s e p a r a t e d the o b s e r v e r s but did not interfere w i t h the ability to read the sphygmomanometer.  T h e o b s e r v e r s w e r e e x p e r i e n c e d paediatric n u r s e s w h o s e blood  pressure  r e a d i n g skills w e r e t e s t e d prior to t h e initiation of the s t u d y by the m e a n s of validating r e a d i n g s with the o n e of the investigators ( G S M ) , f i g u r e 1 .  47  Fig 1 :  S e t - u p of t h e validation p r o c e s s  T h e B P M - 1 0 0 is a n a u t o m a t e d oscillometric d e v i c e that m e a s u r e s t h e m e a n arterial p r e s s u r e ( M A P ) directly f r o m t h e cuff p r e s s u r e ; a n d t h e n u s e s this M A P to c a l c u l a t e t h e systolic a n d diastolic p r e s s u r e s . It h a s a linear deflation rate of 4 m m H g / s e c o n d a n d c a n be set at cycle interval t i m e s of 1 to 5 m i n u t e s .  It  r e c o r d s six r e a d i n g s , at the e n d of its r e a d i n g p e r i o d , it also g e n e r a t e s t h e a v e r a g e of t h e systolic a n d diastolic r e a d i n g s 2 to 6 ( m a x i m u m of 5 ) . T h e first r e a d i n g is not u s e d in d e t e r m i n i n g the overall a v e r a g e a n d is u s e d h e r e to establish o b s e r v e r a g r e e m e n t ( s c r e e n i n g m e a s u r e m e n t ) a n d d e t e r m i n e if satisfactory a u s c u l t a t i o n c o u l d be o b t a i n e d .  G S M c h e c k e d t h e d a t a collection c o m p u t e r a n d e n t e r e d a s u b j e c t c o d e to r e c o r d all cuff p r e s s u r e a n d pulse i n f o r m a t i o n .  T h e B P M - 1 0 0 , blinded to t h e o b s e r v e r s , w a s s t a r t e d by G S M w h e n t h e dual h e a d e d  s t e t h o s c o p e w a s p l a c e d o v e r t h e brachial artery by o n e of the o b s e r v e r s .  T h e o b s e r v e r s a u s c u l t a t e d for  systolic b l o o d p r e s s u r e ( K o r o t k o f f s o u n d s p h a s e I - the first s o u n d h e a r d ) a n d t h e n diastolic p r e s s u r e ( K o r o t k o f f s o u n d p h a s e V - the d i s a p p e a r a n c e of all s o u n d s ) . A t the e n d of e a c h m e a s u r e m e n t t h e o b s e r v e r s i n d e p e n d e n t l y r e c o r d e d t h e systolic a n d diastolic blood pressures. from  T h e B P M - 1 0 0 blood p r e s s u r e m e a s u r e m e n t s , blinded f r o m t h e o b s e r v e r s , a n d t h e heart rate  the N o n i n f i n g e r  pulse oximeter w a s  recorded  48  by G S M w h e n t h e B P M - 1 0 0  h a d deflated  to  a p p r o x i m a t e l y 9 0 m m H g . All m e a s u r e m e n t s w e r e i n d e p e n d e n t l y r e c o r d e d o n t o s e p a r a t e d a t a s h e e t s , a n d triple-blinded b e t w e e n t h e o b s e r v e r s a n d t h e investigator.  In this m a n n e r a m a x i m u m of six m e a s u r e m e n t s w e r e r e c o r d e d . T h e first b l o o d p r e s s u r e m e a s u r e m e n t w a s u s e d to d e t e r m i n e i n t e r - o b s e r v e r a g r e e m e n t a n d to d e t e r m i n e that s a t i s f a c t o r y a u s c u l t a t i o n w a s p o s s i b l e ; it w a s not u s e d in a n y s u b s e q u e n t analysis. A m i n i m u m of 3 s u b s e q u e n t s a t i s f a c t o r y r e a d i n g s w e r e r e q u i r e d to b e included t h e study.  After all m e a s u r e m e n t s w e r e c o m p l e t e d t h e cuff w a s r e m o v e d ,  t h e a r m c h e c k e d , a n d the s u b j e c t s w e r e a l l o w e d to l e a v e .  Data Analysis For all included s u b j e c t s a g e , s e x a n d a r m size w a s r e c o r d e d . T h e m e a n , s t a n d a r d d e v i a t i o n a n d r a n g e s w e r e c a l c u l a t e d for e a c h of t h e s e .  T h e first or s c r e e n i n g blood p r e s s u r e s w a s u s e d to d e t e r m i n e the  p r i m a r y d e t e r m i n a n t in our hierarchy of inclusion a n d e x c l u s i o n criteria, a n d w a s not included in a n y subsequent  breakdown.  All o t h e r d a t a w a s put t h r o u g h our r e m a i n i n g  h i e r a r c h y of inclusion  and  e x c l u s i o n criteria, a n d t h e resulting i n f o r m a t i o n w a s u s e d in t h e a n a l y s i s .  A s in our s t u d y in adults, m e a n s w e r e c a l c u l a t e d f r o m t h e i n c l u d e d systolic a n d diastolic m e a s u r e m e n t s r e c o r d e d by t h e o b s e r v e r s , a n d w a s k n o w n a s the r e f e r e n c e systolic or diastolic blood p r e s s u r e [2].  For  each m e a s u r e m e n t the observer agreement, difference between the observers (observer 1 - observer 2), the m e a n difference ± standard deviation w a s calculated.  T h e p e r c e n t a g e less t h a n 5 m m H g a n d 10  m m H g was also expressed.  T h e p e r c e n t a g e s of systolic blood p r e s s u r e s a s m e a s u r e d by t h e o b s e r v e r s w a s e x p r e s s e d for t h o s e < 1 0 0 m m H g , t h o s e > 1 0 0 m m H g but < 1 8 0 m m H g a n d t h o s e > 1 8 0 m m H g . T h e s e p e r c e n t a g e s w e r e also e x p r e s s e d for diastolic m e a s u r e m e n t s , < 6 0 m m H g , > 6 0 m m H g but < 1 0 0 m m H g a n d t h o s e > 1 0 0 m m H g . T h e m e a n d i f f e r e n c e ± s t a n d a r d deviation ( d i f f e r e n c e b e t w e e n t h e B P M - 1 0 0 a n d t h e o b s e r v e r r e f e r e n c e ) w a s a l s o d e t e r m i n e d for both t h e systolic a n d diastolic m e a s u r e m e n t s .  T h e a g r e e m e n t b e t w e e n the t w o  t e c h n i q u e s w a s a l s o e x p r e s s e d a s t h e p e r c e n t a g e a g r e e m e n t within 5 m m H g , 10 m m H g a n d 15 m m H g for e a c h of t h e systolic a n d diastolic blood p r e s s u r e m e a s u r e m e n t s .  49  T h e m e a n difference ± standard  d e v i a t i o n w a s a l s o d e t e r m i n e d for t h e d i f f e r e n c e b e t w e e n t h e N o n i n f i n g e r p u l s e o x i m e t e r a n d t h e observer reference values.  W e a l s o c a l c u l a t e d t h e individual s u b j e c t m e a n s ± s t a n d a r d d e v i a t i o n ( d i f f e r e n c e b e t w e e n the B P M - 1 0 0 a n d the o b s e r v e r r e f e r e n c e ) for both systolic a n d diastolic blood p r e s s u r e m e a s u r e m e n t s a n d e x p r e s s e d the a g r e e m e n t a s p e r c e n t a g e s within 5, 10 a n d 15 m m H g a s a b o v e .  T h i s g a v e u s a better e s t i m a t e of  individual s u b j e c t m e a s u r e m e n t s a s o p p o s e d to total m e a s u r e m e n t s in t h e g r o u p .  For all e x c l u d e d s u b j e c t s the a g e , s e x a n d a r m size w a s a l s o r e c o r d e d .  T h e r e a s o n for e x c l u s i o n w a s  a l s o listed a n d all s u b j e c t s w e r e ultimately a c c o u n t e d for.  T h e m a g n i t u d e of d i f f e r e n c e in blood p r e s s u r e m e a s u r e m e n t s by t h e B P M - 1 0 0 a n d t h e a u s c u l t a t o r y r e f e r e n c e v a l u e s by t h e o b s e r v e r s , w a s plotted against, t h e m e a n s of b l o o d p r e s s u r e m e a s u r e m e n t s by t h e t w o m e t h o d s f o r e a c h of the systolic a n d diastolic m e a s u r e m e n t s . s u g g e s t e d by B l a n d a n d A l t m a n [4].  50  T h i s is a n a c c e p t e d m e t h o d a s  Results  Enrolled subjects There were 4 6 subjects enrolled. were excluded.  O f t h e s e , 36 ( 7 8 . 3 % ) s u b j e c t s w e r e i n c l u d e d a n d 10 ( 2 1 . 7 % ) s u b j e c t s  O f t h e included s u b j e c t s a v e r a g e a g e w a s 9.4 y e a r s w i t h a s t a n d a r d d e v i a t i o n of 4 . 2 .  Enrolled s u b j e c t s i n c l u d e d t h o s e with h y p e r t e n s i o n , renal artery s t e n o s i s , k i d n e y failure a n d congenital c o - a r c t a t i o n of t h e heart.  S o m e of t h e s e s u b j e c t s w e r e t a k i n g m a n y different m e d i c a t i o n s including anti-  hypertensives, steroids and immunosuppressants.  Excluded subjects T e n ( 2 1 . 7 % ) s u b j e c t s w e r e e x c l u d e d ; all w e r e p o s t - m e a s u r e m e n t e x c l u s i o n s .  T h e a v e r a g e a g e w a s 6.9  with a s t a n d a r d d e v i a t i o n of 4.2 y e a r s . T h e a g e r a n g e of this g r o u p w a s b e t w e e n 3 a n d 15 y e a r s .  There  w e r e 3 ( 3 0 . 0 % ) m a l e s u b j e c t s a n d 7 ( 7 0 . 0 % ) f e m a l e s u b j e c t s a m o n g t h o s e e x c l u d e d . Six ( 6 0 % ) of t h o s e e x c l u d e d w e r e b e c a u s e o b s e r v e r a g r e e m e n t o n the first or s c r e e n i n g m e a s u r e m e n t did not m e e t the p r e specified  criteria.  measurement.  Of these, one was  because  o n e of the o b s e r v e r s  did  not h e a r the  screening  T h r e e s u b j e c t s w e r e e x c l u d e d b e c a u s e of t e c h n i c a l e r r o r s p r o d u c e d by t h e B P M - 1 0 0 that  did not allow t h r e e s a t i s f a c t o r y blood p r e s s u r e m e a s u r e m e n t s to b e a c h i e v e d . O n e s u b j e c t had r e a d i n g s that b e c a u s e of t e c h n i c a l r e a s o n s a n d o b s e r v e r a g r e e m e n t o n individual d a t a points did not allow for t h r e e s a t i s f a c t o r y m e a s u r e m e n t s to b e c o l l e c t e d .  Target population results All of t h e target p o p u l a t i o n o b j e c t i v e s w e r e m e t , e x c e p t for t h e h y p e r t e n s i v e s u b j e c t s . ( 6 3 . 9 % ) m a l e s u b j e c t s a n d 13 ( 3 6 . 1 % ) f e m a l e s u b j e c t s i n c l u d e d .  There were 23  T h e a g e s r a n g e d f r o m 3 to 18 y e a r s .  T h e r e w e r e 6 s u b j e c t s a g e d 3 to 5 y e a r s , 10 s u b j e c t s a g e d 6 to 8 y e a r s , 9 s u b j e c t s a g e d 9 to 11 y e a r s , 5 s u b j e c t s a g e d 12 to 14 y e a r s a n d 6 s u b j e c t s a g e d 15 to 18 y e a r s .  Of these 28 (60.9%) subjects were  b e t w e e n t h e a g e s of 3 a n d 12 y e a r s , this m e t all a g e r e q u i r e m e n t s s p e c i f i e d in t h e m e t h o d s section a n d fulfilled the A A M I Draft S P 10 criteria [d]. T h e r e w e r e 5 h y p e r t e n s i v e s u b j e c t s that enrolled a n d all w e r e i n c l u d e d . T h i s did not m e e t the e n r o l m e n t criteria s p e c i f i e d in t h e m e t h o d s s e c t i o n a n d will b e d i s c u s s e d later.  S e v e n ( 1 5 . 2 % ) of t h e enrolled s u b j e c t s , all of w h o m w e r e i n c l u d e d , w e r e t e s t e d w i t h t h e infant cuff  ( 1 3 to 18 c m c i r c u m f e r e n c e at m i d - b i c e p s w i t h t h e cuff, a s s p e c i f i e d in t h e t a r g e t p o p u l a t i o n section) a n d 51  m e t t h e A A M I Draft S P 10 criteria [5]. T h e r e w e r e 16 ( 4 4 . 4 % ) s u b j e c t s w i t h a r m sizes less t h a n or equal to 18 c m , a n d t h e r e m a i n i n g 20 ( 5 5 . 6 % ) had a r m sizes g r e a t e r t h a n 18 c m m e a s u r e d at m i d - b i c e p s .  The  m e a n p o p u l a t i o n a r m size w a s 2 0 . 8 ± 5.2 c m with a r a n g e f r o m 15 - 33.5 c m .  Included b l o o d pressure measurements O f the included 162 sets of r e a d i n g s ; 6 2 ( 3 8 . 3 % ) m e a s u r e m e n t s w e r e less t h a n 100 m m H g for systolic blood p r e s s u r e , 100 ( 6 1 . 7 % ) m e a s u r e m e n t s w e r e g r e a t e r t h a n or e q u a l to l O O m m H g but less t h a n 180 m m H g . T h e r e w e r e no r e a d i n g s g r e a t e r t h a n 180 m m H g for t h e systolic blood p r e s s u r e s .  For diastolic  blood p r e s s u r e 13 ( 8 . 0 % ) m e a s u r e m e n t s w e r e b e l o w 60 m m H g , 149 ( 9 2 . 0 % ) of m e a s u r e m e n t s w e r e g r e a t e r t h a n or e q u a l to 6 0 m m H g w i t h no r e a d i n g s g r e a t e r t h a n 100 m m H g .  In the included p o p u l a t i o n 5 or 1 3 . 9 % s u b j e c t s w e r e previously d i a g n o s e d a s h a v i n g h y p e r t e n s i o n by their Primary Care Physicians. section. which  T h i s did not m e e t the target criteria of 6 s u b j e c t s a s s p e c i f i e d in t h e m e t h o d s  T h i s p r e - s p e c i f i e d target criteria w a s i n t e n d e d to reflect t h e A A M I S P 1 0 - 1 9 9 2 s t a n d a r d [6],  requires  10%  of  the  systolic  measurements  to  be  greater  than  180  mmHg  (or  stage  3  h y p e r t e n s i o n ) , a n d 1 0 % of the diastolic m e a s u r e m e n t s s h o u l d b e g r e a t e r t h a n 100 m m H g (or s t a g e 2 h y p e r t e n s i o n ) [7].  It s h o u l d b e n o t e d that the d e t e r m i n a t i o n of h y p e r t e n s i o n in c h i l d r e n is b a s e d o n the  child's height, a n d t h e r e f o r e a r a n g e of blood p r e s s u r e s are c o n s i d e r e d h y p e r t e n s i v e [1].  However  r e g a r d l e s s of a g e or height of t h e child a systolic blood p r e s s u r e g r e a t e r t h a n 140 m m H g for boys or 132 m m H g for girls, or diastolic p r e s s u r e s g r e a t e r t h a n 8 9 m m H g for b o y s or 8 6 m m H g for girls w o u l d be c o n s i d e r e d h y p e r t e n s i v e [8]. T h e 2 3 m e a s u r e m e n t s c o l l e c t e d f r o m t h e s e s u b j e c t s a c c o u n t e d for 1 4 . 2 % of the total 162; a l t h o u g h of t h e s e only 9 ( 5 . 6 % ) systolic m e a s u r e m e n t s e x c e e d e d t h e 140 m m H g for boys or 132 m m H g for girls a n d 1 ( 0 . 6 % ) diastolic m e a s u r e m e n t s e x c e e d e d t h e 8 9 m m H g for b o y s or 8 6 m m H g for girls.  Excluded b l o o d pressure measurements F r o m t h e 10 s u b j e c t s e x c l u d e d , thirty-five m e a s u r e m e n t s w e r e r e c o r d e d that w e r e not u s e d in the d a t a analysis for t h e study.  T h e i r m e a n r e f e r e n c e systolic a n d diastolic blood p r e s s u r e s w e r e 9 8 . 6 ± 9.5  m m H g ( r a n g e 8 2 . 5 - 118.5 m m H g ) a n d 6 3 . 5 ± 7.0 m m H g ( r a n g e 4 8 . 5 - 7 6 . 0 m m H g ) respectively, with heart r a t e s f r o m the N o n i n f i n g e r p u l s e o x i m e t e r of 8 5 . 3 ± 2 0 . 2 b p m ( r a n g e 5 4 - 1 1 3 b p m ) . T h e r e w e r e 2 2 52  ( 6 2 . 9 % ) systolic blood p r e s s u r e m e a s u r e m e n t s less t h a n 100 m m H g a n d 13 ( 3 7 . 1 % ) w e r e g r e a t e r t h a n or e q u a l to 100 m m H g but l e s s t h a n 180 m m H g . mmHg.  T h e r e w e r e n o systolic m e a s u r e m e n t s g r e a t e r t h a n 180  T h e r e w e r e 8 ( 2 2 . 9 % ) diastolic p r e s s u r e m e a s u r e m e n t s less t h a n 6 0 m m H g a n d 2 8 ( 7 7 . 1 % )  w e r e g r e a t e r t h a n or e q u a l to 6 0 m m H g but less t h a n 100 m m H g , w i t h n o m e a s u r e m e n t s g r e a t e r t h a n 100 mmHg.  Reference standard b l o o d pressure readings T h e r e f e r e n c e s t a n d a r d ( m e a n of the t w o o b s e r v e r ' s m e a s u r e m e n t s ) i n c l u d e d 162 s e t s of r e a d i n g s .  The  m e a n systolic blood p r e s s u r e ( a v e r a g e of the t w o o b s e r v e r s ) w a s 1 0 0 . 9 w i t h a s t a n d a r d deviation of 15.3. T h e m e a s u r e m e n t s r a n g e d f r o m 7 8 . 0 to 1 5 1 . 5 m m H g .  T h e m e a n r e f e r e n c e s t a n d a r d diastolic b l o o d  p r e s s u r e m e a s u r e m e n t w a s 6 2 . 3 ± 9.3 m m H g with a r a n g e of 4 5 . 0 to 8 9 . 5 m m H g .  Similarly t h e m e a n  r e f e r e n c e heart rate u s i n g t h e f i n g e r pulse o x i m e t e r w a s 8 8 . 2 ± 13.0 b p m w i t h a r a n g e of pulse rates f r o m 5 9 to 116 b p m .  O b s e r v e r a g r e e m e n t ( o b s e r v e r 1 - o b s e r v e r 2) for systolic m e a s u r e m e n t s s h o w e d a m e a n d i f f e r e n c e of 0.4 ± 2.8 m m H g ( r a n g e - 1 0 to 10 m m H g ) . O f t h e s e 154 ( 9 5 . 1 % ) m e a s u r e m e n t s w e r e less t h a n or equal to 5 m m H g .  For diastolic m e a s u r e m e n t s , o b s e r v e r a g r e e m e n t m e a n d i f f e r e n c e w a s 0.8 ± 4.0 m m H g  ( r a n g e - 1 0 t o 10 m m H g ) w i t h 135 ( 8 3 . 3 % ) m e a s u r e m e n t s l e s s t h a n or e q u a l t o 5 m m H g .  T h i s did not  m e e t t h e 8 5 % a g r e e m e n t level listed in t h e A A M I S P 1 0 - 1 9 9 2 , a l t h o u g h this s t a n d a r d w a s e s t a b l i s h e d f r o m s t u d i e s in adult p o p u l a t i o n s with m u c h higher blood p r e s s u r e s [6].  Measurements o f B p T R U ™ (model BPM-100) T h e r e w e r e a l s o 162 sets of included m e a s u r e m e n t s collected by t h e B P M - 1 0 0 . T h e m e a n systolic blood p r e s s u r e m e a s u r e m e n t w a s 102.3 w i t h a s t a n d a r d deviation of 14.6 m m H g a n d a r a n g e of 7 7 to 145 mmHg.  M e a n diastolic blood p r e s s u r e m e a s u r e m e n t s w e r e 59.1 ± 8.6 m m H g ( r a n g e of 4 0 to 83 m m H g ) .  T h e p u l s e r a t e s c o l l e c t e d b y t h e B P M - 1 0 0 h a d a m e a n o f 8 8 . 4 ± 12.8 b p m a n d s h o w e d r a n g e s f r o m 6 3 to 116 b p m .  53  Accuracy The  difference  between  the  mean  B P M - 1 0 0 ' readings  and the reference  standard  measurements,  d e t e r m i n e d by t h e o b s e r v e r s , a s d i s p l a y e d in T a b l e 1 for systolic b l o o d p r e s s u r e s w a s 1.45 ± 5.67 m m H g ( r a n g e - 1 5 to 2 2 . 5 m m H g ) a n d for diastolic m e a s u r e m e n t s w a s - 3 . 2 4 ± 7.39 m m H g ( r a n g e -22.5 to 17 m m H g ) , w h i c h m e t t h e criteria set by t h e A A M I s t a n d a r d [c]. T h e a c c u r a c y of t h e B P M - 1 0 0 a g a i n s t the heart rate r e f e r e n c e s h o w e d a m e a n d i f f e r e n c e of 0.20 ± 2.47 b p m ( r a n g e -8 to 7 b p m ) .  T a b l e 2 s h o w s the p r o p o r t i o n of individual a n d t h e n s u b j e c t m e a s u r e m e n t s of b o t h systolic a n d diastolic blood p r e s s u r e d i f f e r e n c e s within 5, 10 a n d 15 m m H g a n d h o w this c o m p a r e s to t h e B H S protocol [9].  A l s o t h e m e a n systolic blood p r e s s u r e b e t w e e n t h e B P M - 1 0 0 a n d t h e o b s e r v e r r e f e r e n c e s t a n d a r d s w a s 101.6 ± 14.7 m m H g a n d t h e diastolic blood p r e s s u r e w a s 6 0 . 7 ± 8.2 m m H g .  54  Discussion  M o s t International b o d i e s a g r e e that all a u t o m a t e d blood p r e s s u r e d e v i c e s s h o u l d h a v e validation p e r f o r m e d .  independent  H o w e v e r this is not t h e c a s e for m o s t d e v i c e s [10]. R e c e n t l y t h e w o r k i n g g r o u p o n  blood p r e s s u r e m o n i t o r i n g of the E u r o p e a n S o c i e t y of H y p e r t e n s i o n h a s c o m e u p w i t h a revised B H S protocol that will b e k n o w n a s the 'International P r o t o c o l ' in o r d e r to e n c o u r a g e blood p r e s s u r e d e v i c e manufacturers  to validate their d e v i c e s  and  make  the  process  easier  and  potentially  less  costly.  H o w e v e r , it is d e s i g n e d f o r a d u l t s g r e a t e r t h a n 3 0 y e a r s o f a g e a n d d o e s not m a k e r e c o m m e n d a t i o n s f o r special a g e s or c i r c u m s t a n c e s including children [11].  A s d i s c u s s e d a b o v e , t h e h y p e r t e n s i v e criterion w a s i n t e n d e d to reflect t h e A A M I S P 1 0 - 1 9 9 2 s t a n d a r d a n d ultimately e n s u r e t h e B P M - 1 0 0 to b e a c c u r a t e in s u b j e c t s with e l e v a t e d b l o o d p r e s s u r e s . H y p e r t e n s i o n in c h i l d r e n is not a c o m m o n o c c u r r e n c e a n d , t h e r e f o r e , d e s p i t e n u m e r o u s a t t e m p t s to locate this population s u b s e t , V S M M e d t e c h L t d . c h o s e to stop e n r o l m e n t at 5 s u b j e c t s . A l t h o u g h this s t u d y only included 5 p r e - d e t e r m i n e d h y p e r t e n s i v e s u b j e c t s , e l e v a t e d blood p r e s s u r e s w e r e t e s t e d a s part of t h e m a i n (original) clinical study [2], studies [2] [3].  T h e B P M - 1 0 0 p e r f o r m e d well in both original  In t h e c o m p a n i o n p a p e r that c o m b i n e s the adult a n d child d a t a a s a m e t a - a n a l y s i s it c a n  b e s e e n that all h y p e r t e n s i v e criteria a r e clearly m e t .  H y p o t e n s i o n w a s not directly t e s t e d in this study b e c a u s e t h e A A M I s t a n d a r d r e q u e s t s that in adults 1 0 % of systolic m e a s u r e m e n t s to be less t h a n 100 m m H g a n d 1 0 % of diastolic m e a s u r e m e n t s to be less t h a n 60 m m H g .  In o u r s t u d y 6 1 . 7 % (n = 100) of the systolic r e a d i n g s w e r e < 1 0 0 m m H g a n d 4 2 . 6 % (n = 6 9 ) of  diastolic r e a d i n g s w e r e < 6 0 m m H g .  T h e i n t e r - o b s e r v e r a g r e e m e n t required 8 5 % of r e a d i n g s to be within ± 5 m m H g . diastolic r e a d i n g s w e r e within this r e q u i r e m e n t .  In o u r study 8 3 . 3 % of  T h i s is not totally u n e x p e c t e d a s a u s c u l t a t i n g diastolic  blood p r e s s u r e in c h i l d r e n w i t h low blood p r e s s u r e s a n d rapid heart rates is m o r e difficult t h a n in adults [8] [12].  55  T h e 8 5 % a g r e e m e n t d e s c r i b e d in t h e A A M I S P 1 0 - 1 9 9 2 s t a n d a r d w a s e s t a b l i s h e d b a s e d o n adult studies for adults in a s a m p l e size of 8 5 . T h i s r e q u i r e m e n t m a y b e unrealistic w h e n l o o k i n g at a s m a l l s u b s e t of s u b j e c t s m a d e up of only c h i l d r e n .  G e r i n et al d e s c r i b e d in their p a p e r o n , ' H o w w e s h o u l d be m e a s u r i n g b l o o d p r e s s u r e in the d o c t o r ' s o f f i c e ? ' that " R o u t i n e blood p r e s s u r e m e a s u r e m e n t w o u l d be m o r e r e p r e s e n t a t i v e of daily a m b u l a t o r y p r e s s u r e s if a n a u t o m a t e d d e v i c e , without d o c t o r or n u r s e present, w e r e u s e d " [13]. T h e B p T R U ™ ( B P M 100 m o d e l ) is not only a s a f e a n d a c c u r a t e d e v i c e for d e t e r m i n i n g b l o o d p r e s s u r e in children in the p r i m a r y c a r e s e t t i n g , but a l s o m e e t s the r e q u i r e m e n t s of t h e A N S I / A A M I S P 1 0 - 1 9 9 2 a n d a c h i e v e d a ' B ' g r a d e a c c o r d i n g to a m o d i f i e d B H S p r o t o c o l .  56  o  'c o o  co££ c | E iS 0 E  0 LU  (0 "0 •—'  o  o oo  CO  1^  cd  o  CN  CN in  in  CO  co"  V  O  O -4—<  CO  co  ro  CZ  ro co  0  ^  c £ °> ro CD -L. 0 S- p cr 0 3= E  ro c o  c  E  ro Z  +i  •  1  ro o  '\  0  E < 0  1-a E  .c:  JS 0  CO T3  CD i_  O  CL  "(0 >>  co  o  E  co  CD  CO CN  in  V  O  E  o  co  o  w CD  0  ^  CO Q) - L .  E  0 c  CD i_ ZZ CO CO CD  E  i0  P "  O  £  st E T3 '  in  '  in t—  o  CD  +i  CO  CN CD  "O  c ro "oo  CD  CO  CD o  c  CD L_  CD H— CD v_  ro x> c ro to  CD  sz -«—I  "O  c ro  0  o o  o  c 0  1_  CO  0_ CO  TJ  0  £ 0  0 E  cz  Q  CN  CD  CL  c cz o 0  k_  CO  c  cz  2  E o o  0  £  ro  3  I— <  ro E o  0  ®  S  CL CO  CL CO  T>  ro  o  0  CO  T -  CO  o  a  o  -O  0  0  ro E  0  0 _ 0  ro "co  1  sz 0 E cz o CD c  o  C  CO  CD  0  H—  CO CL  co  ic? CO  X  E E  ^8  LO  O)  VI  O  CO  o o  o  CO  CD  CN  T—  CO  CO  aj  o o  co cd  Al  03  D) X  E E  o  VI  in  o  Al  CD  X  E E  CO VI  ^8  O LO  CN CN 1^  CN  CN CD  CN CD  en  CD  CD CD CO CO  0  13  to to  0  o c:  0  T3 O O XI  O  ~o "to >< to  0  -a i»  co •o c  3 "to  CO X CO CO  o c  0 L_  0  M—  0 l_  C O  c E  0 l_  a. T3  o o o o "to co  T3  0 O  c  0 0 i in 13  c E  o o  o o  Q. CQ  Q. CO  2  o  0  1_  0 0  M—  o  o *5 to  CO T>  0 o c  0 0 0  c: co  c co  E  0  0  O  E o  3"  la"  CO </>  to w c E  0  c E  0  o o  o o  0_  Q. CD  CO  c co  0  c co  0  o  E o  CO  CO  0  CD T3  i_ Q.  .O O  0  to to  0  O  o  3  </) </)  T3 O  "to  to to  £ 3  T3 O  o  0  in  0  D  oo  Fig. 2  Bland-Altman Display of Systolic Measurements, All Cuffs, 162 measurements M e a n D i f f e r e n c e : 1 . 4 5 m m H g S D o f D i f f e r e n c e s : 5 . 6 7 m m H g  30 U)  CO > «s  <»  ° o c  •  20 I £  E  1 0  • I  0  iH £ - 1 0 Q  •  * •  +2SD  •  #  — w  3  i  ,  Mean -2SD  •  -20 50  75  100  125  150  175  M e a n of B P M a n d O b s A v g ( m m H g )  B l a n d A l t m a n display of all systolic blood p r e s s u r e m e a s u r e m e n t s ( n = 1 6 2 ) . B P M , B p T R U ™ ( m o d e l B P M - 1 0 0 ) monitor; O b s A v g , o b s e r v e r a v e r a g e ( r e f e r e n c e s t a n d a r d )  59  Fig. 3  Bland Altman Display of Diastolic Measurements, All Cuffs, 162 measurements Mean Difference: -3.23 mmHg SDof Differences: 7.39 mmHg  &1  20  +2SD  ° ^ 10 <u > <1>  £.  CO  O  is  re  22:  0 -10 -20 -30  • V •  30  45  Mean  '«» 4«~ * •  •  -2SD  60  75  90  105  M e a n of B P M a n d O b s A v g (mmHg)  Bland Altman display of all diastolic blood pressure measurements (n = 162). BPM, BpTRU™ (model BPM-100) monitor; Obs Avg, observer average (reference standard)  60  References 1.  National Heart, Lung and Blood Institute. Report of the Second Task Force on Blood Pressure Control in Children-1987. Paediatrics 1987; 79: 1-25.  2.  Mattu GS, Perry TL Jr, Wright JM. Comparison of the oscillometric blood pressure monitor (BPM-100 ta) with the auscultatory mercury sphygmomanometer. Blood Pressure Monitoring 2001; 6: 153-159. Be  3.  Wright JM, Mattu GS, Perry TL Jr, Gelfer M, Strange KD, Zorn A, Chen Y. Validation of a new algorithm for the BPM-100 electronic oscillometric office blood pressure monitor. •* Blood Pressure Monitoring 2001; 6: 161.165.  4.  Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1:307-310.  5.  Manual, electronic or automated sphygmomanometers, 3ed (proposed AAMI / American National Standard. Draft ID: AAMI / CDV-1 SP10-2001. Arlington, VA.  6.  American National Standard for Electronic or Automated Sphygmomanometers. ANSI / AAMI SP10-1992. Arlington, VA: AAMI, 1993.  7.  The Sixth Report on the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. NIH Publication No. 98-4080, November 1997.  8.  Update on the Task Force Report (1987) on High Blood Pressure in Children and Adolescents: A working Group Report from the National High Blood Pressure Education Program. NIH Publication No. 96-3790 September 1996. Paediatrics 1996; 98: 649-658.  9.  O'Brien E, Petrie J, Littler W, de Swiet M, Padfield PI, Altman DG, et al. The British Hypertension Society protocol for the evaluation of blood pressure measuring devices. Journal of Hypertension 1993; 11(suppl 2): S43-S62.  10. O'Brien E. State of the market in 2001 for blood pressure measuring devices. Blood Pressure Monitoring 2001; 6: 171-176. 11. O'Brien E, Pickering T, Asmar R, Myers M, Parati G, Staessen J, Mengden T, Yutaka I, Waeber B, Palatini P, and with statistical assistance of Atkins N, Gerin W. Working Group on Blood Pressure Monitoring of the European Society of Hypertension International Protocol for validation of blood pressure measuring devices in adults. Blood Pressure Monitoring 2002; 7: 3-17. 12. Nehal US, Ingelfinger JR. Pediatric hypertension: recent literature. Current Opinion in Pediatrics 2002; 14: 189-196. 13. Gerin W, Marion RM, Friedman R, James GD, Bovbjerg DH, Pickering TG. How should we measure blood pressure in the doctor's office? Blood Pressure Monitoring 2001; 6: 257-262.  61  ABSTRACT  Background T o c o m b i n e t h e d a t a f r o m an earlier adult s t u d y with the d a t a f r o m t h e s u b s e q u e n t paediatric study using the B p T R U ™ ( B P M - 1 0 0 m o d e l ) in o r d e r to d e t e r m i n e t h e overall a c c u r a c y a g a i n s t r e c o g n i s e d s t a n d a r d a u s c u l t a t o r y m e r c u r y s p h y g m o m a n o m e t e r in t h e g e n e r a l population.  Design T h e individual blood p r e s s u r e points r e c o r d e d for both adult a n d paediatric s t u d i e s w a s c o m p a r e d directly to its c o r r e s p o n d i n g o b s e r v e r r e f e r e n c e m e a s u r e m e n t s f r o m d a t a collected a n d stored f r o m the t w o separate studies.  T h e r e w e r e 2 5 5 sets of r e a d i n g s in t h e adult s t u d y a n d 162 s e t s f r o m the paediatric  study, w h i c h w e r e c o m b i n e d to m a k e 4 1 7 pairs of blood p r e s s u r e r e a d i n g s for this study.  Methods T h e overall o b s e r v e r s t a n d a r d r e f e r e n c e m e a n for 4 1 7 m e a s u r e m e n t s w a s c a l c u l a t e d a n d t h e difference b e t w e e n this a n d t h e overall m e a n B P M - 1 0 0 w a s calculated with S D a n d r a n g e s .  M e a s u r e m e n t s within  5, 10 a n d 15 m m H g a g r e e m e n t w e r e e x p r e s s e d as p e r c e n t a g e s .  Results A total of 121 s u b j e c t s w e r e included for this s t u d y (85 f r o m t h e adult s t u d y a n d 3 6 f r o m the paediatric study).  F r o m t h e s e , 4 1 7 paired m e a s u r e m e n t s w e r e r e c o r d e d .  T h e m e a n d i f f e r e n c e b e t w e e n the  B p T R U ™ a n d t h e r e f e r e n c e s t a n d a r d systolic BP w a s 0.47 + 5.40 m m H g w i t h 8 9 . 2 % within 5 m m H g , 9 6 . 4 % within 10 m m H g a n d 9 9 . 3 % within 15 m m H g .  measurements  Comparatively w e found a mean  d i f f e r e n c e b e t w e e n the B p T R U ™ a n d r e f e r e n c e diastolic BP w a s - 2 . 1 2 ± 5.93 m m H g with 8 1 . 1 % within 5 m m H g , 9 2 . 1 % within 10 m m H g a n d 9 7 . 6 % within 15 m m H g a g r e e m e n t .  Conclusion T h e B p T R U ™ h a s b e e n s h o w n to be an a c c u r a t e n o n - i n v a s i v e b l o o d p r e s s u r e m o n i t o r i n g d e v i c e in the g e n e r a l p o p u l a t i o n f r o m a g e 3 up to t h e elderly.  T h i s c o m b i n e d s t u d y m e e t s all r e q u i r e m e n t s of the  A s s o c i a t i o n of A d v a n c e m e n t of Medical I n s t r u m e n t a t i o n a n d a c h i e v e d a g r a d e 'A' in t h e B H S protocol. 63  Introduction  T h e B p T R U ™ ( m o d e l B P M - 1 0 0 ) is a n o n - i n v a s i v e a u t o m a t e d e l e c t r o n i c b l o o d p r e s s u r e m o n i t o r that u s e s t h e o s c i l l o m e t r i c t e c h n i q u e t o d e t e r m i n e t h e m e a n arterial p r e s s u r e a n d t h e n c a l c u l a t e t h e systolic a n d diastolic blood p r e s s u r e s f r o m this.  It r e c o r d s six m e a s u r e m e n t s a u t o m a t i c a l l y , s e p a r a t e d by a t i m e  period o f 1 t o 5 m i n u t e s s e t a s required b y t h e o p e r a t o r .  It u s e s t h e first r e a d i n g t o a c c l i m a t i s e to t h e  patient's p r e s s u r e s a n d t h e n g e n e r a t e s t h e a v e r a g e of t h e r e m a i n i n g five r e a d i n g s .  H o m e blood p r e s s u r e r e a d i n g s w i t h a n a u t o m a t e d d e v i c e h a s b e e n s h o w n t o h a v e g r e a t e r predictive v a l u e t h a n office blood p r e s s u r e s f o r mortality in a r e c e n t p o p u l a t i o n - b a s e d o b s e r v a t i o n a l s t u d y [ 1 ] .  H y p e r t e n s i o n h a s a m a j o r i m p a c t o n o u r health s e r v i c e s ; it is t h e m a j o r risk f a c t o r f o r heart d i s e a s e , s t r o k e a n d renal d i s e a s e .  Heart d i s e a s e is t h e leading c a u s e of d e a t h in t h e U S , w i t h c e r e b r o v a s c u l a r d i s e a s e  being t h e third leading c a u s e of d e a t h [2]. J o f f r e s et al d i s c u s s d i f f e r e n c e s in h y p e r t e n s i o n a w a r e n e s s , t r e a t m e n t a n d control o f h y p e r t e n s i o n b e t w e e n t h e U S a n d C a n a d a y e t p l a c e little i m p o r t a n c e o n t h e t w o v e r y different s e t s of o b s e r v e r s taking t h e blood p r e s s u r e s , s a y i n g that t h e s e s h o u l d h a v e m i n i m a l i m p a c t . In c o n t r a s t G e r i n et al clearly e m p h a s i z e d t h e d i f f e r e n c e s a n d c o n c l u d e d that a n a u t o m a t e d d e v i c e w o u l d be better t h a n both m e t h o d s [3] [4].  T h e m o s t a c c u r a t e t e c h n i q u e s f o r m e a s u r i n g blood p r e s s u r e ( e g : intra-arterial c a t h e t e r i z a t i o n ) a r e not practical or f u n c t i o n a l f o r t h e p r i m a r y c a r e physician w h o is t h e frontline f o r d i a g n o s i n g , m o n i t o r i n g a n d managing  hypertension.  If  performed  correctly,  office  blood  pressures  with  a  mercury  s p h y g m o m a n o m e t e r m a y b e a c c u r a t e ; h o w e v e r , it h a s b e e n s h o w n that at least 2 0 % of h y p e r t e n s i o n is m i s d i a g n o s e d this w a y [5]. In addition t h e difficulties of m a n a g i n g m e r c u r y spills is a g r o w i n g c o n c e r n t o a d e g r e e that m a n y E u r o p e a n a n d U S cities h a v e a l r e a d y b a n n e d m e r c u r y a n d o t h e r s a r e s e t to f o l l o w suit [6] [7].  It h a s b e e n s h o w n m a n y t i m e s that blood p r e s s u r e s r e c o r d e d in t h e p h y s i c i a n s office by t h e physician c a n be m i s l e a d i n g a n d r e a d i n g s p e r f o r m e d by t h e office n u r s e or t h e patient a r e m o r e r e p r e s e n t a t i v e .  64  In f a c t  s u c h m e a s u r e m e n t s w o u l d result in less t r e a t m e n t initiation, c h a n g e in c u r r e n t t r e a t m e n t or e s c a l a t i o n of d o s a g e [8].  T h e i m p o r t a n c e of correctly d i a g n o s i n g a n d m a n a g i n g blood p r e s s u r e clearly h a s a potential for i m p a c t on mortality, m o r b i d i t y a n d health c a r e c o s t s .  H o w e v e r , t h e s e benefits c a n only be realized if w e h a v e a  m e t h o d of a c c u r a t e l y r e c o r d i n g blood p r e s s u r e s in a m a n n e r similar to that s e e n in t h e clinical trial setting.  T h e p u r p o s e of this s t u d y w a s to c o m b i n e t h e d a t a for t h e g e n e r a l p o p u l a t i o n f r o m 3 y e a r s of a g e to the elderly in o r d e r to d e t e r m i n e t h e overall a c c u r a c y of t h e a u t o m a t e d b l o o d p r e s s u r e monitor, against t h e g o l d s t a n d a r d m e r c u r y s p h y g m o m a n o m e t e r .  BpTRU™  T o a c h i e v e this, t h e s t u d y w a s a s s e s s e d in  a c c o r d a n c e with t h e s t a n d a r d guidelines of the A A M I S P 1 0 - 1 9 9 2 p r o v i d e d by t h e A s s o c i a t i o n for the A d v a n c e m e n t of Medical I n s t r u m e n t a t i o n ( A A M I ) a n d in a c c o r d a n c e with t h e British H y p e r t e n s i o n Society p r o t o c o l - 1 9 9 3 ; t h e regulating bodies for validating t h e s e t y p e s of m o n i t o r s .  65  Methods  A d u l t s u b j e c t s w e r e recruited d u r i n g S e p t e m b e r a n d O c t o b e r 1 9 9 9 at t h e U n i v e r s i t y of British C o l u m b i a using s u b j e c t s f r o m t h e H y p e r t e n s i o n clinic a n d affiliated p r i m a r y c a r e p r a c t i c e s . T h e paediatric s u b j e c t s w e r e recruited f r o m J u n e to A u g u s t 2 0 0 1 at the R e s e a r c h office of V S M M e d T e c h Ltd f r o m B.C.'s C h i l d r e n ' s Hospital a n d a l s o f a m i l y practice offices.  Details of all ethical a p p r o v a l , c o n s e n t a c q u i r e d , inclusion, e x c l u s i o n criteria a n d target  population  r e q u i r e m e n t s c a n be o b t a i n e d f r o m t h e c o m p a n i o n p a p e r a n d t h e t w o original adult publications [9] [10] [11]. In t h e adult p o p u l a t i o n t w o e x p e r i e n c e d n u r s e s w e r e u s e d w h o s e blood p r e s s u r e r e a d i n g skills w e r e t e s t e d prior to t h e initiation of a n y d a t a collection. Similarly in t h e paediatric p o p u l a t i o n t h r e e e x p e r i e n c e d n u r s e s rotated a s t h e t w o o b s e r v e r s .  T h e set up w a s the s a m e for both studies with the B p T R U ™ b e i n g c o n n e c t e d in parallel w i t h the T r i m l i n e p r e c i s i o n s t a n d a r d m e r c u r y s p h y g m o m a n o m e t e r a n d t h e N o n i n f i n g e r p u l s e o x i m e t e r b e i n g c o n n e c t e d to t h e o t h e r a r m or alternate b o d y part.  T h e o b s e r v e r s , w h o w e r e s e a t e d o p p o s i t e the s t a n d a r d m e r c u r y  s p h y g m o m a n o m e t e r , w e r e blinded by a curtain b e t w e e n t h e m a n d a l s o blinded to t h e B p T R U ™ d e v i c e . O n e of t h e m w o u l d p a l p a t e the brachial pulse a n d put the d i a p h r a g m of t h e d u a l - h e a d e d  stethoscope  o v e r it. T h e only d i f f e r e n c e b e t w e e n the t w o p o p u l a t i o n s u b - g r o u p s w a s that t h e paediatric s u b j e c t s w e r e a l l o w e d to sit o n t h e laps of their a c c o m p a n y i n g parent or g u a r d i a n .  All d a t a r e c o r d e d by the B p T R U ™ d e v i c e w a s s i m u l t a n e o u s l y s a v e d o n t o a c o n n e c t e d laptop f r o m w h i c h s u b s e q u e n t analysis c o u l d b e p e r f o r m e d .  F r o m t h e 121 s u b j e c t s r e c r u i t e d f o r this study, 4 1 7 data points  w e r e o b t a i n e d , all of w h i c h w e r e u s e d in our s t u d y h a v i n g a l r e a d y c o n f o r m e d to t h e inclusion a n d e x c l u s i o n criteria s p e c i f i e d in the p r e v i o u s s t u d i e s .  66  Data Analysis A f t e r c o m b i n i n g t h e 8 5 adult s u b j e c t s (at least 18 y e a r s of a g e ) a n d t h e 3 6 paediatric s u b j e c t s ( f r o m 3 to 18 y e a r s of a g e ) , a total of 121 s u b j e c t s w e r e i n c l u d e d .  For t h e s e s u b j e c t s t h e s e x a n d a g e distributions  were determined.  For e a c h of t h e i n c l u d e d m e a s u r e m e n t s , distribution of blood p r e s s u r e s w a s d e t e r m i n e d a n d e x p r e s s e d a s t h e n u m b e r a n d p e r c e n t a g e s in t h e r a n g e s 180 m m H g < systolic < 100 m m H g a n d 100 m m H g < diastolic < 6 0 m m H g .  Included in this w a s a n e x p r e s s i o n of t h e m e a n , s t a n d a r d d e v i a t i o n a n d r a n g e of  blood p r e s s u r e s in t h e p o p u l a t i o n g r o u p .  F r o m t h e 4 1 7 m e a s u r e m e n t s the m e a n , s t a n d a r d d e v i a t i o n s a n d r a n g e of blood p r e s s u r e a n d heart rate w a s also d e t e r m i n e d for o b s e r v e r 1 a n d o b s e r v e r 2.  S u b s e q u e n t l y , t h e m e a n of t h e t w o o b s e r v e r s w a s  also c a l c u l a t e d a n d b e c a m e k n o w n a s t h e r e f e r e n c e s t a n d a r d m e a s u r e m e n t s . within 5 a n d 10 m m H g w a s a l s o e x p r e s s e d .  A g r e e m e n t of r e a d i n g s  Similarly, the m e a n , s t a n d a r d d e v i a t i o n a n d r a n g e of blood  p r e s s u r e w e r e a l s o d e t e r m i n e d for the B p T R U ™ d e v i c e .  T o a s s e s s the a c c u r a c y of the d e v i c e , the m e a n d i f f e r e n c e a n d s t a n d a r d d e v i a t i o n , b e t w e e n the B p T R U ™ and  the  reference  standard was  determined  as  per t h e A N S I  / AAMI  SP10-1992  standard  [12].  S u b s e q u e n t l y , in o r d e r to reflect this a c c u r a c y in t h e clinical s e t t i n g , t h e s u b j e c t m e a n d i f f e r e n c e with s t a n d a r d d e v i a t i o n w a s a l s o d e t e r m i n e d ( s u b j e c t m e a n B p T R U ™ m e a s u r e m e n t s m i n u s the s u b j e c t m e a n r e f e r e n c e m e a s u r e m e n t s ) . T h e p e r c e n t a g e a g r e e m e n t of m e a s u r e m e n t s w i t h i n 5, 10 a n d 15 m m H g w a s also e x p r e s s e d in o r d e r to r e p r e s e n t t h e r e q u i r e m e n t s of the British H y p e r t e n s i o n S o c i e t y protocol [13].  67  Results  Included subjects T h e r e w a s a total of 121 s u b j e c t s included f r o m t h e t w o studies (85 f r o m t h e adult s t u d y [10] a n d 3 6 f r o m t h e paediatric s t u d y [11] - s e e c o m p a n i o n p a p e r ) . (44.6%) were female subjects.  O f t h e s e 6 7 ( 5 5 . 4 % ) w e r e m a l e s u b j e c t s a n d 54  T h e a v e r a g e a g e of included s u b j e c t s w a s 33.1 y e a r s of a g e , ranging  f r o m 3 to 8 3 y e a r s . Details of included a n d e x c l u d e d s u b j e c t s c a n b e s e e n in t h e original adult study [10] a n d t h e paediatric c o m p a n i o n paper [11]. All of t h e target p o p u l a t i o n r e q u i r e m e n t s for e a c h study w e r e m e t , e x c e p t the h y p e r t e n s i v e criteria specified in t h e paediatric study, this w a s d i s c u s s e d at s o m e length in the paediatric p a p e r .  Included b l o o d pressure measurements F r o m t h e 121 s u b j e c t s included t h e r e w a s a total of 4 1 7 sets of r e a d i n g s o b t a i n e d .  Of these, 27 (6.5%)  h a d systolic m e a s u r e m e n t s greater t h a n 180 m m H g a n d 137 ( 3 2 . 8 % ) h a d systolic m e a s u r e m e n t s less t h a n 100 m m H g .  T h e r e m a i n i n g or 2 5 3 ( 6 0 . 7 % ) h a d blood p r e s s u r e m e a s u r e m e n t s e q u a l to or greater  t h a n 100 m m H g a n d e q u a l to or less t h a n 180 m m H g a s a c c o r d i n g to t h e m e a n r e f e r e n c e o b s e r v e r standard  measurements.  g r e a t e r t h a n 100 m m H g  Twenty-five  ( 6 . 0 % ) ^ blood p r e s s u r e r e a d i n g s  h a d diastolic  measurements  a n d 108 ( 2 5 . 9 % ) h a d diastolic blood p r e s s u r e s less t h a n 60 m m H g  remaining 284 (68.1%) between these.  with  T h e overall a v e r a g e systolic b l o o d p r e s s u r e w a s 117.7 ± 2 9 . 2 3  m m H g ( r a n g e 7 8 to 2 2 3 . 5 m m H g ) a n d the overall a v e r a g e diastolic blood p r e s s u r e w a s 71.5 ± 15.95 m m H g ( r a n g e 4 5 to 119.5 m m H g ) . T h e overall m e a n heart rate w a s 77.1 + 15.41 b p m ( r a n g e 4 2 to 116 b p m ) u s i n g the N o n i n f i n g e r p u l s e o x i m e t e r .  T h e s e overall v a l u e s w e r e d e t e r m i n e d f r o m the m e a n  observer reference measurements.  Excluded b l o o d pressure measurements T h e r e w e r e six s u b j e c t s e x c l u d e d b e c a u s e of t e c h n i c a l e r r o r s m a d e by t h e B p T R U ™ d e v i c e that did not allow for a m i n i m u m of t h r e e blood p r e s s u r e r e a d i n g s to b e r e c o r d e d .  M o r e d e t a i l e d e x p l a n a t i o n s of all  e x c l u d e d s u b j e c t s a n d m e a s u r e m e n t s c a n be o b t a i n e d f r o m t h e p r e v i o u s p u b l i c a t i o n s [9] [10] [11].  68  Reference standard b l o o d pressure readings O b s e r v e r a g r e e m e n t (or the m e a n d i f f e r e n c e b e t w e e n o b s e r v e r o n e a n d t w o ) for the 4 1 7  systolic  m e a s u r e m e n t s w a s - 0 . 2 6 ± 2.38 m m H g ( r a n g e - 1 0 to 10 m m H g ) a s r e c o r d e d u s i n g a T r i m l i n e m e r c u r y sphygmomanometer.  O f t h e s e 4 0 4 ( 9 6 . 9 % ) r e a d i n g s w e r e within 5 m m H g .  Similarly t h e o b s e r v e r  a g r e e m e n t f o r the 4 1 7 diastolic blood p r e s s u r e r e a d i n g s w a s - 0 . 3 5 ± 3.27 m m H g ( r a n g e - 1 0 to 10 m m H g ) with 3 7 8 or 9 0 . 6 % b e i n g within 5 m m H g , a s s e e n in T a b l e 1 . A l t h o u g h m o s t of t h e r e a d i n g s w e r e within 5 mmHg  agreement  (as  m e a n values greater than  10 m m H g  were  excluded  a s o n e of t h e  post-  m e a s u r e m e n t e x c l u s i o n criteria), t h e diastolic m e a s u r e m e n t s h a d a s m a l l e r n u m b e r within this a g r e e m e n t range.  T h i s highlights the difficulty of a c c u r a t e l y m e a s u r i n g diastolic b l o o d p r e s s u r e , particularly in the  paediatric p o p u l a t i o n s or y o u n g f e m a l e adults w h e n reading v a l u e s f r o m a s low a s 4 5 m m H g .  Measurements of B p T R U ™ (model BPM-100) T a b l e 1 a l s o s h o w s is that the overall m e a n systolic blood p r e s s u r e r e c o r d e d by t h e B p T R U ™ w a s 118.2 ± 2 8 . 4 7 m m H g with a r a n g e of 77 to 221 m m H g , a n d diastolic blood p r e s s u r e of 6 9 . 4 ± 16.3 m m H g ( r a n g e 4 0 to 120 m m H g ) for 4 1 7 m e a s u r e m e n t s . T h e overall m e a n heart rate r e c o r d e d by the B p T R U ™ w a s 7 7 . 3 + 15.33 b p m with a r a n g e of 116 to 4 1 7 b p m for t h e 4 1 7 r e a d i n g s .  Accuracy T h e a c c u r a c y of t h e B p T R U ™ , or the m e a n d i f f e r e n c e b e t w e e n t h e B p T R U ™ a n d t h e o b s e r v e r r e f e r e n c e s t a n d a r d systolic b l o o d p r e s s u r e w a s 0.47 ± 5.40 m m H g w h i c h is well within t h e A N S I / A A M I S P 1 0 - 1 9 9 2 s t a n d a r d . Similarly t h e m e a n d i f f e r e n c e b e t w e e n t h e B p T R U ™ a n d t h e r e f e r e n c e diastolic b l o o d p r e s s u r e w a s 2.12 ± 5.93 m m H g w h i c h is also within t h e A N S I / A A M I S P 1 0 - 1 9 9 2 s t a n d a r d , a s s e e n in T a b l e 2. T h e m e a n d i f f e r e n c e of t h e o b s e r v e r r e f e r e n c e a n d t h e B p T R U ™ f o r the heart rate w a s 0.18 + 2.20 b p m .  In T a b l e 3 it c a n b e s e e n that f r o m t h e s e v a l u e s 3 7 2 ( 8 9 . 2 % ) systolic m e a s u r e m e n t s w e r e less t h a n or e q u a l to 5 m m H g , 4 0 2 ( 9 6 . 4 % ) w e r e within 10 m m H g a n d 4 1 4 ( 9 9 . 3 % ) w e r e within 15 m m H g a g r e e m e n t . For t h e diastolic m e a s u r e m e n t s 3 3 8 ( 8 1 . 1 % ) w e r e within 5 m m H g , 3 8 4 ( 9 2 . 1 % ) w e r e within 10 m m H g a n d 4 0 7 ( 9 7 . 6 % ) w e r e within 15 m m H g .  69  T h e s e d e t e r m i n a n t s all fall within t h e British H y p e r t e n s i o n S o c i e t y ( B H S ) g r a d e 'A' p r o t o c o l . It c a n a l s o be s e e n that t h e p e r c e n t a g e of systolic m e a s u r e m e n t s in a g r e e m e n t w a s better t h a n that of t h e diastolic.  A s s t a t e d p r e v i o u s l y t h e B p T R U ™ is a n a u t o m a t e d d e v i c e that r e c o r d s a n d c a l c u l a t e s t h e a v e r a g e of five blood p r e s s u r e m e a s u r e m e n t s .  It is i n t e n d e d to be u s e d in t h e p h y s i c i a n ' s office in this m a n n e r . T h u s t h e  s u b j e c t m e a n d i f f e r e n c e w a s d e t e r m i n e d in o r d e r to reflect t h e a c c u r a c y of t h e d e v i c e in the clinical setting.  T h e s u b j e c t m e a n d i f f e r e n c e for systolic blood p r e s s u r e s w a s 0.4 ± 4 . 3 m m H g ,  diastolic  m e a s u r e m e n t s p r o d u c e d -2.0 + 5.1 m m H g a n d the s u b j e c t m e a n d i f f e r e n c e for heart rate w a s 0.2 + 1.1 bpm.  F r o m t h e s e , for systolic blood p r e s s u r e 91 ( 7 5 . 2 % ) s u b j e c t s w e r e w i t h i n 5 m m H g , 119 ( 9 8 . 3 % )  w e r e within 10 m m H g a n d 121 ( 1 0 0 % ) w e r e within 15 m m H g .  For diastolic blood p r e s s u r e , 8 6 ( 7 1 . 1 % )  s u b j e c t s w e r e within 5 m m H g , 112 ( 9 2 . 6 % ) w e r e within 10 m m H g a n d 119 ( 9 8 . 3 % ) w e r e within 15 m m H g a g r e e m e n t b e t w e e n t h e B p T R U ™ a n d t h e m e a n o b s e r v e r r e f e r e n c e s t a n d a r d , a s s h o w n in T a b l e 3.  Bland A l t m a n plots w e r e a l s o d i s p l a y e d a s t h e d i f f e r e n c e of t h e B P M a n d t h e o b s e r v e r a v e r a g e a g a i n s t t h e m e a n of t h e B p T R U ™ a n d t h e o b s e r v e r a v e r a g e for both systolic a n d diastolic p r e s s u r e s ( s e e f i g u r e s 1 a n d 2) [14].  70  Discussion  T h e r e h a v e b e e n s e v e r a l publications o n t h e i m p o r t a n c e of t a k i n g a c c u r a t e a n d r e p r o d u c i b l e pressures.  C a m p b e l l a n d M c K a y h a v e illustrated t h e potential difficulties w i t h i n a c c u r a t e  blood  readings;  d e m o n s t r a t i n g that c o n s i s t e n t o v e r e s t i m a t i o n of diastolic blood p r e s s u r e by 5 m m H g w o u l d i n c r e a s e the hypertension  in a p h y s i c i a n s practice by 1 0 0 % a n d c o n v e r s e l y , u n d e r e s t i m a t i n g the diastolic  blood  p r e s s u r e by j u s t 5 m m H g w o u l d r e d u c e by 6 2 % t h e n u m b e r of patients s e e n to b e h y p e r t e n s i v e [15].  Blood p r e s s u r e s h o u l d b e r e c o r d e d b e a r i n g in m i n d t h e following f a c t o r s : - [4] [16] [17] [18] patients s h o u l d refrain f r o m s m o k i n g or ingesting c a f f e i n e at least 30 m i n u t e s b e f o r e having their blood p r e s s u r e s r e c o r d e d blood p r e s s u r e s h o u l d be r e c o r d e d in a quiet a n d c a l m e n v i r o n m e n t patients s h o u l d be s e a t e d with their b a c k s well s u p p o r t e d , f e e t flat o n t h e g r o u n d with the mid-point of t h e b a r e u p p e r a r m s u p p o r t e d at heart level a n a p p r o p r i a t e sized cuff (the bladder inside the cuff s h o u l d b e at least 8 0 % of the c i r c u m f e r e n c e ) s h o u l d b e p l a c e d o n the u p p e r a r m of the patient 2 to 2.5 c m a b o v e t h e a n t e c u b i t a l f o s s a blood p r e s s u r e m e a s u r e m e n t s s h o u l d only be r e c o r d e d after at least 5 m i n u t e s of rest in this position m e a s u r e m e n t s s h o u l d be t a k e n either with a n a u t o m a t e d blood p r e s s u r e d e v i c e or a regularly calibrated m e r c u r y s p h y g m o m a n o m e t e r inflate t h e cuff to at least 30 m m H g a b o v e t h e d i s a p p e a r a n c e of t h e radial p u l s e of the a r m f r o m w h i c h p r e s s u r e s are being r e c o r d e d allow a linear deflation of 2 m m H g / s e c K o r o t k o f f V or t h e d i s a p p e a r a n c e of s o u n d s s h o u l d be r e c o r d e d a s t h e diastolic blood p r e s s u r e t h e a v e r a g e of at least t w o r e a d i n g s , at least t w o m i n u t e s apart s h o u l d b e t a k e n at e a c h visit at least t w o visits a r e required to m a k e the d i a g n o s i s of h y p e r t e n s i o n u n l e s s t h e r e is e v i d e n c e of e n d - o r g a n d a m a g e w i t h h y p e r t e n s i o n at o n e visit  71  T h e a u t o m a t e d d e v i c e a s s e s s e d h e r e s a v e s t i m e a n d m a k e s it m o r e likely t h a t t h e a b o v e criteria will be followed: patients c a n b e p l a c e d in a quiet r o o m by t h e m s e l v e s a v o i d i n g t h e e f f e c t s of w h i t e c o a t or office hypertension different c u f f s s u p p l i e d w i t h t h e d e v i c e are clearly m a r k e d to allow f o r t h e m o s t a p p r o p r i a t e cuff to be u s e d a c c o r d i n g to a r m size the d e v i c e a u t o m a t i c a l l y calibrates to a t m o s p h e r i c p r e s s u r e a n d a m b i e n t t e m p e r a t u r e b e f o r e e a c h m e a s u r e m e n t r e d u c i n g e r r o r s of calibration it inflates to 35 m m H g t h e level of o c c l u s i o n of t h e radial p u l s e s o a s not to m i s s a u s c u l t a t o r y g a p s it h a s linear deflation to r e d u c e e r r o r s of d e t e c t i n g pulse w a v e s the  device  has  reproducible  smooth  inflation  and  deflation  that  can  only  be  obtained  using  s t a n d a r d i s e d c o m p u t e r s or a d e v i c e a n d not by a n y o b s e r v e r s the d e v i c e is calibrated to a g r e e with K o r o t k o f f V g e n e r a t i n g a c c u r a t e diastolic b l o o d p r e s s u r e s t h e first m e a s u r e m e n t is i g n o r e d s i n c e t h e p e r s o n starting t h e d e v i c e m a y still b e in the r o o m five m e a s u r e m e n t s c a n be o b t a i n e d at 1 to 5 m i n u t e intervals w i t h t h e a v e r a g e c a l c u l a t e d at the e n d giving a m o r e r e p r e s e n t a t i v e r e c o r d i n g of their blood p r e s s u r e s t a t u s  W i t h t h e a d v e n t of n e w e r blood p r e s s u r e m e a s u r i n g d e v i c e s , t h e r e h a s b e e n r e n e w e d call for m o r e validation trials a n d s t a n d a r d i s a t i o n of the c o m p a r i s o n s of t h e s e d e v i c e s . [19].  Recently The European  Society of H y p e r t e n s i o n W o r k i n g G r o u p h a s u s e d p u b l i s h e d d a t a to d e v i s e a n e w International protocol that is h o p e d w o u l d e n c o u r a g e all d e v i c e m a n u f a c t u r e r s to p e r f o r m a n d a d h e r e to m i n i m u m validation a n d s u b s e q u e n t l y a p p r o v a l protocols [20].  T h e d e v i c e t e s t e d h e r e m e t t h e r e q u i r e m e n t s set by the g o v e r n i n g b o d i e s m e n t i o n e d , w h i c h are far m o r e rigorous t h a n t h e n e w International P r o t o c o l . H o w e v e r , it w a s d e s i r a b l e to s e e if a s t u d y in all a g e g r o u p s w o u l d a l s o m e e t t h e s e strict r e q u i r e m e n t s .  D u e to t i m e , a n d f i n a n c i a l c o n s t r a i n t s it w a s m o r e a p p r o p r i a t e  to c o m b i n e t h e s t u d y d a t a if r e a s o n a b l e to d o s o .  It w a s felt that b e c a u s e w e w e r e c o m b i n i n g r a w  individual d a t a rather t h a n m e a n s a n d i m p u t e d s t a n d a r d d e v i a t i o n s that this w o u l d be a p p r o p r i a t e to d o . In reality w e w e r e d o i n g m u c h t h e s a m e a s if w e w e r e c o m b i n i n g d a t a f o r a m e t a - a n a l y s i s ; h o w e v e r w e w e r e better off in that w e had original d a t a d o all a n a l y s e s f r o m s c r a t c h .  72  T h e B p T R U ™ is t h e only n o n - i n v a s i v e a u t o m a t e d oscillometric blood p r e s s u r e d e v i c e c u r r e n t l y available that h a s b e e n t e s t e d in a p o p u l a t i o n g r o u p a g e d f r o m 3 y e a r s to t h e elderly; a n d that h a s satisfied the criteria set out by t h e A m e r i c a n National S t a n d a r d for Electronic or A u t o m a t e d ANSI / AAMI  SP10-1992  [12].  Sphygmomanometers,  Overall it has also a c h i e v e d a g r a d e 'A' a c c o r d i n g to the  H y p e r t e n s i o n S o c i e t y protocol for the e v a l u a t i o n of blood p r e s s u r e m e a s u r i n g d e v i c e s - 1 9 9 3 [13].  73  British  c CD E C Q. CO J3 0  co  T—  co  T—  CN Tf  CM Tf  Tf  T f  iri  iri  TT iri  CNI Tf  ^  —  CO  CO  T—  CM Tf  i CO  0 "co  •c  CO 0 X  Q  E  CO Q. +1 -O  o CM CM  T—  00  co E 0 Q. E -o  o  =3 hQ. CO  0  T3  c  0 .£?  CD T  ii  Tf Tf  -  o CM  co Tf  a>  T— •>T—  o  o  CM  o  LO T f  Tf  CD  CN CN  CO i  CD £ 0 10 JD  O  o o "GO  CO  Q  co  co X E  CN  00  LO CN  LO  CD  in  CO  CO  in  o CN  CO  CO CD  CO  CD  in"  LO  o 0  c ™ co X 0 F  0 E 0 L_  CO CO 0  0 °> cnX  0  1  P  co  E  T f  CN CM 00  1^  CO CM CNI co  in CO  d  I  un CO CM CM CO  co  ai co  CM CM i  CM CM"  LO CN CN i  in oo  -— *•  co co 0 _c T3 c CO 0 CO CO  0  o o .o  o o "to CO  +1  c  CZ CO CO X 0 E E E  co  CO CN  CM  CD CN  CO T—  Tf  oi  ar>  CM  co  co CO  csi  CD CN  CD  Tf  O Tf  CO CM  LO  CN  Tf  00  d  o  o "oo co  1^ T f  Tf  Tf  T f  Tf  T f  U  o to  CM  co 0 c o i_ 0 0 CO  1-  0 to  o  o  c co 0  0  0  cCO  0 CO .a  O  o  0  c 0 E 0 0 L—  to CO c T3 CO 0  CO co  3  .a  \— CL  O  OH GO  0  §| CO  X3  C  ^  1-2 E 03  CD  CO T 3  o  CO o  oo iri  in iri  V  O O  -«—»  CO  ro o ro  •D  §  C  I E E  in +i  ^~  O  o  CN  CN  i  i  ^  c | £ iS 0 E CO T 3  CN  o  ^  o cd  o  co  in  V  O o -*—'  CO >»  CO 03  ro  CD  Q) i l  X  C  o  o  iri  o  +1  XI  r-  ^  1^ CN  -3-  ro x> c ro CD  ro  o c  CD  XI c ro "to  03 o c  CD i  CO  c  0  CN C3 03  CD H— CD L  co  0. CO  3 co  c o o  DC H CL  CQ c ro  E 3 DC I— CL CQ  o  0 !£? CO  CO  X  E E  LO  VI  X  E E  o  LO  CO  00  co  CD CD  CD  Al  ^8 LO  00  T-  cb CD  CM CD  o O o  co cd CD  CO 00  co csi  CD  CD  VI  co  o o o o a.  X  CM O LO  VI  co Al  CD  CM  co  oo  •3"  -3"  LO  1^  0 T J CD  CO X  CN  CM  m  CD CD  3 00 00  'o  O CO  0  c o co c 0 tr  I CL T J O O  J3  0 CL >,  O  03  3 CO CO  0  0 CD  TJ  O O  -Q  o o  CL  CJ  o  3  \—  00  0  CL  o cz  CQ  CD X)  0  l_  0  O  cz  0  CD  0  O  CO  CO  oo 0 CD  3 CO CO  0 TJ  o o  O  o -•—' CO  Cd  0 0.  CL T J O O JD  CO X CQ 0  TJ CD  l_  o  M— 1  c £ s Qi  I—  CL CQ  CD T J  0 O  CZ  0  CO CD T J  0  CZ  CZ  0  0  o t:  l_  0 O  co  CD  0  O O  03  X  CZ  £ 3 CO 00  O  0  0  0  c:  c  CD  CD  0  0  E o o 0 0 !c? Ic? CO CO 3  c E t-  3 CO CO 3  CZ  E s I-  £  Q£ H  3 DH h-  1  CQ  CQ  0  CO  c  3 DC r-  Q. CQ  CL  CL  cz c: CD 0  CD  0  E o Eo 0 0 Ic? Ic?  CO  3  CO  Fig. 1  Bland-Altman Display of Systolic Measurements, All Cuffs, 417 measurements M e a n D i f f e r e n c e :0 . 4 7 m m H g S D o f D i f f e r e n c e s :5 . 4 0 m m H g  30 C  « a? 20 S X ^ E 10 £ E ° D) <1> >  0  =2  -10  £  4  j^ i i H i 4  ^  a  *w.y  •  •  •  * •  +2SD  •  • — * • * — *  -is  z —  .—-  Mean -2SD  O -20 -30 50  75  100  125  150  175  200  225  Mean of BPM and Obs Avg (mmHg)  Bland A l t m a n display of all systolic blood p r e s s u r e m e a s u r e m e n t s (n = 4 1 7 ) . BPM, B p T R U ™ (model BPM-100) monitor; Obs A v g , observer average (reference standard)  77  Fig. 2  Bland Altman Display of Diastolic Measurements, All Cuffs, 417 measurements Mean Difference: -2.12 mmHg SD of Differences: 5.93 mmHg  tf)  O  A  3 0  TJ C  2 0  « o5 2 x  1 04 *  0  ° u> 0)  >  J2 < a  - 1 0  *  5  *  • 1  :  —  - 2 0 - 3 0 3 0  4 5  6  0  7  5  9  0  1 0 5  Mean of BPM and Obs A v g (mmHg)  Bland A l t m a n display of all diastolic blood p r e s s u r e m e a s u r e m e n t s ( n = 4 1 7 ) . B P M , B p T R U ™ ( m o d e l B P M - 1 0 0 ) monitor; O b s A v g , o b s e r v e r a v e r a g e ( r e f e r e n c e s t a n d a r d )  78  References 1.  O h k u b o T, Imai Y, T s u j i I, N a g a i K, K a t o J , K i k u c h i N, N i s h i y a m a A , A i h a r a A, S e k h i n o M, K i k u y a M, Ito S, S a t o h H, H i s a m i c h i S. H o m e b l o o d p r e s s u r e m e a s u r e m e n t h a s a s t r o n g e r p r e d i c t i v e p o w e r f o r mortality t h a n d o e s s c r e e n i n g b l o o d p r e s s u r e : a p o p u l a t i o n - b a s e d o b s e r v a t i o n in O h a t a m a , J a p a n . J o u r n a l of H y p e r t e n s i o n 1 9 9 8 ; 16: 9 7 1 - 9 7 5 .  2.  N a t i o n a l C e n t r e f o r H e a l t h Statistics.  A d v a n c e report of final mortality statistics, 1 9 8 6 .  Monthly  vital statistics report. [ S u p p l ] , vol 3 7 , no 6. Hyattsville, M d . : Public H e a l t h S e r v i c e , 1 9 8 8 . ( P u b l i c a t i o n no D H S S ( P H S ) 88-1120). 3.  J o f f r e s M R , H a r n e t P, M a c l e a n D R , L'italien G J , F o d o r G . Distribution of B l o o d P r e s s u r e a n d H y p e r t e n s i o n in C a n a d a a n d t h e U n i t e d S t a t e s . A m e r i c a n J o u r n a l of H y p e r t e n s i o n 2 0 0 1 ; 14: 1 0 9 9 - 1 1 0 5 .  4.  G e r i n W , M a r i o n R M , F r i e d m a n R, J a m e s G D , B o v b j e r g D H , P i c k e r i n g T G . H o w s h o u l d w e m e a s u r e blood p r e s s u r e in t h e d o c t o r ' s o f f i c e ? B l o o d P r e s s u r e M o n i t o r i n g 2 0 0 1 ; 6: 2 5 7 - 2 6 2 .  5.  P i c k e r i n g T G , J a m e s G D , B o d d i e C, H a r s h f i e l d G A , B l a n k S, L a r a g h J H . H o w c o m m o n is w h i t e c o a t h y p e r t e n s i o n ? T h e J o u r n a l of t h e A m e r i c a n M e d i c a l A s s o c i a t i o n 1 9 8 8 ; 2 5 9 : 2 2 5 - 2 2 8 .  6.  M a r k a n d u N D , W h i t c h e r F, A r n o l d A, C a r n e y C . T h e m e r c u r y s p h y g m o m a n o m e t e r s h o u l d be a b a n d o n e d b e f o r e it is p r o s c r i b e d . J o u r n a l H u m a n H y p e r t e n s i o n 2 0 0 0 ; 14: 3 1 - 3 6 .  7.  O ' B r i e n E. Replacing the mercury sphygmomanometer. British M e d i c a l J o u r n a l 2 0 0 0 ; 3 2 0 : 8 1 5 - 8 1 6 .  8.  Little P, B a r n e t t J , B a r n s l e y L, M a r j o r a m J , F i t z g e r a l d - B a r r o n A, M a n t D. C o m p a r i s o n of a g r e e m e n t b e t w e e n different m e a s u r e s of b l o o d p r e s s u r e in p r i m a r y c a r e a n d daytime ambulatory blood pressure. British M e d i c a l J o u r n a l 2 0 0 2 ; 3 2 5 : 2 5 4 .  9.  M a t t u G S , P e r r y T L Jr, W r i g h t J M . C o m p a r i s o n of t h e o s c i l l o m e t r i c b l o o d p r e s s u r e m o n i t o r ( B P M - 1 0 0 t a ) with t h e mercury sphygmomanometer. B l o o d P r e s s u r e M o n i t o r i n g 2 0 0 1 ; 6: 1 5 3 - 1 5 9 . B e  auscultatory  10. W r i g h t J M , M a t t u G S , P e r r y T L Jr, G e l f e r M, S t r a n g e K D , Z o r n A , C h e n Y . V a l i d a t i o n of a n e w a l g o r i t h m f o r t h e B P M - 1 0 0 e l e c t r o n i c o s c i l l o m e t r i c office blood  pressure  monitor. B l o o d P r e s s u r e M o n i t o r i n g 2 0 0 1 ; 6: 1 6 1 - 1 6 5 . 11. Mattu GS, Heran BS, Wright J M . C o m p a r i s o n of t h e a u t o m a t e d n o n - i n v a s i v e o s c i l l o m e t r i c b l o o d p r e s s u r e m o n i t o r ( B p T R U ™ ) with t h e a u s c u l t a t o r y m e r c u r y s p h y g m o m a n o m e t e r in t h e paediatric p o p u l a t i o n . Ready for submission 2003. 12. A m e r i c a n N a t i o n a l S t a n d a r d for Electronic or A u t o m a t e d S p h y g m o m a n o m e t e r s . A N S I / A A M I SP10-1992. Arlington, VA: A A M I , 1993. 13. O ' B r i e n E, Petrie J , Littler W , d e Swiet M , Padfield PI, A l t m a n D G , et a l . T h e British H y p e r t e n s i o n S o c i e t y protocol f o r t h e e v a l u a t i o n of b l o o d p r e s s u r e m e a s u r i n g d e v i c e s . J o u r n a l of H y p e r t e n s i o n 1 9 9 3 ; 11 ( s u p p l 2 ) : S 4 3 - S 6 2 .  79  14. Bland J M , A l t m a n D G . Statistical m e t h o d s for a s s e s s i n g a g r e e m e n t b e t w e e n t w o m e t h o d s of clinical m e a s u r e m e n t . Lancet 1986; 1:307-310. 15. C a m p b e l l N R C , M c K a y D W . A c c u r a t e blood p r e s s u r e m e a s u r e m e n t : W h y d o e s it m a t t e r ? C a n a d i a n M e d i c a l A s s o c i a t i o n J o u r n a l 1999; 1 6 1 : 2 7 7 - 2 7 8 . 16. M c A l i s t e r FA, S t r a u s S E . M e a s u r e m e n t of blood p r e s s u r e : a n e v i d e n c e b a s e d review. British M e d i c a l J o u r n a l 2 0 0 1 ; 3 2 2 : 9 0 8 - 9 1 1 . 17. A b b o t t D, C a m p b e l l N R C , C a r r u t h e r s - C z y z e w s k i P. G u i d e l i n e s for m e a s u r e m e n t of blood p r e s s u r e , f o l l o w - u p a n d lifestyle c o u n s e l l i n g . Canadian Journal of Public Health 1994; 8 5 : s29-s43. 18. B e e v e r s G, Lip G Y H , O ' B r i e n E. Blood p r e s s u r e m e a s u r e m e n t : Part 1 - S p h y g m o m a n o m e t r y : f a c t o r s c o m m o n to all t e c h n i q u e s . British m e d i c a l J o u r n a l 2 0 0 1 ; 3 2 2 : 9 8 1 - 9 8 5 . 19. O ' B r i e n E. State of t h e m a r k e t in 2 0 0 1 for blood p r e s s u r e m e a s u r i n g d e v i c e s . B l o o d P r e s s u r e M o n i t o r i n g 2 0 0 1 ; 6: 1 7 1 - 1 7 6 . f  2 0 . O ' B r i e n E, P i c k e r i n g T, A s m a r R, M y e r s M, Parati G, S t a e s s e n J , M e n g d e n T, Y u t a k a I, W a e b e r B, Palatini P, a n d w i t h statistical a s s i s t a n c e of A t k i n s N, G e r i n W . W o r k i n g G r o u p o n Blood P r e s s u r e M o n i t o r i n g of the E u r o p e a n S o c i e t y of H y p e r t e n s i o n International Protocol for validation of blood p r e s s u r e m e a s u r i n g d e v i c e s in a d u l t s . B l o o d P r e s s u r e M o n i t o r i n g 2 0 0 2 ; 7: 3-17.  80  CHAPTER VI  OVERALL DISCUSSION  In N o r t h A m e r i c a t h e m o s t c o m m o n r e a s o n for patients to visit their p h y s i c i a n ' s o f f i c e s is h y p e r t e n s i o n , a n d o n e of t h e c o m m o n e s t d i a g n o s t i c p r o c e d u r e s to be p e r f o r m e d is t h e m e a s u r e m e n t of blood p r e s s u r e T h e s c r e e n i n g , d i a g n o s i s a n d o n g o i n g m a n a g e m e n t of h y p e r t e n s i o n d e p e n d e x t e n s i v e l y o n an  [14].  a c c u r a t e a n d s t a n d a r d i s e d m e t h o d of blood p r e s s u r e m e a s u r e m e n t . e x a m p l e s of t h e potential difficulties with i n a c c u r a t e r e a d i n g s .  In t h e literature t h e r e are n u m e r o u s  T h e c o n s e q u e n c e s of i n a c c u r a c y h a v e  b e e n e s t i m a t e d : the c o n s i s t e n t o v e r e s t i m a t i o n of diastolic blood p r e s s u r e by 5 m m H g w o u l d i n c r e a s e the d i a g n o s i s of h y p e r t e n s i o n in a physicians practice by 100% blood p r e s s u r e by 5 m m Hg w o u l d r e d u c e by 62%  a n d c o n v e r s e l y u n d e r e s t i m a t i n g the diastolic  t h e n u m b e r of patients d i a g n o s e d to be h y p e r t e n s i v e .  In o t h e r w o r d s t h e potential for large n u m b e r s of f a l s e positive a n d f a l s e n e g a t i v e blood  pressure  m e a s u r e m e n t s is significant, with possible a d v e r s e c o n s e q u e n c e s for t h e patient [15].  T h e c o m p l e t i o n of t h e s e t w o trials h a s d e m o n s t r a t e d t h e difficulty in enrolling t h e n u m b e r of s u b j e c t s required a n d h a v i n g t h e m m e e t the required p a r a m e t e r s s u c h a s b l o o d p r e s s u r e r a n g e , a r m size a n d a g e r a n g e . H o w e v e r , after c o m p l e t i n g t h e s e r e q u i r e m e n t s a n d o b t a i n i n g t h e results s e e n here, it is possible to gain a fair a m o u n t of c o n f i d e n c e in the a c c u r a c y a n d reproducibility of t h e d e v i c e u n d e r q u e s t i o n .  This  c o n f i d e n c e t a k e s c o g n i z a n c e of the p r o b l e m s a s s o c i a t e d w i t h t h e g o l d s t a n d a r d , t h e a u s c u l t a t o r y m e r c u r y sphygmomanometer. these  trials.  If  T h i s is partly reflected in the s o m e w h a t s u r p r i s i n g i n t e r - o b s e r v e r variability s e e n in  trained  research  nurses  under  research  standards  measuring  blood  s i m u l t a n e o u s l y get variable results, o n e c a n i m a g i n e the m u c h larger variability of blood  pressure pressures  m e a s u r e d in a b u s y p r i m a r y c a r e office. T h e variability in that usual setting is p r o b a b l y s o large that m o s t d i a g n o s t i c a n d t r e a t m e n t d e c i s i o n s c a n n o t be m a d e with a n y d e g r e e of c o n f i d e n c e .  S o m e e x a m p l e s of t h e m a n y different c i r c u m s t a n c e s that c a n affect blood p r e s s u r e a r e : •  talking c a n i n c r e a s e the systolic blood p r e s s u r e by up to 17 m m H g  •  h a v i n g patients a r m 10 c m b e l o w the heart level c a n i n c r e a s e t h e blood p r e s s u r e by 8 m m H g  •  m e a s u r i n g blood p r e s s u r e with a cuff that is too s m a l l c a n i n c r e a s e t h e systolic blood p r e s s u r e by up to 8 m m H g .  All potential e r r o r s h a v e to be r e c o g n i s e d a n d s t e p s put into p l a c e to a v o i d t h e s e e r r o r s [16].  An  a u t o m a t e d blood p r e s s u r e m e a s u r i n g d e v i c e c a n be a n i m p o r t a n t s t e p t o w a r d s a v o i d i n g s o m e of t h e s e errors.  82  M o d e r n b l o o d p r e s s u r e - m e a s u r i n g d e v i c e s h a v e to be a c c u r a t e , r e p r o d u c i b l e , a n d e a s y to o p e r a t e , convenient, time saving and affordable.  M a n y a v a i l a b l e d e v i c e s h o w e v e r , d o not h a v e t h e m o s t b a s i c of  m e r i t s s u c h a s a c c u r a c y a n d reproducibility d e m o n s t r a t e d in a p u b l i s h e d r e p o r t .  D e v i c e s that h a v e  p u b l i s h e d v a l i d a t i o n d a t a , a n d fulfill s o m e of t h e o t h e r criteria s p e c i f i e d h a v e significant a d v a n t a g e over t h o s e that d o not [17].  T h e B p T R U ™ is a n electronic a u t o m a t e d blood p r e s s u r e d e v i c e that h a s b e e n s h o w n to be of similar a c c u r a c y a n d reproducibility to t h e c u r r e n t gold s t a n d a r d of a u s c u l t a t o r y m e r c u r y s p h y g m o m a n o m e t r y in a w i d e r a n g e of p a t i e n t s .  In t h e original s t u d y in a d u l t s it w a s s e e n that t h e earlier v e r s i o n of t h e d e v i c e t h e  B P M - 1 0 0 t a w a s s h o w n to u n d e r e s t i m a t e systolic b l o o d p r e s s u r e s o v e r 1 5 0 m m H g . Be  This only b e c a m e  e v i d e n t w h e n t h e d a t a w a s plotted o n a B l a n d - A l t m a n plot. T h i s v e r s i o n of t h e d e v i c e m e t t h e s t a n d a r d s of b o t h r e g u l a t o r y b o d i e s a n d c o u l d h a v e b e e n m a r k e t e d as s u c h .  However, both the investigators and  t h e m a n u f a c t u r e r s f o u n d this limitation u n a c c e p t a b l e . A s a result a r a n d o m s a m p l e of t h e d a t a w a s u s e d to c r e a t e a m o d i f i e d a l g o r i t h m , w h i c h c o r r e c t e d t h e p r o b l e m .  T h e rest of t h e d a t a w a s t h e n available to  test t h e m o d i f i e d a l g o r i t h m a n d it w a s c l e a r u s i n g t h e B l a n d - A l t m a n plot t h a t it h a d c o r r e c t e d t h e p r o b l e m . T h e m e t h o d s d e s c r i b e d c o u l d set a p r e c e d e n t allowing m a n u f a c t u r e r s to r e - v a l i d a t e altered a l g o r i t h m s u s i n g d a t a a l r e a d y c o l l e c t e d by their e m b e d d e d s o f t w a r e . T h i s c o u l d s a v e t i m e a n d r e s o u r c e s a n d allow testing of m o r e d e v i c e s especially t h o s e that h a v e m o d i f i e d a l g o r i t h m s .  I believe t h e p r e s e n t s t a n d a r d s f o r validation of b l o o d p r e s s u r e m e a s u r i n g d e v i c e s a r e not sufficiently stringent a n d s h o u l d be r e v i s e d in t h e f o l l o w i n g w a y s .  •  T h e r e g u l a t i o n s s h o u l d r e q u i r e validation u s i n g s i m u l t a n e o u s m e a s u r e m e n t s a s w a s d o n e in o u r p r o t o c o l . T h e n e w International protocol a n d p r e v i o u s s t a n d a r d s a l l o w or r e c o m m e n d t h e u s e of s e q u e n t i a l b l o o d p r e s s u r e m e a s u r e m e n t s rather t h a n s i m u l t a n e o u s m e a s u r e m e n t s .  T h e sequential  m e a s u r e m e n t s a r e r e c o r d e d at least 30 s e c o n d s apart, but not m o r e t h a n 6 0 s e c o n d s apart. T h i s h a s t h e significant d i s a d v a n t a g e of a d d i n g t h e variability of blood p r e s s u r e o v e r t i m e a n d d o e s not allow e n o u g h t i m e b e t w e e n m e a s u r e m e n t s f o r resolution of v e n o u s c o n g e s t i o n , w h i c h c a n also affect t h e measurement.  83  •  T h e d e v i c e blood p r e s s u r e is c o m p a r e d to p r e s s u r e s m e a s u r e d by r e f e r e n c e s t a n d a r d o b s e r v e r s both b e f o r e a n d after. T h e d i f f e r e n c e b e t w e e n t h e o b s e r v e r a n d t h e d e v i c e is d e t e r m i n e d a n d t h e smaller of t h e t w o v a l u e s u s e d . T h i s invariably c r e a t e s a bias to m a k e t h e d e v i c e look m o r e a c c u r a t e t h a n it is [18].  •  T h e r e g u l a t i o n s s h o u l d a l s o require that a d e v i c e m e e t s b o t h t h e A A M I s t a n d a r d a n d t h e  BHS  s t a n d a r d . T h e A A M I s t a n d a r d a p p e a r s to be the m o r e r o b u s t of t h e t w o , h o w e v e r the r e q u i r e m e n t for a s t a n d a r d d e v i a t i o n of the d i f f e r e n c e of a s m u c h a s 8 m m H g is relatively lenient.  •  T h e r e q u i r e m e n t for a Bland A l t m a n plot is essential a s d e m o n s t r a t e d by t h e first trial. A d e v i c e could u n d e r e s t i m a t e blood p r e s s u r e for high v a l u e s a n d o v e r e s t i m a t e for low v a l u e s a n d p a s s t h e s t a n d a r d in t e r m s of a m e a n d i f f e r e n c e f r o m t h e m e r c u r y m e a s u r e m e n t s .  S t a n d a r d s n e e d to b e e s t a b l i s h e d a s  to w h a t d e v i a t i o n s s e e n o n t h e Bland A l t m a n plot w o u l d be a c c e p t a b l e .  [ 2 0 ] . It w a s clearly s e e n in  the first adult p a p e r that the m a c h i n e w a s u n d e r - e s t i m a t i n g higher systolic blood p r e s s u r e s w h i c h w a s rectified in t h e revalidation p a p e r w i t h the m o d i f i e d a l g o r i t h m .  In addition t h e n e w International protocol i n t r o d u c e s additional p r o b l e m s .  It r e q u i r e s that if the inter-  o b s e r v e r d i f f e r e n c e f o r systolic or diastolic p r e s s u r e s is not within 4 m m H g a g r e e m e n t it m u s t repeated.  T h i s l e a d s to lesser inter-observer variability a n d c o u l d lead to b i a s .  be  If a S p h y g m o c o r d e r is  u s e d to r e c o r d the s o u n d s a n d t h e o b s e r v e r s d o not a g r e e , t h e y a r e r e q u i r e d to r e - a s s e s s until a g r e e m e n t is r e a c h e d .  A g a i n this a p p e a r s to i n t r o d u c e s o m e bias.  S i n c e the B p T R U ™ h a s m e t t h e m o r e stringent r e q u i r e m e n t s set out by t h e A m e r i c a n National S t a n d a r d for  Electronic  or A u t o m a t e d  Sphygmomanometers  and the  British  Hypertension  Society,  it c a n  be  a s s u m e d that it w o u l d a l s o m e e t the m o r e r e c e n t a n d less r i g o r o u s International Protocol f o r validation of blood p r e s s u r e m e a s u r i n g d e v i c e s  in adults as set out by t h e W o r k i n g  M o n i t o r i n g of the E u r o p e a n S o c i e t y of H y p e r t e n s i o n [18].  G r o u p o n Blood  O n e of the a i m s of this International protocol  w a s to e n c o u r a g e m o r e d e v i c e m a n u f a c t u r e r s to u n d e r g o validation b e f o r e m a r k e t i n g .  I  84  Pressure  If clinical d e c i s i o n s a r e g o i n g to m a d e b a s e d o n t h e best available e v i d e n c e t h e n blood p r e s s u r e s n e e d to be m e a s u r e d in a m a n n e r that is similar to that w h i c h w a s u s e d in t h e trials.  It is clear that single blood  p r e s s u r e s m e a s u r e d by a physician in the office r e p r e s e n t a significant o v e r e s t i m a t e of the resting blood p r e s s u r e m e a s u r e m e n t s by a n u r s e in a clinical trial.  A n y n e w blood p r e s s u r e m e a s u r i n g m e t h o d o l o g y  m u s t b e s h o w n to b e a better e s t i m a t e of t h e r e s e a r c h s t a n d a r d t h a n c a s u a l office m e a s u r e m e n t s by a physician.  M y r e c o m m e n d a t i o n to the m a n u f a c t u r e r is that t h e y f u n d a trial c o m p a r i n g B p T R U ™ with the r e s e a r c h s t a n d a r d a n d c a s u a l office m e a s u r e m e n t s by a p h y s i c i a n .  T h e best d e s i g n for this trial w o u l d be to  a s s e s s 50 patients in a p r i m a r y c a r e clinic s e t t i n g . T h e best d e s i g n w o u l d b e a c r o s s - o v e r d e s i g n w h e r e all m e a s u r e m e n t s a r e t a k e n o n the s a m e day, but t h e o r d e r of m e a s u r e m e n t s is r a n d o m i z e d . In the clinic setting w h e r e in o n e r o o m t h e B p T R U ™ m a c h i n e is set u p , t h e patient f o l l o w s t h e s t a n d a r d routine of resting for 5 m i n u t e s ; t h e first p r e s s u r e is t a k e n w i t h t h e investigator in t h e r o o m a n d is d i s c a r d e d , the blood p r e s s u r e r e c o r d e d is the m e a n of t h e r e m a i n i n g 5 m e a s u r e m e n t s w i t h n o b o d y in the r o o m .  The  r e s e a r c h s t a n d a r d w o u l d b e resting 5 m i n u t e s f o l l o w e d by 3 m e a s u r e m e n t s t a k e n by a n u r s e in the correct standardised way. her b u s y practice d a y .  T h e third w o u l d be o n e or t w o m e a s u r e m e n t s by a p h y s i c i a n a s part of his or  T h e c h a l l e n g e in the trial w o u l d be to not allow t h e r e s e a r c h d e s i g n to affect h o w  the p r e s s u r e s a r e t a k e n by t h e p h y s i c i a n .  T h e trial s h o u l d a n s w e r t h e q u e s t i o n a s to w h e t h e r physician  m e a s u r e m e n t s or B p T R U ™ m e a s u r e m e n t s m o s t closely m i m i c s b l o o d p r e s s u r e s a s t a k e n in the clinical trial setting (ie: t h o s e m e a s u r e m e n t s r e c o r d e d by the n u r s e r e a d i n g w i t h r e s e a r c h s t a n d a r d s ) .  With  the  wave  of  newer  devices  coming  to  the  market  and  the  end  of  an  era  with  mercury  s p h y g m o m a n o m e t e r s getting closer, w e c a n be c o n f i d e n t that t h e B p T R U ™ is o n e of t h o s e d e v i c e s that h a s attained t h e a c c u r a c y that is required of it by t h e c u r r e n t g o v e r n i n g b o d i e s o n blood measuring instruments.  pressure  T h e B p T R U ™ c a n be u s e d w i t h c o n f i d e n c e a n d u n d e r s t a n d i n g that patients in  the physician's office will h a v e a p p r o p r i a t e d e c i s i o n s b a s e d o n a c c u r a t e , r e p r o d u c i b l e a n d c o m p l e t e l y o b j e c t i v e blood p r e s s u r e m e a s u r e m e n t s . with  'white  coat  hypertension'  and  It c a n t h u s not only r e d u c e i n a p p r o p r i a t e p r e s c r i b i n g to t h o s e  consequently  reduce  iatrogenic  disease  elements,  but  also  a p p r o p r i a t e l y identify that 3 0 % of t h e population u n a w a r e of their h y p e r t e n s i o n a n d c o n s e q u e n t l y monitor  85  their blood p r e s s u r e to help avoid or r e d u c e t h e h u g e n u m b e r of d e a t h s directly related to  being  u n c o n t r o l l e d [19].  H e n c e f o r t h w h e n t h e B p T R U ™ w a s t e s t e d in c h i l d r e n ( a g e d 3 to 18 y e a r s w i t h a m e a n of 9.4 y e a r s ) it also m e t t h e r e q u i r e m e n t s of t h e A N S I / A A M I S P 1 0 - 1 9 9 2 a n d a c h i e v e d a ' B ' g r a d e a c c o r d i n g to a modified BHS protocol.  It is o n e of the f e w d e v i c e s to h a v e b e e n v a l i d a t e d in c h i l d r e n a n d to h a v e  a c h i e v e d significant levels of a c c u r a c y .  W h e n t h e r a w paediatric d a t a w a s c o m b i n e d w i t h the r a w adult  d a t a , t h e B p T R U ™ m e t t h e A N S I / A A M I S P 1 0 - 1 9 9 2 criteria a n d a c h i e v e d a n overall g r a d e 'A' f r o m the British H y p e r t e n s i o n S o c i e t y p r o t o c o l .  86  CHAPTER VII  CONCLUSIONS  f  87  Regarding the B p T R U ™ :  •  T h e B p T R U ™ , a n electronic n o n - i n v a s i v e a u t o m a t e d o s c i l l o m e t r i c b l o o d p r e s s u r e d e v i c e h a s b e e n s h o w n to be a s a c c u r a t e as the c u r r e n t gold s t a n d a r d of a u s c u l t a t o r y m e r c u r y s p h y g m o m a n o m e t r y .  •  W h e n t e s t e d in adults ( a g e s 18 to elderly - oldest included s u b j e c t w a s 8 3 y e a r s o l d , m e a n a g e of 4 3 . 1 y e a r s ) it m e t all r e q u i r e m e n t s of the A s s o c i a t i o n for the A d v a n c e m e n t of M e d i c a l I n s t r u m e n t a t i o n a n d a c h i e v e d a n "A" g r a d e a c c o r d i n g to t h e British H y p e r t e n s i o n S o c i e t y s t a n d a r d .  •  W h e n t e s t e d in c h i l d r e n ( a g e d 3 to 18 y e a r s with a m e a n 9.4 y e a r s ) it a l s o m e t t h e r e q u i r e m e n t s of t h e A N S I / A A M I S P 1 0 - 1 9 9 2 a n d a c h i e v e d a ' B ' g r a d e a c c o r d i n g to a m o d i f i e d B H S p r o t o c o l .  •  W h e n t h e r a w d a t a f r o m both p o p u l a t i o n g r o u p s w a s c o m b i n e d to d e t e r m i n e t h e overall a c c u r a c y of this blood p r e s s u r e d e v i c e o v e r a n a g e r a n g e of 3 y e a r s to 8 3 y e a r s ( m e a n a g e 33.1 y e a r s ) it satisfied the  criteria  set  out  by  the  American  National  Standard  for  Electronic  or  Automated  Sphygmomanometers, ANSI / AAMI SP10-1992.  •  Overall it h a s also a c h i e v e d a g r a d e 'A' a c c o r d i n g to the British H y p e r t e n s i o n S o c i e t y protocol for the e v a l u a t i o n of blood p r e s s u r e m e a s u r i n g d e v i c e s - 1 9 9 3 .  •  T h e B p T R U ™ is t h e only a u t o m a t e d blood p r e s s u r e m e a s u r i n g d e v i c e that h a s b e e n validated a n d h a s attained this high level of a c c u r a c y o v e r this b r o a d a g e r a n g e .  88  R e g a r d i n g t h e validation p r o c e s s , m y opinion is s u c h that:  •  All blood p r e s s u r e d e v i c e s irrespective of the target a u d i e n c e ( h o m e or office u s e ) s h o u l d u n d e r g o validation.  •  D e v i c e m a n u f a c t u r e r s s h o u l d be m o r e t r a n s p a r e n t a b o u t their a l g o r i t h m s .  •  T h e m e t h o d s a n d r e q u i r e m e n t s for calibration s h o u l d be clearly s t a t e d .  •  In o r d e r to validate a n a u t o m a t e d blood p r e s s u r e m e a s u r i n g d e v i c e , s i m u l t a n e o u s  measurements  f r o m the s a m e a r m s h o u l d be directly c o m p a r e d to the r e f e r e n c e s t a n d a r d .  •  T h e m e a n of t w o o b s e r v e r ' s m e a s u r e m e n t s s h o u l d be r e g a r d e d a s t h e g o l d or r e f e r e n c e s t a n d a r d .  •  D e v i c e s s h o u l d be m a d e to clearly d e m o n s t r a t e the a c c u r a c y a c r o s s a full r a n g e of blood p r e s s u r e s a n d cuff sizes u s i n g t h e Bland A l t m a n plot.  •  All d e v i c e s s h o u l d m e e t t h e r e q u i r e m e n t s set forth by both t h e A N S I / A A M I S P 1 0 - 1 9 9 2 a n d the British H y p e r t e n s i o n S o c i e t y p r o t o c o l .  •  N e w e r validation g u i d e l i n e s , s u c h a s the International P r o t o c o l that a p p e a r to e n c o u r a g e m a n u f a c t u r e r s to u n d e r t a k e the validation p r o c e s s , but h a v e less rigid criteria a r e u n a c c e p t a b l e .  89  device  REFERENCES 1.  W r i g h t J M , L e e C, C h a m b e r s G K . S y s t e m a t i c r e v i e w of a n t i h y p e r t e n s i v e t h e r a p i e s : D o e s t h e e v i d e n c e a s s i s t in c h o o s i n g a first-line drug? Canadian Medical Association Journal 1999; 1 6 1 : 25-32.  2.  Hajjar I, K o t c h e n T A . T r e n d s in p r e v a l e n c e . A w a r e n e s s , t r e a t m e n t , a n d c o n t r o l of h y p e r t e n s i o n in t h e U n i t e d S t a t e s , 1988-2000. T h e J o u r n a l of t h e A m e r i c a n M e d i c a l A s s o c i a t i o n 2 0 0 3 ; 2 9 0 : 1 9 9 - 2 0 6 .  3.  M a r k a n d u N D , W h i t c h e r F, A r n o l d A, C a r n e y C. T h e m e r c u r y s p h y g m o m a n o m e t e r s h o u l d b e a b a n d o n e d b e f o r e it is p r o s c r i b e d . J o u r n a l H u m a n H y p e r t e n s i o n 2 0 0 0 ; 14: 3 1 - 3 6 .  4.  O ' B r i e n E. Replacing the mercury sphygmomanometer. British M e d i c a l J o u r n a l 2 0 0 0 ; 3 2 0 : 8 1 5 - 8 1 6 .  5.  O ' B r i e n E. D e m i s e of t h e m e r c u r y s p h y g m o m a n o m e t e r a n d t h e d a w n i n g of a n e w e r a in b l o o d p r e s s u r e measurement. B l o o d p r e s s u r e m o n i t o r i n g 2 0 0 3 ; 8: 1 9 - 2 1 .  6.  Little P, B a r n e t t J , B a r n s l e y L, M a r j o r a m J , F i t z g e r a l d - B a r r o n A, M a n t D. C o m p a r i s o n of a g r e e m e n t b e t w e e n different m e a s u r e s of b l o o d p r e s s u r e in p r i m a r y c a r e a n d daytime ambulatory blood pressure. » British M e d i c a l J o u r n a l 2 0 0 2 ; 3 2 5 : 2 5 4 . f  7.  A m e r i c a n N a t i o n a l S t a n d a r d f o r Electronic or A u t o m a t e d S p h y g m o m a n o m e t e r s . A N S I / A A M I SP10-1992. Arlington, VA: A A M I , 1993.  8.  O ' B r i e n E, Petrie J , Littler W , d e S w i e t M, Padfield PI, A l t m a n D G , et a l . T h e British H y p e r t e n s i o n S o c i e t y protocol f o r t h e e v a l u a t i o n of b l o o d p r e s s u r e m e a s u r i n g d e v i c e s . J o u r n a l of H y p e r t e n s i o n 1 9 9 3 ; 11 (suppl 2 ) : S 4 3 - S 6 2 .  9.  T h e Sixth R e p o r t o n t h e Joint National C o m m i t t e e o n P r e v e n t i o n , D e t e c t i o n , E v a l u a t i o n , a n d T r e a t m e n t of H i g h B l o o d P r e s s u r e . NIH Publication No. 98-4080, N o v e m b e r 1997.  10. M a t t u G S , P e r r y T L Jr, W r i g h t J M . C o m p a r i s o n of t h e o s c i l l o m e t r i c blood p r e s s u r e m o n i t o r ( B P M - 1 0 0 t a ) w i t h t h e mercury sphygmomanometer. B l o o d P r e s s u r e M o n i t o r i n g 2 0 0 1 ; 6: 1 5 3 - 1 5 9 . B e  auscultatory  1 1 . W r i g h t J M , M a t t u G S , P e r r y T L Jr, G e l f e r M, S t r a n g e K D , Z o r n A, C h e n Y. V a l i d a t i o n of a n e w a l g o r i t h m f o r t h e B P M - 1 0 0 e l e c t r o n i c o s c i l l o m e t r i c office blood monitor. B l o o d P r e s s u r e M o n i t o r i n g 2 0 0 1 ; 6: 1 6 1 - 1 6 5 .  pressure  12. M a t t u G S , H e r a n B S , W r i g h t J M . C o m p a r i s o n of t h e a u t o m a t e d n o n - i n v a s i v e o s c i l l o m e t r i c b l o o d p r e s s u r e m o n i t o r ( B p T R U ™ ) with t h e a u s c u l t a t o r y m e r c u r y s p h y g m o m a n o m e t e r in t h e p a e d i a t r i c p o p u l a t i o n Ready for submission 2003. 13. M a t t u G S , H e r a n B S , W r i g h t J M . A c c u r a c y of t h e B p T R U ™ , a n a u t o m a t e d electronic b l o o d p r e s s u r e d e v i c e . Ready for submission 2003.  90  14. W o o d w e l l D A . National a m b u l a t o r y m e d i c a l c a r e survey: 1995 s u m m a r y . A d v a n c e D a t a 1 9 9 7 ; 2 9 5 : 1-25. 15. C a m p b e l l N R C , M c K a y D W . A c c u r a t e blood p r e s s u r e m e a s u r e m e n t : W h y d o e s it m a t t e r ? Canadian Medical Association Journal 1999; 1 6 1 : 277-278. 16. M c A l i s t e r FA, S t r a u s S E . M e a s u r e m e n t of blood p r e s s u r e : a n e v i d e n c e b a s e d review. British M e d i c a l J o u r n a l 2 0 0 1 ; 3 2 2 : 9 0 8 - 9 1 1 . 17. O ' B r i e n E. S t a t e of t h e m a r k e t in 2 0 0 1 for blood p r e s s u r e m e a s u r i n g d e v i c e s . Blood P r e s s u r e M o n i t o r i n g 2 0 0 1 ; 6: 1 7 1 - 1 7 6 . 18. O ' B r i e n E, P i c k e r i n g T, A s m a r R, M y e r s M, Parati G, S t a e s s e n J , M e n g d e n T, Y u t a k a I, W a e b e r B, Palatini P, a n d w i t h statistical a s s i s t a n c e of A t k i n s N, G e r i n W . W o r k i n g G r o u p o n Blood P r e s s u r e M o n i t o r i n g of t h e E u r o p e a n S o c i e t y of H y p e r t e n s i o n International Protocol for validation of blood p r e s s u r e m e a s u r i n g d e v i c e s in a d u l t s . B l o o d P r e s s u r e M o n i t o r i n g 2 0 0 2 ; 7: 3-17. 19. J o f f r e s M R , H a m e t P, M a c L e a n D R , L'italien G J , F o d o r G. Distribution of blood p r e s s u r e a n d h y p e r t e n s i o n in C a n a d a a n d t h e U n i t e d S t a t e s . A m e r i c a n J o u r n a l of H y p e r t e n s i o n 2 0 0 1 ; 14: 1 0 9 9 - 1 1 0 5 . 2 0 . Bland J M , A l t m a n D G . Statistical m e t h o d s for a s s e s s i n g a g r e e m e n t b e t w e e n t w o m e t h o d s of clinical m e a s u r e m e n t . Lancet 1986; 1: 307-310.  91  

Cite

Citation Scheme:

    

Usage Statistics

Country Views Downloads
United States 10 0
China 2 3
Hong Kong 1 0
Bangladesh 1 0
City Views Downloads
Ashburn 4 0
Mountain View 4 0
Beijing 2 2
Redmond 1 0
Dhaka 1 0
Central District 1 0
Sunnyvale 1 0

{[{ mDataHeader[type] }]} {[{ month[type] }]} {[{ tData[type] }]}
Download Stats

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0091081/manifest

Comment

Related Items