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The effect of body position on lung functiion in older healthy individuals Manning, Fiona


The purpose of this study was to investigate the interrelationships between postural change and indices of lung function in healthy older individuals. Nineteen nonsmoking subjects (mean age 62.8 ± 6.8 years) with no known history of pulmonary disease were tested over two sessions; on one session the test positions were sitting and left side lying and on the other the positions were sitting and right side lying. In each of the three positions, tests of forced expiration [forced vital capacity (FVC), forced expiratory volume in one second (FEVl), and forced expiratory flow during 25 to 75% of the vital capacity (FEF25-75%)], a single-breath test of pulmonary diffusing capacity for carbon monoxide (DLCO), and the single-breath nitrogen test [slope of Phase III (DN2%/L)] were conducted using the SensorMedics 2200 Pulmonary Function Laboratory (SensorMedics, Anaheim, CA). Standards and procedures of the American Thoracic Society and the National Heart and Lung Institute were followed for all tests. On the basis of 95th percent confidence intervals, the individual subject results were generally normal; in the sitting position, results for both spirometry and DLCO were above the lower limit of normal (with the exception of three subjects who fell below this limit for FEF25-75%) and results for DN2%/L were below the upper limit of normal. Repeated measures within subjects were reproducible and were comparable to those in the literature. Specifically, the coefficients of variation for all dependent variables, with the exception of DN2%/L, were less than 10%. With reference to the sitting position, the effects of side lying on the dependent variables were: (i) a decrease in FVC, FEVl, and FEF25-75% in both left and right side lying; (ii) a decrease in FEV1/FVC from sitting to left side lying only; (iii) an increase in DN2%/L from sitting to left side lying only; and (iv) no change in DLCO or DLCO?VA (diffusing capacity corrected for alveolar volume) in left or right side lying. The degree to which age contributes to these position-related phenomena is unknown; however, certain aspects of aging, for example, a decrease in elastic recoil of the lung and an increase in the weight and volume of the heart, are likely to have a significant role. A further contribution to these phenomena is the effect of recumbency, for example, external compression of the chest wall and impingement of the abdominal contents on the diaphragm, on respiratory mechanics. With regard to the interrelationships between dependent variables, there was a positive correlation for FVC versus DLCO, reflecting the volume-dependence of DLCO. The results of this study support the differential effects of body positioning on aspects of lung function which are reflective of oxygen transport. Further investigation of these effects in younger and older individuals and of their underlying mechanisms are required. With a greater understanding of the complexities of position-related phenomena in a variety of age groups and in the presence or absence of cardiopulmonary disease, the effects of body positioning can be exploited therapeutically and potential negative effects can be minimized.

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