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Diaphragm injury in people shown post-mortem

University of British Columbia

Exertion induced diaphragm muscle injury has been shown in several animal models, however, substantial evidence in humans is still forthcoming. The purpose of this study was to describe and quantify diaphragm morphology in humans and relate injury to clinical factors including: age, body mass index (BMI), gender, acute respiratory disease, and/or chronic respiratory disease. Biopsies from 59 subjects undergoing autopsy were examined. Full-thickness diaphragm biopsies were obtained from the lateral costal region of the diaphragm and fixed in formalin. Biopsies were paraffin embedded, sectioned at 5 μm and stained with H&E and Masson's trichrome. Diaphragm cross-sections were viewed at 400x using light microscopy and images from multiple fields for each cross-section were captured using a SPOT digital camera and the Image Pro Plus 4 computer program. A 64- point grid was superimposed on each image and the points were assigned to 1) normal; 2) abnormal if the fiber had internal nuclei or abnormal cytoplasm, if it was inflamed, necrotic, degenerated, small or angular; or 3) connective tissue. The area fraction (AA) was determined by summing the points for each category, and dividing it by the total points for the cross-section. Immunohistochemistry was also performed on diaphragm cross-sections using the APAAP method for the monoclonal antibody NP57 against human neutrophil elastase molecule. A retrospective chart review was performed to determine the age, gender, BMI and the presence of acute respiratory disease(s) and/or chronic respiratory diseases(s). Of the 59 subjects, 20 were females and 39 were males. In this group of subjects, two women were undernourished and ten men were obese considering a normal BMI range of 18.5 - 27.3 kg/m² for women and 18.5 - 27.8 kg/m² for men. Mean ages for men and women were 65.5 + 13.7 yrs. and 72.4 + 24.5 yrs. (p < 0.05). Thirty-eight subjects had acute respiratory disease, 33 had chronic respiratory disease, 22 had a combination of acute respiratory disease superimposed on chronic respiratory disease, and 10 had neither acute nor chronic respiratory disease. Analysis by the non-parametric Mann-Whitney U test showed the following differences. Men had more abnormal diaphragm (31.6 + 15.8%) and less normal (51.6 + 21.2%) diaphragm than women (19.3 + 10.7% and 65.3 + 15.5%, respectively) (p< 0.015) (Figure 11, upper panel). Men (65.5 + 13.7 yrs.) were younger than women (72.4 +24.5 yrs.) (P<0.049). Men with acute respiratory disease compared to men without acute respiratory disease had more abnormal diaphragm morphology (35.69 +14.34% vs. 24.61 +16.46%) (PO.021) (Figure 11, upper panel), less normal diaphragm (45.08 +18.26% vs. 63.98 +21.6%) (p<0.006), and more connective tissue (19.23 +11.17% vs. 11.40 +6.73%) (P<0.021). Analysis of the whole group of patients (both M & F) showed trends toward more abnormal diaphragm in those with acute respiratory disease (Figure 13, lower panel) or chronic respiratory disease (Figure 11, lower panel) compared to those without (P<0.067 and P< 0.082, respectively). Patients with acute respiratory disease compared to those without showed a trend toward less normal diaphragm (PO.067) (Figure 13, upper panel). Lastly, men with chronic respiratory disease were older (mean age 69.8 yrs) than men without chronic respiratory disease (mean age 58.7 yrs.) (P<0.048). Neutrophils were quantified in the diaphragm of 38 subjects (22 with chronic respiratory disease and 28 with acute respiratory disease). The mean number of neutrophils per fiber was 0.0044 (0 to 0.06) and the mean number of neutrophils per cross-sectional area was 1.46 (0 to 22.8). We conclude that the diaphragm in humans is susceptible to exertion-induced diaphragm injury represented by abnormal diaphragm morphology and inflammatory cell infiltrates. Men are more susceptible to diaphragm injury. Likewise, individuals with acute respiratory disease and/or chronic respiratory disease tend to have more abnormal diaphragm.

Thesis/Dissertation

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2009-07-09

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http://hdl.handle.net/2429/10576

Experimental Medicine

University of British Columbia

UBCV

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