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Diaphragm injury in people shown post-mortem Clarke, Tyler James

Abstract

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

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