| Summary: | It has been postulated that exertion-induced diaphragm injury occurs due to overload during acute and chronic respiratory diseases. The presence of inflammatory cells in the injured diaphragm has been well documented in animals but not in humans. Purpose: To relate the number of inflammatory cells in the human diaphragm to 1. clinical factors 2. area fraction of abnormal diaphragm (A[sub A]) 3. fiber cross-sectional area (CSA). Methods: Biopsies from 59 postmortem subjects (20 F, 39 M) were examined. Subjects were divided into four groups: acute respiratory disease (ARD), chronic respiratory disease (CRD), ARD+CRD and no respiratory disease. Fullthickness biopsies collected from the lateral costal region of the diaphragm were formalin fixed, paraffin embedded, sectioned at 5 um and stained with H & E . Alkaline phosphatase-anti-alkaline phosphatase (APAAP) staining with antibodies directed to CD68 (macrophages), CD20 (B-cells), CD8 (T-lymphocytes) and neutrophil elastase (NP57 antibody) was done. Images of 20 randomly selected fields/biopsy were captured by a SPOT digital camera and inflammatory cells were counted in captured images. H & E images were point-counted to determine the A[sub A] and the CSA of 200 fibers/biopsy. A retrospective chart review was done to determine the age, gender, BMI and presence/absence of respiratory disease. Data were analyzed using non-parametric statistics. Results: Macrophages (97.5% of total inflammatory cells) and neutrophils (2.4% of total inflammatory cells) were common inflammatory cells found in the diaphragm of postmortem subjects. B-cells were rare (0.1% of total inflammatory cells) and no T-lymphocytes were detected. There was a positive low correlation between BMI and inflammatory cells (r=0.286, p=0.049). The number of the different types of inflammatory cells in the diaphragm did not differ between genders. Age was not correlated to the number of inflammatory cells in the diaphragm. Lastly, neutrophils, macrophages and neutrophils + macrophages were not correlated to A[sub A] . Conclusion: Inflammatory cells are present in the diaphragm of people with or without respiratory disease. Macrophages and neutrophils have a more important role to play in diaphragm injury and repair in people with/without respiratory disease, than T-lymphocytes and B-cells. This study also shows that overweight people have more inflammatory cells in their diaphragm.
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