Injury of the human diaphragm associated with exertion and chronic obstructive pulmonary disease

Injury of the diaphragm may have clinical relevance having been reported in cases of sudden infant death syndrome or fatal asthma. However, examinatio n of diaphragm injury after acute inspiratory loading has not been reported . The purpose of this study was to determine whether an acute inspiratory o verload induces injury of the human diaphragm and to determine if diaphragm from chronic obstructive pulmonary disease (COPD) is more susceptible to i njury. Eighteen patients with COPD and 11 control patients with normal pulm onary function (62 +/- 10 yr) undergoing thoracotomy or laparotomy were stu died. A threshold inspiratory loading test was performed prior to surgery i n a subset of seven patients with COPD and five control patients. Samples o f the costal diaphragm were obtained during surgery and processed for elect ron microscopy analysis. Signs of sarcomere disruption were found in all di aphragm samples. The range of values of sarcomere disruption was Wide (dens ity: 2-45 abnormal areas/100 mum(2), area fractions: 1.3-17.3%), significan tly higher in diaphragm from patients with COPD (p < 0.05) and with the gre atest injury after inspiratory loading. We conclude that sarcomere disrupti on is common in the human diaphragm, is more evident in patients with COPD, and is higher after inspiratory loading, especially in the diaphragm of th ose with COPD.