Diaphragmatic changes in emphysema.

The diaphragms and lungs of 95 men were quantitatively examined at autopsy, and the following observations were made. The area of the whole diaphragm had a significant inverse correlation (r= -0.412, P less than 0.001) with the percentage of the lung occupied by emphysematous lesions. Most of the reduction in the area of the whole diaphragm associated with advanced emphysema occured in the muscular portion; in contrast, the thickness of the diaphragm was not affected by percentage of the lung occupied by emphysematous lesions. Neither body height nor postmortem lung volume had as close a relation to area of the whole diaphragm as did percentage of the lung occupied by emphysematous lesions. The conclusion drawn from these observations is that the diaphragm area reduction associated with emphysema is related to altered thoracic shape, probably diaphragm flattening in particular, and is better described as contracture than as atrophy. It is speculated that these morphologic changes contribute to the altered diaphragmatic function characteristic of chronic obstructive pulmonary disease, and thereby to the ventilatory abnormalities seen in patients with this disorder.