The Total Work of Breathing in Normal and Obese Men*

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Abstract
Total respiratory mechanics were measured in eight normal subjects, ten obese subjects, and four patients with the obesity-hypoventilation (O.H.) syndrome. Total respiratory compliance was significantly decreased in both obese groups, averaging 0.081 [plus or minus] 0.007 in obese normal subjects and 0.045 [plus or minus] 0.003 in the O.H. patients as compared to 0.104 [plus or minus] 0.003 in the O.H. patients as compared to 0.104 [plus or minus] 0.005 L per cm H2O in the normal subjects. The decreased total compliance in the O.H. group was due principally to lowered thoracic compliance. Results of two methods of measuring total respiratory compliance were highly correlated (r = + 0.93). Although total respiratory resistance is somewhat increased in the obese, the amount of increase is not clear. Two independent methods for measuring total respiratory resistance gave disparate results. Differences in the frequencies at which the measurements are made are probably responsible for this methodologic discrepancy, although the effects of respiratory muscle activity have not been entirely excluded. Obese normal subjects had total respiratory work values up to twice normal and averaging 1.3 times normal. Four patients with the O.H. syndrome had values from 2.2 to 3.4 times the average normal value averaging 2.9 times normal.