The respiratory defects in extreme obesity

Abstract

Severely obese patients, including patients with normal lungs, myxedema and pulmonary emphysema, have been studied. Three of these patients had the hypoventilation syndrome at the time the studies were performed. All the patients exhibited marked reduction in expiratory reserve volume and a low maximal breathing capacity. Many patients had mild desaturation of the arterial blood. Unless concurrent thoracic disease was present, the oxygen cost of breathing and work of breathing were normal or near normal, and did not appear to be important in the pathogenesis of the hypoventilation syndrome. It is concluded that the basic respiratory defect in severe obesity is the low expiratory reserve volume and that the reduction of maximal breathing capacity and arterial oxygen unsaturation are a consequence of this. The hypoventilation syndrome occurring in occasional obese patients is due to a complex combination of factors that vary from case to case.