Pulmonary Function in Obese Persons12

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Abstract
A study of 28 persons who weighed at least 100 pounds more than their ideal weight. Of this group 13 had normal arterial oxygen saturation. Fifteen had hypoxemia and 10 of the 15 had alveolar hypoventilation as manifested by increased PCO2- Alveolar hypoventilation was associated with myxedema or lung disease. Obese persons who had normal arterial O saturation had reduced expiratory reserve volumes, reduced maximal breathing capacities, and reduced maximal flow rates. When those patients lost weight, their lung function returned toward normal. Some obese persons who did not have lung disease did have arterial hypoxemia without hypercapnia. The authors believe this is caused by a disturbance in ventilation perfusion ratios in the lungs. However, when alveolar hypoventilation is present (arterial hypoxemia and hypercapnia), one should suspect intrinsic lung disease, a disturbance of the respiratory musculature, or a central nervous system lesion. In the authors'' experience obese persons with normal lungs, normal respiratory muscles, and an apparently normal respiratory center did not have alveolar hypoventilation. Most obese persons with pulmonary insufficiency are benefited by weight loss. Presumably the improvement is caused by reduction in the work of breathing. Obese persons who have lung disease need therapy which is directed toward correcting or alleviating the basic lung disease.