Abstract
Objectives
(1) To describe the pulmonary findings in severely obese individuals and (2) to describe the changes in resting pulmonary function and exercise performance after clinically significant weight loss.
Methods
We performed flow-loop spirometry, lung volumes, diffusing capacity for carbon monoxide (DLco), and cycle ergometry with expired and blood gas analysis in 16 (14 women, 2 men) very obese (body-mass index > 40 kg/mβ) subjects before and immediately after 6 months of treatment including a very-low-calorie diet. Patients with a smoking history, hypoventilation and/or sleep apnea syndromes, or other cardiac or lung disease were carefully excluded.
Results
Patients lost 23 ± 9.0 kg. There were significant increases in thoracic gas volume (2.3 ± 0.54 L versus 2.7 ± 1.1 L, p < 0.025) and expiratory reserve volume (0.89 ± 0.21 L versus 1.46 ± 0.72 L, p < 0.01), a decrease in the inspiratory capacity (2.8 ± 0.56 L versus 2.5 ± 0.49 L, p < 0.01), and a change in the relationship between thoracic gas volume and total lung capacity. There were no significant changes in other lung volumes, expiratory flow rates (peak flow or forced expiratory flow rate during the middle 50% of the forced vital capacity), airway resistance, or DLco. Resting oxygen consumption did not change, but at peak exercise the oxygen consumption per kilogram weight increased, as did the ventilatory equivalent for the level of oxygen consumption.
Conclusions
Our results among carefully-selected patients accurately reflect the pulmonary function changes in uncomplicated ("healthy"), severely obese women. When changes in other lung volumes, airway resistance, DLco, or blood gas tensions are found, evaluation for other causes of pulmonary disease should be undertaken. Weight loss leads to clinically important increase in lung volume and modest improvement in maximum aerobic capacity, even when normal weight is not attained. [Respir Care 1999;44(12):1458-1464]
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