Effect of weight loss and body position on pulmonary function and gas exchange abnormalities in morbid obesity

Abstract

Objective: To determine, whether behavioral management of obesity including very-low-calorie-diet would produce weight loss enough to improve pulmonary mechanics and gas exchange in morbid obesity.

Design: Pulmonary function and arterial oxygenation were studied before and after weight loss in 11 patients attending a group therapy with the program of VLCD for 6 weeks and 16 weeks' behavioral intervention.

Measurements: Spirometry, diffusing capacity, body plethysmograph, closing volume and arterial blood gas analyses.

Results: The mean initial BMI was 45.4 kg/m2 (range 39.8-58.7 kg/m2) and decreased to 39.4 kg/m2 (range 31-49.8 kg/m2) (P < 0.01). Expiratory reserve volume (ERV) and functional residual capacity (FRC) improved significantly with weight loss. Closing capacity (CC) exceeded FRC in 10 cases of 11 at the initial stage, but after weight loss only in three patients. The mean arterial oxygen tension with the patients in supine position did not change after weight loss, but standing up improved PaO2 significantly before and after weight loss.

Conclusion: The dietary treatment of morbid obesity was sufficient to induce improvement in lung volumes, but not enough to improve arterial oxygenation, although ventilatory mechanics was improved significantly and the tendency to early small airway closure was decreased. Hypoxemia was significantly relieved by standing up both before and after weight loss.