Pulmonary function in the morbidly obese.

BACKGROUND: Only limited data exist on the relationship of lung function to patients with extreme obesity. To assess the relationship between lung function tests and clinical characteristics in a cohort of morbidly obese patients undergoing evaluation for bariatric procedures in a university hospital in the United States.
METHODS: Consecutive patients undergoing clinical evaluation were reviewed. The variables included demographic, anthropometric, clinical, and pulmonary function data.
RESULTS: A total of 229 patients underwent a standardized preoperative evaluation. Of these 229 patients, 136 (59%) had evaluable data and 102 (75%) were women. The mean +/- standard deviation age was 45 +/- 10 years, the mean weight was 164 +/- 42 kg, and the mean body mass index was 57 +/- 13 kg/m2. Smoking or asthma was reported in 38% and 24% of patients, respectively. The mean forced vital capacity and forced expiratory volume in 1 s was 80% +/- 17% of predicted and 76% +/- 19% of predicted, respectively. Of the 136 patients, 29% had a measured forced expiratory volume in 1 s/forced vital capacity of >or=.08 below the predicted ratio. The mean total lung capacity was 86% +/- 14% of predicted; 26% of subjects had a total lung capacity <80% of predicted. Multivariate logistic regression analysis demonstrated an association of obstructive ventilatory defects with male gender (odds ratio [OR] 2.35, 95% confidence interval [CI] 1.00-5.50) and current or previous smoking (OR 2.41, 95% CI 1.10-5.30), but not body mass index. Restrictive defects were associated with body mass index (OR 1.06, 95% CI 1.01-1.10), in particular, obesity hypoventilation syndrome (OR 3.7, 95% CI 1.2-11.1).
CONCLUSION: The mean preoperative spirometry, lung volumes, and gas exchange values were within the established reference ranges. Restrictive ventilatory defects were less common than obstructive ventilatory patterns and were most prominently associated with obesity hypoventilation syndrome.