Improvement of restrictive and obstructive pulmonary mechanics following laparoscopic bariatric surgery

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Abstract
Morbidly obese patients often have impaired respiratory mechanics leading to restrictive and obstructive lung diseases. Weight loss after bariatric surgery has been shown to improve or resolve many obesity-related comorbidities. However, few studies have examined long-term changes in pulmonary mechanics after bariatric surgery. We hypothesize that pulmonary function improves after surgically induced weight loss. We examined the pulmonary function of 104 morbidly obese patients who underwent laparoscopic gastric bypass or gastric banding. Pulmonary studies, including forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF), and forced expiratory volume at midexpiratory phase (FEV25–75%) were measured preoperatively and at 3-month intervals. All results are expressed as a percentage of the baseline values. There were 80 females and 24 males with a mean age of 41 years. The mean body mass index was 48 kg/m2. The mean percentage of excess body weight loss at 12 months was 54%. At 12 months postoperatively, restrictive pulmonary mechanics significantly improved as demonstrated by an increase in the FEV1 to 112% of baseline value, increase in the FVC to 109% of baseline value, increase in the PEF to 115% of baseline value, and increase in the FEV25–75% to 130% of baseline value. Additionally, the percentage of patients with obstructive lung pattern (FEV1/FVC ratio less than 0.8) decreased from 9.6% preoperatively to 1.9% postoperatively (p = 0.03). Weight loss after laparoscopic gastric bypass significantly improves restrictive and obstructive respiratory mechanics. The improvements were observed as early as 3 months postoperatively.