Pulmonary function tests in obese people candidate to bariatric surgery.

Obesity is considered one of the most serious public health problems of the modern world. Because it alters the relationship between the lungs, chest wall and diaphragm, it is to be expected that it impacts on the respiratory function. In Portugal, there is not much data about the relationship between obesity and pulmonary function. The aim of this study was to characterize respiratory function in morbidly obese patients and to evaluate whether weight loss in patients submitted to bariatric surgery affects pulmonary function tests (PFT). We conducted a retrospective study with 36 morbidly obese patients submitted to bariatric surgery, with a mean age of 40.6 years, 64% female and with a mean body mass index (BMI) of 49.7 kg/m². All patients were clinical and functionally evaluated before surgery and after their weight had stabilized following surgery. They underwent a complete pulmonary function testing with spirometry, lung volumes, carbon monoxide diffusing capacity (DLCO), maximum respiratory pressures and arterial blood gases analysis. Prior to surgery almost all the patients had functional respiratory changes, 34 had a decrease in functional residual capacity (FRC) 6 of whom a restrictive syndrome. Only 2 patients did not show any functional or arterial blood gas change. After bariatric surgery, BMI decreased to 34 kg/m² and there was a significant improvement in almost all functional parameters with resolution of restrictive disorders. Nevertheless, in 13 patients the FRC remained decreased. After weight loss, the only correlation found was between reduction of BMI and increased FRC (r = -0.371; p = 0.028). This study suggests a relationship between obesity and pulmonary restriction and a positive impact of bariatric surgery in PFT.