Effects of progressive increase in body weight on lung function in six groups of body mass index

To evaluate the effects of the progressive increase in body weight on lung function by oxygen peripheral saturation, spirometry and maximal respiratory pressures in different degrees of obesity. Cross-sectional study including 140 patients in clinical and surgical evaluation for obesity treatment. The selected patients were divided into six groups of body mass index (BMI), including a control group of non-obese and a subdivision for the morbidly obese into three subgroups. Significant differences were demonstrated between the groups regarding oxygen peripheral saturation (SpO2) (p < 0.001), forced vital capacity (FVC) (p < 0.002, p < 0.02) and forced expiratory volume in one second (FEV1) (p < 0.001, p < 0.03) in relative and absolute values, respectively. Group VI (BMI > 50.9 kg/m²) showed significant differences (SpO2, FVC and FEV1) when compared with the other groups (except group V) and group V (BMI > 45 to 49.9 kg/m²) with the group control. The other variables (FEV1/FVC ratio, forced expiratory flow 25-75 [FEF25-75] and maximal respiratory pressure) did not show any statistical differences. Lung function is influenced by the progressive increase in BMI, with changes in lung function better demonstrated when BMI > 45 kg/m²; these changes are more evident when BMI > 50.9 kg/m².