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

SummaryObjectiveTo 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.MethodsCross-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.ResultsSignificant 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.ConclusionLung 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.