Correlation of lung function and respiratory muscle strength with functional exercise capacity in obese individuals with obstructive sleep apnea syndrome

OBJECTIVE: To evaluate lung function and inspiratory muscle strength, correlating them with exercise tolerance, in obese individuals with obstructive sleep apnea syndrome (OSAS). METHODS: The sample comprised 31 adult subjects with moderate-to-severe OSAS diagnosed by polysomnography. We used spirometry to measure FVC, FEV(1), and FVC/FEV(1) ratio, using pressure manometry to measure MIP and MEP. The incremental shuttle walk test (ISWT) and the six-minute walk test (6MWT) were used in order to determine functional exercise capacity. RESULTS: In this sample, the mean values for FVC (% of predicted), FEV(1) (% of predicted): MIP, and MEP were 76.4 ± 12.3%, 80.1 ± 6.3%, 60.0 ± 21.9 cmH(2)O, and 81.3 ± 22.2 cmH(2)O, respectively. The mean distances covered on the ISWT and 6MWT were 221 ± 97 m and 480.8 ± 67.3 m, respectively. The ISWT distance showed moderate positive correlations with FVC (r = 0.658; p = 0.001) and FEV(1) (r = 0.522; p = 0.003). CONCLUSIONS: In this sample of obese subjects with untreated OSAS, lung function, inspiratory muscle strength, and exercise tolerance were all below normal. In addition, we found that a decline in lung function, but not in respiratory muscle strength, was associated with exercise tolerance in these patients.