Respiratory Muscle Endurance in Obesity Hypoventilation Syndrome

BACKGROUND: An increase in respiratory work load and resistance to respiration cause a decrease in respiratory muscle endurance (RME) in patients with obesity hypoventilation syndrome (OHS). We aimed to evaluate and compare RME in subjects with OHS and a control group using an incremental load test and compare the RME of subjects with OHS in whom noninvasive ventilation (NIV) was and was not used.

METHODS: Forty subjects with OHS (divided according to body mass index [BMI] as group I: 30–40 kg/m²; and group II: ≥ 40 kg/m²) and 20 subjects with obesity (control group: 30–40 kg/m²) were included in the study. RME was evaluated using the incremental load test, and respiratory muscle strength (RMS) was evaluated using mouth pressure measurements. The 6-min walk test, Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), Fatigue Severity Scale (FSS), EQ-5D Health-Related Quality of Life Questionnaire (EQ-5D), and the Obesity and Weight-Loss Quality of Life Instrument (OWLQOL) were performed.

RESULTS: RME and RMS (%) in group I were lower than the control group (P = .001, P = .005, and P = .001, respectively). No significant difference was found between the 3 groups in terms of 6-min walk distance (6MWD) percentage predicted values (P = .98). RME in the NIV user group was higher than the non-user group (P = .006). ESS, total PSQI, and FSS scores in the control group were less than group I (P = .01, P = .009, and P = .005, respectively) and group II (P = .01, P < .001, and P < .001, respectively). The EQ-5D scores of the control group were higher than group II only (P = .005 and P = .005, respectively). There were no differences in OWLQOL between the groups (P = .053).

CONCLUSIONS: RME was low in subjects with OHS but higher in those who used NIV. The incremental load test could be performed easily and safely in a clinic setting.