A randomized trial of continuous positive airway pressure for the asthma of obesity

People with obesity and asthma often experience poor asthma control and frequent exacerbations, and exhibit airway hyperresponsiveness (AHR) that may be mitigated by elevating lung volume. Our objective was to determine if nocturnal continuous positive airway pressure (CPAP) mitigates AHR in people with obesity, both with and without asthma. We performed a double-blinded randomized controlled trial at two centers. Participants with BMI ≥ 30 kg/m2 with (n = 20) and without (n = 20) asthma were randomized to 7 nights of CPAP of 10 cmH2O or sham CPAP (4 cmH2O). Baseline airway physiology and response to methacholine were measured by oscillometry before and after CPAP intervention. Airway responsiveness was quantified by PC100AX - the concentration of methacholine producing a 100% increase in the area under the reactance curve, and also by the concentration response change in R5 and AX at the peak concentration of methacholine. The change in resistance at 19 Hz improved numerically in controls assigned to CPAP 10 cmH2O versus sham (-0.29 ± 0.08 versus − 0.07 ± 0.31 H2O.s.L−1, p = 0.07). AHR to methacholine was reduced numerically in controls assigned to CPAP 10 cmH2O versus sham, with the mean PC100AX (SD) being 0.43 (0.64) versus − 0.87 (0.64) mg/ml, p = 0.17. There was a modest difference in the change in the R5 concentration response in controls with CPAP 10 versus sham (median (IQ range): -0.55 (-1.14, 0.05) versus 0.31 (-0.20, 0.51), p = 0.04). CPAP 10 cmH2O versus sham did not change lung function or airway responsiveness in participants with asthma, but there was a trend toward an ameliorating effect in individuals with obesity alone. AHR in obese asthma is not simply related to the mechanical effects of obesity causing a reduction in lung volume. Subclinical abnormalities in airway responsiveness in people with obesity but without asthma might improve with nocturnal CPAP. This study was registered on clinicaltrials.gov (NCT02953431, last update June 21, 2024).