Effects of short-term CPAP withdrawal on cerebral vascular reactivity measured by BOLD MRI in OSA: a randomised controlled trial

Abstract

Impaired cerebral vascular reactivity (CVR) increases long-term stroke risk. Obstructive sleep apnoea (OSA) is associated with peripheral vascular dysfunction and vascular events. The aim of this trial was to evaluate the effect of continuous positive airway pressure (CPAP) withdrawal on CVR. 41 OSA patients (88% male, mean age 57±10 yrs.) were randomised to subtherapeutic, or continuation of therapeutic, CPAP. At baseline, and after two weeks, patients underwent a sleep study and magnetic resonance imaging (MRI). CVR was estimated by quantifying the blood oxygen level dependent (BOLD MRI) response to breathing stimuli. OSA did recur in the subtherapeutic-CPAP group (mean treatment effect apnoea-hypopnoea-index [95%CI] +38.0 [+24.2/+52.0] events·h, p<0.001) but remained controlled in the therapeutic group. Although there was a significant increase in blood pressure upon CPAP withdrawal (mean treatment effect [95%CI] +9.37 [+1.36 to 17.39] mmHg, p=0.023), there was no significant effect of CPAP withdrawal on CVR assessed BOLD MRI under either, hyperoxic or hypercapnic conditions. Short-term CPAP withdrawal did not result in statistically significant different changes of CVR assessed by functional MRI despite recurrence of OSA. We thus conclude that unlike peripheral endothelial function, CVR is not affected by short- term CPAP withdrawal.