Effects of CPAP and its withdrawal on cardiovascular outcomes in patients with obstructive sleep apnoea - a two phase interventional trial

<bold>Background:</bold> The aim was to investigate whether cardiovascular changes during short-term reactivation of obstructive sleep apnoea (OSA) by continuous positive airway pressure (CPAP)-withdrawal are comparable to the reverse treatment effect of CPAP to validate the CPAP-withdrawal model for the investigation of OSA sequelae. <bold>Methods:</bold> In a biphasic intervention study, the effect of several weeks of CPAP for newly diagnosed OSA was compared with the subsequent effect of two weeks of CPAP withdrawal on daytime heart rate variability (HRV), baroreflex sensitivity (BRS) and pulse rise index (PRI). HRV was assessed from 5-minute ECG segments. Time domain (RMSSD and pRR50) and frequency domain HRV indices (high frequency, HF; low frequency, LF) were evaluated. <bold>Results:</bold> In 25 patients with OSA (20% female, age 51.0 ± 8.8 years, AHI 45.1 ± 23.3/h, Epworth Sleepiness Scale 10.2 ± 2.9), CPAP resulted in a significant increase in RMSSD, pRR50, LF, HF and a decrease in LF/HF ratio and PRI but no change in BRS. A 2-week CPAP withdrawal resulted in a comparable reverse effect (figure) <bold>Conclusions:</bold> CPAP treatment resulted in a significant change in HRV in OSA indicating a shift towards lower sympathetic modulation in the sympatho/vagal balance while CPAP withdrawal had a comparable reverse effect. CPAP-withdrawal is a valid model to study the autonomic cardiovascular consequences of OSA.