Randomized-controlled Trial (RCT) on CPAP-withdrawal and Microvascular Function in OSA

Inclusion criteria: * Objectively confirmed OSA (at the time of original diagnosis) with an oxygen desaturation index (ODI, =4% dips) of \>20/h and an ESS of \>10. * Currently \>20/h oxygen desaturations (=4% dips) during an ambulatory nocturnal pulse oximetry performed at the end of a 4-night period without CPAP. * Treated with CPAP for more than 12 months, minimum compliance 4h per night, AHI\<10 with treatment (according to CPAP machine download data). * Current ESS \<10. Exclusion criteria: * Previous ventilatory failure (awake SpO2 \<93% and PaCO2\>6kPa). * Unstable, untreated coronary or peripheral artery disease, severe arterial hypertension or hypotension (\>180/110 or \<90/60mmHg) * Previously diagnosed with Cheyne-Stokes breathing. * Current professional driver; Any previous sleep related accident. * Age \<20 or \>75 years at trial entry. * Acute inflammatory disease