Acute and Long-term Effects of CPAP in OSA

Background and Aim: Obstructive sleep apnoea (OSA) is a prevalent sleep-related breathing disorder. OSA is associated with daytime sleepiness, impaired quality of life, and adverse cardiovascular outcome. OSA can be effectively treated with nocturnal continuous positive airway pressure (CPAP) that restores normal breathing during sleep by preventing upper airway collapse. However, many patients in whom treatment of OSA is indicated are not able to adhere to CPAP, and the consequences of untreated OSA seem to differ between OSA phenotypes. Therefore, treatment alternatives to CPAP and a better understanding of treatment implications in different phenotypes of OSA are important targets in this research field. Thus, effective and controlled study designs are needed to address these research questions. Conventional randomised controlled CPAP trials are limited by low CPAP adherence resulting in an underestimation of the treatment effect. In addition, the impracticability of withholding an effective treatment from symptomatic patients resulting in inclusion of less symptomatic and patients with less severe OSA has limited the conclusions from previous trials. The CPAP therapy withdrawal model was introduced to allow studying the pathophysiological consequences of OSA and treatment effects of CPAP in an effective and controlled way. Optimally treated patients previously diagnosed with OSA established on CPAP therapy are included and undergo a short-term therapy interruption. A therapy withdrawal results in recurrence of OSA and pathophysiological changes can be attributed to OSA in this controlled model. However, it is uncertain whether the consequences of OSA during a short-term CPAP therapy withdrawal are comparable to long-term consequences of untreated OSA. The aim of this two-phase interventional trial is to assess the effects of intermediate and long-term CPAP therapy as well as acute CPAP therapy withdrawal resulting in OSA recurrence compared to longstanding untreated OSA on cardiovascular and symptom outcomes in moderate and severe OSA. The objective is to study the comparability of conventional CPAP therapy trials with the CPAP withdrawal model in terms of evaluating relevant cardiovascular and patient-centred outcomes in OSA. The investigators hypothesise that the treatment effect of CPAP in previously treatment-naïve patients with OSA - if adherent to CPAP - will support the same conclusions on OSA pathophysiology and therapy effects as a short-term CPAP withdrawal in treatment-adherent patients having a recurrence of OSA in response to CPAP withdrawal and thus support the use of this effective CPAP withdrawal model to use as future study design in interventional trials in OSA. It is hypothesised that the CPAP withdrawal is non-inferior to conventional CPAP trials in studying the effect on blood pressure and OSA-symptoms.