• Sleep apnoea

In recent years, a number of meta-analyses have consistently concluded that CPAP therapy elicits modest, yet significant, reductions in 24-hour ambulatory blood pressure (BP).1–4 These improvements in 24-hour BP appear to be more dramatic in patients with resistant hypertension,5 and reductions in nocturnal BP tend to be more dramatic than daytime BP.1–4 There is also evidence indicating that CPAP adherence plays a critical role in the potential BP-lowering effects of CPAP therapy.6

Pepin et al7 conducted the largest double-blind randomised-controlled trial (RCT) to date comparing the efficacy of 4 months of therapy with fixed-pressure CPAP (FP-CPAP, n=161) versus auto-adjusting CPAP (auto-CPAP, n=161) in reducing BP in patients with moderate-to-severe obstructive sleep apnoea (OSA). In an intention-to-treat analysis, there was no difference in the primary outcome of change in office systolic BP between FP-CPAP and auto-CPAP groups.

Auto-CPAP devices analyse flow and pressure signals on a breath-by-breath basis and use a variety of algorithms to adjust the delivered pressure in order to resolve detected residual obstructive events while trying to apply the lowest effective pressure. Thus far, the preponderance of data suggests that this modality is no better than FP-CPAP in improving adherence to therapy or quality of life. What remains unclear is whether the inherent fluctuations in delivered pressure by an auto-CPAP device can lead to microarousals and sleep fragmentation, ultimately leading to less effective reduction in nocturnal and daytime BP compared with FP-CPAP. Accordingly, the study by Pepin et al is important and timely, and the authors are to be commended for executing such a large and well-designed RCT to provide clinically useful information for the care of patients with OSA.

Pepin et al7 estimated their sample size and set their a priori primary end point of office BP based on a prior smaller …