Recent evidence shows that obstructive sleep apnea (OSA) increases nocturnal blood pressure and is a risk factor for arterial hypertension during the day. While nasal continuous positive airway pressure (nCPAP) has been shown to improve symptoms in patients with OSA, its role in reducing blood pressure is questionable. Becker and colleagues performed a prospective randomized study involving 60 patients with moderate to severe OSA to evaluate the effect of nCPAP on blood pressure.
Inclusion criteria for the study were five or more apneas or hypopneas per hour of sleep and excessive daytime sleepiness according to the Epworth sleepiness scale. Exclusion criteria were central sleep apnea, respiratory failure, heart failure, recent myocardial infarction, arrhythmias, and being a professional driver. Polysomnography and continuous noninvasive blood pressure monitoring were performed before and with treatment. Patients were treated with effective (preventing apneas, hypopneas, snoring in all sleep stages in supine position; 9 cm H2O of pressure on average) or subtherapeutic (lowest possible pressure for nCPAP device; 3 to 4 cm H2O) nCPAP for about nine weeks. Hypertensive patients who had a change in medication were considered dropouts, and only 32 patients (16 in the effective treatment group and 16 in the subtherapeutic group) out of 118 completed the study. The primary measurement of the study was change in mean arterial blood pressure; the secondary measurements were changes in systolic and diastolic pressures; the tertiary measurements were the apnea-hypopnea index (AHI) and sleepiness.
The mean arterial blood pressure decreased about 10 mm Hg in the effective nCPAP group, while it increased in the subtherapeutic group. The diastolic and systolic blood pressures also significantly decreased in the effective group (approximately 10 mm Hg and 9.5 mm Hg, respectively). In addition, the AHI and measures of sleepiness were significantly better in the effective treatment group. The AHI was reduced by 50 percent in the subtherapeutic group. The authors conclude that even though AHI is reduced with subtherapeutic nCPAP, optimal control of blood pressure is achieved with effective nCPAP treatment.
editor's note: A similar study performed by Pepperell and colleagues (Pepperell JC, et al. Ambulatory blood pressure after therapeutic and subtherapeutic nasal continuous positive airway pressure for obstructive sleep apnoea: a randomised parallel trial. Lancet January 19, 2002; 359:204–10) also demonstrated that blood pressures were significantly reduced in the therapeutic versus the subtherapeutic group. However, the differences in blood pressure were lower (mean pressure decreased 2.5 mm Hg). Perhaps the discrepancies can be explained by the shorter treatment period in this study, one month versus nine weeks in the trial by Becker and colleagues. Another explanation is the larger number of patients (118) in the study, suggesting that Becker's results in 32 patients lack power. Regardless, nCPAP appears to reduce blood pressure consistently.—S.M.S.