Sleep Apnea Treatment Effects on CV Hemodynamics
What are the effects of continuous positive airway pressure (CPAP) therapy on cardiovascular (CV) measures among middle-aged adults with obstructive sleep apnea (OSA)?
A prospective interventional study was performed using CPAP therapy on patients referred to a sleep center for a sleep study. Excluded were patients >50 years of age, prior apnea treatment, apnea-hypopnea index (AHI) <10 events/hour, or hypertension. However, patients could have prior hypertension on stable treatment for at least 6 weeks. Baseline measurements were done, including blood pressure (BP), arterial stiffness, and tone assessed by pulse wave velocity (PWV). Endothelial function was measured by brachial artery flow-mediated dilation (FMD). Echocardiography measures were performed. Studies were repeated at 4 and 12 weeks. Compliance with CPAP and average hours of CPAP use were downloaded from the patient’s equipment. Measurements were repeated in a subset after 1 week of CPAP withdrawal.
A total of 90 subjects were enrolled and 84 returned for follow-up studies, including 44 who returned for CPAP withdrawal analysis. Average age was 41.1 ± 7.6 years, 77% were male, average AHI was 39.8 ± 24.5 events/hour, average body mass index was 35.4 ± 7.4 kg/m2, and 20% used BP lowering medication, mostly a single agent. Residual AHI was effectively lowered to 3.42 ± 2.89 events/hour. Significant reductions in mean and diastolic BP were observed (3.7 ± 6.1 and 4.6 ± 6.6 mm Hg; p = 0.008), as well as left ventricular diastolic function and systemic and pulmonic vascular resistance. Endothelial function and arterial tonometry were improved in this short follow-up (p < 0.001). In adjusted models, reductions in BP, FMD, and PWV were relative to CPAP hours/night use. After a week of CPAP withdrawal, BP readings, FMD, and arterial tonometry reversed to the baseline as compared to the 12-week readings (p < 0.01).
The authors concluded that CPAP therapy reduces BP and arterial tone as well as improves endothelial and diastolic function, after a short duration of therapy. This improvement depends on CPAP duration of use. Observed improvements reversed to baseline after 1 week.
OSA is associated with hypertension, and may contribute to the increased fatal and nonfatal CV events observed in patients with moderate and severe OSA. Prior studies evaluating the independent role of OSA on the hemodynamic consequences of hypertension were criticized due to overlapping comorbidities found in this population. Studying a young population and showing an impact on vascular stiffness, hemodynamics, and endothelial function were strengths of this study. Additionally, objective use of CPAP was studied, and its use directly correlated with outcomes. Other indexes previously shown to be impacted by use of CPAP, such as left ventricular mass, were not observed here, likely due to the relatively healthy subjects studied. Further long-term studies are needed to address the impact of CPAP on moderate to severe OSA on major adverse CV outcomes, before the development of hypertension.
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