Effects of CPAP on "vascular" risk factors in patients with obstructive sleep apnea and arterial hypertension

Abstract

Background: The aim of this study was to assess the effects of continuous positive airway pressure (CPAP) on arterial stiffness, central blood pressure, and reflected pulse wave characteristics in patients with severe obstructive sleep apnea (OSA) and stage 2-3 arterial hypertension.

Methods: Forty-four patients with hypertension and severe OSA (apnea/hypopnea index > 30) received stepped dose titration of antihypertensive treatment, consisting of valsartan 160 mg + amlodipine 5-10 mg + hydrochlorothiazide 25 mg. CPAP therapy was added after 3 weeks of continuous antihypertensive treatment with BP < 140/90 mmHg or after adjusting triple treatment in patients with resistant arterial hypertension. The patients were randomized to effective CPAP (4-15 mm H2O) or placebo CPAP (pressure 4 mm H2O) for three weeks, then crossed over to the alternative treatment in a single-blind manner. Office blood pressure (BP), ambulatory BP monitoring, ambulatory arterial stiffness index (AASI), aortic BP, carotid-femoral pulse wave velocity (cfPWV), and systolic wave augmentation index were measured using a Sphygmocor® device at baseline, after antihypertensive treatment, placebo CPAP, and effective CPAP.

Results: Baseline cfPWV was above the normal range in 94% of patients. After reaching target BP, the cfPWV decreased by 1.9 ± 1.0 msec (P = 0.007). Effective CPAP achieved a further cfPWV reduction of 0.7 msec (P = 0.03). Increased arterial stiffness (pulse wave velocity > 12 msec) persisted in 35% of patients on antihypertensive treatment and effective CPAP, in 56% of patients on antihypertensive treatment alone, and in 53% of patients on placebo CPAP. Only the combination of antihypertensive treatment with effective CPAP achieved a significant reduction in augmentation index and AASI, along with a further reduction in aortic and brachial BP.

Conclusion: Effective CPAP for 3 weeks resulted in a significant additional decrease in office BP, ambulatory BP monitoring, central BP, and augmentation index, together with an improvement in arterial stiffness parameters, ie, cfPWV and AASI, in a group of hypertensive patients with OSA.

Trial registration: ClinicalTrials.gov NCT00801671.

Keywords: antihypertensive therapy; arterial stiffness; blood pressure; continuous positive airway pressure; hypertension; obstructive sleep apnea; ulse wave velocity.

Figure 1

Study design. Note: Of the remaining 44 patients, two subjects refused pCPAP because of complaints of “shortness of breath” and fail to fall asleep, This was taken into account in the statistical analysis. Abbreviations: ABPM, ambulatory blood pressure monitoring; BP, blood pressure; val, valsartan; aml, amlodipine; HCT, hydrochlorothiazide; CPAP, continuous positive airways pressure; eCPAP, effective CPAP; pCPAP, placebo CPAP; OSA, obstructive sleep apnea.

Figure 2

Pulse wave velocity recordings (normal < 12 m/sec). Note: *P < 0.05 vs AT. Abbreviations: AT, antihypertensive therapy; CPAP, continuous positive airways pressure; eCPAP, effective CPAP; pCPAP, placebo CPAP; PWV, pulse wave velocity.

Figure 3

Changes in carotid-femoral PWV and AASI after antihypertensive therapy and CPAP therapy. Notes: *P > 1.05 vs baseline; ^#P > 1.05 vs AHT. Abbreviations: AHT, antihypertensive therapy; eCPAP, effective continuous positive airways pressure; cfPWV, carotid-femoral pulse wave velocity; AASI, ambulatory arterial stiffness index.