Effect of CPAP on Blood Pressure in Patients With Obstructive Sleep Apnea and Resistant Hypertension: The HIPARCO Randomized Clinical Trial

Study Questions:

What is the impact of continuous positive airway pressure (CPAP) on blood pressure (BP) in patients with resistant hypertension and obstructive sleep apnea (OSA)?


Men and women ages 18-75 were recruited from 24 teaching hospitals. All had resistant hypertension, defined as uncontrolled BP, despite concurrent use of at least three antihypertensive agents to control BP. Patients were excluded for secondary causes of hypertension or heart failure, arrhythmias, valvular heart disease, renal failure, smoking, regular alcohol intake, long-term corticosteroid or nonsteroidal anti-inflammatory drug use, or pregnancy. Prescriptions were not changed during the study. A 24-hour BP monitor was performed at study entry and after 12 weeks. All patients underwent attended respiratory polygraphy. All patients had moderate to severe OSA, defined as apnea-hypopnea index (AHI) ≥15 events/hour. Patients were randomly assigned to CPAP or no therapy while maintaining usual BP medication for 12 weeks. Subjects were randomly allocated by a computer program and by site. Adherence was verified by Haynes-Sackett test. Optimal CPAP treatment was titrated in the laboratory using a fixed pressure. CPAP compliance was objectively measured by downloading a card that contained the time counter of the device. Data were collected from June 2009 to October 2011.


Initially, 266 patients were assessed and 72 (27%) were excluded, mostly for normal ambulatory BP readings. Following exclusions, 194 patients were randomized; 133 (69%) were men. No patients changed antihypertensive medication. No patient had central sleep apnea. The percentage of patients using CPAP for 4 or more hours per day was 72.4%. The mean AHI was 40.4 (standard deviation, 18.9) and an average of 3.8 antihypertensive drugs were taken per patient. Baseline 24-hour mean BP was 103.4 mm Hg; systolic BP (SBP), 144.2 mm Hg; and diastolic BP (DBP), 83 mm Hg. The CPAP group achieved a greater decrease in 24-hour mean BP (3.1 mm Hg; [95% confidence interval [CI], 0.6-5.6; p = 0.02) and 24-hour DBP (3.2 mm Hg [95% CI, 1.0-5.4; p = 0.005), but not in 24-hour SBP (3.1 mm Hg [95% CI, −0.6 to 6.7; p = 0.10) compared with the control group. There was a significant positive correlation between hours of CPAP use and the decrease in 24-hour mean BP (r = 0.29; p = 0.006), SBP (r = 0.25; p = 0.02), and DBP (r = 0.30; p = 0.005).


The authors concluded that CPAP treatment for 12 weeks compared with control resulted in a decrease in 24-hour mean and diastolic BP, but not systolic BP.


There was no difference in percentage of subjects reaching normotensive BP (<130/80 mm Hg) between study groups. The study was too short to report on any hard outcomes related to hypertension. Quality-of-life surveys were not used; however, average Epworth Sleepiness Scale scores fell significantly in the intervention group. Interestingly, the differences in BP appeared greater for nocturnal readings compared with daytime BP, which is opposite of a recent report in Chest by Pedrosa and colleagues. Further studies are needed on long-term consequences of CPAP intervention in this population.

Clinical Topics: Prevention, Hypertension, Sleep Apnea

Keywords: Continuous Positive Airway Pressure, Hypertension, Sleep Apnea, Obstructive

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