VALENCIA, SPAIN — Individuals with sleep apnea and resistant hypertension treated with continuous positive airway pressure (CPAP) over the course of 12 weeks had significant improvements in their 24-hour mean and diastolic blood pressures, but no change in their systolic blood pressure, according to the results of a new study.
In the small study, known as the HIPARCO trial, individuals randomized to CPAP therapy also showed an improvement in their nocturnal blood-pressure pattern, with more patients treated with CPAP displaying the nocturnal dipper pattern when compared with individuals who did not receive CPAP.
"The recovery of the dipper nocturnal pattern with antihypertensive treatment may be advantageous because the presence of nondipper or riser blood-pressure nocturnal patterns has emerged as an independent cardiovascular risk factor," according to Dr Miguel-Angel Martinez-Garcia (Hospital Universitario y Politécnico La Fe, Valencia, Spain) and colleagues. "In our study, more than 70% of patients had a nondipper or riser pattern, and CPAP treatment normalized the blood-pressure nocturnal pattern in a significant percentage of these patients."
Writing in the December 11, 2013 issue of the Journal of the American Medical Association, the Spanish researchers state that obstructive sleep apnea is very common in patients with resistant hypertension. Past CPAP research has shown mixed results with regard to the effect on blood pressure but has led to studies looking at potential subgroups of hypertensive patients who might benefit from treatment.
In the present study, including 98 patients randomized to CPAP therapy and 96 who were not, all patients were diagnosed with resistant hypertension for more than a decade and were taking, on average, 3.8 antihypertensive medications. At baseline, the 24-hour mean, systolic, and diastolic blood pressures were 103 mm Hg, 144 mm Hg, and 83 mm Hg, respectively. At baseline, 25% of patients had a dipper nocturnal blood-pressure pattern, which was defined as a >10% decrease in the average nighttime pressure compared with the average daytime pressure.
After 12 weeks of CPAP, the reduction in the 24-hour mean and diastolic blood pressures was 3.1 mm Hg and 3.2 mm Hg, respectively, but there was no change observed in the 24-hour mean systolic blood pressure. In the per-protocol analysis, the reductions in the 24-hour mean and diastolic blood pressure were 4.4 mm Hg and 4.1 mm Hg, respectively. In addition, the per-protocol analysis showed a significant 4.9-mm-Hg decrease in the 24-hour systolic blood pressure.
In terms of the nighttime blood-pressure patterns, 36% of the CPAP patients had a nocturnal dipper pattern after 12 weeks vs just 21.6% in the control arm.
"Some authors have reported that the effect of CPAP treatment on blood-pressure levels depends on the number of hours of CPAP use," write Martinez-Garcia and colleagues. "Our study corroborates this finding, with a significant correlation between the hours of CPAP use (especially in patients with at least four hours of use per night) and the decrease in blood-pressure levels."
The researchers say they elected not to use a sham procedure for the control arm as the excessive air that leaks from a sham device, as well as the low air pressure, along with the patients' continuing symptoms, "makes patients realize that they are not receiving an effective treatment."
The authors report no conflicts of interest.
Heartwire from Medscape © 2013 Medscape, LLC
Cite this: CPAP Reduces Blood Pressure in Resistant Hypertension - Medscape - Dec 10, 2013.