CPAP bests supplemental oxygen for lowering blood pressure

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Even 3.5 hours of continuous positive airway pressure (CPAP) use a night can make a difference to average blood pressure throughout the day in patients with obstructive sleep apnea and cardiovascular disease or cardiovascular risk factors, a study published online June 12 in the New England Journal of Medicine found.

In heart disease patients, obstructive sleep apnea often can play such an integral role in the physio-dynamics of the disease progression that it can be difficult to determine if one evolved from the other or whether it exacerbated an underlying condition. The use of a CPAP machine has been a long-term treatment for obstructive sleep apnea, but had not been studied against other methods in improving both the sleep apnea and any underlying or potential heart disease.

Daniel J. Gottlieb, MD, MPH, of Brigham & Women’s Hospital in Boston and colleagues enrolled 318 cardiology patients into three groups—education only, education plus nighttime oxygen or education plus a CPAP machine—to test the effects on markers for heart disease. All participants had mild obstructive sleep apnea symptoms and were already on blood pressure medication at the time of the study.

The researchers found that compared with oxygen or the education-only control, patients using a CPAP machine saw a mean 2 mm Hg reduction in 24-hour arterial blood pressure after the 12-week study. While CPAP adherence was lower, on average 3.5 hours a night, the group still saw improvement to mean blood pressure not seen in the other two groups. In addition, there were benefits to nocturnal systolic blood pressure seen with each additional CPAP use per night of around 0.93 mm Hg per hour. No significant difference in mean blood pressure was noted between the oxygen and control groups.

“A meta-analysis of 61 observational studies that evaluated the relation of blood pressure to mortality from vascular disease showed that a reduction of 2 mm Hg in systolic blood pressure would reduce mortality from stroke by 10% and mortality from ischemic heart disease or other vascular causes by 7%, with reductions in diastolic blood pressure having effects that were approximately twice as large,” Gottlieb et al stated. Considering the observed effect of greater adherence, better outcomes may be possible through even as small an increment as one extra hour overnight.

While no treatment effect was seen in other blood panel markers, they noted there was a 20 percent reduction of the mean level of C-reactive protein in CPAP users at 12 weeks compared with the control group. Because no other biomarkers were affected, Gottlieb et al recommended caution. “It is possible that the recruitment of patients from cardiology practices, which provided effective risk factor management at baseline, limited our ability to detect further improvement in biochemical measures,” they noted.

Considering the overall effect of CPAP on blood pressure with little to no change in blood pressure or biochemical markers using oxygen, the team determined that unless other reasons exist for putting a patient on oxygen, clinicians should consider and encourage CPAP use and adherence in patients.