Wearing a continuous positive airway pressure (CPAP) device not only helps heart failure patients with obstructive sleep apnea get a good night’s rest, it lowers blood pressure and heart rate well into the morning, apparently, by reducing sympathetic nervous system activity, according to a new study (PDF) in the June 21, 2005, issue of the Journal of the American College of Cardiology.
“The bottom line is that when we abolished obstructive apnea during sleep by applying CPAP at night, we caused a number of changes that carried over into the morning during wakefulness. Specifically, we’ve shown that the sympathetic drive from the brain to resistance blood vessels in skeletal muscle is attenuated. At the same time, there is a fall in blood pressure and a fall in heart rate. The net result is a reduction in the work of the heart, which is evident in the morning when the patient is awake and now breathing normally,” said John S. Floras, M.D., D.Phil., F.A.C.C., at the University of Toronto in Canada.
In patients with obstructive sleep apnea, tissue in the upper throat collapses intermittently, temporarily cutting off breathing and sometimes waking patients. This study did not include patients with central sleep apnea, which has a different cause.
The researchers, including lead author Kengo Usui, M.D., Ph.D., randomly assigned 17 patients referred from the Heart Failure programs of the Mount Sinai and Toronto General Hospitals, who also had moderate to severe obstructive sleep apnea, to two groups. The eight patients in the treatment group were treated with CPAP, in addition to the optimal heart failure management given to all participants. After one month, patients in the CPAP group had fewer obstructive sleep apnea events. In addition, several variables related to heart failure were improved even during the morning after waking. Muscle sympathetic nerve activity, which is related to the constriction of blood vessels, was lower, as were blood pressure and heart rate.
While an earlier study by this research team had shown CPAP could reduce blood pressure and heart rate and improve ejection fraction in heart failure patients with obstructive sleep apnea, this study is the first of its kind to demonstrate suppression of the sympathetic nervous system after long term treatment with CPAP.
“This was the novel observation. No one has shown this before in a randomized clinical trial involving patients with heart failure and obstructive sleep apnea,” Dr. Floras said.
Dr. Floras noted that further work is needed to determine whether these changes after one month of CPAP use lead to long term benefit for these heart failure patients.
“We have no data that tells us that by treating such patients, we will prolong life, so that’s the subject of future study,” he said.
Nevertheless, he advised clinicians to watch for signs of sleep apnea in their heart failure patients because obstructive sleep apnea puts extra stress on hearts during sleep, normally a restorative period. However, he noted that unlike most patients with obstructive sleep apnea, those with heart failure often do not report daytime fatigue.
“Our view is that it would be important to identify and treat obstructive sleep apnea in a heart failure population because the drug therapy of heart failure does not address the pathophysiology of sleep apnea. So, in order to optimize medical treatment, we believe that treatment of sleep apnea is an important component of the overall management of these patients,” Dr. Floras said.