By Steven Reinberg
Continuous positive airway pressure (CPAP) is the standard treatment for sleep apnea, a condition characterized by disrupted breathing during sleep. The sleep disorder has been linked to high blood pressure.
Patients in this study were taking three or more drugs to lower their blood pressure, in addition to having sleep apnea. Participants who used the CPAP device for 12 weeks reduced their diastolic blood pressure (the bottom number in a blood pressure reading) and improved their overall nighttime blood pressure, the researchers found.
"The prevalence of sleep apnea in patients with resistant [high blood pressure] is very high," said lead researcher Dr. Miguel-Angel Martinez-Garcia, from the Polytechnic University Hospital in Valencia.
"This [sleep apnea] treatment increases the probability of recovering the normal nocturnal blood pressure pattern," he said.
Patients with resistant high blood pressure should undergo a sleep study to rule out obstructive sleep apnea, Martinez-Garcia said. "If the patient has sleep apnea, he should be treated with CPAP and undergo blood pressure monitoring."
The report, published in the Dec. 11 issue of the Journal of the American Medical Association, was partly funded by Philips-Respironics, maker of the CPAP system used in the study.
The CPAP system consists of a motor that pushes air through a tube connected to a mask that fits over the patient's mouth and nose. The device keeps the airway from closing, and thus allows continuous sleep.
Sleep apnea is a common disorder. The pauses in breathing that patients experience can last from a few seconds to minutes and they can occur 30 times or more an hour.
Dr. Gregg Fonarow, a spokesman for the American Heart Association and professor of cardiology at the University of California, Los Angeles, agrees that most patients with hard-to-control high blood pressure also suffer from sleep apnea.
"Close to three out of four patients with resistant [high blood pressure] have been found to have obstructive sleep apnea, and this sleep apnea may contribute to the difficulty to control the blood pressure in these patients," he said.
Although this study showed a benefit from CPAP in controlling blood pressure, questions remain about the treatment's overall effectiveness, Fonarow said.
"Whether these improvements in blood pressure can be sustained in the long term and will translate to improved health outcomes will require additional studies," he said.
According to the chief medical liaison for Philips Respironics, Dr. Teofilo Lee-Chiong, the CPAP device allows the patient to sleep, and thus lets the blood pressure drop normally as it would at night.
"Patients have to get used to it, and most patients do," said Lee-Chiong, who is also a professor of medicine at National Jewish Health at the University of Colorado Denver.
The sound of the device is akin to a fan and can be lessened by placing the device under the bed or using earplugs, he added.
For the study, Martinez-Garcia and colleagues randomly assigned 194 patients with sleep apnea and high blood pressure to CPAP or no CPAP. During the study the patients continued to take their blood pressure medications.
The researchers found that those receiving CPAP lowered their 24-hour average blood pressure 3.1 mm Hg more than those not receiving CPAP.
In addition, those treated with CPAP had a 3.2 mm Hg greater reduction in 24-hour average diastolic blood pressure.
The difference in systolic pressure wasn't statistically significant between the two treatment groups, the researchers noted.
Over the 12 weeks of the study, about 36 percent of those receiving CPAP had at least a 10 percent drop in nighttime blood pressure, compared with 22 percent of patients not receiving CPAP, they added.
The systolic pressure, the top number, measures the pressure in the arteries when the heart beats. The diastolic pressure, the bottom number, measures the pressure in the arteries between beats.