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Pacemaker treats sleep apnea

Experimental device works for many patients who can’t use breathing machines

BREATHE IN, BREATHE OUT  An electronic pacemaker (neurostimulator) implanted just beneath the skin of the chest gets signals from a sensor between ribs (fourth intercostal region) whenever the chest expands. The pacemaker shoots an impulse to a lead attached to the hypoglossal nerve, which controls the muscle at the base of the tongue. This causes the tongue to protrude, opening the throat just in time for the person to inhale — all while asleep.

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An implantable gizmo can halt obstructive sleep apnea, a nighttime breathing disorder that disrupts rest and robs the body of oxygen. The experimental device, an electronic pacemaker that syncs breathing with opening of the throat, relieved sleep apnea in two-thirds of people who tested it.

The volunteers had moderate-to-severe sleep apnea but couldn’t tolerate a standard treatment with a breathing machine that requires wearing a mask. That machine, called CPAP for continuous positive airway pressure, delivers air at a steady pace to keep airways open. Beyond CPAP, few treatments are available for severe sleep apnea, says study coauthor Ryan Soose, an otolaryngologist at the University of Pittsburgh Medical Center. “Other solutions are needed,” he says, and the pacemaker “comes at it in a really unique way, mainly targeting the anatomy of the throat.”

Soose and other researchers implanted pacemakers in 126 apnea patients, who were instructed to turn it on each night for a year. On average, the patients reported substantially less daytime sleepiness than before getting the pacemaker. They had fewer sharp drops in blood oxygen levels per hour, a sleep test found, and struggled for breath less during sleep — dropping from 29 gasps per hour to nine. The report appears in the Jan. 9 New England Journal of Medicine.

When the scientists randomly assigned 23 of the volunteers who had benefited from the pacemaker to get the device shut off for a week, the patients rapidly began having sleep apnea problems again.

H. Klar Yaggi, a pulmonologist and sleep researcher at Yale School of Medicine, expects the device to succeed. “This has the potential for changing practice.” He says the pacemaker’s effects on breathing are comparable to CPAP’s. But while CPAP remains the first option for patients, Yaggi says, 40 percent use the device inconsistently or abandon it.

Surgeons implant the pacemaker beneath the skin of the upper chest. A wire extends from the device to a nearby spot between ribs, where a sensor detects the start of each breath as the chest expands. An electrical signal then shoots along a wire threaded beneath the skin up to the neck to stimulate a nerve that controls tongue and throat muscles. The nerve makes the tongue stick out and the throat open. In many patients, this change freed up breathing.

Sleep apnea carries an increased risk of stroke, high blood pressure and heart attack. In 66 percent of the volunteers, says Soose, the pacemaker reduced stoppages of breath to 20 per hour, the threshold for cardiovascular risk. About one in five reported some tongue weakness or soreness, but this went away. Two people needed to have their device repositioned. One other patient asked to have the pacemaker removed, and one died of a heart problem unrelated to the implant.

Study coauthor Patrick Strollo Jr., a physician and sleep researcher also at Pittsburgh, acknowledges that the participants weren’t randomly selected. The study largely excluded people who were obese, had very severe or very mild sleep apnea or had large tonsils. The study also didn’t compare the pacemaker with other sleep therapies.  

Patients in the study have been allowed to keep their pacemakers and will continue to be monitored, Strollo says. The technology comes with lithium batteries that can last six to eight years, he says. The device is made by Inspire Medical Systems in Maple Grove, Minn., which provided support for the study.

The pacemaker is unlikely to get tested against sham surgery — the equivalent of a placebo — because sleep apnea is too serious to leave untreated, says Atul Malhotra, a pulmonologist at the University of California, San Diego. But, he says, the study “does set the stage for a comparative-effectiveness study against CPAP.” 

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