BY KRISTA CONGER
Stanford, May 17 -- The noisy sleeping habits of some people may be more than just a nuisance to their families and bed partners. The choking, gasping sounds that accompany the slumber of people suffering from obstructive sleep apnea are symptoms of what could be a life-threatening medical condition. Stanford researchers have introduced a technology that could help solve the problem by shrinking the excess tissues that obstruct breathing when the airway relaxes during sleep. The nearly painless outpatient procedure takes about 30 to 45 minutes to perform and, after being monitored overnight, patients can return to their normal activities.
"This is a breakthrough in the treatment of sleep apnea," said Nelson Powell, MD, co-director of the Stanford University Sleep Disorders Center, who conducted a recent study on the procedure. "We haven't had a new efficacious treatment with a scientific basis in years," he said.
The researchers used radiofrequency energy to heat internal tissue in the base of the tongue to about 80š C. The heat-induced lesion is reabsorbed by the body during the natural healing process, reducing the size of the tongue and its propensity to block the airway during sleep. Powell's group reported its findings in the May issue of Otolaryngology - Head and Neck Surgery, documenting an average 17 percent decrease in tongue volume in patients who underwent a series of treatments.
Severe medical problem
Obstructive sleep apnea affects some 20 million Americans, and it is associated with nearly 38,000 cardiac deaths annually. The condition is characterized by frequent disruption of nighttime breathing when the base of the tongue or the soft palate blocks the upper airway. When breathing stops, the person rouses him or herself just enough to clear the obstruction by snorting or gasping for air. This cycle can be repeated more than 100 times each hour.
People who suffer from severe sleep apnea complain of uncontrollable daytime fatigue. They are seven times more likely to have an automobile accident. In addition to compromised efficiency during their daily routine, affected people are more likely to have high blood pressure and heart disease.
According to Powell, sleep apnea is caused by loss of tissue tone around the airway. When the floppy tissue partially blocks breathing, the person is forced to take in the same amount of air through a smaller opening. As the breathing becomes more forced, the tissue moves in and out with each breath, further decreasing tissue tone and causing even more blockage.
"The opening may start out the size of a quarter, and then gets to be the size of a straw," said Powell. "It takes years for the tissue to completely block the airway, and that's called sleep apnea."
Traditional treatments for sleep apnea include medical management, such as dental devices and masks worn at night to maintain positive air pressure to keep the airway open. In severe cases, surgery is used to reduce tissue volume. According to Powell, the new radiofrequency treatment, called SomnoplastySM, is a cost-effective, minimally invasive alternative to surgery, and it may be even more effective for cases in which both the palate and the tongue are involved in the blockage.
"The tongue is the portion that is most difficult to treat because of its size," said Powell. "If you just fix one and not the other you still have a blockage in the tube," he said.
Powell's group studied 18 patients with mild to severe sleep apnea and their responses to radiofrequency. A small electrode was placed at the base of the tongue to deliver low dosages of energy below the mucosal lining, heating the internal tissue for about five minutes per site. Two sites were targeted during each session. The treatments were delivered every three to four weeks to allow for healing and absorption of the affected tissue between sessions. Most patients reported minor discomfort for a few days following each treatment.
Prior to treatment, the patients suffered an average of 40 incidences of disrupted breathing per hour every night. After receiving about six treatments, patients experienced a more than 50 percent reduction in apnea episodes to about 18 per hour. They also reported less daytime sleepiness and an increased quality of life. The results were so dramatic that Powell temporarily discontinued the study to further analyze the findings.
Magnetic resonance imaging of the tongue before and after the series of treatments confirmed that the volume of the tongue had decreased by an average of 17 percent, with one patient experiencing a 33 percent decrease. Each patient's speech and swallowing ability was evaluated before and after treatment to confirm that other normal functions of the tongue were not impaired by the procedure.
The quick and effective treatment enabled patients to immediately resume their normal activities. This contrasts markedly with surgery, which requires hospitalization and can often result in a painful recovery, Powell said.
New use envisioned
Powell learned how other physicians were using radiofrequency energy to decrease tissue size to treat cancer tumors and shrink enlarged prostates and thought the same technique could be used to treat sleep apnea. He started working with Stuart Edwards, founder of Somnus Medical Technologies, to develop the clinical application of this technique in the upper airway.
After testing his idea on an animal model to correlate the amount of energy applied with the physical effects of the treatment, he began using the procedure to reduce the size of the palate and to clear chronic nasal obstructions in habitual snorers, or people with mild sleep apnea. He had such success with the method that he began treating the tongues of patients with more severe sleep problems and embarked on his current study.
Powell presented the results of this and previous radiofrequency studies at the American Thoracic Society Workshop on Alternative Therapy May 10 and 11 in Pittsburgh.
"This is the study that everyone in the sleep community has been waiting for," he said, adding that if Somnoplasty becomes a standard treatment for obstructive sleep apnea, it won't only be physicians who are cheering. Patients and their families may be able to look forward to their first peaceful night's sleep in years.
Somnus Medical Technologies of
Sunnyvale, Calif., funded and designed the proprietary system used
in the current study. The company offers instructional classes to
physicians on the appropriate techniques and uses of the
radiofrequency SomnoplastyTM System.