CONTACT: Heather Rock Woods, (415) 725-5371 or 723- 6911; e-mail [email protected]
BROADCAST MEDIA CONTACT: M.A. Malone, (415) 723-6912 or 723-6911; e-mail [email protected]
COMMENT: Dr. Nelson Powell, (415) 328-0511
5/8/97
RADIO ENERGY SHRINKS AIRWAY TISSUE, SUGGESTING CURE FOR SNORING, APNEA
STANFORD -- A wand-like instrument that emits radio- frequency energy can selectively shrink excess soft tissue, potentially offering a way to cure sleep apnea, a Stanford sleep specialist reports.
The experimental method safely and successfully shrank the tongues of research animals, Dr. Nelson Powell and his colleagues show in the May issue of the peer-reviewed journal Chest. And so far, the method appears to reduce heavy snoring in humans by shrinking palate tissue, more recent research suggests.
The next step is to try shrinking people's tongues to reduce sleep apnea, a disorder in which people temporarily stop breathing while they sleep.
"We're doing this in a scientific manner, in a step-wise fashion," said Powell, who co-directs the Stanford Sleep Disorders and Research Center. He is a clinical associate professor of psychiatry and a head-and-neck surgeon at Stanford University Medical Center.
"At this time we're not using it to treat sleep apnea. But that's our ultimate goal, if everything goes well," Powell said.
Obstructive sleep apnea syndrome, in which the airway collapses during sleep, afflicts approximately 2 percent of women and 4 percent of men in the United States. It can result from excess soft tissue in the upper airway, including the tongue, palate and nose.
Sleep apnea leads to dangerous levels of fatigue. Current treatments include removing excess tissue by scalpel or electrocautery (which burns away tissue); cutting out extra tissue with a high-temperature laser beam; and delivering continuous positive airway pressure (more commonly abbreviated as CPAP) through a mask worn at night.
But Powell's study in Chest presents a solid foundation for a new treatment that is quick, relatively painless and done without hospitalization, he said.
The technique relies on a custom needle electrode pushed into soft tissue. The electrode relays radio-frequency energy to nearby cells, destroying them. As the lesion heals, it is replaced by scar tissue, which takes up less space.
Physicians using this method can target tissues with precision because the radio-frequency energy quickly drops off as it travels from the electrode. That makes it possible to shrink excess tissue without damaging nearby structures.
"The heat dissipates so rapidly that you have very precise targeting of an area," Powell said. "We watched the healing process of the wound. There was very little edema [fluid buildup]. We saw the usual inflammatory reaction, which is part of the healing process. The tissue shrank and was replaced by fibrous scar tissue."
The radio-frequency generator creates relatively low-heat energy, between 40 and 90 degrees Celsius (104 to 194 degrees Fahrenheit). Lasers and electrocautery work at much higher temperatures, causing more extensive thermal damage, he said.
Radio-frequency energy has been used medically for two decades, first for cranial nerve problems and then for cancer, cardiology and enlarged prostates.
For the animal study published in Chest, Powell and his colleagues measured volume changes in pig tongues after radio-frequency treatment. Compared with untreated controls, the treated animals showed significant reductions in tissue volume. And the researchers found that the reductions were larger when more time had elapsed since the procedure, culminating at a 26.3 percent reduction in an animal measured 10 days after treatment.
The animal study was the first step in evaluating the safety and efficacy of the radio-frequency treatment. Powell is now working on step two: a clinical trial to determine the treatment's safety and pain level when applied to human airway tissue. He is currently collecting data on its use to shrink palate tissue in obstreperous snorers. When he finishes all of these treatments in July, he will submit the data to a peer-reviewed journal, he said.
Snoring is a sign of a partly obstructed airway, Powell said. He first tested snorers who do not have an underlying sleep condition because snoring is often a warning sign in people with sleep problems, and he did not want to remove that alarm.
He is treating 23 snorers with small doses of radio- frequency repeated every few weeks for a total of three to five sessions. All of these patients have experienced at least a 70 percent improvement on a snoring scale of 1 to 10, he said.
(Most of the patients started at a snoring level of 10, which Powell defines as being so intense that another person can't sleep in the same room. Levels 1 to 3 involve soft, occasional snoring, and 4 to 7 involve loud, bothersome snoring.)
During the 20-minute outpatient procedure, patients sit back in a dental-like chair with their mouths open and tongues depressed. They typically feel pressure when the medical team pushes a needle electrode several millimeters into the locally anesthetized palate. Up to 20 percent of patients feel warmth during the 1.5 minutes that the electrode delivers 3 to 5 watts of radio-frequency power.
Powell said his patients reported little pain during and after the procedure and experienced minimal swelling the next day. There were no instances of bleeding or infection, he said. Most of the patients did not feel the need for pain medication after the procedure, Powell said. "With people who did, we have found the pain medication of choice has been Tylenol. But most take nothing. Radio-frequency doesn't affect their speech or swallowing, even right after the procedure.
"It's been far beyond my expectations," he added.
The third step in testing, which Powell will begin soon, is to determine whether radio-frequency applied to the human tongue will cure sleep apnea. He will measure tongue volume with magnetic resonance imaging and will rigorously test swallowing and speech abilities before and after the procedure.
"I want it to work, but the main thing is that I don't want it to hurt. All the other techniques have pain, so this would really be something. I originally developed this for older patients who are too rickety to undergo surgery," Powell said.
In the Chest paper, he and his co-authors wrote that future treatment approaches for apnea "will need to be minimally invasive, easy to perform, short in treatment time with minimal patient discomfort, and cost-effective with acceptable clinical outcomes. Our investigation of [radio- frequency] tissue reduction could fulfill these parameters."
Three of his co-authors work in the Stanford University Sleep Disorders and Research Center: Dr. Robert W. Riley, Powell's head-and-neck surgery partner and a clinical associate professor in psychiatry; Dr. Robert J. Troell, a head-and-neck surgeon, medical sleep specialist and clinical instructor; and Dr. Christian Guilleminault, professor of psychiatry and medical sleep specialist. Another co-author, Dr. Marc B. Blumen, is a head-and-neck surgeon with the University of Paris.
The newly reported research was funded by Somnus Medical Technologies Inc. of Sunnyvale, Calif., the company that developed the needle electrode.
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