New Heat Technology Helps Asthma Patients

It thins out airway muscle for better breathing, study finds

WEDNESDAY, March 28, 2007 (HealthDay News) -- A new technology that uses radio waves to burn off overgrown muscle in the airways of asthma sufferers helped them breathe better, have fewer symptoms and use less medication, researchers report.

The technique, called bronchial thermoplasty, now is being tested in a larger trial that could lead to its approval by the U.S. Food and Drug Administration.

"This is the first trial that shows a fairly remarkable response," said co-researcher Dr. John D. Miller, an associate professor of surgery at McMaster University in Canada. "It also is the first non-drug treatment for asthma to be developed recently."

The report is published in the March 29 issue of the New England Journal of Medicine.

With thermoplasty, doctors snake wires that can emit radio waves into the lungs. These radio waves emit heat that can burn off some smooth muscle in the airways.

The basic idea behind thermoplasty is that "smooth muscle sits around the airway, and when it contracts it makes the airway narrower," Miller explained. "When the amount of muscle is reduced and it is triggered to contract, there is nothing to contract."

The trial included 112 people with moderate to severe asthma. Half underwent three sessions of thermoplasty; the other half had their usual drug treatment.

One year later, air flow was much better in patients receiving thermoplasty -- 39 liters per minute compared to 8.5 liters per minute for those getting standard treatment.

The thermoplasty group also reported an average of 40 symptom-free days, compared to 17 for the others, with fewer asthma symptoms and less medication used.

"Now a second trial, which uses information from this one, moves forward," Miller said. "It is similar to the first trial except that it will use a sham procedure in the control arm."

Full enrollment of 350 asthma patients for the new trial has been completed, said Dr. Elliot Israel, an associate professor of medicine at Harvard Medical School and a member of the research group. "They are in different phases of treatment, with some on their second or third sessions," Israel said. The participants will be followed for up to two years to assess the results of the treatment.

The therapy may also produce other beneficial effects besides just giving air more space to move in, Israel said. "Living muscle cells produce chemicals and biological signals that increase inflammation," he said. "It may also change some of the dynamics of connective tissue in the airway."

One important aspect of the method is that it has turned attention back to the role of muscle tissue in asthma, which has been more or less ignored for many years, said Charles G. Irvin, director of the Vermont Lung Center of the University of Vermont and co-author of an accompanying editorial. Attention has been focused on immunology and inflammation, rather than on airway muscle, he said.

Thermoplasty may not be the best way to affect that muscle tissue, Irvin said. "The current procedure is not trivial," he said. "The patient must come in three times, and there is risk every time you do a bronchoscopy."

The editorial proposes other possible methods, such as drugs that would paralyze muscles in the airways or delete muscle chemically.

"But the more important thing is that this procedure improves outcome," Irvin said. "That is exciting. It makes us rethink conventional wisdom."

Thermoplasty ultimately may be especially useful for asthma sufferers whose problem is severe enough to bring them to the emergency room, Irvin said.

"Maybe we can learn to do this in a less invasive way," Miller said. "Right now, it is a pretty stunning intervention with good results."

More information

Find out more about asthma at the U.S. National Heart, Lung, and Blood Institute.

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