The thermoplasty experiment targets patients who do poorly despite multiple medications -- based on evidence that overgrown muscle tissue lining air tubes inside the lungs is one of asthma's underlying causes.

It's not without risk. Irritating those super-sensitive airways can trigger wheezing, and no one knows the long-term effects. Nor does it promise a cure. But the hope is that physically altering spasm-prone airways might one day help thousands of patients with hard-to-control asthma breathe easier.

"People still get very sick from asthma. People still die of asthma. You'd think we'd have better control, but it seems to be escalating rather than going down," said Dr. Michael Simoff, interventional pulmonology chief at Detroit's Henry Ford Medical Center, one of 17 US hospitals, and 29 worldwide, enrolling patients in the experiment.

"We have a real potential here, I think, to influence a very common disease."

Two Million Emergency Room Visits

More than 20 million Americans have asthma, and the chronic lung disease is on the rise. While medications can be very effective in preventing and treating asthma attacks, the disease kills 5,000 people every year and accounts for 2 million emergency-room visits.

The thermoplasty experiment targets patients who do poorly despite multiple medications -- based on evidence that overgrown muscle tissue lining air tubes inside the lungs is one of asthma's underlying causes.

So-called smooth muscle encircles those airways. When something irritates the lungs, the muscle spasms, narrowing air passages to leave patients gasping. Swelling further closes off their air. Repeated attacks thicken muscle so airways can become habitually narrowed, and the muscle becomes even more sensitive to asthma triggers.

Bronchial thermoplasty promises to get rid of half of that thickened muscle, in hopes that the airways will behave more normally.

'Real Test' Underway

Coughing and wheezing are common side effects for a few days but clear once lung irritation subsides, said Dr. Gerard Cox of Canada's McMaster University, who reported the first study results -- on 16 patients tracked for two years -- this month in the American Journal of Respiratory and Critical Care Medicine.

Most breathed a little bit easier on an asthma test and had more symptom-free days by three months after treatment, he reports. A second pilot study of 108 patients found similar improvements in the half given thermoplasty, researchers reported Monday at an American Thoracic Society meeting.

Now under way is the real test, a clinical trial funded by device manufacturer Asthmatx Inc. that is enrolling at least 300 severe asthmatics.

Asthmatx won't yet estimate the cost, but simple bronchoscopies cost up to $2,000 each.