Asthma Zap: Heated scope reduces attacks
A new tool cools asthma by heating lung tissue to kill overgrown smooth muscle in airways, a hallmark of the disease.
People with severe asthma who received the treatment experienced, on average, 10 fewer asthma attacks and 86 more days per year without wheezing and coughing than untreated patients did.
A small metal element at the tip of a bronchoscope heats to 65°C. The tip radiates enough heat to kill the smooth muscle lining the lung’s airways without permanently harming underlying tissue, says Gerard Cox of McMaster University in Hamilton, Ontario, who led the multicenter study. “It’s the difference between getting suntanned and sunburned.”
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Charles G. Irvin of the Vermont Lung Center in Burlington says that the cost and immediate discomfort of the technique, called bronchial thermoplasty, make it suitable only for “frequent fliers”—people with asthma who visit the emergency room at least a few times per year.
“It’s for patients whose [asthma] can’t be controlled with standard therapy or … who just aren’t taking their meds,” he notes. “I’d say every pulmonologist will have two or three patients who are candidates.”
Observing progress through the bronchoscope, a physician slides the tool into the lung airways, heats the tip, repositions it, and then heats it again. The bronchoscope is too large to reach the small airways deep in the lungs.
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In the study, 52 adults with severe asthma received bronchial thermoplasty in addition to standard medication. At 3, 6, and 12 months after the series of three half-hour procedures, patients in this group were compared with 49 similar patients who didn’t get thermoplasty. Daily symptom diaries, quality-of-life surveys, and clinical exams showed evidence of improvement only for the thermoplasty group.
Besides experiencing fewer attacks and more symptomfree days, patients in the treated group exhaled larger air volumes in the morning and needed their inhalers less than those in the control group did. The benefits were still apparent 1 year after treatment, the team reports in the March 29 New England Journal of Medicine.
However, this long-term gain cost some short-term pain. In the days after thermoplasty, patients experienced “coughing, wheezing, spitting, [being] short of breath, needing more inhaler [than usual],” says Cox. A few of the patients were hospitalized for these symptoms. But the “vast majority” of the side effects disappeared within a week, he reports.
According to earlier research, the tool kills about half of the smooth muscle in the airways. It also damages the airway walls lying under the muscle. But, says Cox, “the other tissue grows back and the muscle doesn’t.”
Asthmatx of Mountain View, Calif., the company that makes the tool, funded the study along with a larger test that is under way. In the newer work, some participants are getting sham bronchial thermoplasty, in which the tool is inserted into the lungs but not heated. Karen Passafaro, an Asthmatx spokesperson, adds that the company plans to seek Food and Drug Administration approval of the tool in 2008.