NEW YORK (Reuters Health) - The removal of muscle tissue in the overly active airways of asthma sufferers by exposing the tissue to heat -- a procedure called bronchial thermoplasty -- can help improve the control of moderate to severe persistent asthma, new research suggests.

The so-called smooth-muscle fibers that surround the airways are what cause constriction of the airways in asthma. Bronchial thermoplasty aims to reduce smooth muscle activity by delivering thermal energy to the walls of the airways. The experimental treatment is given in a series of procedures using a bronchoscope and a device at the end for generating heat in a controlled fashion.

Dr. Gerard Cox, from McMaster University in Hamilton, Ontario, Canada, and colleagues assessed the outcomes of 112 asthma patients who were randomly assigned to bronchial thermoplasty or standard care.

Patients in the thermoplasty group experienced a significant drop in asthma flare-ups, according to the team's report in this week's issue of The New England Journal of Medicine.

By contrast, no change in the rate of asthma flares was seen in the comparison group.

At the 12-month mark, significantly greater improvements in lung function and quality of life were noted in the thermoplasty group compared with the standard-care group. The thermoplasty group also had more days free of asthma symptoms and used less "rescue" medication.

As has been shown before, thermoplasty patients are apt to experience a worsening of asthma symptoms immediately after the procedure, but this subsides with time.

Although promising, bronchial thermoplasty is probably not ready for general use, Dr. Julian Solway, from the University of Chicago, and Dr. Charles G. Irvin, from the University of Vermont in Burlington, note in an accompanying editorial.

"Because of the considerable effort involved (three separate bronchoscopic procedures, each with a small but significant risk of complications), notable adverse effects (in the short-term, at least), and likely expense, bronchial thermoplasty will probably need further refinements if it is to emerge as a widely applicable, practical treatment for moderate or severe asthma," they conclude.