Drug-free advance in asthma therapy
TheStar.com - News - Drug-free advance in asthma therapy
Experimental heat procedure improved patients' lives dramatically, study says
March 29, 2007
Joseph Hall
Health reporter
These are the things that asthma took from Brenda Donahue: the sight of sun-dappled forests, the smell of horses, the feel of sand between her toes.
"I grew into asthma, I didn't have it all my life, so I was used to going on hikes, going through the woods, going to parks and beaches.
"I loved those things," Donahue says.
"Once I developed the asthma, I was very restricted in what I could do, especially outdoor activities.
"I had a huge reaction to animal life, all of a sudden – even to grasses and plants."
After an experimental procedure that used low doses of energy from radio frequencies to zap her stricken airways, Donahue has reclaimed the great outdoors.
The 44-year-old Hamilton woman was one of the first patients in Canada to receive the treatment, known as bronchial thermoplasty.
Almost five years later, she has reduced her use of inhalers from five to six times a day to one at most.
A study detailing the "tremendous" potential of the thermoplasty procedure to control asthma was published yesterday in the New England Journal of Medicine.
It suggests the procedure – the first non-drug therapy for asthma – can significantly improve the lives of many patients with moderate to severe forms of the disease.
The treatment will only be available to adults, since doctors are reluctant to alter the bronchial airways of children until they are fully developed.
"It brings a whole new energy to (asthma research)," says the study's co-author, Dr. Gerard Cox, a respirologist at St. Joseph's Healthcare in Hamilton. He also heads McMaster University's department of respirology.
The study, which included Donahue, shows people receiving the treatment have, on average, 80 to 90 more symptom-free days a year than those who take medications alone.
They also experienced about 10 fewer severe attacks a year.
Asthma affects the body's two bronchial passages, which are treelike structures that fork off from the trachea into the lungs.
During asthma attacks, muscles encircling these airways constrict, making breathing difficult.
During severe attacks, patients can die from the disorder.
With the thermoplasty procedure, doctors feed a thin tube down the throat into the bronchial airways and insert a catheter that carries an array of four electrodes at its end.
The electrodes are spread out to touch the bronchial walls when the array emerges from the bottom of the tube.
A radio frequency current then heats up the electrodes to 60 or 70C, about the temperature of a warm cup of coffee.
"We're not dealing with heat that's enough to burn. When we do a treatment we can hardly see any effect on the airway wall ... the effect is microscopic," Cox says.
After 10 seconds, the electrode array is collapsed and pulled about a centimetre up the bronchial passage, where it zaps the next segment.
"You go (down) as far as you can in the airways ... and you march backwards, giving a continuous treatment delivery," Cox explains.
The thermoplasty procedure is done on an outpatient basis in three sessions, one for each of the lower two bronchial passages and a third for the upper portion of both.
While it causes an increase in wheezing for a few days afterward, the symptoms soon dissipate.
Researchers don't know yet why it works, but they believe the elevated temperatures produce microscopic changes in the bronchial muscles, restricting their ability to contract with the same force they did during asthma attacks.
Cox says the procedure will be used first on those with moderate to severe forms of asthma for whom traditional drug therapy – usually delivered with an inhaler – doesn't control the disease.
It is being touted as a companion to drug therapy not a replacement, although a major benefit has been its ability to significantly reduce the need for medication in many of the people who have undergone the procedure.
The study looked at 110 patients who were split into two groups. One used their traditional drug therapies. The other underwent bronchial thermoplasty while continuing their medications.
After a year, the bronchial thermoplasty group had far more symptom-free days than the control group, fewer significant asthma attacks each year and a substantial improvement in the quality of life.
Measured on a scale from zero to seven, the quality of life measurement for the bronchial thermoplasty group improved by a full point over the group who had medication alone, Cox says.
"A half a point change is regarded as clinically significant, so we had twice that size," he says.
While it's too early to say how long its effects last, Cox says animal experiments show the results may well be permanent.
The study was part of a larger global trial that is to be completed in the next 12 months. After that, Cox says it will be up to regulatory agencies such as Health Canada to determine when the procedure will be generally available.
About 3 million Canadians suffer from asthma and six out of 10 do not have the disease under control, according to the Asthma Society of Canada. |
