Clinical Trial Tests New Asthma Interventional Procedure
DURHAM, N.C. -- Pulmonary specialists from the U.S., Canada,
Brazil, Australia and the United Kingdom are testing a new
non-pharmacological strategy for treating difficult cases of
asthma by entering the effected airways and delivering thermal
energy to the airway walls to reduce the presence of airway
smooth muscle, the tissue responsible for causing the disease's
If the effectiveness of this minimally invasive approach is
borne out by clinical trials, Duke University Medical Center
pulmonologist Monica Kraft, M.D., said it could mark a paradigm
shift in how asthma patients are treated, in that physicians
will now have a procedure-based therapy for the disease.
"While there are many underlying causes, or triggers, for
asthma, the end result is inflammation of the airways and
smooth muscle contraction leading to airway constriction," said
Kraft, who also serves as the director of the
Duke Asthma, Allergy and Airway Center and principal
investigator for the Duke site. "This process leads to the
hallmark symptoms of asthma – shortness of breath, wheezing and
"With this new approach, we insert into the airways
themselves a flexible bronchoscope which delivers heat energy
directly to the walls of the airway," she continued. "The heat
reduces the volume of smooth muscle, which should reduce the
tendency of the airways to constrict when triggered."
The Asthma Intervention Research 2 Trial (AIR2) is a
randomized, double-blind clinical trial, which is being carried
out at over 30 sites throughout the world, and plans to enroll
more than 300 patients between the age of 18 and 65 with severe
asthma whose symptoms cannot be controlled by conventional
therapies. These therapies include high doses of inhaled
steroids or other agents. Kraft estimated that about one in
four asthma patients fall into this category.
According to Kraft, previous safety trials in Canada and
Europe have shown that after two-year follow-up, the smooth
muscle did not appear to return in the airways and patients did
not develop any significant complications.
Like traditional bronchoscopy procedures, patients enrolling
in the trial will receive medications to block the gag reflex
and to numb the areas where the scope is inserted. No incisions
or general anesthesia is involved.
During the procedure, physicians insert a flexible
bronchoscope either through the nose or the mouth. The scope is
then threaded to the target airway, where thermal energy is
deployed, heating the smooth muscle tissue at the specific site
for 10 seconds. Physicians then move the scope farther down the
airway and deliver therapy again, until the length of the
airway has been treated.
At Duke, Kraft will work with Momen Wahidi, M.D., a
pulmonologist with additional training in interventional
bronchoscopy. "I feel we have a great team for this study, as
we have considerable expertise with asthma and bronchoscopy,"
For the trial, physicians will treat about one-third of the
airways at each visit. Each treatment session takes about one
hour, followed by a four-hour observation period. Patients in
the control group will have the bronchoscope inserted, but the
thermal energy will not be applied.
"We plan to follow patients for at least one year, and while
the procedure will not cure asthma, we hope that it will
improve the quality of life for patients," Kraft said. "The
success of the new technology will be based on standard asthma
quality-of-life questionnaires filled out by participants
throughout the course of the trial. Additionally, we'll be
measuring such parameters as days without symptoms, the results
of different breathing tests and the degree to which rescue
medications are used to control symptoms."
The new system being tested is manufactured by Asthmatx,
Inc., Mountain View, Calif., which is sponsoring the trial.
Kraft has no financial interests in Asthmatx.
According to the American Lung Association, more than 20
million Americans have asthma, with about 6.2 million of those
being under the age of 18. Asthma attacks lead to more than 2
million emergency rooms visits each and are responsible for
5,000 deaths each year.