A new "anatomic" treatment for severe asthma
In this entry, I would like to provide a little background on a new treatment for severe asthma. Most asthma treatments are directed at avoiding triggers and taking medications that decrease inflammation and open up (dilate) twitchy breathing tubes (airways) -- both are key features of asthma that cause wheezing and shortness of breath. For some individuals with severe asthma, symptoms persist despite careful environmental controls and diligent medication adherence.
In an earlier entry, I discussed a "next step" treatment for persistent, severe allergic asthma: omalizumab (Xolair). In the past two years, scientists and doctors who take care of patients with severe asthma have reported results on directly opening up the chronically narrowed airways of severe asthmatics. I call this an "anatomic" approach as the treatment seeks to physically cause airways to dilate, rather than by taking medications by inhaler or by mouth. This treatment is called "bronchial thermoplasty."
Changes to the airways in severe asthma
As mentioned earlier, key features of the airways of asthmatics are inflammation and twitchiness -- small triggers cause the smooth muscle of the airways to constrict significantly, leading to wheeze. In most asthmatics, the inflammation can be controlled with inhaled medications, especially inhaled steroids (such as Flovent, Pulmicort, Azmacort, and others).
Narrowing of the airways can be controlled by inhaled bronchodilators (such as like albuterol, Serevent, Singulair). The narrowing (and wheeze) are temporary and can be reversed with medication.
For a subset of individuals with severe asthma, the airways are chronically narrowed or constricted. Even with aggressive treatment, they remain partly narrowed, and can become more so when the come in contact with triggers.
Bronchial thermoplasty for severe asthma
Bronchial thermoplasty is a treatment in which the smooth muscle of the smaller airways in the lungs are directly treated with a heat probe, resulting in mild intentional scarring and opening of the airways. The treatment, which does not involve surgery, is performed with a flexible bronchoscope that goes through the nose and into the airways. Patients are typically given medication to make them relax and in some cases put to sleep. With the bronchoscope in the lungs, a thin wire with a heat probe on the tip is passed beyond the tip of the bronchoscope and heat applied to the walls of the airways for 10 seconds. This is repeated in nearby airways thereafter, covering about a third of lungs in each treatment. The entire procedure is repeated 3 weeks later and again 3 weeks after that.
The two largest clinical studies to date, both in prominent medical journals, have shown that patients' asthma is significantly improved 12 months after treatment with respect to number of severe exacerbations and symptoms based on questionnaires. However, it is clear that shortly after treatment there is increased shortness of breath and wheeze, with some episodes requiring brief hospital treatment.