A prospective feasibility study of bronchial thermoplasty in the human airway.

BACKGROUND: Bronchial thermoplasty is a novel procedure being developed as a potential treatment for asthma. Experience with animal studies has enabled development of appropriate reliable equipment, definition of therapeutic parameters, and descriptions of tissue effects of treatment. STUDY OBJECTIVES: This study was undertaken to assess the feasibility and general safety of the application of bronchial thermoplasty in the human airway, and to determine if the reduction in airway smooth muscle seen in animal studies could be replicated. DESIGN: A prospective study. SETTING: Academic thoracic surgery center. PARTICIPANTS: Nine patients scheduled to undergo lung resection for suspected or proven lung cancer. INTERVENTIONS: Bronchial thermoplasty was performed during routine preoperative bronchoscopy up to 3 weeks prior to prescheduled lung resection. Treatment was limited to areas of the segmental bronchi within the lobe that was to be removed. Treated airways were inspected via bronchoscopy at the time of thoracotomy, and were examined histologically following surgical resection. RESULTS: There were no adverse clinical effects of the procedure, including no new symptoms and no unscheduled visits for medical care. Treated sites exhibited slight redness and edema of the mucosa within 2 weeks of treatment, and appeared normal at later time points. There was narrowing (visually estimated at 25 to 50%) in four airways in two subjects examined at 5 days and 13 days after treatment, with excess mucus in two of these airways. There was no bronchoscopic evidence of scarring in any of the airways examined. Histologic examination showed a reduction in airway smooth muscle, and the extent of the treatment effect was confined to the airway wall and the immediate peribronchial region. CONCLUSION: Application of bronchial thermoplasty to the human airway appears to be well tolerated. Treatment resulted in significant reduction of smooth muscle mass in the airways. Bronchial thermoplasty may provide therapeutic benefit in disease states such as asthma.

Reduction in airway hyperresponsiveness to methacholine by the application of RF energy in dogs.

We delivered controlled radio frequency energy to the airways of anesthetized, ventilated dogs to examine the effect of this treatment on reducing airway narrowing caused by a known airway constrictor. The airways of 11 dogs were treated with a specially designed bronchial catheter in three of four lung regions. Treatments in each of the three treated lung regions were controlled to a different temperature (55, 65, and 75 degrees C); the untreated lung region served as a control. We measured airway responsiveness to local methacholine chloride (MCh) challenge before and after treatment and examined posttreatment histology to 3 yr. Treatments controlled to 65 degrees C as well as 75 degrees C persistently and significantly reduced airway responsiveness to local MCh challenge (P < or = 0.022). Airway responsiveness (mean percent decrease in airway diameter after MCh challenge) averaged from 6 mo to 3 yr posttreatment was 79 +/- 2.2% in control airways vs. 39 +/- 2.6% (P < or = 0.001) for airways treated at 65 degrees C, and 26 +/- 2.7% (P < or = 0.001) for airways treated at 75 degrees C. Treatment effects were confined to the airway wall and the immediate peribronchial region on histological examination. Airway responsiveness to local MCh challenge was inversely correlated to the extent of altered airway smooth muscle observed in histology (r = -0.54, P < 0.001). We conclude that the temperature-controlled application of radio frequency energy to the airways can reduce airway responsiveness to MCh for at least 3 yr in dogs by reducing airway smooth muscle contractility.