PURPOSE: To achieve lung volume reduction (LVR) without the adverse effects of thoracic surgery and lung excision, intrabronchial approaches have been developed including placement of airway plugs and valves. Although these methods generally reduce ventilation to targeted regions, collateral ventilation often limits the expected volume reduction. We tested the hypothesis that delivery of heated water vapor into the bronchial tree of targeted lung regions would produce ablation of the parenchyma due to subsequent remodeling of damaged tissue, thus producing effective LVR.
METHODS: To date, this hypothesis has been tested in dogs and sheep, both in normal animals (28 dogs, 9 sheep) and in animals previously exposed to aerosolized papain (18 dogs, 12 sheep), an agent known to produce emphysema-like changes in lung function. Vapor was delivered to targeted regions via flexible bronchoscopy, after deploying a balloon-tipped catheter in the appropriate segmental or sub-segmental bronchus. Each animal received one treatment to several upper lobe segments (dogs), and upper and middle lobe segments (sheep), with time of vapor administration ranging from 1 to 47 seconds. Six of the animals received sham treatments (3 of each species). Several methods were used to monitor changes in relevant lung function parameters and to detect potential adverse treatment effects (e.g., air and thromboembolism, infection, pneumothorax, hemodyamic alterations). The animals were survived for up to 180 days following treatment, and the lungs and adjacent organs were examined following sacrifice by necropsy and histological evaluation.
RESULTS: Overall, administration of vapor typically produced substantial loss of lung volume in the treated regions (up to ∼ 80%), in a dose-dependent manner (greater effect with greater calories heat energy per gram of treated tissue), that persisted up to six months. Significant adverse events were largely restricted to animals receiving the longest treatment times.
CONCLUSION: We conclude that BVTA is a technically simple, safe and effective method for producing LVR in animals with experimentally-induced emphysema.
CLINICAL IMPLICATIONS: BTVA is a potentially valuable new treatment for emphysematous humans.
DISCLOSURE: Michael Emery, Grant monies (from industry related sources) Financial support for this project was provided by the Uptake Medical Corporation, and was administered, independent of this sponsor, at the Veteran's Administration Puget Sound Health Care System by the Seattle Institute for Biomedical and Clinical Research; Consultant fee, speaker bureau, advisory committee, etc. I have received consultation fees from the Uptake Medical Corporation; Product/procedure/technique that is considered research and is NOT yet approved for any purpose. Bronchoscopic thermal vapor ablation (BTVA).