Bronchoscopic thermal vapor ablation in a canine model of emphysema

Abstract

Clinical studies indicate the potential of bronchoscopic thermal vapor ablation to result in clinically relevant improvements in severe chronic obstructive pulmonary disease patients with upper lobe-predominant emphysema. However, the mechanisms by which vapor ablation results in lung volume reduction are not fully known. This study determined the 3-month safety and efficacy of vapor ablation in a canine model of emphysema and described the histopathological changes in the lung. The cranial lobes of papain-exposed dogs were treated with a vapor dose of ten calories per gram of lung tissue (n = 8) or were sham treated (n = 3). Safety was monitored peri- and postoperatively for 3 months. Animals were then sacrificed, estimates of lung volume reduction performed, and the lungs processed for histology. Vapor ablation was associated with an average of 20% volume reduction of the treated lobes and an absence of serious adverse events. The amount of lobar volume reduction was correlated with the amount of fibrosis and atelectasis in the treated lobe. Bronchoscopic thermal vapor ablation at a dose of 10 cal/g results in lobar volume reduction associated with remodeling of the targeted tissue characterized by mature collagen formation in the absence of major adverse events.

The Localized Inflammatory Response to Bronchoscopic Thermal Vapor Ablation

“…It resembles lung volume reduction surgery in that lung tissue is ablated, but with the advantage of a minimally invasive approach. Lung volume reduction is achieved with BTVA by delivering thermal energy in the form of heated water vapor through a disposable bronchoscopic catheter that leads to contraction fibrosis of targeted lung compartments [4,5,7]. Following BTVA in the described clinical trial, patients experienced improvements in airflow, lung volumes, exercise capacity and health-related quality of life that were present for the 12 months of follow-up [4,7].…”

“…The BTVA system delivers thermal energy in the form of heated water vapor to the most emphysematous destroyed areas of the lungs and thus induces a localized inflammatory response (LIR). The treated area heals with fibrosis and scarring, resulting in lung volume reduction [3,4,5]. Due to decreased hyperinflation in favor of adjacent healthier lung parenchyma and optimized respiratory mechanics, breathlessness is reduced and exercise capacity increases, leading to an improved quality of life [3,4].…”

Evaluation of Energy in Heated Water Vapor for the Application of Lung Volume Reduction in Patients with Severe Emphysema

“…microwaves, radiofrequency, laser and water vapor). The use of thermal energy delivered via heated water vapor to the lung in patients with emphysema to induce lung volume reduction through tissue ablation is a relatively recent application and has been based on the TE delivered, a mix of the energy contained in gas and liquid [2][3][4][5] . The dose of energy has been evaluated in several clinical trials to determine an optimal application dose that is efficacious with an acceptable safety profile.…”

“…Preclinical studies have demonstrated that a fibrotic response can be provoked after administration of TE in the dose range of 7.5-10.0 cal/g of tissue [5] . Clinical studies have indicated that a TE dose in the aforementioned range is safe and efficacious.…”

“…It is the thermal energy within the water vapor that elicits the response [5] . Vapor is a mixture of fine water droplets (liquid) and vapor (gas).…”