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Gas Flow During Bronchoscopic Ablation Therapy Causes Gas Emboli to the Heart^*

A Comparative Animal Study

^* From the Department of Interventional Pulmonology (Dr. Feller-Kopman), Johns Hopkins Hospital, Baltimore, MD; the Division of Thoracic Surgery (Drs. Lukanich and Bueno and Ms. Edenfield), and the Department of Anesthesiology (Dr. Fox), Brigham and Women’s Hospital, and the Department of Interventional Pulmonology (Dr. Ernst), Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA; and Omni-Guide, Inc (Mr. Shapira, Mr. Kolodny, Mr. Schori, Mr. Temelkuran, and Drs. Schindel and Fink), Cambridge, MA.

Correspondence to: David Feller-Kopman, MD, FCCP, Director, Interventional Pulmonology, Associate Professor of Medicine, Johns Hopkins Hospital, 1830 East Monument St, Fifth Floor, Baltimore, MD 21205; e-mail: dfellerk{at}jhmi.edu

Abstract

Background: Thermal ablation is one of the most commonly used modalities to treat central airway obstruction. Both laser and argon plasma coagulation (APC) have been reported to cause gas emboli and cardiac arrest. We sought to determine whether bronchoscopic ablation therapy can result in systemic gas emboli, correlate their presence with the rate of gas flow, and establish whether a zero-flow (ZF) modality would result in the significant reduction or elimination of emboli.

Methods: CO₂ laser delivered through a photonic bandgap fiber (PBF) and APC were applied in the trachea and mainstem bronchi of six anesthetized sheep at varying dosages and gas flow rates. Direct epicardial echocardiography was used to obtain a four-chamber view and detect gas emboli.

Results: The presence of gas flow accompanying APC and the CO₂ laser with forward flow correlated significantly with the appearance of gas bubbles in the atria. A definite dose response was observed between the gas flow rate and the number of bubbles seen. When the CO₂ laser was delivered through a PBF with ZF to the trachea or bronchi, no bubbles were observed.

Conclusion: Bronchoscopic thermal ablation therapy using gas flow is associated with gas emboli in a dose-dependent fashion. The use of the flexible PBF with ZF is not associated with the development of gas emboli. Further study is required to determine whether a clinically safe threshold of gas emboli exists, and the relationships among the pathologic depth of tissue destruction, gas flow, pulse duration, and the development of gas emboli.

Key Words: bronchoscopy • central airway obstruction • gas emboli • laser • thermal ablation