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Airway Bypass Improves the Mechanical Properties of Explanted Emphysematous Lungs

¹ Division of Cardiothoracic Surgery, Washington University School of Medicine, St. Louis, Missouri; ² Jacqueline Maritz Lung Center, Barnes-Jewish Hospital and Washington University School of Medicine, St. Louis, Missouri; ³ Division of Cardiothoracic Surgery, Papworth Hospital, University of Cambridge, Cambridge, United Kingdom; ⁴ Meakins-Christie Laboratories, Montreal Chest Institute, McGill University Health Centre Research Institute, Montreal, Canada; ⁵ Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, St. Louis, Missouri; ⁶ Department of Surgery, University of Texas Health Science Center San Antonio, San Antonio, Texas; and ⁷ Division of Thoracic Surgery, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

Correspondence and requests for reprints should be addressed to John A. Pierce, M.D., Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, 660 S. Euclid Avenue, Box 8052, St. Louis, MO 63110. E-mail: john.a.pierce{at}sbcglobal.net

Rationale: By creating artificial communications through bronchial walls into the parenchyma of explanted lungs (airway bypass), we expect to decrease the amount of gas trapped and to increase the rate and volume of air expelled during forced expirations.

Objectives: To describe the mechanism by which airway bypass improves the mechanical properties of the emphysematous lung.

Methods: Lung compartments and mechanics were measured before and after airway bypass, which was created by placement of three or four stent-suppported fenestrations in 10 emphysematous lungs removed at transplantation surgery.

Measurements and Main Results: Minimal volume after passive deflation decreased by a mean of 1.54 L (range, 0.7–2.5 L) or 60% (range, 37–86%). Explanted VC increased by 1.30 L or 132% (range, 78–318%). Maximal expiratory flows and volumes increased. Flow resistance decreased.

Conclusions: Because these data show that airway bypass improves the mechanics of breathing in severely emphysematous lungs in vitro, there is now strong empirical support that this procedure can improve ventilatory function in patients by reducing gas trapping and flow resistance.

Key Words: transbronchial fenestrations • airway bypass • collateral ventilation

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Airway bypass has been proposed as a therapy for treatment of emphysema, but there is only limited information available on its physiologic effects. What This Study Adds to the Field Increased collateral ventilation achieved by stent-supported transairway fenestrations results in enhanced vital capacity and airflow as well as decreased airway resistance in lung removed from patients receiving transplantation for emphysema. These results suggest that airway bypass may improve ventilatory function in severely emphysematous lung.