Airway Bypass Treatment of Severe Homogeneous Emphysema: Taking Advantage of Collateral Ventilation

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Concept and evaluation of airway bypass

Airway bypass is the creation of transbronchial passages through the bronchial wall at the segmental or subsegmental level (ie, the creation of extra-anatomic bronchopulmonary passages); the passages are supported with self-expanding stents. The airway bypass stent therefore connects lung parenchyma to large airways.6, 7, 8, 9, 10, 11 It takes advantage of the increased collateral ventilation in patients who have emphysema to bypass collapsing and obstructed small airways, thereby allowing

Laboratory studies evaluating the safety and feasibility of airway bypass

Following a proof of concept that airway bypass improved lung mechanics, expiratory flow, and volume, and reduced trapped gas in explanted emphysematous lungs, the next step was to assess the feasibility and safety of in vivo airway bypass stent placement.8 A canine model was chosen for the in vivo study because the airway anatomy and size of the study dogs resemble those of humans. With the dogs under general anesthesia, suitable segmental and subsegmental bronchial wall sites were selected by

Clinical study evaluating the safety and feasibility of airway bypass

Having shown that airway bypass stent placement was feasible and safe in animal studies, it was also important to assess the feasibility and safety of airway bypass in human subjects. A critical step in the safe performance of this procedure is to create passages through the airway wall into lung parenchyma while avoiding injury to adjacent blood vessels.10 This clinical study consisted of selection of a target site bronchoscopically, the use of a Doppler catheter to detect and avoid

Clinical application of airway bypass with paclitaxel-eluting stents: early results

Following the demonstration of the proof of concept, and the feasibility and safety data in animal and human studies, the next important step was to assess the safety and early clinical results of airway bypass with paclitaxel-eluting stents for selected patients who had severe emphysema.11 In a multicenter study the airway bypass was performed with a fiberoptic bronchoscope in three steps: identification of a blood vessel–free location with a Doppler probe at the level of segmental bronchi,

The exhale airway stents for emphysema trial

The EASE Trial sets out to evaluate airway bypass and is a multicenter, prospective, randomized, sham-controlled, double-blind study.18 It is presently ongoing, though enrollment has been completed. The trial is being undertaken by Broncus Technologies, Inc.18 Broncus is a medical technology company focused on developing minimally invasive medical devices for emphysema and other lung diseases. The company has patented the airway bypass using Exhale Drug-Eluting Stents (DES) and is investigating

Summary

Airway bypass is being investigated as a new form of minimally invasive therapy for the treatment of homogeneous emphysema. It is a bronchoscopic catheter-based procedure that creates transbronchial extra-anatomic passages at the bronchial segmental level. The passages are expanded, supported with the expectation that the patency is maintained by paclitaxel drug-eluting airway bypass stents. The concept of airway bypass has been demonstrated in two separate experimental studies.6, 7 These

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Cited by (15)

  • Additive effect on pulmonary function and disability of intensive pulmonary rehabilitation following bronchoscopy lung volume reduction (BLVR) for severe emphysema

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    LVRS has been clearly shown to improve outcomes in selected patient groups, namely the most emphysematous patients [22–24], even those with significant morbidity and mortality [22,23]. New treatment approaches that can reduce lung volumes and gas trapping more safely than LVRS include the placement of endobronchial valves to prevent airflow to the worst affected areas and the PneumRxTM coils (PneumRx Inc., Mountain View, CA, USA) to compress the emphysematous lung [8,25–31]. These treatments have different degrees of efficacy, but all have proven able to reduce lung hyperinflation, improving both lung mechanics at rest and during exercise, thus ameliorating exertional dyspnea and disability [8,23,24].

  • Tracheal Self-Expandable Metallic Stents: A Comparative Study of Three Different Stents in a Rabbit Model

    2016, Archivos de Bronconeumologia
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    One report presented a positive effect of a mitomycin C-eluting, bioabsorbable stent implanted in the trachea of rabbits, in comparison to four other types of stents.26 Several authors have also used paclitaxel-eluting stents in the treatment of patients with emphysema to maintain airway patency.27–30 Although the results were initially promising, the improvement was only temporary.

  • Medical pneumoplasty, surgical resection, or lung transplant

    2012, Medical Clinics of North America
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    Because of increased airway resistance in emphysematous lung, collateral ventilation provides an important channel for alveolar gas distribution. In creating an endoscopic airway bypass between the emphysematous lung and bronchial airways, gas emptying is enhanced by bypassing obstructed airways and through collateral ventilation.10 Interlobar collateral ventilation occurred more commonly in homogeneous than in heterogeneous emphysema patterns, lending support to the concept that this procedure, unlike other LVR procedures, should work better in patients with homogeneous emphysema.11

  • Bronchoscopic lung-volume reduction with Exhale airway stents for emphysema (EASE trial): Randomised, sham-controlled, multicentre trial

    2011, The Lancet
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    Airway bypass is a bronchoscopic procedure to reduce lung volume that is designed for treatment of severe homogeneous emphysema. With this technique, passages are created in the bronchial airways to deflate air trapped in the emphysematous regions, and paclitaxel-eluting stents are placed to maintain passageway patency.4,5 In preclinical, ex-vivo, and pretransplant studies, airway bypass released trapped air by bronchoscopic creation of transbronchial passageways.5–8

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