There has been a surge of interest in endoscopic lung volume reduction (ELVR) strategies for advanced COPD. Valve implants, coil implants, biological LVR (BioLVR), bronchial thermal vapour ablation, and airway stents are used to induce lung deflation with the ultimate goal of improving respiratory mechanics and chronic dyspnea. Patients presenting with severe air trapping (e.g., inspiratory capacity/total lung capacity (TLC) < 25%, residual volume > 225% predicted) and thoracic hyperinflation (TLC > 150% predicted) have the greatest potential to derive benefit from ELVR procedures. Pre-LVRS or ELVR assessment should ideally include cardiological evaluation, high resolution CT scan, ventilation and perfusion scintigraphy, full pulmonary function tests, and cardiopulmonary exercise testing. ELVR procedures are currently available in selected Canadian research centers as part of ethically approved clinical trials. If a decision is made to offer an ELVR procedure, one-way valves are the first option in the presence of complete lobar exclusion and no significant collateral ventilation. When the fissure is not complete, when collateral ventilation is evident in heterogeneous emphysema or when emphysema is homogeneous, coil implants or BioLVR (in that order) are the next logical alternatives.
The efficacy of pharmacological approaches in promoting lung deflation in COPD is limited when the main mechanism of lung hyperinflation is no longer bronchial constriction and airway narrowing but the anatomical consequences of extensive alveolar destruction. Ever since the encouraging results of the landmark National Emphysema Treatment Trial (NETT), there has been a surge of interest in novel nonsurgical lung volume reduction (LVR) strategies for advanced COPD. Endoscopic procedures (ELVR) (Table
Overview of the currently available procedures for lung volume reduction (LVR) in advanced emphysema.
Technique | Dependence on collateral ventilation | Reversibility | Mechanisms of action | Principal complications |
---|---|---|---|---|
Valve implantation | Yes | Fully reversible | Prevention of inspired air from entering target airways whilst allowing exit of trapped air | Pneumothorax, hemoptysis |
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Coil implantation | No | Partially reversible (within 4 weeks) | Torquing of the bronchi (intrabronchial) |
Hemoptysis, COPD exacerbations |
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Bronchoscopic thermal vapour ablation | No | Irreversible | Inflammatory reaction | Local and systemic inflammatory reaction |
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Airway stent | Yes | Partially reversible | Bypassing airway | Stent loss, stent obliteration |
Severe lung hyperinflation places the inspiratory muscles, especially the diaphragm, at a significant mechanical disadvantage by shortening its fibers and compromising its force generating capacity. The increase in dyspnea intensity at any given ventilation during exercise in advanced COPD ultimately reflects the inability of the compromised respiratory system to respond appropriately to increasing respiratory neural drive, that is, neuromechanical dissociation [
While surgical LVR (SLVR) excises lung areas of predominant high ventilation/perfusion ratios, endoscopic LVR (ELVR) may decrease or, ideally, obliterate ventilation to those areas. Thus, physiological dead space is expected to decrease in response to effective LVR and, with it, respiratory neural drive and ventilatory requirements for a given external power output. Improvements in cardiopulmonary interactions may also occur due to enhancement of venous return and lower right ventricle afterload with benefits for left ventricular filling, When these mechanical and cardiocirculatory improvements are coupled with reduced respiratory neural drive (due to improved pulmonary gas exchange), the net effect is reduced neuromechanical dissociation of the respiratory system and improved activity-related dyspnea.
The one-way valves are intended to work by preventing inspired air from entering target airways whilst allowing exit of trapped air from distal airways (Table
The most recent meta-analyses showed that one-way valves were associated with minor, but significant, increases in mean FEV1 (~7%) compared to standard medical care in patients with severe to very severe COPD (Table
Characteristics and outcomes of the larger published studies on endoscopic LVR for advanced emphysema (references [
Author, year | Study design | Patient population | Time point | ΔFEV1 | Δ6-MWD | ΔSGRQ (units) | |
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Valves | Wan et al. 2006 [ |
Prospective multicenter registry |
|
90 days | 11 ± 3% | 37 ± 90 m | — |
Sciurba et al. 2010 [ |
RCT | Treatment group ( |
6 months | 4% | 9 m | −3 | |
Complete fissure ( |
16% | 8 m | — | ||||
High heterogeneity ( |
11% | 12 m | — | ||||
Sterman et al. 2010 [ |
Multicenter prospective cohort study |
|
12 months | −2 ± 12% | 14 ± 104 m | −8.2 ± 16 | |
Herth et al. 2012 [ |
RCT | Treatment group ( |
6 months | 7 ± 20% | 15 ± 91 m | −5 ± 14 | |
Complete fissure, lobar occlusion ( |
26 ± 24% | 22 ± 38% | −10 ± 15 | ||||
Eberhardt et al. 2012 [ |
Prospective, randomized, noncontrolled | Complete unilateral occlusion ( |
3 months | 21 ± 11% | 49 ± 53 m | −12 ± 11 | |
Partial bilateral occlusion ( |
−3 ± 15% | −52 ± 81 m | 2 ± 9 | ||||
Ninane et al. 2012 [ |
RCT | Partial occlusion ( |
3 months | −90 mL | 7 m | −4 | |
Herth et al. 2013 [ |
Prospective, noncontrolled | CV negative ( |
1 month | 16 ± 22% | 24 ± 57 m | −10 ± 13 | |
CV positive ( |
1 ± 15% | 10 ± 57 m | −5 ± 15 | ||||
Wood et al. 2014 [ |
RCT | Treatment group ( |
6 months | −2 ± 5% pred | −24 ± 69 m | 2 ± 16 | |
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Coils | Slebos et al. 2012 [ |
Prospective, noncontrolled |
|
6 months | 15 ± 17% | 84 ± 73 m | −15 ± 12 |
Shah et al. 2013 [ |
RCT | Treatment group ( |
3 months | 14% | 52 m | −8 | |
Zoumot et al. 2015 [ |
RCT | Treatment group ( |
12 months | 9 ± 22% | 34 ± 52 m | −6 ± 14 | |
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BioLVR | Criner et al. 2009 [ |
Open-label, multicenter, non-RCT | Low-dose hydrogel ( |
6 months | 6.7 ± 12.9% | 25.5 ± 53.2 m | −6.9 ± 8.8 |
High-dose hydrogel ( |
15.6 ± 16.8% | 9.9 ± 51.2 m | −9.7 ± 18.8 | ||||
Herth et al. 2010 [ |
Open-label, multicenter, non-RCT |
|
3 months | 3.3 ± 3.2% | 10.8 ± 8.8% | −7.8 ± 3.7 | |
Magnussen et al. 2012 [ |
Retrospective analysis from multicenter non-RCTs |
|
12 weeks | 19.1 ± 21.5% (0.18 ± 0.22 L) | 30.9 ± 50.2 m | −11.6 ± 12.4 | |
Kramer et al. 2012 [ |
Multicenter open-label non-RCT |
|
12 months | 25.0 ± 33.4% | 8.6 ± 65.2 m | −7.0 ± 15.8 | |
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BTVA | Snell et al. 2012 [ |
Prospective, noncontrolled |
|
6 months | 17% | 47 m | −14 |
Herth et al. 2012 [ |
Two multicenter single-arm prospective studies |
|
12 months | 86 ± 174 mL | 18.5 ± 63.7 m | −11 ± 14 | |
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Stents | Cardoso et al. 2007 [ |
Multicenter non-RCT |
|
6 months | 0.6% | −12 m | −1.8 |
Shah et al. 2011 [ |
Multicenter RCT |
|
12 months | −20 ± 200 mL | −21 m | −1 | |
−0.15 ± 7% |
Values for changes (Δ) are means ± SD.
6-MWD: 6 min walking distance; BTVA: bronchial thermal vapour ablation; FEV1: forced expiratory volume in one second; RCT: randomized controlled trial; SGRQ: St. George’s Respiratory Questionnaire.
With this method, a deployed coil conforms to a predetermined shape (“memory-shape” coil). By bending in the airway and causing compression of adjacent lung tissue, it induces local LVR (intrabronchial coil). Alternatively, multiple endobronchial coils may be implanted throughout a lobe achieving deflation through increased radial tension across the airway network which might also open small airways by increased tethering effects. A potential advantage is that the implants do not depend on (the absence of) collateral ventilation and therefore could be useful for patients with relatively homogeneous emphysema (Table
BioLVR aims to promote LVR through intra-airway polymerization of fibrinogen suspension and thrombin solution with the purpose of inducing a localized inflammatory reaction (Table
BTVA uses heated water (steam) to produce thermal injury of the target tissue, usually a segmental airway. Similar to BioLVR, the treatment aims to induce lung volume reduction regardless of the presence of collateral ventilation (Table
Airway bypass stents have been used to create and maintain passages between the bronchi and emphysematous lobes. Efficacy of the technique, therefore, depends strongly on the lack of collateral ventilation (Table
Patients presenting with severe air trapping (e.g., inspiratory capacity (IC)/TLC < 25%, residual volume > 225% predicted) and thoracic hyperinflation (TLC > 150% predicted) have the greatest potential to derive benefit from ELVR procedures (Figure Pre-LVRS or ELVR assessment should ideally include cardiological evaluation, high resolution CT scan, ventilation and perfusion scintigraphy, full pulmonary function tests, cardiopulmonary exercise testing, and measurements of quality of life and dyspnea (Figure If a decision is made to offer an ELVR procedure, one-way valves are the first option in the presence of complete lobar exclusion and no significant collateral ventilation (Figure No ELVR procedures have been approved by Health Canada. To date (June 2015), they are available except in research centers as part of clinical trials.
Algorithm for endoscopic LVR evaluation and selection of procedure. BioLVR: biological lung volume reduction; BTVA: bronchial thermal vapour ablation; CT: computed tomography; IC: inspiratory capacity; pred: predicted; RV: residual volume; TLC: total lung capacity; V/Q: ventilation/perfusion.
The authors declare that there are no competing interests regarding the publication of this paper.