Pulmonary Perspectives®

Endobronchial valves for lung volume reduction: What can we offer patients with advanced emphysema?


 

The global burden COPD is considerable. In the United States, it is the third most common cause of death and is associated with over $50 billion in annual direct and indirect health-care expenditures (Guarascio AJ, et al. Clinicoecon Outcomes Res. 2013;5:235). For patients with severe emphysema with hyperinflation, dyspnea is often a quality of life (QOL)-limiting symptom (O’Donnell DE, et al. Ann Am Thorac Soc. 2017;14:S30). Few proven palliation options exist, particularly for patients with dyspnea refractory to smoking cessation, medical management with bronchodilators, and pulmonary rehabilitation. The recent Food and Drug Administration (FDA) approval of two endobronchial valves for lung volume reduction has established the increasing importance of bronchoscopy as a management tool in advanced COPD.

Why were these valves developed?

Courtesy of Dr. Catherine L. Oberg

Zephyr® valve

For decades, lung volume reduction has been investigated as a mechanical approach to counter-act the physiologic effects of emphysematous hyperinflation. Its goal is to improve lung elastic recoil, respiratory muscle mechanical advantage and efficiency, and ventilation/perfusion matching. The landmark National Emphysema Treatment Trial (NETT), published in 2001 and 2003, demonstrated that in a select patient population (upper lobe-predominant emphysema and low exercise capacity), lung volume reduction surgery (LVRS) lowers mortality and improves QOL and exercise tolerance (Fishman A et al. N Engl J Med. 2003;348:2059). Despite the encouraging results in this study subpopulation, LVRS is per-formed infrequently (Decker MR, et al. J Thorac Cardiovasc Surg. 2014;148:2651). Concern about its morbidity and the specialized nature of the procedure has hindered widespread adoption. Subsequently, endobronchial techniques have been developed as an alternative to surgical lung volume reduction.

How does bronchoscopic lung volume reduction (BLVR) benefit patients with emphysema?

Courtesy of Dr. Catherine L. Oberg

Spiration® valve

Valves used for ELVR are removable one-way flow devices placed by flexible bronchoscopy into selected airways supplying emphysematous lung. The valves block air entry but allow the exit of secretions and trapped air. This results in atelectasis of the targeted lobe and a decrease in lung volume.

Which endobronchial valves are available in the United States?

In 2018, two valves were approved by the FDA for bronchoscopic lung volume reduction (BLVR) – the Zephyr® EBV (Pulmonx) ( (Fig 1) and the Spiration® Valve System (Olympus) (IBV) (Fig 2). The Zephyr® EBV is a duckbill-shaped silicone valve mounted within a self-expanding nitinol (nickel titanium alloy) stent. It comes in three sizes for airways with a diameter 4 - 8.5 mm. The Spiration® IBV umbrella-shaped valve is com-posed of six nitinol struts surfaced with polyurethane. Its four sizes accommodate airway diameters 5 - 9 mm.

What’s the evidence behind BLVR?

Zephyr® Valves

The Endobronchial Valve for Emphysema Palliation Trial (VENT), the largest valve trial thus far, randomized patients with severe heterogeneous emphysema to receive unilateral Zephyr® valve placement or standard medical care (Sciurba FC, et al. N Engl J Med. 2010;363:1233). Overall improvement in spirometry and dyspnea scores was modest in the valve group. Post-hoc analysis identified an important subgroup of patients with significant clinical benefit, those with a complete fissure. This finding gave guidance to further EBV studies on patients with severe emphysema and absent collateral ventilation (CV).

Identifying a complete fissure on imaging is now used as a surrogate for assessing CV and is an integral part of the initial profiling of patients for EBV therapy (Koster TD, et al. Respiration. 2016;92(3):150).

In the STELVIO trial, 68 patients were randomized to Zephyr ® EBV placement or standard medical care (Klooster K, et al. N Engl J Med. 2015;373:2325). Those with EBV placement had significantly improved lung function and exercise capacity. TRANSFORM, a multicenter trial evaluating Zephyr® EBV placement in heterogeneous emphysema, showed similar results (Kemp SV, et al. Am J Respir Crit Care Med. 2017;196:1535).

The IMPACT trial compared patients with homogenous emphysema without CV to standard medical therapy alone. It showed improvement in FEV1, QOL scores, and exercise tolerance in the EBV group. This study affirmed that the absence of CV, rather than the pattern of emphysema, correlates with the clinical benefit from EBV therapy (Valipour A, et al. Am J Respir Crit Care Med. 2016;194(9):1073). Finally, LIBERATE, a multicenter study on the Zephyr® EBV, examined its placement in patients with heterogenous emphysema. This study demonstrated improvement in spirometry, QOL, and 6-minute walk test (6-MWT) distance (Criner GJ, et al. Am J Respir Crit Care Med. 2018;198:1151) over a longer period, 12 months, bolstering the findings of prior studies. These results prompted the Zephyr® valve’s FDA approval.

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