Bronchoscopic lung volume reduction in severe emphysema

Abstract

Lung volume reduction surgery (LVRS) produces physiological, symptomatic, and survival benefits in selected patients with advanced emphysema. Because it is associated with significant morbidity, mortality, and cost, nonsurgical alternatives for achieving volume reduction have been developed. Three bronchoscopic lung volume reduction (BLVR) approaches have shown promise and reached later-stage clinical trials. These include the following: (1) placement of endobronchial one-way valves designed to promote atelectasis by blocking inspiratory flow; (2) formation of airway bypass tracts using a radiofrequency catheter designed to facilitate emptying of damaged lung regions with long expiratory times; and (3) instillation of biological adhesives designed to collapse and remodel hyperinflated lung. The limited clinical data currently available suggest that all three techniques are reasonably safe. However, efficacy signals have been substantially smaller and less durable than those observed after LVRS. Studies to optimize patient selection, refine treatment strategies, characterize procedural safety, elucidate mechanisms of action, and characterize short- and longer-term effectiveness of these approaches are ongoing. Results will be available over the next few years and will determine whether BLVR represents a safe and effective alternative to LVRS.

Figure 1.

Patterns of response to bronchoscopic lung volume reduction (BLVR) therapy in terms of exercise capacity, lung volumes and recoil, and expiratory flows. Pattern 1 produces no change in any objective parameters. Pattern 2 produces a beneficial effect in exercise capacity by altering dynamic hyperinflation during exercise (A) through changes in regional lung impedance, without affecting static lung volumes and recoil (B) or expiratory flows (C). Pattern 3 produces larger changes in exercise capacity by altering both static lung volumes (A and B) and dynamic hyperinflation (A), but because lung recoil is not affected, maximal expiratory flows and FEV₁ (C) do not substantially change. Pattern 4 produces changes in exercise capacity (A) and residual lung volume (B) similar to pattern 3, but also results in an increase in FEV₁ by improving maximal expiratory flows (C) as a result of an increase in recoil pressure.

Figure 1.

Patterns of response to bronchoscopic lung volume reduction (BLVR) therapy in terms of exercise capacity, lung volumes and recoil, and expiratory flows. Pattern 1 produces no change in any objective parameters. Pattern 2 produces a beneficial effect in exercise capacity by altering dynamic hyperinflation during exercise (A) through changes in regional lung impedance, without affecting static lung volumes and recoil (B) or expiratory flows (C). Pattern 3 produces larger changes in exercise capacity by altering both static lung volumes (A and B) and dynamic hyperinflation (A), but because lung recoil is not affected, maximal expiratory flows and FEV₁ (C) do not substantially change. Pattern 4 produces changes in exercise capacity (A) and residual lung volume (B) similar to pattern 3, but also results in an increase in FEV₁ by improving maximal expiratory flows (C) as a result of an increase in recoil pressure.

Figure 1.

Patterns of response to bronchoscopic lung volume reduction (BLVR) therapy in terms of exercise capacity, lung volumes and recoil, and expiratory flows. Pattern 1 produces no change in any objective parameters. Pattern 2 produces a beneficial effect in exercise capacity by altering dynamic hyperinflation during exercise (A) through changes in regional lung impedance, without affecting static lung volumes and recoil (B) or expiratory flows (C). Pattern 3 produces larger changes in exercise capacity by altering both static lung volumes (A and B) and dynamic hyperinflation (A), but because lung recoil is not affected, maximal expiratory flows and FEV₁ (C) do not substantially change. Pattern 4 produces changes in exercise capacity (A) and residual lung volume (B) similar to pattern 3, but also results in an increase in FEV₁ by improving maximal expiratory flows (C) as a result of an increase in recoil pressure.

Figure 2.

Patterns of response to bronchoscopic lung volume reduction (BLVR) pattern 1: treatment produces no change in lung physiology. Pattern 2: treatment reduces dynamic gas trapping (dynamic RV), which improves exercise capacity. Static volumes and spirometry are unaffected. Pattern 3: treatment reduces static and dynamic gas trapping (static RV and dynamic RV), but has minimal effect on total lung capacity (TLC). FVC increases, but FEV₁ does not. Pattern 4: treatment reduces static and dynamic gas trapping (static RV and dynamic RV) and TLC. FVC and FEV₁ improve. Beyond a critical threshold, further reductions in TLC have a negative impact on VC and then FEV₁, and the benefits of treatment diminish.