Review of lung sealant technologies for lung volume reduction in pulmonary disease

Emphysema is an incurable and underdiagnosed disease with obstructive ventilatory impairment of lung function. Despite decades of research, medical treatments available so far did not significantly improve the survival benefits. Different bronchoscopic methods for lung volume reduction (LVR) in emphysema were used in the past 2 decades aiming to close the airways serving the hyperinflated lung regions and to allow the gas in the more distal bullas to be absorbed. Sealants and adhesives can be natural/biological, synthetic and semisynthetic. In lung surgery, lung sealants are used to treat prolonged air leak, which is the most common complication. Sealants can also be applied in bronchoscopic lung volume reduction (BLVR) as they administer into the peripheral airways where they polymerize and act as tissue glue on the surface of the lung to seal the target area to cause durable permanent absorption atelectasis. Initial studies analyzed the efficacy of bronchoscopic instillation of a fibrinogen-thrombin complex solution in advanced emphysema. Future studies will analyze the effects of adding chondroitin sulfate and poly-L-lysine to thrombin-fibrinogen complex thus promoting fibroblast attachment, proliferation and scarring, causing bronchial fibrostenosis and preventing ventilation of the affected part of the lung. Modifications of these methods were later developed, and the efficacy of BLVR with other sealants was analyzed in clinical studies. Results from current studies using this treatment method are promising showing that it is effective in improving exercise tolerance and quality of life in patients with advanced emphysema. It seems that subjective benefits in dyspnea scores and quality of life are more marked than improvements in lung function tests. The safety profile of sealant techniques in BLVR was mostly acceptable in clinical studies. The definite conclusions about the effectiveness of sealant in BLVR could be difficult because only a small population was involved in the current studies. More randomized large controlled studies are needed in establishing the definite role of biological BLVR in the bronchoscopic treatment of emphysema.