History of lung volume reduction procedures.

Lung volume reduction (LVR) procedures for emphysematous patients were firstly introduced in the second half of the twentieth century. Over time, from the first invasive surgical procedures, new less invasive techniques have been conceived. In regards to the surgical approach, the adoption of VATS and the execution, in selected centers, of a non-resectional approach, with folding of less functional lung tissue, reduced mortality and adverse events risks. As regards to the bronchoscopic approach, endobronchial valves (EBV) and intrabronchial valves (IBV) were initially proposed in the early 2000s to obtain segmental or lobar atelectasis of the more compromised lung parenchyma. Despite showing promising results with respect to improvement of pulmonary function tests, particularly forced expiratory volume in 1st second (FEV1 ), and quality of life, and a good safety profile, valves showed disappointing results in presence of collateral ventilation, such as in cases of incomplete fissures. To overcome this technical issue, in the last 10 years, endobronchial coils have been designed and used. Having a compressive effect on the lung parenchyma where they are located, they are not affected by collateral ventilation. Randomized control trials (RCTs) on endobronchial coils showed a significant improvement in FEV1 and quality of life, however this technique was not immune to side effects, particularly low respiratory tract infections and pneumothoraces. Besides bronchial valves (BV) and coils, airway by-pass stents have also been evaluated in a RCT but without reaching the desired endpoints. Other innovative procedures recently considered and delivered through bronchoscopy regards thermal energy, with vapour therapy, to achieve a scarring reaction of the emphysematous lung parenchyma, and polymeric foams used as lung sealants to achieve absorptive atelectasis. In conclusion, LVR procedures may be considered in carefully selected patients with symptomatic emphysema and severe lung hyperinflation, and might be personalized according to the anatomical characteristics of emphysematous area.