Bronchoscopic lung volume reduction is springing with potential for patients with homogenous emphysema.

However, perceptions from the NETT study influenced the design of subsequent randomised controlled trials with endobronchial valves [7, 8] . The inclusion and exclusion criteria were similar and the focus was on patients with heterogeneous emphysema. Furthermore, the same CT scoring method was employed. This system is based on visually estimating severity of emphysema in three zones (upper, middle and lower) and scoring them as: 0 (no destruction), 1 (1–25%), 2 (26–50%), 3 (51–75%) and 4 (76–100%). Heterogeneous emphysema was defined as a difference in scores of at least 2 among the three zones in one lung whereas a difference of zero or 1 was classified as homogeneous emphysema. The flaw with this method is that obvious heterogenous emphysema with 75% destruction in the upper lobe and 26% destruction in the lower lobe is scored as 3 and 2, respectively, and is hence classified as homogenous disease. Conversely, 76% destruction in the upper lobe and 50% destruction in the lower lobe are scored as 4 and 2, respectively, and with the difference in scores being 2, this is classified as heterogenous disease. Consequently, some patients may have been included who did not have the optimal emphysema phenotype. Interpreting the phenotypical composition of patients in these studies is also impossible. The consequence is that, although these trials met their end points COPD is currently the third leading cause of death globally [1] and has a prevalence of >5% in both Europe [2] and the USA [3] . It is the cause of physical impairment, incapacity and a reduced quality of life as well as extensive utilisation of healthcare resources. Reducing the volume of hyperinflated lungs is a logical approach to treatment, especially if this can be achieved by removing or shrinking the most diseased portions of the lung, thereby contributing to the least gas exchange. Lung volume reduction surgery, where the worst affected areas of emphysematous lungs are resected, improves survival and quality of life, but is associated with significant morbidity and a 5.5% mortality [4] . The message from the NETT (National Emphysema Treatment Trial) and a Cochrane collaboration analysis was that patients with homogenous emphysema have the greatest risk for mortality and morbidity [4, 5] . Thus, a view developed that only a minority of patients with emphysema, those with heterogeneous upper-lobe disease and a low exercise capacity benefitted, and then at a high financial cost. There has therefore been a push in the last decade to develop simpler, safer and cheaper methods of emulating the volume loss achieved by surgical resection. Unidirectional endobronchial valves were the first to be used in human trials and appeared promising [6] . Published online: July 2, 2014