Springing forward to medium‐term results for endobronchial coils for emphysema

Emphysema is a destructive process that leads to permanent enlargement of air spaces distal to the terminal bronchioles, accompanied by the destruction of their walls and without obvious fibrosis, most commonly as a consequence of tobacco smoking. Proteolytic damage results in coalescence of alveolar structures and destruction of the elastic connective tissues within the lung, leading to a reduction in the surface area available for gas exchange, small airway collapse on expiration and hyperinflation. Increasing severity of the emphysema leads to progressive impairment of diaphragmatic and chest wall muscle function, a situation further exacerbated by the development of diaphragm and chest wall muscle asynchrony. Pharmacological therapy does little to restore these effects of emphysema, and although pulmonary rehabilitation tries to compensate by improving muscle strength and exercise capacity it does not change the underlying pulmonary pathophysiology. In contrast, lung volume reduction surgery (LVRS) aims to reduce hyperinflation by resecting some of the grossly damaged areas of lung, thus restoring diaphragmatic and muscle function. Recent data showing zero mortality across 81 unilateral LVRS procedures suggest that with appropriate patient selection and in the right hands, the risks of surgery can be minimized, but safety concerns about mortality and morbidity, in particular prolonged air leaks, persist and have driven the development of minimally invasive bronchoscopic techniques for the treatment of emphysema. Endobronchial valves, designed to induce volume loss by lobar atelectasis, initially appeared to have a very acceptable safety profile but with only modest clinical benefits. Improvements in patient selection have significantly improved efficacy outcomes but at the cost of increased complications, especially the increased incidence of pneumothoraces. Endobronchial coils are constructed from nitinol wire, and work by returning some of the elastic recoil forces to the lung and reducing whole lung compliance. This promotes small airway splinting and improved lung emptying on expiration, and reduces hyperinflation without significant parenchymal compression. The literature to date reports on 98 patients who have had bilateral placement of endobronchial coils, and a further 38 patients with unilateral placement. Data from a further 24 patients (18 bilateral and 4 unilateral treatments) in the cross-over arm of the RESET study is currently being prepared for publication. Endobronchial coils certainly appear to have a very good short-term safety profile. The randomized RESET study reported six serious adverse events (SAE) in treatment group within the first 30 days, and three events between 30 and 90 days. The corresponding control group experienced one and three SAEs, respectively, with all SAEs in both groups beyond 30 days related to infection or exacerbation. There were no late pneumothoraces, and no deaths occurred within the follow-up period. Other open-label trials report similar short-term safety results. This favourable safety profile now seems to extend out to several years. The article in this journal by Hartman and colleagues is the first to report more long-term coil data on patients collected from two earlier trials. Thirtyeight patients were originally enrolled and were invited for annual follow-up, with assessments of pulmonary function, walking distance and symptom scores. They report an excess of early respiratoryrelated adverse events but little or no coil associated events beyond 1 year. Migration of coils over time and tearing of lung parenchyma were early concerns for endobronchial coils, but no imaging evidence to this effect was seen, and bacterial or fungal colonization of the devices has not been reported. Significant mean improvements at 1 year were seen in pulmonary function, exercise performance and symptoms, but there did appear to be a waning of benefit over time, with only the modified Medical Research Council dyspnoea score significantly different at 3 years. Responder analyses point to greater optimism, however, with 59% of those attending at 3 years continuing to have a clinically meaningful improvement in St George’s Respiratory Questionnaire, 40% in 6-min walk distance, 38% in forced expiratory volume in 1 s and 19% in residual volume. Drawing conclusions from small cohorts of patients can be difficult, and the data are inevitably subject to bias. Selection bias and survival bias are almost impossible to avoid in such follow-up studies, with some of the more severely affected patients dying or being lost to follow-up, and those not benefiting from the initial treatment less motivated to attend for Conflict of interest statement: PLS and SVK have received honoraria from PneumRx for lecturing at independent meetings. SVK has received a travel grant. bs_bs_banner