Lessons learned: Risk factors and clinical impact of severe pneumothorax after endoscopic lung volume reduction with endobronchial valves.

Background: Pneumothorax is a major complication following endoscopic lung volume reduction with valves with a prevalence of up to 34%. While some patients benefit from valve implantation despite pneumothorax, others are significantly impaired after lung collapse.

Research question: What are the differences in the severity grades of pneumothorax and how does that affect our clinical practice?

Study design and methods: This single-center retrospective study analyzed patients undergoing endoscopic valve implantation with and without post-interventional pneumothorax. Emphysema characteristics, collateral ventilation, management, and outcome of patients with pneumothorax 3 months after valve implantation were assessed. Pneumothorax was categorized as "severe pneumothorax" (chest tube insertion, prolonged air leak requiring valve removal), "moderate pneumothorax" (chest tube, no valve removal), and "mild pneumothorax" (no chest tube).

Results: Pneumothorax occurred in 102/532 patients (19%) and was significantly more common after valve placement in the upper lobes (31.3%) compared to the lower lobes (11.3%, p < 0.001). Fissure integrity was significantly higher in patients with pneumothorax (mean 96.6 ± 6.3 % vs. 93.4 ± 10.3 %, p = 0.002). Of all pneumothoraces, 30.4% were mild, 30.4% moderate, 39.2% severe. Severe pneumothorax caused multiple complications and prolonged hospitalization. Valve placement in the left upper lobe and a larger size of the target lobe were identified as risk factors for severe pneumothorax. Patients with pneumothorax developed complete lobar atelectasis in >60% as a sign of therapeutic success, but obviously only when valves could be left in place or re-implanted. However, valve re-implantation resulted in re-pneumothorax in 42.9%.

Interpretation: Patients could be more individually informed about their risk of pneumothorax, which varies with target lobe location, fissure integrity and re-implantation. The poor outcome and high complication rate of severe pneumothorax calls for future research into the prediction of severe pneumothorax.