Mucus plug reduction after endobronchial valve implantation – Results from the MMCOPD study

<bold>Introduction:</bold> Patients with advanced COPD and pulmonary emphysema undergo endoscopic valve implantation to improve symptoms and quality of life. As a side effect, some patients report an increase in mucus production due to the implantation of foreign material. Mucus scoring on chest computed tomography (CT) is an objective method of quantifying mucus load. <bold>Aim:</bold> The prospective, single-center MMCOPD study aims to characterize the microbiome, metabolome, mucus load, symptoms (COPD assessment test, CAT) and exacerbation history of COPD patients before and after bronchoscopic interventions. Chest CT scan-based mucus scoring was performed to assess mucus load before and after endoscopic valve implantation, separately for each lung segment. <bold>Results:</bold> 50 patients (emphysema index 34 ± 10%) were analyzed with a mean total mucus score of 5.4 ± 4.9 plugs. 2.9% of all segments were unscorable due to highly diseased regions or motion artifact. 58% of all patients had ≥3 mucus plugs in total. Mucus plugs were more prevalent in lower lobes (highest score in segment LB10) than in upper lobes. For 42 patients with a follow up CT scan, mucus score decreased significantly from 5.5 ± 3.6 to 3.6 ± 4.4 plugs (p=0.002). After exclusion of all unscorable segments the results were still significant. The first two questions on cough and sputum in the CAT score did not change significantly. <bold>Conclusion:</bold> Mucus load is high in patients with pulmonary emphysema. Unexpectedly and fortunately, the mucus score on the chest CT scan decreased after endoscopic valve implantation. This finding needs further evaluation and interpretation.