FIGURE 2.

Schematic overview of mechanisms of action of bronchoscopic interventions for chronic bronchitis. a) Chronic bronchitis airway epithelium with an increased number of hyperplasic goblet cells causing increased mucus secretion. b) The Karakoca resector balloon consists of a latex balloon with a mesh structure of polyurethane/lycra fibres. Inside the airway the balloon is repeatedly inflated and deflated resulting in a force applied to the bronchial mucosa, which mechanically disrupts the hyperplasic goblet cells. c) The RheOx bronchial rheoplasty catheter delivers short bursts of high-frequency electrical energy to the airway epithelium and submucosal tissue layers targeting the goblet cells and glands, aiming to replace the destroyed cells with healthier tissue. d) The RejuvenAir System Metered Cryospray catheter delivers liquid nitrogen at −196°C to the airways, aiming to destroy the goblet cells and inducing a nonscarring healing response with healthier tissue regeneration as a result. e) The Nuvaira dual-cooled balloon catheter uses radiofrequency to disrupt the local vagal nerve branches and therefore the parasympathetic nerve transmission, aimed to decrease acetylcholine levels, resulting in a decreased airway smooth muscle contraction and mucus production.