Chest drainage systems restore and maintain negative intrapleural pressure by evacuating air, blood, or fluid from the pleural space. The traditional three-chamber system includes: a collection chamber (collects drainage), a water seal chamber (acts as one-way valve allowing air out but not in; tidaling indicates tube patency), and a suction control chamber (regulates negative pressure, typically -20 cmH2O). Modern digital drainage systems (e.g., Thopaz) provide continuous objective measurement of air leak and pleural pressure, enabling more reliable assessment of readiness for tube removal. The water seal chamber bubbling indicates an active air leak — continuous bubbling with respiration suggests bronchopleural communication, while intermittent bubbling only with cough may represent a small, resolving leak. 'Tidaling' (fluid oscillation with respiration) confirms tube patency and communication with the pleural space. Loss of tidaling suggests tube obstruction, lung re-expansion, or tube displacement.