Argyle™ Thora-Seal™ III Chest Drainage UnitThe Argyle Thora Seal III chest drainage unit (CDU) is a wet suction CDU used to reestablish negative pressure within the pleural space. The CDU incorporates three basic chambers: a replaceable collection chamber for monitoring volume, rate, and nature of drainage; a water seal chamber that acts as a one way valve, as well as a window into the patient's pleural space; and a suction control chamber to regulate suction and help re expand the lung. Case