Persistence of a pneumothorax after closed tube thoracostomy is usually indicated by fluctuance within the chest drainage tubes. Reasons for incomplete lung expansion include (1) inadequacy of the suction device, if such a device is used, (2) air leaks within the system, or (3) an air leak into the pleura greater per volume time than the volume of air that can be displaced by the suction device. Occlusion of the tubing with maintenance of negative suction usually assures that the system is airtight.1 In our hospital, pleurovacs, commercially prepared units of the classical three-bottle controlled suction systems, are used extensively.
We have recently experienced two situations where pleurovac drainage systems thought to be intact were the source of a persistent residual space. In one case, a pneumothorax secondary to the insertion of a hyperalimentation catheter persisted until the pleurovac unit was empirically changed. Following a trial of waterseal drainage,