A hydrodynamic study of pleural drainage systems: some practical consequences.
BACKGROUND: A pleural drainage system must be capable of efficiently evacuating the air or fluids from the pleural cavity so that adequate lung reexpansion can take place. The air flow and negative pressure of the system will depend on the particular design of each model. This experimental study analyzes the specifications and performance of the pleural drainage systems currently on the market. METHODS: Thirteen models of pleural drainage systems connected to wall suction were examined. The models were classified into the following three groups: dry systems; wet systems; and single-chamber systems. We determined the ambient air flow and the negative pressure generated according to the suction level. The components of each model are also described. RESULTS: Under normal conditions, dry (except for the Sentinel Seal; Sherwood Medical; Tullamore, Ireland), wet, and single-chamber systems reach similar air flow rates (17 to 30, 24 to 27, and 22 to 28 L/min, respectively). With higher wall suction levels, wet systems increase the air flow (26 to 49 L/min) but the negative pressure becomes unstable because of the water loss phenomenon, dry systems increase the air flow (29 to 50 L/min) without modifying the regulator pressure, and single-chamber systems also raise the air flow (45 to 51 L/min) but increase the negative pressure. When there is an air leak, dry systems (except for the Sentinel Seal) lose less negative pressure than the other systems. CONCLUSIONS: The functioning of these systems can be optimized only by applying a suitable wall suction level adjusted to each case. Although the three types of systems are capable of evacuating adequate air flow rates, the negative pressure and the capacity to maintain it in the presence of an air leak are different in each system. Being fitted with valves and not water compartments makes the dry systems the safest and the ideal for use when the patient has to be moved.