BACKGROUND: Maintaining a chest drainage tube in a position that is free of dependent loops, as is commonly recommended, can be very difficult. Is there a beneficial effect on the patient's outcome when the drainage tubing is free of dependent loops? OBJECTIVE: The purpose of this study was to determine, under controlled laboratory conditions, (1) what are the differences in drainage with tubing in straight, coiled, or dependent-loop (with and without periodic lifting) positions and (2) what are the differences in pressure with each of the four tubing conditions? METHODS: In laboratory simulations, pressure and drainage were observed in a chest tube drainage system that was connected to a glass bottle simulating the lung. Pressure and drainage were measured for 1 hour with the drainage tubing placed in straight, coiled, and dependent-loop positions. For the periodic lifting condition, the dependent loop was lifted and drained every 15 minutes. RESULTS: We found no differences in pressure or drainage between straight and coiled positions of the drainage tubing. However, with the dependent-loop position, pressure at the "lung" side increased from about -18 cm H2O to as high as +8 cm H2O. Drainage dropped to zero without tube lifting. When the tube was lifted and drained every 15 minutes, there was no difference in drainage with the tubing in the straight or coiled positions. CONCLUSION: Findings support recommendations to maintain tubing free of dependent loops by placing tubing in straight or coiled positions. Frequently lifting and draining a dependent loop will provide the same total drainage amount as maintaining the tubing in a straight or coiled position, but pressures may be altered sufficiently within the tube to exceed recommended levels.

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