BACKGROUND: The nursing practice of avoiding dependent loops in the tubing of chest drainage systems because such loops may impede drainage and alter the intrapleural pressure is not research based. OBJECTIVES: To determine if the volume of fluid drained and pressure vary when the chest drainage tubing is straight, coiled, has a dependent loop, or has a dependent loop that is periodically lifted and drained. METHODS: A repeated-measures design was used. For each tubing position, 500 mL of fluid was infused into the pleural space of 8 adult pigs during 45 minutes. The volume of fluid drained and the pressure at 2 locations within the drainage tubing were measured for 1 hour. RESULTS: After 60 minutes, significantly less fluid (least significant difference test, P = .03) was drained with the dependent-loop tubing position (65 mL) than with the other 3 positions. However, the amount of fluid drained was not significantly different among the lift and drain (250 mL), coiled (301 mL), or straight (337 mL) tubing positions. Throughout the entire study, pressure at the connection between the chest tube and the drainage tube was significantly higher (least significant difference test, P = .003) for the dependent loop with and without periodic lifting and draining. CONCLUSIONS: Straight and coiled tube positions are optimal for draining fluid from the pleural space. If a dependent loop cannot be avoided, lifting and draining it every 15 minutes will maintain adequate drainage.

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