Flow dynamic comparison of peripheral venous cannulas used with centrifugal pump assistance in vitro

Because of the risk of vein collapse, the benefits of using a centrifugal pump to assist venous drainage for cardiopulmonary bypass are limited when the tips of peripheral cannulas are maintained within the vena cava. Using a mock circuit including 20 mm diameter latex tubing to mimic a vena cava, we compared the performance of 6 commercially available peripheral venous cannulas and attempted to determine potential factors influencing maximal flow drainage before vein collapse. A close correlation was observed with the total hole area of the cannula. Best performance (5.10 +/- 0.08 L/min) was obtained with an 8 mm internal diameter (ID) cannula and 343 mm2 total hole area. A larger cannula (ID 9.2 mm) with only 209 mm2 total hole area drained 5.03 +/- 0.05 L/min whereas a smaller cannula (ID 6.7 mm) with a total hole area of 586 mm2 also allowed a similar flow of 5.03 +/- 0.12 L/min. Therefore, the total hole area appears to be a critical factor in designing peripheral cannulas used in restricted chambers such as vena cavae.