In Vitro Analysis of the Physical Characteristics of Femoral Bypass Cannulae

The physical dimensions and flow characteristics of arterial and venous femoral cannulae were evaluated. An in vitro femoral bypass simulator was employed to measure pressure drop across various O.D. arterial and venous cannulae from Cook Inc., C.R. Bard Inc., D.L.P. Inc., Shiley, Inc. and BioMedicus Inc. 30°C, 40% hematocrit bovine blood was employed with a Biomedicus BP-80 vortex pump. Pressure drop, peak flow velocity, shear rate, and Reynold's numbers were statistically compared. The maximum "safe" flow rate for each cannula was determined. The blood flow rate that yielded a pressure drop greater than 200 mmHg for the arterial cannulae, and the blood flow rate achieved at 300 mmHg Bio-pump inlet pressure for the venous cannulae are: Arterial Cannula Blood Flow L/min @ 200 mmHg Venous Cannula Blood Flow 1/min @300 mmHg 16 Fr. Biomedicus 3.5 18 Fr. Biomedicus 3.0 20 Fr. Canyon 4.0 20 Fr. Canyon 4.0 19 Fr. Biomedicus 5.0 18 Fr. Bard 4.5 20 Fr. Cook 6.0 20 Fr. Bard 6.5 17 Fr. CR Bard 6.0 21 Fr. DLP 6.5 20 Fr. Shiley >6.5 26 Fr. Shiley >6.5 20 Fr. C.R. Bard >7.0 24 Fr. Biomedicus >7.5 21 Fr. DLP >7.0 29 Fr. Cook >8.0 For the smallest Fr. O.D. to facilitate insertion and to yield the maximum safe (turbulence and friction) blood flow rate, the 20 Fr. C.R. Bard arterial cannula in tandem with the 20 Fr. C.R. Bard, or 21 Fr. DLP venous cannula, appear to be the optimal choice for full-flow femoral bypass.