Hydrodynamical comparison of aortic arch cannulae

The high velocity of blood flow exiting aortic arch cannulae may erode athe rosclerotic material from the aortic intima causing non-cardiac complicatio ns such as stroke, multiple organ failure and death. Five 24 Fr cannulae fr om the Sarns product line (straight open tip, angled open tip with and with out round side holes, straight and angled closed tip with four rectangular, lateral side holes), and a flexible cannula used at the University Hospita l of Gent (straight open tip) are compared in an in vitro steady flow setup , to study the spatial velocity distribution inside the jet. The setup cons ists of an ultrasound Doppler velocimeter, mounted opposite to the cannula tip in an outflow reservoir An elevated supply tank supplies steady flow of 1.3 L/min of water. Exit forces at various distances from the tip are calc ulated by integrating the assessed velocity profiles. The pressure drop acr oss the cannula tip is measured using fluid filled pressure transducers. Th e four sidehole design provides the lowest exit velocity (0.85 versus 1.08 m/s) and force per jet (0.03 vs 0.15-0.20 N). The round sideholes are usele ss as less than 1% of the flow is directed through them. Furthermore, the u se of angled tip cannulae is suggested because the force exerted on the aor tic wall decreases the more the angle of incidence of the jet deviates from 90 degrees. Pressure drop is the lowest for the 4 side hole design and hig hest for the open tip and increases when an angled tip is used.