The utilization of a centrifugal pump during extracorporeal circulation may result in retrograde blood flow through the circuit. The non-occlusive characteristics of a centrifugal pump could create a condition where regurgitant flow is possible when the pressure in the cannulated vessel exceeded the pressure in the extracorporeal circuit. The reversal of flow, from patient to pump, could entrain air from multiple points including cannulation sites, suture holes, or open vessels or chambers. The following study was conducted to evaluate the ability of an arterial check valve (ACV) to prevent retrograde flow.
An in vitro circuit was designed to evaluate the flow dynamics of an ACV under a variety of test conditions including the following: flow rates between 0 and 7.5 L/min, and at temperatures of 37°, 25° and 15°C. The design characteristics of the ACV permitted easy priming, aided by gentle turbulence at the junction of the valve attachment to the casing. There was no difference in pressure drop across the ACV at any flow when compared to an identical circuit without the valve. The pressure drop across the ACV never exceeded 5 mmHg, at any temperature, when flow was less than 2 L/min. Retrograde leak volume was determined by creating "back" pressures on the valve, ranging from 25 to 500 mmHg. One ACV malfunctioned at a back pressure of 250 mmHg, and the data for that valve was omitted for comparative purposes. On the remaining valves, leak volume did not exceed 1.2 ml, and was a result of the compliance of the leaflet structures causing a slight volume displacement due to valve motion in a retrograde fashion. The results of this study show that the ACV permitted unimpeded, unidirectional flow at all operating conditions considered clinically relevant, and may be efficacious in alleviating the chance of retrograde circuit flow
