Carbon dioxide flushing prior to priming the bypass circuit. An experimental derivation of the optimal flow rate and duration of the flushing process

Abstract

The practice of flushing the cardiopulmonary bypass circuit and oxygenator with carbon dioxide (CO ₂) has been shown to reduce priming time. However, the optimal flow rate of CO₂ and the time for which it must be flushed through the circuit in order to remove the air, have not been determined. In this experiment, CO₂ was passed through the arterial filter and arteriovenous (AV) loop at various flow rates and serial gas samples were taken from the circuit. The residual concentration of air in each sample was measured using a gas chromatograph. It was shown that as the flow rate of CO₂ was increased, the time taken to remove the residual air decreased. Flushing the circuit with CO₂ at a flow rate of 6 l/min for four minutes ensures a residual air concentration of less than 0.01%.