The effect of oxygenator mechanical characteristics on energy transfer during clinical cardiopulmonary bypass

The hollow-fibre oxygenator is a key component of any extracorporeal circuit used to provide cardiopulmonary bypass (CPB) during open-heart surgery. Since the oxygenator is placed downstream of the pump, the energy losses over it have a direct impact on the quality of pulsatile pressure and flow waveforms. The objective of this study was to describe the effects of hydrodynamic characteristics of the oxygenator on energy transfer during pulsatile, normothermic CPB. Twenty-three adult patients scheduled for coronary bypass surgery were divided randomly into two groups, using either an oxygenator (Group 1) with a relatively high-resistance and low-compliance (2079 +/- 148 dyn(.)s(.)cm(-5) and 0.00348 +/- 0.00071 ml(.)mmHg(-1), respectively) or an oxygenator (Group 2) with a relatively low-resistance and high-compliance (884 +/- 464 dyn(.)s(.)cm(-5) and 0.01325 +/- 0.00161 ml(.)mmHg(-1), respectively). During perfusion, pre- and post-oxygenator pressures, radial artery pressure, and blood flow were recorded simultaneously. A 32% decline of mean pressure was observed in Group 1 and a 16% decline in Group 2 (p