Under pressure- test, test, maybe? A survey of heat exchanger integrity testing at cardiac centres in Australia and New Zealand

Introduction Heat exchanger (HE) integrity is vital for patient safety during cardiopulmonary bypass (CPB), as failures can lead to severe complications including haemolysis and toxemia. While manufacturers mandate pre-use integrity testing, adherence and methods vary significantly. This study aimed to identify current practices across Australia and New Zealand and assess the mechanical efficacy of manufacturers recommended testing protocols. Methods A telephone survey was conducted of the most senior perfusionist available at all 80 cardiac surgical hospitals in Australia and New Zealand regarding HE testing customs and known failures. Simultaneously, an in vitro assessment measured the pressures generated by two common heater cooler units (HCUs)- the 3T and HCU40, in conjunction with oxygenator and cardioplegia HEs to evaluate the generated pressures during usage. Results Nine unverified historical HE failure events were recalled by surveyed senior perfusionists across the region. While 100% of programs were successfully surveyed, only 49% complete perfusion teams consistently perform pre-clinical integrity testing. Of those that test, the most common method (82%) is running water through the HE, as per manufacturers instructions. However, in vitro data revealed that while the HCU40 maintains positive pressure, the 3T HCU generates negative pressure at the HE outlet during use. This negative pressure gradient creates a theoretical risk of masking defects near the outlet during a standard ‘water-run’ test, as a positive pressure gradient is not uniformly maintained across the HE. Such an occurrence would render the manufacturers “water-run” test insufficient for detecting defects near the outlet. Conclusion Current HE testing practices are non-uniform and often limited by logistical barriers. Reliance on fluid-based testing is hemodynamically flawed in certain HCU configurations. To enhance adherence and safety, manufacturers should validate gas pressure testing for end users, and perfusion departments should adopt standardised, positive-pressure testing protocols and documented emergency failure algorithms.