Efficacy and safety of strategies to preserve stable extracorporeal life support flow during simulated hypovolemia

Aim: Without volume-buffering capacity in extracorporeal life support (ELS) systems, hypovolemia can acutely reduce support flow. This study aims at evaluating efficacy and safety of strategies for preserving stable ELS during hypovolemia. Material & Methods: Flow and/or pressure-guided servo pump control, a reserve-driven control strategy and a volume buffer capacity (VBC) device were evaluated with respect to pump flow, venous line pressure and arterial gaseous microemboli (GME) during simulated normovolemia and hypovolemia. Results: Normovolemia resulted in a GME-free pump flow of 3.1 +/- 0.0 L/min and a venous line pressure of -10 +/- 1 mmHg. Hypovolemia without servo pump control resulted in a GME-loaded flow of 2.3 +/- 0.4 L/min with a venous line pressure of -114 +/- 52 mmHg. Servo control resulted in an unstable and GME-loaded flow of 1.5 +/- 1.2 L/min. With and without servo pump control, the VBC device stabilised flow (SD = 0.2 and 0.0 L/min, respectively) and venous line pressure (SD=51 and 4 mmHg, respectively) with near-absent GME activity. Reserve-driven pump control combined with a VBC device restored a near GME-free flow of 2.7 +/- 0.0 L/min with a venous line pressure of -9 +/- 0 mmHg. Conclusion: In contrast to a reserve-driven pump control strategy combined with a VBC device, flow and pressure servo control for ELS show evident deficits in preserving stable and safe ELS flow during hypovolemia.