Ad-hoc Assembly of Lean Extracorporeal Membrane Oxygenation Systems for COVID-19

Patrick Hunziker; Urs Zenklusen

Multiday test runs were done first in a simple closed loop system ( Figure 1F ) with saline and then in a complete system incorporating the Impella pump, venous drainage and return catheters and gas exchange modules with reconstituted blood from packed red blood cells and fresh frozen plasma at a hematocrit of 30% with heparin anticoagulation. Flows and pressures were determined using the sensors built into the Impella catheters/consoles and using external pressure sensors. Oxygenators were tested visually for clots formation and pressure gradients were determined over time. In the setup using two sequential gas exchange modules (the first flushed with N2 for partial deoxygenation) and the second with O2 for oxygenation, gas exchange over time was followed by blood gas analysis. Figure 2a shows predicted, pressure-gradient dependent pump performance of the Impella pumps used, based on available Impella performance charts and shows observed system flow performance in our CP-based systems. Figure 2b shows expected pressure drops across typical cannulas according to publicly available data 11 , 12 , 13 , 14 and gives the measured pressure drops across the used oxygenator type when driven at various flows using standard ECMO consoles in patients with a hematocrit of approximately 30%, based on own historical observations. Benefit/risk analysis was performed. This included patient risk and selection, probability of survival with/without added treatment, institutional setup and known risks of blood pumps including device thrombosis, embolism, infection, bleeding, hemolysis and air embolism.