Investigations of Differential Hypoxemia During Venoarterial Membrane Oxygenation with and Without Impella Support.

Purpose: Venoarterial extracorporeal membrane oxygenation (VA ECMO) is used in patients with refractory cardiac or cardio-pulmonary failure. Native ventricular output interacts with VA ECMO flow and may hinder sufficient oxygenation to the heart and the brain. Further on, VA ECMO leads to afterload increase requiring ventricular unloading. The aim of the study was to investigate aortic blood flow and oxygenation for various ECMO settings and cannula positions with a numerical model.

Methods: Four different aortic cannula tip positions (ascending aorta, descending aorta, abdominal aorta, and iliac artery) were included in a model of a human aorta. Three degrees of cardiac dysfunction and VA ECMO support (50%, 75% and 90%) with a total blood flow of 6 l/min were investigated. Additionally, the Impella CP device was implemented under 50% support condition. Blood oxygen saturation at the aortic branches and the pressure acting on the aortic valve were calculated.

Results: A more proximal tip orientation is necessary to increase oxygen supply to the supra-aortic and coronary arteries for 50% and 75% support. During the 90% support scenario, proper oxygenation can be achieved independently of tip position. The use of Impella reduces afterload by 8-17 mmHg and vessel oxygenation is similar to 50% VA ECMO support. Pressure load on the aortic valve increases with more proximal tip position and is decreased during Impella use.

Conclusions: We present a simulation model for the investigation of hemodynamics and blood oxygenation with various mechanical circulatory support systems. Our results underline the intricate and patient-specific relationship between extracorporeal support, cannula tip orientation and oxygenation capacity.