Flow mixing during peripheral veno-arterial extra corporeal membrane oxygenation - A simulation study.

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Medical Simulation

Background:

• Peripheral veno-arterial extracorporeal membrane oxygenation (ECMO) is a life-support technology for severe cardiac and respiratory failure.
• Differential hypoxia, a discrepancy in oxygen levels between the upper and lower body, is a known complication of ECMO.
• This phenomenon is hypothesized to result from the mixing of oxygenated ECMO blood and deoxygenated blood from the left ventricle within the aorta.

Purpose of the Study:

• To quantify the relationship between the level of ECMO support and the location of the mixing zone (MZ) where ECMO and left ventricular (LV) flows interact.
• To investigate how changes in ECMO flow rate affect the position and stability of the MZ within the aorta.
• To provide insights for optimizing ECMO management and device design to mitigate differential hypoxia.

Main Methods:

• Utilized patient-specific computational fluid dynamics (CFD) models of the aorta.
• Performed both steady-state and transient simulations to analyze blood flow dynamics.
• Evaluated a comprehensive range of ECMO support levels, from 5% to 95% of total cardiac output.

Main Results:

• For ECMO support levels exceeding 70%, the mixing zone (MZ) was consistently located in the aortic arch.
• This high-flow MZ position leads to the perfusion of critical arch branches (supplying the brain and upper body) with poorly oxygenated blood from the LV.
• At 60% ECMO support, the MZ location exhibited significant movement (up to 5 cm) between systole and diastole, indicating dynamic changes in flow patterns.

Conclusions:

• The location of the mixing zone in peripheral veno-arterial ECMO is highly dependent on the support level.
• High ECMO flows (>70%) place the MZ in the aortic arch, posing a risk of inadequate oxygen delivery to the brain and upper body.
• CFD modeling is a valuable tool for understanding intra-aortic flow dynamics during ECMO, with potential to personalize patient treatment and enhance ECMO system design.