title: Computational Fluid Dynamics Study of Mixing Zones in Extracorporeal Membrane Oxygenation Circuits to Improve Outcomes
Creators: name: Kanagarajan, Dhayananth
Publisher: name: Griffith University
Year: 2024
Subjects: subject: computational fluid dynamics
subject: extracorporeal membrane oxygenation
subject: pulsatile flow
subject: haemodynamics

description: Background: Extracorporeal Membrane Oxygenation (ECMO) is a critical care treatment for patients with severe heart and/or lung illnesses which provides external cardiopulmonary support. Veno-arterial ECMO (V-A ECMO) is a type of extracorporeal support modality for refractory cardiogenic shock patients with or without lung failure. During this therapy, the V-A ECMO device drains deoxygenated blood from a venous source (femoral or jugular, typically); pumps it across a membrane lung; and returns oxygenated blood to the arterial side (femoral artery) of the human body. This extracorporeal circuit supplies oxygenated blood at a steady flow rate in retrograde manner through the aorta, in contrast to pulsatile antegrade flow from the native heart. However, this continuous blood flow with V-A ECMO devices can lead to complications, such as left ventricular distension and suboptimal microcirculatory perfusion with end organ failure. In addition to this, VA ECMO treated patients with respiratory failure exhibit differential hypoxia - a condition in which major organs in the upper body, including the brain, receive blood with low levels of oxygen relative to the lower body. In this condition, oxygen-poor blood from the left ventricle meets oxygen-rich blood from the ECMO circuit at what is called the mixing zone, which can occur anywhere along the aorta. Due to the above-mentioned complications and other factors, including the patient's underlying disease, the severity of cardiogenic shock, and other critical care-related complications, the mortality rate in V-A ECMO patients has remained close to 50% for the past five years. Motivation: A recent innovation in V-A ECMO technologies is the development of a novel pump design capable of producing pulsatile propulsion of blood, a key feature that is not present in contemporary devices. Restoration of pulsatile blood flow in ECMO has been hypothesized to reduce inflammation, allow cardiac unloading, decrease bleeding events, and perhaps improve blood flow in the microcirculatory network. A systematic review of preclinical studies (in vitro, in silico, and animal studies) on pulsatile flow V-A ECMO showed that pulsatile flow transfers greater haemodynamic energy than continuous flow V-A ECMO devices. Similarly, many animal studies exhibited major clinical benefits, namely reduced cardiac afterload, increased microcirculatory flow, better renal function, increased cerebral oxygenation, and reduced inflammation. Aims: The main aim of this research was to develop a computational fluid dynamics (CFD) model to simulate the haemodynamics inside the human aorta for a representative patient with severe heart and lung conditions supported by pulsatile flow V-A ECMO. The second aim was to validate the CFD model by conducting particle image velocimetry (PIV) experiments in a silicone aortic phantom. The final aim of this study was to determine the optimum level of pulsatility to achieve maximum clinical benefits for pulsatile flow V-A ECMO. [...]