TY - JOUR
T1 - Blood flow and emboli transport patterns during venoarterial extracorporeal membrane oxygenation
T2 - A computational fluid dynamics study
AU - Khamooshi, Mehrdad
AU - Wickramarachchi, Avishka
AU - Byrne, Tim
AU - Seman, Michael
AU - Fletcher, David F.
AU - Burrell, Aidan
AU - Gregory, Shaun D.
N1 - Funding Information:
This work was supported by the National Health and Medical Research Council (NHMRC) ( APP2002567 ). A/Prof. Shaun D Gregory was supported by an NHMRC Investigator Grant ( 2016995 ) and Fellowship ( 106675 ) from the National Heart Foundation of Australia .
Funding Information:
In clinical practice, various arterial return cannula sizes are used in VA ECMO to cater to individual patient needs. The flow and level of support provided by VA ECMO during an ECMO run can vary significantly as it is adjusted based on the patient's condition and response to treatment. These variations in cannula size and ECMO support may influence emboli and oxygenated blood transport patterns, thus it is crucial to investigate their potential impact on patient care and outcomes. In this study, CFD simulations were utilized to assess the blood oxygen level at different branches and emboli distribution during VA ECMO associated with different sizes of arterial return cannulae at various levels of support. By introducing diverse sources of emboli, this study makes a significant contribution to discerning the varying risks of embolization associated with different support levels and cannula sizes in the context of VA ECMO. Additionally, this investigation advances understanding by analysing the potential risks of oxygen imbalances across different scenarios, thereby enhancing knowledge crucial for optimizing patient care during VA ECMO procedures.This study did not utilize the aortic waveform directly obtained from the patients; instead, patient-derived measurements of the aortic waveform from a separate study were employed. These measurements were acquired via gated PC-MRI [20], ensuring that the waveforms remained representative of those from healthy adult patients. To simulate various severities, the waveforms were then scaled, following a methodology commonly applied in existing literature [7,8]. For different ECMO support levels (various degrees of cardiac dysfunction) the aortic valve flow profile was scaled to represent a total flow (aortic valve flow + VA ECMO flow) of 5 L/min [7,21] (Fig. 2). Each arterial branch was subjected to boundary conditions utilizing a 3-element Windkessel model. By incorporating compliance effects, the 3-element Windkessel model combines various components of the systemic circulation into peripheral and distal resistances, thus resulting in a pressure outlet waveform that approximates the behavior of the arterial system during the cardiac cycle. A rigid vessel wall assumption was made for all vessels [22].Blood flow modelling was performed assuming a transient, turbulent flow through the aorta and main branches and the cannula using the commercial CFD code, Ansys Fluent 2022R2 (ANSYS Inc, Canonsburg, PA, US). A species transport model was used to differentiate the blood's oxygen level and to model the mixing between the blood originating from the LV and ECMO circuit. Partial pressures of oxygen of 150 and 40 mmHg were used for blood originating from the VA ECMO circuit and the heart, respectively, as suggested by the Extracorporeal Life Support Organization (ELSO) [23]. Pressure levels were transformed to oxygen saturation through a dissociation curve. The diffusion coefficient of oxygen in blood was 1.2 × 10−9 (m2/s) [24]. Simulations were performed for 23 cycles at a heart rate of 60 beats per minute. The first ten cycles were discarded from the analysis to allow the simulation to stabilize and remove the startup effects, and particles were released at the start of the eleventh cycle.This work was supported by the National Health and Medical Research Council (NHMRC) (APP2002567). A/Prof. Shaun D Gregory was supported by an NHMRC Investigator Grant (2016995) and Fellowship (106675) from the National Heart Foundation of Australia.
Publisher Copyright:
© 2024 The Authors
PY - 2024/4
Y1 - 2024/4
N2 - Problem: Despite advances in Venoarterial Extracorporeal Membrane Oxygenation (VA-ECMO), a significant mortality rate persists due to complications. The non-physiological blood flow dynamics of VA-ECMO may lead to neurological complications and organ ischemia. Continuous retrograde high-flow oxygenated blood enters through a return cannula placed in the femoral artery which opposes the pulsatile deoxygenated blood ejected by the left ventricle (LV), which impacts upper body oxygenation and subsequent hyperoxemia. The complications underscore the critical need to comprehend the impact of VA-ECMO support level and return cannula size, as mortality remains a significant concern. Aim: The aim of this study is to predict and provide insights into the complications associated with VA-ECMO using computational fluid dynamics (CFD) simulations. These complications will be assessed by characterising blood flow and emboli transport patterns through a comprehensive analysis of the influence of VA-ECMO support levels and arterial return cannula sizes. Methods: Patient-specific 3D aortic and major branch models, derived from a male patient's CT scan during VA-ECMO undergoing respiratory dysfunction, were analyzed using CFD. The investigation employed species transport and discrete particle tracking models to study ECMO blood (oxygenated) mixing with LV blood (deoxygenated) and to trace emboli transport patterns from potential sources (circuit, LV, and aorta wall). Two cannula sizes (15 Fr and 19 Fr) were tested alongside varying ECMO pump flow rates (50%, 70%, and 90% of the total cardiac output). Results: Cannula size did not significantly affect oxygen transport. At 90% VA-ECMO support, all arteries distal to the aortic arch achieved 100% oxygen saturation. As support level decreased, oxygen transport to the upper body also decreased to a minimum saturation of 73%. Emboli transport varied substantially between emboli origin and VAECMO support level, with the highest risk of cerebral emboli coming from the LV with a 15 Fr cannula at 90% support. Conclusion: Arterial return cannula sizing minimally impacted blood oxygen distribution; however, it did influence the distribution of emboli released from the circuit and aortic wall. Notably, it was the support level alone that significantly affected the mixing zone of VA-ECMO and cardiac blood, subsequently influencing the risk of embolization of the cardiogenic source and oxygenation levels across various arterial branches.
AB - Problem: Despite advances in Venoarterial Extracorporeal Membrane Oxygenation (VA-ECMO), a significant mortality rate persists due to complications. The non-physiological blood flow dynamics of VA-ECMO may lead to neurological complications and organ ischemia. Continuous retrograde high-flow oxygenated blood enters through a return cannula placed in the femoral artery which opposes the pulsatile deoxygenated blood ejected by the left ventricle (LV), which impacts upper body oxygenation and subsequent hyperoxemia. The complications underscore the critical need to comprehend the impact of VA-ECMO support level and return cannula size, as mortality remains a significant concern. Aim: The aim of this study is to predict and provide insights into the complications associated with VA-ECMO using computational fluid dynamics (CFD) simulations. These complications will be assessed by characterising blood flow and emboli transport patterns through a comprehensive analysis of the influence of VA-ECMO support levels and arterial return cannula sizes. Methods: Patient-specific 3D aortic and major branch models, derived from a male patient's CT scan during VA-ECMO undergoing respiratory dysfunction, were analyzed using CFD. The investigation employed species transport and discrete particle tracking models to study ECMO blood (oxygenated) mixing with LV blood (deoxygenated) and to trace emboli transport patterns from potential sources (circuit, LV, and aorta wall). Two cannula sizes (15 Fr and 19 Fr) were tested alongside varying ECMO pump flow rates (50%, 70%, and 90% of the total cardiac output). Results: Cannula size did not significantly affect oxygen transport. At 90% VA-ECMO support, all arteries distal to the aortic arch achieved 100% oxygen saturation. As support level decreased, oxygen transport to the upper body also decreased to a minimum saturation of 73%. Emboli transport varied substantially between emboli origin and VAECMO support level, with the highest risk of cerebral emboli coming from the LV with a 15 Fr cannula at 90% support. Conclusion: Arterial return cannula sizing minimally impacted blood oxygen distribution; however, it did influence the distribution of emboli released from the circuit and aortic wall. Notably, it was the support level alone that significantly affected the mixing zone of VA-ECMO and cardiac blood, subsequently influencing the risk of embolization of the cardiogenic source and oxygenation levels across various arterial branches.
KW - Cannula
KW - Emboli transport
KW - Harlequin syndrome
KW - Mechanical circulatory support
KW - Stroke
KW - Watershed region
UR - http://www.scopus.com/inward/record.url?scp=85187792362&partnerID=8YFLogxK
U2 - 10.1016/j.compbiomed.2024.108263
DO - 10.1016/j.compbiomed.2024.108263
M3 - Article
C2 - 38489988
AN - SCOPUS:85187792362
SN - 0010-4825
VL - 172
JO - Computers in Biology and Medicine
JF - Computers in Biology and Medicine
M1 - 108263
ER -