Development of a computational fluid dynamic model to investigate the hemodynamic impact of REBOA

Abstract

Background: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a lifesaving intervention for major truncal hemorrhage. Balloon-tipped arterial catheters are inserted via the femoral artery to create a temporary occlusion of the aorta, which minimizes the rate of internal bleeding until definitive surgery can be conducted. There is growing concern over the resultant hypoperfusion and potential damage to tissues and organs downstream of REBOA. To better understand the acute hemodynamic changes imposed by REBOA, we developed a three-dimensional computational fluid dynamic (CFD) model under normal, hemorrhage, and aortic occlusion conditions. The goal was to characterize the acute hemodynamic changes and identify regions within the aortic vascular tree susceptible to abnormal flow and shear stress.Methods: Hemodynamic data from established porcine hemorrhage models were used to build a CFD model. Swine underwent 20% controlled hemorrhage and were randomized to receive a full or partial aortic occlusion. Using CT scans, we generated a pig-specific aortic geometry and imposed physiologically relevant inlet flow and outlet pressure boundary conditions to match in vivo data. By assuming non-Newtonian fluid properties, pressure, velocity, and shear stresses were quantified over a cardiac cycle.Results: We observed a significant rise in blood pressure (∼147 mmHg) proximal to REBOA, which resulted in increased flow and shear stress within the ascending aorta. Specifically, we observed high levels of shear stress within the subclavian arteries (22.75 Pa). Alternatively, at the site of full REBOA, wall shear stress was low (0.04 ± 9.07E-4 Pa), but flow oscillations were high (oscillatory shear index of 0.31). Comparatively, partial REBOA elevated shear levels to 84.14 ± 19.50 Pa and reduced flow oscillations. Our numerical simulations were congruent within 5% of averaged porcine experimental data over a cardiac cycle.Conclusion: This CFD model is the first to our knowledge to quantify the acute hemodynamic changes imposed by REBOA. We identified areas of low shear stress near the site of occlusion and high shear stress in the subclavian arteries. Future studies are needed to determine the optimal design parameters of endovascular hemorrhage control devices that can minimize flow perturbations and areas of high shear.

Computational investigation of outflow graft variation impact on hemocompatibility profile in LVADs

“…Some assumptions were made that could potentially limit the scope of this study. In this study, we assumed that the flow is laminar, as is the case with previous similar studies, 16,17 even though it is conceivable that the flow may be turbulent. However, we did expect that the flow would have more turbulence if the aortic valve opened, but that was not the case with our patients.…”

“…Furthermore, we assumed the aortic wall to be rigid. A rigid wall is an assumption that computational studies commonly make to model flow in the proximal vasculature 10–31 . Additionally, the geometrical features used in this study correspond to an elderly patient, where we can perhaps assume that the compliance is lower.…”

“…The patient in this simulation had a closed aortic valve based on echocardiography. Given that there was no aortic valve opening, we assumed the flow to be laminar (Re < 2100), similar to prior studies 16,17 . Inlet and outlet boundaries were obtained from a subrogated model of a patient under continuous high LVAD support 18 .…”

“…Given that there was no aortic valve opening, we assumed the flow to be laminar (Re < 2100), similar to prior studies. 16,17 Inlet and outlet boundaries were obtained from a subrogated model of a patient under continuous high LVAD support. 18 The waveform was mapped into a uniform velocity profile and used as an inlet boundary condition.…”

Investigating the Relationship Between Bleeding, Clotting, and Coagulopathy During Automated Partial Reboa Strategies in a Highly Lethal Porcine Hemorrhage Model

“…Our group has previously leveraged computational fluid dynamic models to better understand the acute hemodynamic environment during REBOA and pREBOA (20). We observed areas of low, stagnant flow proximal to the full occlusion and an increase in velocity past a partial occlusion.…”