Optimizing cerebral perfusion and hemodynamics during cardiopulmonary bypass through cannula design combining in silico, in vitro and in vivo input

Figure 1. In vitro testing results comparing optiCAN to reference. (a) Photography of optiCAN design (upper cannula) in comparison to common reference cannula (lower cannula); both 24 Fr. The inset highlights the optiCAN tip design with outflow side hole. (b) Ink-stained outflow-jet visualization at 6 L/min for optiCAN design and reference. The outflow contours are marked with red-dashed lines, which engulf the outflow angle. Note the second outflow jet for the optiCAN design at the side hole with a smaller outflow angle. (c) Pressure loss over cannula flow comparing optiCAN design with the reference. (d) Normalized index of hemolysis (NIH) measured over six hours comparing a baseline circuit without cannula, to a reference cannula and optiCAN circuits. The NIH values after 6 h are marked (orange box) and explicit values are given for comparison.

Figure 2. In vivo animal trial in swine during CPB. (a) The cerebral flow through the carotid arteries was measured using two flow sensors. (b) Comparison of the absolute carotid flow provided by reference and optiCAN cannula and the physiological flow without CPB.

Figure 3. CFD simulation results for a human anatomy. (a) Flow field in the aorta and supra-aortic vessels for reference (left) and optiCAN cannula (right) in anterior view (upper) and left lateral view (lower). Gray shades mark the area of low blood flow (velocity below 0.01 m/s). (b) Comparison of carotid artery flow (normalized to physiological cerebral flow) comparing reference cannula with optiCAN design from CFD simulation (shaded) and in vivo animal trial. (cf. Fig. 2b). Dashed line marks physiological cerebral flow.

Figure 4. Wall shear stress (WSS) on the intima of the aortic arch. (a) WSS during physiological conditions in anterior (upper) and left lateral (lower) view. These can be prone to atherosclerotic plaque formation. (b,c) WSS during CPB for reference and optiCAN, respectively. High WSS resembles high impact on the intima and can lead to detachment of plaque. (d) Accumulated area of WSS above the critical threshold versus the respective critical threshold of WSS for both cannula designs. Inset shows a zoom for high thresholds of WSS.

Figure 5. Results for further CFD-optimized design opti2CAN. (a) 3D models of the optiCAN and opti2CAN design. Different inner wall geometry is highlighted with dashed lines. (b) WSS on the intima of the aortic arch for opti2CAN during CPB. High WSS resembles high impact on the intima and can lead to detachment of plaque. (c) Pressure loss over cannula flow predicted from CFD simulations comparing reference, optiCAN and opti2CAN design. (d) Comparison of relative carotid artery flow for reference, optiCAN and opti2CAN design. Dashed line marks physiological level. (e) Accumulated area of WSS above the critical threshold versus the respective critical threshold of WSS for all three cannula designs. Inset shows a zoom for high thresholds of WSS.