Design Modifications and Computational Fluid Dynamic Analysis of an Outflow Cannula for Cardiopulmonary Bypass

Abstract

Cardiopulmonary bypass is a well-established technique during open heart surgeries. However, neurological complications due to insufficient cerebral oxygen supply occur and the severe consequences must not be neglected. Recent computational fluid dynamics (CFD) studies showed that during axillary cannulation the cerebral perfusion is strongly affected by the distance between the cannula tip and the vertebral artery branch. In this study we use two modifications of the cannula design to analyze the flow characteristics by means of CFD and experimental validation with particle image velocimetry (PIV). One approach applies a spin to the blood stream with a helical surface in the cannula cross section. Another approach uses radial bores in a constricted cannula tip to split the outflow jet. The additional helicity improves the perfusion of the cerebral vessels and suppresses the blood suction in the right vertebral artery observed with a standard cannula. The cannula with a helix throughout the entire length changes the blood flow from 2124 to 32 mL/min in comparison with an unmodified design and has the lowest prediction of blood damage. Separating the blood stream does not deliver satisfying results. The PIV measurements validate the simulations and correspond with the velocity distribution as well as vortex locations.

High resolution hemodynamic profiling of murine arteriovenous fistula using magnetic resonance imaging and computational fluid dynamics

“…A study using an in vitro model of human AVG reported directional vorticity of ±550 1/s at the AVG anastomosis [31], and a CFD simulation of intracranial arterial aneurysms reported directional vorticity of -1000 to +1600 1/s [12]. In addition, in a CFD analysis of blood flow in an outflow cannula for cardiopulmonary bypass, helicity magnitude was reported up to 1.5x10 5 cm/s 2 [13]. Increasing positive values of Q-criterion (indicating vortices) have been reported in a CFD model of arterial stenosis, with greater regions of positive Q-criterion throughout the artery volume as the stenosis becomes more constrictive [14].…”

“…Comparing these previous findings to our work, we find that similar vorticity was seen in our mouse AVF in 4 mm averages (349 ± 768 1/s at Day 21) compared to human AVF and AVG in the vein (550-1600 1/s) [12, 31]. In our mouse AVF vein at Day 21, we calculated increased helicity (96.4 ± 5460 cm/s 2 ) and positive Q-criterion (1.21 ± 100×10 3 1/s 2 ) when compared to non-surgery veins, indicating helical, disturbed flow, and the formation of vortices in the AVF veins, as seen in vascular studies of helical, disturbed flow in cannulated cardiopulmonary bypass and arterial stenosis [13, 14, 32]. …”

“…7). Specifically, helicity measures the local linkage or knottedness of streamlines, either in a right-handed helical pattern (positive) or a left-handed helical pattern (negative) [13]. Q-criterion is a derived measurement used to identify local vortices in a flow field.…”

Heart valve inspired and multi‐stream aortic cannula: Novel designs for cardiopulmonary bypass improvement in neonates

“…Howbeit, internal structure manipulation in the latter case showed outflow pattern improvements, it is suspicious to thrombosis and hemolysis due to flow disturbance and stagnation caused by internal stator. Furthermore, an internal profile alteration for spiral flow generation produces less area for the blood flow which can result in a higher internal velocity, and therefore, higher shear stresses. A recent study proposed to use an inlet chamber to induce spiral jet flow which was reported to reduce the impinging velocity by 21%.…”

Computational Fluid Dynamic Analysis of the Hemodialysis Plastic Cannula

“…Plastic cannulae have been developed for use in other fields of medicine such as ventricular assist devices , cardiopulmonary bypass , and central venous catheters . The outcomes of these developments have resulted in an optimized geometry of the tip and side holes as well as improved placement in the respective blood vessel to reduce the risk of thrombus formation.…”