An Atraumatic Mock Loop for Realistic Hemocompatibility Assessment of Blood Pumps

Objective: Conventional mock circulatory loops (MCLs) cannot replicate realistic hemodynamic conditions without inducing blood trauma. This constrains in-vitro hemocompatibility examinations of blood pumps to static test loops that do not mimic clinical scenarios. This study aimed at developing an atraumatic MCL based on a hardware-in-the-loop concept (H-MCL) for realistic hemocompatibility assessment. Methods: The H-MCL was designed for 450
$\pm$
50 ml of blood with the polycarbonate reservoirs, the silicone/polyvinyl-chloride tubing, and the blood pump under investigation as the sole blood-contacting components. To account for inherent coupling effects a decoupling pressure control was derived by feedback linearization, whereas the level control was addressed by an optimization task to overcome periodic loss of controllability. The HeartMate 3 was showcased to evaluate the H-MCL's accuracy at typical hemodynamic conditions. To verify the atraumatic properties of the H-MCL, hemolysis (bovine blood, n = 6) was evaluated using the H-MCL in both inactive (static) and active (minor pulsatility) mode, and compared to results achieved in conventional loops. Results: Typical hemodynamic scenarios were replicated with marginal coupling effects and root mean square error (RMSE) below 1.74
$\pm$
1.37 mmHg while the fluid level remained within
$\pm$
4% of its target value. The normalized indices of hemolysis (NIH) for the inactive H-MCL showed no significant differences to conventional loops (
$\Delta$
NIH = −1.6 mg/100 L). Further, no significant difference was evident between the active and inactive mode in the H-MCL (
$\Delta$
NIH = +0.3 mg/100 L). Conclusion and significance: Collectively, these findings indicated the H-MCL's potential for in-vitro hemocompatibility assessment of blood pumps within realistic hemodynamic conditions, eliminating inherent setup-related risks for blood trauma.