Development and Validation of a Life-Sized Mock Circulatory Loop of the Human Circulation for Fluid-Mechanical Studies

Abstract

Mock circulatory loops (MCLs) are usually developed for assessment of ventricular assist devices and consist of abstracted anatomical structures represented by connecting tubing pipes and controllable actuators which could mimic oscillating flow processes. However, with increasing use of short-term peripheral mechanical support (extracorporeal life support [ECLS]) and the upcoming evidence of even counteracting flow processes between the failing native circulation and ECLS, MCLs incorporating the peripheral vascular system and preserved anatomical structures are becoming more important for systematic assessment of these processes. For reproducible and standardized fluid-mechanical studies using magnetic resonance imaging, Doppler ultrasound, and computational fluid dynamics measurements, we developed a MCL of the human circulation. Silicon-based life-sized dummies of the human aorta and vena cava (vascular module) were driven by paracorporeal pneumatic assist devices. The vascular module is placed in a housing with all arterial branches merging into peripheral resistance and compliances modules, and blood-mimicking fluid returns to the heart module through the venous dummy. Compliance and resistance chambers provide for an adequate simulation of the capillary system. Extracorporeal life support cannulation can be performed in the femoral and subclavian arteries and in the femoral and jugular veins. After adjusting vessel diameters using variable Hoffmann clamps, physiologic flow rates were achieved in the supraaortic branches, the renal and mesenteric arteries, and the limb arteries with physiologic blood pressure and cardiac output (4 L/min). This MCL provides a virtually physiologic platform beyond conventional abstracted MCLs for simulation of flow interactions between the human circulation and external circulation generated by ECLS.

Watershed phenomena during extracorporeal life support and their clinical impact: a systematic in vitro investigation

“…The major and venous vascular branches were equipped with several antegrade and retrograde large‐bore haemostasis valve ports for peripheral and central cannulation. A previously described and validated blood‐mimicking fluid for ultrasound studies was used as a blood analogue for the MCL 18,22 . CO was adjusted from the assist device control unit with driving and suction pressure and measured with ultrasound‐based transit time clamp‐on flow probes Transonic HXL (Transonic Systems Inc., Ithaca, NY, USA) connected to the vascular branches and corresponding vascular compartments.…”

“…A previously described and validated blood-mimicking fluid for ultrasound studies was used as a blood analogue for the MCL. 18,22 CO was adjusted from the assist device control unit with driving and suction pressure and measured with ultrasound-based transit time clamp-on flow probes Transonic HXL (Transonic Systems Inc., Ithaca, NY, USA) connected to the vascular branches and corresponding vascular compartments. Blood pressure was measured with clinical strain gauge pressure transducers (Combitrans; Braun, Melsungen, Germany).…”

“…The reproduction of the several stages of cardiac depression required a sole adjustment of the driving pressures of the VADs without any changes in the preset resistive and capacitive parameters. 18…”

“…Repeated shut down manoeuvres with resulting fluid and pressure equilibrium of the MCL allowed reproducible parameters within 10 min with continued stability. The reproduction of the several stages of cardiac depression required a sole adjustment of the driving pressures of the VADs without any changes in the preset resistive and capacitive parameters 18 …”

Development of a circulatory mock loop for biventricular device testing with various heart conditions

“…Recent mock loops can be classified as either simple and non-pulsatile in nature or complex and pulsatile, with some parameters that imitate the physiology of the actual human circulation. 1 assembly, supported by a hydrodynamic bearing. 2,3 These total artificial hearts (TAHs) can also be used as biventricular assist devices (BiVADs).…”