Automation of the Harvard Apparatus Pulsatile Blood Pump

Abstract

Producing accurate physiological circulatory conditions in vitro is integral to the evaluation of cardiac assist technologies. The ability to simulate cardiac function, normal or pathological, is dependent on the capabilities of the pump deployed for this purpose. Presented is a reference standard for this in vitro analysis, with automation features targeted for robust bench-top testing. Cardiac performance is typically described in terms of stroke volume, heart rate, and percent systole. Respectively, these three settings prescribe the volume of fluid ejected, the rate of pumping, and the percentage of the pumping cycle spent in ejection. A pump that provides settings for each of these parameters and precise repeatability allows for accurate construction of simulation conditions. These capabilities are present in the commercially available Harvard Apparatus 1423 pulsatile blood pump. Modifications have been made to this particular model that allow for the automation of its function and real-time performance determination. Discussed in this publication is the design and performance of a modified 1423 pump that employs universal serial bus (USB) communication in the control of its stroke volume, heart rate, and percent systole. The percent systole is denoted as the phase ratio on the hardware. Utilization of an embedded microcontroller (MCU) allows for not only the digital communication via a computer terminal, but process control of the subsystems maintaining each parameter. Care was taken to preserve the mechanical design employed by Harvard Apparatus; the modifications were not invasive to the mechanical driveline of the pump. Electromechanical design characterization was performed in Simulink® using the following Simscape™ block sets: Simscape™ Foundation Library, SimElectronics®, and SimMechanics™. This provided an accurate model of the systems during the design process, which assisted in the deployment of the process controllers with minimal prototype construction. Communication with the MCU is achieved with American Standard Code for Information Interchange (ASCII) commands delivered through a LabVIEW VI interface. Continuous readbacks on fill/ejection rate, pump rate (HR), percent systole (PS), and stroke volume (SV) are possible with these modifications. The deployed upgrade allows for complete automation of the Harvard Apparatus 1423 pulsatile blood pump, with the capability to run sequences of conditions without the need for manual intervention.