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Axial flow blood pumps for cardiac assistance have proven their clinical viability and benefit in recent years. However, the clinical systems to date have no direct mechanism to decrease pump speed when adequate supply is not available. This may lead to ventricular collapse or increase the probability of hemolysis and thrombotic risks. Based on various experiences with left ventricular assist device (LVAD) patients in various states of recovery, at implant, in the intensive care unit, in the standard ward, and during physical exercise, 11 different algorithms were developed for the automatic detection of ventricular suction. These detection algorithms analyze the flow pattern for the presence of distinct suction indicators. For selection and optimization of the algorithms, 1000 records from approximately 100 patients were collected. Each record contains 5 s of pump flow, current, and arterial pressure. Three experts classified these records in terms of suction probability and other abnormalities. The optimization was developed in Matlab, capable of solving a fifth-dimensional optimization problem with 256 different algorithm combinations. The optimization resulted in a set of 6 algorithms, each with specific thresholds. The system detects 100% of the known suction events with 0.28% of false-positive interpretations. If tuned to avoid any false-positive detection, 90.7% of the certain events would be detected. A strategy for the development of a robust suction detection system for axial blood pumps was found. This system will be integrated into an automatic pump speed control system to provide adequate perfusion for the LVAD recipient, without excessive unloading of the ventricle.

Centrifugal blood pumps are playing a key role in circulatory mechanical assist systems including cardiopulmonary bypass (CPB), right and left ventricular assist devices (RVAD and LVAD), percutaneous cardiopulmonary support (PCPS), and extracorporeal membrane oxygenation (ECMO). Each of these circulatory assist systems requires specific flow and pressure conditions. In vitro hemolysis tests were performed using five compact mock loops with flow and pressure set equivalent to clinical conditions. These studies determined the hemolytic characteristics and clinical applicability of the pivot bearing-supported Gyro centrifugal pump with an eccentric port (C1E3) compared with the Bio-Medicus pump (BP-80). Normalized index of hemolysis (NIH) values of the C1E3 were less than those of the BP-80 under all conditions; in particular, they were significantly less in the CPB, LVAD, and RVAD conditions. In addition, linear correlation was observed between NIH values, rotational pump speed (RPM), total pressure head (delta P), and flow rate (Q) with both the C1E3 and BP-80: NIH = a(RPM/Q) + b, NIH = c(delta P/Q) + d. However, the slopes (a and c) of these equations were smaller with the C1E3 than those with the BP-80, which suggests that the C1E3 has decreased hemolytic characteristics when increasing the RPM and delta P. In other words, the increase of RPM and delta P results in less shear stress with the C1E3 than with the BP-80. One cause of these decreased hemolytic characteristics of the C1E3 is thought to be less pump power loss against an increase of RPM and delta P than with the BP-80. Furthermore, the average exposure time is shorter with the C1E3 than with the BP-80 because the priming volume of the C1E3 (30 ml) is smaller than that of the BP-80 (80 ml). From the point of both shear stress and exposure time, the C1E3 has less hemolytic features than the BP-80.