Clinical Evaluation of an Automatic Physiologically Responsive Control System for Rotary Blood Pumps

Abstract

Rotary blood pumps have become an important tool for the therapy of end stage cardiac failure. However, at the moment most
of these pumps are still operated at constant speed and adjusted by the physician. Adaptation to physiological demand is therefore
provided only by the remaining functionality of the left ventricle. A physiologically responsive control would not only be
important for minimization of suction events and subsequent arrhythmic episodes, but also for better adaptation to exercise
and eventually ventricular recovery. Therefore, an automatic control with integrated suction detection was developed and evaluated
in a clinical study. Here, not only the results of this study but also the potential to optimize the pump efficiency with
this strategy is presented.

The algorithms were developed and implemented with Matlab on a dSpace controller board. The system uses pump speed, pump power,
and pump flow as its only input signals. It was connected to the clinical hardware of the DeBakey VAD® System. The control
is preload-sensitive and uses an expert system to detect excessive unloading and eventual suction. Additionally, a function
for optimization of pump power was implemented. This system was used to quantify the cardiovascular reaction of patients to
both automatically controlled and constant pump speed. A subgroup of five patients underwent bicycle ergometry with Swan-Ganz
catheterization and spiroergometry.

The automatic, closed-loop speed control showed robust and stable performance. It provided an increase in pump flow (± 0.94
± 0.5 l/min, p<0.05) compared to constant-speed mode in response to physical activity. Pulmonary arterial (PA) and capillary
wedge pressure (PCWP) clearly decreased (-7.4 ± 4.1 mmHg for PAP and -8.3 ± 4.2 mmHg for PCWP, p<0.05). Exceeding the aims
of the study the results indicated already an increased exercise capacity and the possibility for power optimization.

Summarizing, a robust and safe control with physiological adaptation could be developed and validated in a first clinical
study.