Controller for an Axial Flow Blood Pump

Abstract

A rotary blood pump inherently provides only one noninvasive "observable" parameter (motor current) and allows for only one "controllable" parameter (pump speed.) To maintain the systemic circulation properly, the pump seed must be controlled to sustain appropriate outlet flows and perfusion pressure while preventing pulmonary damage caused by extremes in preload. Steady-state data were collected at repeated intervals during chronic trials of the Nimbus AxiPump (Nimbus, Inc., Rancho Cordova, California, U.S.A.) in sheep (n = 7) and calves (n = 12). For each data set, the pump speed was increased at increments of 500 rpm until left ventricular and left atrial emptying was observed by left atrial pressure diminishing to zero. The effect of decreasing preload was evaluated perioperatively by inferior vena cava occlusion at a constant pump speed. Fourier analysis established a relationship between changes in the pump preload and the power spectra of the pump current waveform. Based on these results, a control method was devised to avoid ventricular collapse and maintain the preload within a physiologic range. The objective of this controller is the minimization of the second and third harmonic of the periodic current waveform. This method is intended to provide a noninvasive regulation of the pump by eliminating the need for extraneous transducers.

Advanced Suction Detection for an Axial Flow Pump

“…A discussion of venous return and excessive ventricular unloading in implantable rotary blood pumps (7)(8)(9)(10)(11) has continued for many years. The direct way to detect the occurrence of ventricular collapse would be through the use of a reliable pressure measurement; one project was reported (12) in which a strain-gauge-bridge which was built into the concave interior wall of a tubing cannula was used.…”

Hemodynamic and Exercise Performance With Pulsatile and Continuous-Flow Left Ventricular Assist Devices

“…5,8 The hydrodynamic performance of rotary pumps with an axial design is directly proportional to rotor speed and inversely proportional to pressure differences across the inlet and outlet orifices of the pump. 5 Therefore, rotary pumps with an axial design have a potential capacity to adjust flow to increases or decreases in LV preload.…”

Development of a Reliable Automatic Speed Control System for Rotary Blood Pumps

“…[12][13][14][15][16][17] In light of these strategies and clinical experience with a variety of pathologic conditions, the following control strategy was selected because it can fit these clinical situations with a minimal need to determine and set patient-specific parameters.…”