Non-invasive estimation of pulsatile flow and differential pressure in an implantable rotary blood pump for heart failure patients

Abstract

We propose dynamical models for pulsatile flow and head estimation in an implantable rotary blood pump. Pulsatile flow and head data were obtained using a circulatory mock loop where fluid solutions with different values of viscosities were used as a blood analogue with varying haematocrit (HCT). Noninvasive measurements of power and pump speed were used with HCT values as inputs to the flow model while the estimated flow was used with the speed as inputs to a head estimation model. Linear regression analysis between estimated and measured flows obtained from a mock loop resulted in a highly significant correlation (R2=0.982) and a mean absolute error (e) of 0.323 L min(-1), while for head, R2=0.933 and e=7.682 mmHg were obtained. R2=0.849 and e=0.584 L min(-1) were obtained when the same model derived in the mock loop was used for flow estimation in ex vivo porcine data (N=6). Furthermore, in the steady state, the solution of the presented flow model can be described by a previously designed and verified static model. The models developed herein will play a vital role in developing a robust control system of the pump flow coping with changing physiological demands.

Development of a Pump Flow Estimator for Rotary Blood Pumps to Enhance Monitoring of Ventricular Function

“…Several methods have been proposed to estimate average flow and pressure head (4,6,7) based on pump speed, current, and/or power. Recently, the focus has been laid on estimating the instantaneous pump flow employing empirical methods such as autoregressive models (8,9). Other groups have modeled the dynamic behavior of axial and centrifugal flow pumps based on the physical principles of a brushless DC motor (BLDC motor) (10–12).…”

Physiological control of implantable rotary blood pumps for heart failure patients

“…The sensorless device operation has become quite challenging nowadays especially in the case of IRBP flow and pressure estimation. Most recently, this field has received a lot of attention worldwide [29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45]. As the use of additional sensors is not desirable in LVADs due to some inherent drawback like thrombus formation, reduced system reliability and need for periodic recalibration [46].…”

Outflow monitoring of a pneumatic ventricular assist device using external pressure sensors

“…Despite the advantages of VADs, they are not widely implemented because of their high cost and risk of critical failure [6–9]. Malfunctions and inappropriate control of VADs can seriously damage organs and vessels; therefore, the outflow of VADs must be monitored to detect device failure or changes in the patient’s physiology [10–15]. …”

“…The inlet blood pressure of the VAD has been shown to detect abnormal blood inflow; however, blood pressure sensors are difficult to manage for long periods because of their limited life span and difficulties in preventing thrombosis and fibrosis around the sensors [15, 16]. Outflow estimation has been studied based on the relationship between the motor speed and current consumption under normal hemodynamic conditions [17–20].…”