A Non-Invasive Physiological Control System of a Rotary Blood Pump Based on Preload Sensitivity: Use of Frank–Starling-Like Mechanism

Figures

• 

  Figure 1. Equivalent circuit model of the LVAD-cardiovascular system.

• 

  Figure 2. Block diagram of the control system. CVS, reference cardiovascular system; LVAD, left ventricular assist device; ω, motor speed; Qest¯, estimated average pump flow; PLVED, left ventricular end-diastolic pressure; QPr¯, desired average pump flow; PI, proportional and integral controller; CLn, Control Line; S1, original state; S2 and S3, deviated states. Gray circles represent the position of operating points after a change in states. Black circles represent the positions of operating points upon arriving at the new steady-state located at the intersection between the control line and the new system line. The controller drives the changes in the operating points along the path indicated by the arrows along the new system line.

• 

  Figure 3. Pump flow regulator. OPND,t, the original operating point; OPt, the unadjusted state point of the patient at time t; Qest,t¯, the pump flow of the patient at time t; OPt+1, the state point after the patient adjusts at t+1; Qest,t+1¯, the ideal pump flow after the patient adjusts at time t+1 (reference pump flow); θn, the nth control angle of the operating angle of the baseline.

• 

  Figure 4. Effect of CSC control system and NAC-FSL control system on hemodynamic parameters from resting to exercise state. (a) The measured and estimated mean pump flow in two states. QP1¯ and QP2¯ represent the measured mean pump flows of CSC and NAC-FSL, respectively. Qest1¯ and Qest2¯ represent the estimated mean pump flows of CSC and NAC-FSL, respectively. The error between the estimated mean pump flow and the measured mean pump flow was compared. (b) The estimated power corresponding to the motor speed from resting to exercise. NAC-FSLM represents the mean pump power at a variable speed and CSCM represents the mean pump power at a fixed speed. (c) Changes in the P-V loops of the two control systems.

• 

  Figure 5. Changes in hemodynamic parameters as K values change for different degrees of heart failure. (a) Emax = 0.5, severe HF. (b) Emax = 1.0, moderate HF. (c) Emax = 1.5, mild HF. K: Scale factor. Qest¯: estimated average pump flow.