An active approach of pressure waveform matching for stress‐based testing of arteries

Figures

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  FIGURE 1. (A) Schematic illustration of the active compliance chamber, which is integrated in the mock circulation loop (MCL). The arterial segment is shown with a red curve and the venous segment with a blue curve. The arrows indicate the direction of flow. 3V, three‐way valve; AoP, aortic pressure; AV, aortic valve; CoP, compliance pressure; DV, drain valve; FP, flow probe; LVP, left ventricular pressure; MV, mitral valve. (B) Photograph showing the complete setup of the MCL

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  FIGURE 2. Control diagram of the feedback and cascaded controller. The inputs p ref (+ sign) and p RT (− sign) lead to P error and the control loop sends a signal to the PI and its controllers. Then, depending on the signal, the active compliance chamber (ACC) either (i) expands (P error > 0) or reduces (P error < 0) its volume until p RT = p ref, or (ii) remains constant (P error = 0). The reference pressure p ref relates to the target pressure used as input. The measured pressure p RT relates to the real‐time pressure of the MCL. The dashed line encloses the functions of the ACC. P error, pressure deviation; PI, proportional‐integral controller; ref, reference pressure; RT‐pressure, real‐time pressure

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  FIGURE 3. Block diagram of the cascaded control system for the active compliance chamber. The controller creates a movement profile based on the reference input. The position, speed, and current controller consists of a proportional‐integral (PI) controller. Each controller receives signals from the active compliance chamber via the control loop if the actual values deviate from the reference values. The small dashed box indicates the PI controller. The big dashed box indicates the cascaded controller

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  FIGURE 4. Accuracy of ACC performance: (A) comparison of the p reference p ref (black waveform), the reproduced AoP with the ACC enabled (red waveform), and the AoP w/o ACC (blue waveform) for the healthy state; (B) tracking error shows ΔPressure of p ref – p RT, which shows the difference between the reference and the measured waveforms. AoP with ACC, aortic pressure with active compliance chamber activated; AoP w/o ACC, aortic pressure with active compliance chamber deactivated; p RT, measured pressure; p ref, pressure reference

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  FIGURE 5. Mock circulation loop repeatable (n = 20) healthy raw data with mean aortic pressure (MAoP) x¯ ± σ versus time, indicatig the accuracy of the ACC controller. Test‐0 is the reproduced waveform (blue) with σ (light blue area) and deactivated ACC. Test‐1 is the reproduced waveform (red) with σ (light red) and activated ACC. AoP, aortic pressure

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  FIGURE 6. Influence of the ACC on the AoP in the healthy state, (A–C), under hypertension, (D–F), and in HFrEF, (G–I). Measured signals are shown for the pressure‐time, (A), (D), (G), for the flow‐time, (B), (E), (H), and the displacement‐time, (C), (F), (I). ACC, active compliance chamber; AoF, aortic flow; AoP, aortic pressure; CoP, compliance pressure; HFrEF, heart failure reduced ejection fraction; LVP, left ventricular pressure; MAoP, mean aortic pressure; sLV, simulated left ventricle