Virtual patient simulator for the perfusion resource management drill

Abstract

Perfusionists require a detailed understanding of a patient's physiological status while comprehending the mechanics and engineering of the cardiopulmonary bypass system, so it is beneficial for them to obtain relevant practical skills using extracorporeal circulation technology and educational physiological simulators. We designed a perfusion simulator system (ECCSIM: Extracorporeal Circulation SIMulator system) based on a hybrid of a simple hydraulic mock circulation loop linked to a computer simulation model. Patient physiological conditions (height, weight, and cardiac indices) were determined by a parameter estimation procedure and used to accurately reproduce hemodynamic conditions. Extracorporeal circulation trainees in pre-clinical education were able to maintain venous oxygen saturation levels above 50%, except during cardiac standstill and a brief resumption of pulsation. Infant amplitudes of reservoir volume oscillation and flow rate were greatly increased compared with adult cardiovascular parameters, this enabled the instructor to control the difficulty level of the operation using different hemodynamic variations. High-fidelity simulator systems with controllable difficulty levels and high physiological reproducibility are useful in constructing a perfusion resource management environment that enable basic training and periodic crisis management drills to be performed.

Figure 1.

Schematic block diagram of numerical-hydraulic simulator system. DB: Database of predefined scenario and operation record; FSa, FSv, FSx: Flow sensor unit of arterial, venous, and additional port respectively; BR: Blood capacitor reservoir;Va, Vv, Vx: Flow control valve unit of arterial, venous, and additional line respectively; MP: Main pump unit; VP: Vent or suction pump unit; SP: Suction pump unit.

Figure 2.

Hydraulic section of simulator connected to heart lung machine. Hydraulic analog is positioned on an operating table and physically connected to circuit of heart lung machine.

Figure 3.

A, Visual user interface for trainee. Vital sign monitor panel; B, Information panel of blood gases, arterial pressure, and line flows of each circuit line.

Figure 4.

Visual user interface for instructor. Interface is made up of vital sign monitor panel, blood gases monitor panel, status display of heart lung machine, and other controls for instructor’s operation.

Figure 5.

Electrical analog of systemic circulatory system including extracorporeal circulation. The systemic circulatory loop is composed of a modified or simple windkessel model and the variable compliance model. The main pump (BP), venous drainage line (VD), and vent pump (VP) are connected to the systemic circulatory loop.

Figure 6.

Schematic representations of cardiovascular parameter estimation procedure. Blood volume, venous compliance, and pulmonary vein compliance are computed from body weight directly. Cardiac output is computed from body surface area (BSA) computed from W and height (H), then systemic peripheral resistance is derived by presumption model f(CO) shown in Appendix 1. Relationship of unstressed volume and W and CI is then derived. Unstressed volume is derived by presumption model g(CI, W) shown in Appendix 2. The oxygen consumption volume is derived by presumption model h(W, Temp) shown in Appendix 3.

Figure 7.

Schematic representations of blood gas models. The model is made up of three input compartments (from instructor’s console, gas controller for trainee, and simulated results of numerical section), several experimental or analytical equations, and delay for blood gas monitor display. T is time constant of delay set as 2.0 seconds.

Figure 8.

Comparison of target and simulated cardiac index and mean blood pressure to body weight. Simulated mean blood pressure was maintained at target value (85 mmHg), and simulated cardiac index is according to target value (2.0, 3.0, and 4.0) in a range of 10–120 kg body weight.

Figure 9.

A, Time courses of arterial pressure, centrifugal venous pressure, venous oxygen saturation, and heart rate; B, arterial oxygen pressure, carbon dioxide pressure and pH; C, arterial flow rate, oxygen gas flow rate and reservoir volume. Simulation training is carried out using adult cardiovascular parameters (H = 1.67 m, W = 60 kg).

Figure 10.

Time courses of vital signs and operating results. Simulation training is carried out using infant cardiovascular parameters (H = 0.6 m, W = 10 kg).