Figure 2.

Solution process of the lumped ODE model of the circulatory system. The CircAdapt model connects tubes (t), cavities (c), valves (v), and pulmonary and systemic periphery (py). In each timestep the ODE system is solved using a Runge-Kutta-Fehlberg method, see Appendix A.9, to update the ODE variables (in green), i.e., volumes of tubes (V_t) and cavities (V_c); sarcomere contractility (C_c) and sarcomere length $\left(L_c^{\text{cont}}\right)$ for each of the cavities and the septum; flow over valves (q_v); and septal midwall volume $\left(V_{\text{Sep}}^{\text{mid}}\right)$ and radius (y ^mid), see Fig. A.9c. In the following steps the updated variables are used to compute current pressures (p_c, p_t), cross sectional areas (A_c, A_t), and impedances (Z_c, Z_t) for tubes and cavities; fiber strain $\left(E_c^{\text{fib}}\right)$, fiber stiffness $\left({\kappa }_c^{\text{fib}}\right)$, and fiber stress $\left({\sigma }_c^{\text{fib}}\right)$ for the sarcomeres of each cavity and the septum; midwall curvature $\left(C_c^{\text{mid}}\right)$, midwall area $\left(A_c^{\text{mid}}\right)$, and midwall tension $\left(T_c^{\text{mid}}\right)$ for each cavity and the septum; pericardial pressure p _peri; and flow over the systemic and pulmonary periphery q_py.. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Source: Based on [44].