Figure 1.
Hemodynamic analysis of the circulation system.
The circulation system may hydromechanically be divided into two enclosed fluids, the WITS and PITS (the white and the dark parts of the circulation system in the figure). They are operating at a very different pressure level and kept separated by either the atrio-ventricular valves in systole (top panel) or the semilunar valves in diastole (bottom panel), though they are connected in series. The systemic venous return (SVR) system consists of systemic vasculature and right heart, and the pulmonary venous return (PVR) system consists of pulmonary vasculature and left heart. Their location relative to WITS and PITS changes in diastole and systole. Modified from Wang et al. PLoS ONE. [10].
Figure 2.
Five bottles labeled with number 1 to 5 were used and were connected by rubber and glass tubing. No. 5 is a syringe of 50 C.C. without the piston. The top panel is a simulated SVR connected with a negative-positive-pressure-generator (Bottle No.2 and 3) through rubber and glass tubing. The bottom panel is the simulated PVR. SCC = simulated chest cavity, SLV = simulated left ventricle, SRV = simulated right ventricle, SVR = systemic venous return system, PVR = pulmonary venous return system.
Figure 3.
The right part of the figure is the longitudinal view of Model 2. The materials used are the same as those of Model 1. The top crescent structure is simulated right ventricle (SRV) and the bottom circular one is simulated left ventricle (SLV). Their common wall between SRV and SLV is the simulated interventricular septum. The thickness of the walls are 1.7mm, 3.4mm, 3.4mm from top to bottom in the figure. The left part is the short-axis view of model 2 which looks like a 2D-echocardiogram of the Model. The wall of these bottles are thin plastic and thus can be imaged by echocardiography.
Table 1.
Comparison of the SRV volume changes during the adjustments of the SRV filling pressures and the simulated intrathoracic pressures respectively.
Figure 4.
The influence of simulated RIPC on the motion of the simulated IVS.
Under the simulated RIPC, the simulated IVS is swinging left- and rightwards (down and up in the figure) to correspond the pressure change in SCC. To simulate the in vivo condition where the right ventricle anterior wall and the left ventricle posterior walls are kept in touch with the chest wall, the pressures in SRV, SLV, SCC and SP are adjusted to 4 mmHg, 9 mmHg, 0 mmHg and 0 mmHg respectively. Acuson’s Sequoia 512 ultrasonographic system was used to record the M-mode and two-dimensional cineloops of the simulated IVS’s motion under the simulated RIPC. Total of 150 frames were captured. A. With rhythmic pressure change in SCC, or under the simulated RIPC of 0 to −4mmHg, the IVS swung left- and rightwards at amplitude of 2.2 mm. B and C. These two of the total 150 frames demonstrate the 2D echocardiograms of the end-expiration (B) and end-inspiration (C) phases. Their internal LV diameters are 35.0 and 32.8 mm, respectively. RIPC = respiratory intrathoracic pressure change; PVR = pulmonary venous return system; SVR = systemic venous return system, SCC = simulated chest cavity; SRV = simulated right ventricle, SLV = simulated left ventricle; SP = simulated pericardium, IVS: interventricular septum.