## 4 Experimental Validation and Parametric Study
### Parametric Study on Aortic Compliance  
Parametric studies of aortic compliance were performed experimentally. In this paper, aortic compliance is controlled by pressurization of the compliance chamber applied to the ascending aorta. The pressurized additional pressure was adjusted from 3.2 kPa to 14.3 kPa over 5 steps. The air inside the compliance chamber pressurizes the ascending aorta with a pressurizing cylinder and indirectly increases the stiffness of the vascular wall. Therefore, as additional pressure increases, stiffness increases, and inversely, compliance decreases. In addition, the method of directly pressurizing the fluid, the way existing cardiovascular simulators control compliance, was compared with. This is the same as the method of adjusting the minimum pressure through the reservoir in the mock circulatory platform of this study, and is hereinafter referred to as the reservoir method. The reservoir method also adjusted the minimum pressure from \(-40\) mmHg to \(40\) mmHg over 5 steps. Figure 10a shows the pressure waveform according to the minimum pressure of the reservoir method, which is how the existing cardiovascular simulator controls compliance. As a result of the experiment, as the minimum pressure of the reservoir increased, diastolic pressure and systolic pressure  
Figure 9: Experiment result according to resistance valve: (**a**) measured pressure waveforms, : ventricular pressure, : aortic pressure; (**b**) normalized aortic pressure waveform according to valve angle. increased in both the ventricle and the aorta. The amount of diastolic and systolic growth is similar and appears to move parallel. Figure 10b shows the normalized aortic pressure waveforms. To compare the pulse pressures, measured aortic pressures were normalized to the baseline aortic pressure in Figure 8b, and shifted to have zero as the minimum pressure. Theoretically, as the minimum pressure of the reservoir increases, the fluid inside the blood vessel is indirectly pressurized, the stiffness applied to the fluid increases, and it can be predicted that the compliance decreases. According to the simulation model in Figure 7c, it can be predicted that the pulse pressure will increase. However, as a result of the experiment, pulse pressure decreased according to increases in the minimum pressure of the reservoir. This is the opposite of the change in pulse pressure according to the aortic compliance predicted through the simulation model. Figure 10c shows the pressure waveform according to the additional pressure. As a result of the experiment, diastolic and systolic blood pressure increased in both the ventricle and the aorta as the additional pressure in the compliance chamber increased. The increase in systolic pressure is greater than the increase in diastolic pressure, resulting in an increase in peak-to-peak amplitude. Figure 10d shows a normalized aortic pressure waveform. To compare the pulse pressure, measured aortic pressures were normalized to the baseline aortic pressure in Figure 8b, and shifted to have zero as the  
Figure 10: Experiment result according to aortic compliance: (**a**) measured pressure waveforms according to minimum pressure of the reservoir method, : ventricular pressure, : aortic pressure; (**b**) normalized aortic pressure waveform according to minimum pressure of the reservoir method; (**c**) measured pressure waveforms according to additional pressure of the new compliance chamber, : ventricular pressure, : aortic pressure; (**d**) normalized aortic pressure waveform according to additional pressure of the new compliance chamber. minimum value. As expected, as the additional pressure in the compliance chamber increases, stiffness of the vascular wall increases indirectly, and compliance decreases. As a result of the experiment, pulse pressure increased according to increasing the additional pressure of the compliance chamber. This is consistent with the change in pulse pressure according to the aortic compliance predicted through the simulation model in Figure 7c.