# A Novel Radial Artery P-S Curve Model Based on Radial Vibration of Vascular Wall
## 4 Discussion  
Pulse waves contain rich human physiological and pathological information and can be used to diagnose diseases [31; 32]. However, there are some shortcomings in the existing methods, that is, they focus on the pulse shape of the strongest point of the pulse wave and its formation mechanism, and there is no accurate study of the change trend of pulse strength with pressure and its formation mechanism. Therefore, based on the radial vibration theory of the vascular wall, a theoretical model of the pulse P-S curve formation mechanism is established, the relationship between pulse strength and extravascular pressure is analyzed, and the mechanical relationship between \(P>P_{e}\), \(P=P_{e}\) and \(P<P_{e}\) is simulated by using COMSOL software, and the actual human pulse P-S curve data are extracted and analyzed, which verifies the accuracy and applicability of the theoretical method. Specifically, in terms of model establishment, firstly, assuming that the blood vessels are uniform long straight tubes, the blood movement equation in the normal human pulsation process is established, and the relationship between the radial flow rate of blood and the axial flow rate is analyzed. Secondly, according to the fluid-structure interaction between blood movement and the vascular wall, the stress change in the blood vessel wall during blood movement was analyzed. Finally, according to the theory of vascular wall elasticity, the changes in vascular wall stress, blood flow speed and intravascular pressure under the action of vascular wall extravascular pressure are analyzed, and the relationship between the above force and pulse strength is established. In terms of experimental results, this paper uses the bionic parameters of the radial artery of the human body, and uses COMSOL software to simulate the changes in vascular wall stress, blood flow velocity and intravascular pressure under the deformation of extravascular pressure, and found that the change trend of vessel wall stress and intravascular pressure conforms to the theoretical model established in this paper, which verified the accuracy of the theoretical model. At the same time, the pulse data of 69 healthy samples are collected. It was found that the pulse P-S curve of the healthy population showed a trend of first increasing and then decreasing with the increase in number of pressurizations. This was consistent with the theoretical model proposed in this paper that demonstrated that the pulse strength first increased and then decreased with the increase in extravascular pressure, which verified the applicability of the theoretical model. However, in the actual situation, there are many factors that affect the physiological parameters of the pulse of the sample, such as environment, region, temperature, physique, sex, age, etc. These objective factors will eventually be reflected in the changes in cardiovascular physiological parameters. The experimental results found that there are differences in the pulse P-S curve of the individual samples that were extracted, mainly reflected in the difference in pulse strength. According to the theoretical model established in this paper, when the intravascular pressure and extravascular pressure reach equilibrium, the pulse strength is mainly related to blood flow, blood viscosity coefficient and blood vessel radius. [PERSON], [PERSON] and [PERSON] [28; 29; 30] showed that the blood viscosity is positively correlated with BMI, so this paper divides 69 healthy samples into 3 categories based on BMI. The pulse strength of three groups of people is counted, and the results show that the median pulse strength of the group with a BMI <= 18.5 is 10.5 gf, and the mean \(\pm\) variance is 11.7 \(\pm\) 3.7 gf, 18.5, the median pulse strength of the group with 18.5 < BMI <= 23.9 is 17.3 gf, the mean \(\pm\) variance is 21.3 \(\pm\) 11.0 gf, the median pulse strength of the group with a BMI > 23.9 is 23.7 gf, and the mean \(\pm\) variance is 22.7 \(\pm\) 8.7 gf.