## 4 Analysis of Experimental Results
### Dynamic Test Results  
Using the prototype of the pressure measurement catheter and the dynamic testing system, the dynamic measurement accuracy of the compact pressure measurement catheter can be evaluated. The experimental process is as follows: The experimental system's tubing is filled with saline, and the front end of the pressure measurement catheter is introduced into the circulating tubing to simulate the actual use environment. A stepper motor peristalic pump is started to mimic the human heartbeat process. Figure 11a shows the time-domain standard curve of dynamic liquid pressure obtained by squeezing the tubing with the peristalic motor, simulating the human blood pressure waveform. The motor's squeezing cycle for the tubing is 320 ms, with a peak-to-peak pressure of 2.8 kPa. The signal contains various high-frequency components. Figure 11b shows the time-domain signal measured using the compact pressure measurement catheter prototype No. 1, whose peak peak-to-peak values and other information are similar to the original signal, accurately capturing the dynamic liquid pressure peaks and troughs, reaching 96.6% of the original signal's peak-to-peak value. Figure 11c shows the image measured by prototype No. 2, with a catheter body external part length of 30 mm and a diameter of 1.2 mm, where the peak-to-peak value of this group of signals is 82.1% of the original signal. Figure 11d shows the time-domain signal measured by prototype No. 3, with a catheter body external part length of 800 mm and a diameter of 3.4 mm; compared to the original signal, this data set shows significant distortion, making it difficult to obtain accurate peak and trough values, with a peak-to-peak value of only 61.8% of the original signal. By comparing the three groups of signals, it can be concluded that under the same internal part conditions of the catheter, distortion will increase with an increase in catheter length and decrease in diameter. Under the same 3.4 mm diameter, a 30 mm length tubing's peak-to-peak range is 156% of an 800 mm length tubing; under the same 30 mm length, the peak-to-peak range of a 3.4 mm inner diameter tubing is 118% of a 1.2 mm inner diameter tubing. Figure 10: (**a**) Output curve of the pressure measurement catheter; (**b**) positive motion test results; (**c**) negative motion test results. Figure 11: Dynamically varying pressure test Results. (**a**) Time-domain standard curve for dynamic liquid pressure; (**b**) time-domain signal measured by the compact No. 1 pressure measurement catheter previously designed, with an external length of 30 mm and diameter of 3.4 mm; (**c**) time-domain image measured by No. 2 pressure measurement catheter with an external length of 30 mm and diameter of 1.2 mm for the catheter body; (**d**) time-domain signal measured by No. 3 pressure measurement catheter with an external length of 800 mm and diameter of 3.4 mm for the catheter body; (**e**–**h**) frequency energy density spectra corresponding to the four groups of time-domain signals, with the AC component of the standard signal peaking at a frequency of 3.68 Hz. Figure 11e-h shows the power spectral density of the frequency energy of the time-domain signals corresponding to Figure 11a-d, where the standard signal's AC component peaks at a frequency of 3.68 Hz, corresponding to the periodic signal frequency in the time-domain. At this frequency, the attenuation of the No. 1 pressure measurement catheter is minimal, only 0.49 dB; No. 2 pressure measurement catheter attenuates by 1.92 dB; and No. 3 pressure measurement catheter attenuates by 5.09 dB. In some long-term patient monitoring by medical teams, the diastolic pressure deviation of invasive measurement devices is 556 Pa, which complies with international standards for the validation of blood pressure measurement devices [33; 34; 35]. In the dynamically varying pressure testing experiments described in this article, the interventional compact pressure measurement catheter exhibited only a 133.3 Pa deviation during the diastolic process.