Developing an Effective Arterial Stiffness Monitoring System Using the Spring Constant Method and Photoplethysmography

This study aimed to develop a fast and effective arterial stiffness monitoring system for diabetic patients using the spring constant method and photoplethysmography (PPG). The experimental group comprised 70 patients (4 type 1 diabetes mellitus patients and 66 type 2 diabetes mellitus patients); 23 participants suffered from atherosclerosis. All were subjected to the measurements of both the carotid-femoral pulse wave velocity (cfPWV) and the spring constants evaluated using the PPG pulse as well as the radial pulse. The control group comprised 70 normal participants (39 men and 31 women) who did not have diabetes mellitus, with an age range of 40-84 years. All control group members were only subjected to the measurement by the spring constant method. For the experimental group, statistical analysis indicated a significantly high correlation between the spring constants computed using PPG and the radial pulse (p < 0.001, correlation coefficient =0.89). The result also showed a significant negative correlation between the cfPWV and the spring constant of PPG (p < 0.001, correlation coefficient = - 0.72); multivariate analysis similarly indicated a close relationship. In addition, we used Student's t test to examine the difference between the experimental and control groups for the spring constant of PPG. A P value less than 0.05 confirmed that the difference between the two groups was statistically significant. In the receiver operating characteristic curve, area under curve (=0.82) indicates a good discrimination, and a spring constant of PPG below 516 (g/s (2)) may imply a risk of arterial stiffness for diabetic patients. These findings imply that the spring constant of PPG could effectively identify normal versus abnormal characteristics of elasticity in normal and diabetic participants. As a result of some excellent characteristics in clinical monitoring, the spring constant computed using PPG shows the effectiveness and feasibility in the monitoring system of arterial stiffness.