研究目的
To design a portable, wireless PPG sensor for assessing AVF by using class-weighted SVM, providing a small-sized and inexpensive sensor module as opposed to conventional bulky and expensive Doppler machines.
研究成果
The experimental results by the proposed PPG sensor with a class-weighted SVM classifier using RBF kernel achieved successfully high accuracy (89.11%) and a low type II error (9.59%).
研究不足
The proposed PPG sensor can be operated by the users themselves easily without the aid of medical personnel, but it is still inferior to other handheld-free devices. Serious motion artifacts and ambient light interferences may still lead to failure in assessment.
1：Experimental Design and Method Selection:
The study combined dimensionless number analysis and the optical Beer Lambert’s law to derive five input features for the SVM classifier. The front-end readout circuitries were designed to increase the SNR of PPG signals by controlling the circuitries gain and the light intensity of LED. Digital signal processing algorithms were proposed to check and fix signal anomalies.
2：Sample Selection and Data Sources:
A total of 101 ESRD subjects with AVF participated in the experiments, including 73 subjects labeled as positive class and 28 subjects labeled as negative class.
3：List of Experimental Equipment and Materials:
The proposed PPG sensor system includes a sensor probe, analog front-end readout circuitries, microcontroller unit (MCU), and software algorithms in APP or laptop. The sensor probe includes a LED with 904 nm wavelength, a photodiode (PD), and other components.
4：Experimental Procedures and Operational Workflow:
Subjects were asked to rest for at least 15 min before measurements. Each subject was measured for 1 minute using the proposed PPG sensor. SBP and DBP values were measured by an electronic sphygmomanometer, and SpO2 value was measured using an oximeter.
5：Data Analysis Methods:
The class-weighted SVM classifiers employed five different kernel functions to assess AVF quality. The assessment results were provided to doctors for diagnosis and determining ensuing proper treatments.
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