Pulse Waveform Analyzer

Pulse Waveform Analyzer (PWA) is developed based on smartphone photoplethysmogram (PPG) technology. PPG is an optical method that uses sensors to monitor the microvascular blood volume changes in the tissue. The light that travels through biological tissue can be absorbed by different substances, including pigments in the skin, bone, and blood. As hemoglobin absorbs more light than the surrounding tissue, an increase (systole) or decrease (diastole) in the amount of blood can be assessed through the difference in the intensity of the light and converted into waveform.
Smartphone PPG detects heartbeats by recording videos of the fingertips with the inbuilt camera, converting video frames into three color channels, and combining the color signals into pulse contour.
PWA provides three waveform features. The peak-to-peak time (PPT) is the time difference between the first and second peaks in each beat to beat interval (BBI). The Reflection Index (RI) is defined as the ratio of the height of the second peak to the first peak. B/A ratio is the ratio between the smallest second derivative and the largest second derivative of the pressure waveform. As the B/A ratio is negative, PWA uses the absolute value of the ratio to make the interpretation more intuitive. For each collected sample, PWA uses the median of the pulse waveform feature calculated across all the BBIs as the representative value for the sample.