A computer based photoplethysmographic vascular analyzer through derivatives

A computer based photoplethysmographic analyzer was developed. The signal was obtained by infrared light through the finger. It was converted into digital domain by a signal processing circuitry. First, second and fourth derivatives of the signal were computed. The acquisition and mathematical processing programs were implemented in object-oriented programming C. A study with 38 people, 19 healthy volunteers and 19 subjects with previously diagnosed cardiovascular disease (atherosclerosis, hypertension, diabetes mellitus) was carried out. A t-tested distribution between healthy volunteers and patients showed a significant differences in calculated parameters. Photoplethysmographic augmentation index has shown to be a noninvasive parameter for vascular assessments. Using derivatives, the inflection points identification of the digital volume pulse is simpler and more accurate.