Development of a Compact Home Health Monitor for Telemedicine

A compact and easy-to-use home health monitor was developed. A palm-size health monitor contained a finger probe as sensor unit. In the finger probe, light from a light emitting diode (LED) array was illuminated on a finger nail bed, and transmitted light was measured to obtain photoplethysmography (PPG) signals. Hematocrit, pulse, respiration rate, and saturated oxygen in arterial blood (SpO2) were measured simultaneously from PPGs using five different wavelengths: 569, 660, 805, 904, and 975 nm. To predict hematocrit, a dedicated algorithm was used based on scattering theory of red blood cells using these wavelengths. Preliminary clinical tests showed that the achieved percent errors were ± 8.2% for hematocrit when tested with 549 persons (N = 549). Digital filtering techniques were used to extract respiratory information from a single PPG signal. SpO2 was predicted on the basis of the ratio of the wavelengths 660 nm and 940 nm. The accuracies were within clinically acceptable errors. In addition, the c...