Photo-plethysmography measure pulsatile blood flow in real-time and non-invasively.One of widely known application of PPG is a measurement of saturated oxygen in arterial blood (SpO2). In our work , using several wave length more than those used in a pulse oximeter, an algorithm and instrument have been developed to measure hematocrit, saturated oxygen pulse and respiratory rates simultaneously.To predict hemotocrit, a dedicated algorithm is developed based on scattering of RBC and a protocall for detecting outlier signal is used to increase accuracy and reliability.Digital filtering techniques are used to exart respiratory rate signal. Utilization of wave length under 1000nm and a multi-wavelength LED array chip and digital-oriented electronic enable us to make a compact device. Our preliminary clinical trails shown that the achived percent errors are±8.2% for hematocrit when tested with 594 person ,r2 for SpO fitting is 0.99985 when tested with a Bi-Tek pulse oximeter simulator and the SPO2 error for in vivo test is ±2.5% over the range of 75~100%. The error of pulse rates is less than ±5%. We obtained a positive predictive value of 96% for respiratory rates in qualitative analysis.
