Design Of Wearable Reflectance Pulse Oximeter For Dynamic SpO₂Monitoring

Data from the national physical examinations which are conducted every five years suggest that although the average level of citizens’ physical health is improved, issues such as obesity and prematurely aging are becoming more serious. Recommendations have been made to involve citizens in more physical exercising. Thus, in order to noninvasively monitor one’s physical physiological signals, there is a great need for a new type of devices that continuously monitor the vital signals over an extended period of time and detect the early syndromes of disease. This new type of devices should also be affordable so as to make contributions to the "national health of low cost".This study designs a new system of real-time, wearable reflectance pulse oximeter which consists of a light-weight optical reflectance sensor and an arterial oxygen saturation (SpO2) module. This new low-power system can continuously monitor human photoplethysmographic (PPG) signals with a small reflectance probe (including LEDs with wavelengths of630nm and940nm and a photodiode) mounted on a fingertip. The low-power consumption SpO2module is operated by a battery for analog signal processing, and the dynamic SpO2and heart rate are extracted from PPG signals by an intelligent signal processing algorithm. The data is then displayed on the LCD and stored to Flash.Using five healthy subjects under two conditions (i.e., rest and lope), experiments show that the sensor has a robust sensitivity and works properly as designed. This new system can be used in various healthcare situations, such as sports, chronic obstructive pulmonary disease, and other personal ubiquitous healthcare systems.