Miniature Wireless Reflectance Pulse Oximeter Connected to Mobile Application

Abstract

Photoplethysmography is a non-invasive physical method used for measurement and monitoring of arterial blood flow in the subject's body with application of light. Pulse oximetry is the modification of photoplethysmography enriched with monitoring blood oxygen saturation. Acquisition of pulse oximetry data can be achieved using two types of pulse oximeters: transmission or reflectance. Both methods require the use of physical light sources and a receiver, set in specific positions. This results in different construction of devices and may lead to diverse ways of calculating the blood saturation values. One of these ways uses second-degree polynomial made from three constants and a variable calculated with ratio of red- to infrared-based variables. We used this method to develop the wireless pulse oximeter paired with the dedicated mobile application. The device acquired 400 samples per second and calculated oxygen saturation level and heart rate, as well as provided data for photoplethysmography curve. In this system data are transferred in real time to the application, which displays the saturation values and presents photoplethysmography curve for last several heartbeats. Calculation of the values was checked with a commercial pulse oximeter and the results were mostly similar, with the difference in SpO₂ not greater than one percentage point and the difference in heart rate not greater than five beats per minute. The design of the pulse oximeter allows further miniaturization. Mobile application is intuitive for user and does not need any training.