Blood-oxygen saturation (SpO2) is a vital data for our health as it provides a wealth of insights such as heart health, sleep patterns, and respiratory function. Normal levels of blood oxygen fall in the 95% to 100% range, while a measurement of 90% or less warrants a consultation with a doctor. In the past, a person needed to visit their doctor’s office to get their SpO2 checked. But now, with the advent of wearable technology SpO2 and other vital signs can be measured by a wearable device.
Measuring SpO2 on the wrist, however, is much more challenging than doing so on the finger due to the low blood perfusion in the wrist area. The design must consider everything from spacing of the LEDs and photodiodes to biological factors such as skin tone and the presence of tattoos to signal-to-noise requirements.
With wrist-based pulse oximetry, the photodiode and the LED are typically placed on the same side, with the photodiode collecting light reflected from various depths under the skin. To achieve the best PPG signal, the LED illumination wavelength should be near the absorption peaks of oxygenated hemoglobin.
To streamline the development of accurate, wrist-based health-monitoring wearables, Maxim Integrated has unveiled the market’s first complete wrist-based, system-level design for solutions that continuously monitor SpO2 as well as heart rate and heart-rate variability (HRV), writes Neset Tamer Executive Business Manager, Maxim Integrated and Zafer Zambogu, Director of Software; Micros, Security & Software Business Unit, Maxim Integrated.
The MAXREFDES103 demonstrates the high sensitivity and algorithm processing functions for health-sensing applications. The platform includes an enclosure and a biometric sensor hub with an embedded algorithm for heart rate and SpO2 (MAX32664C) which processes PPG signals from the analog-front-end (AFE) sensor (MAX86141). Algorithm output and raw data can be streamed through Bluetooth to an Android app or PC GUI for demonstration, evaluation, and customized development.
MAXREFDES103 can reduce development costs and save up to six months off the development cycle by eliminating some key barriers to entry into this market: opto-mechanical system design and development of high-performance, validated algorithms.
With the combination of SpO2 and HRV, engineers can now deliver meaningful insights for the fitness and wellness markets, including applications such as sleep quality, sleep apnea detection, stress, calories burned, muscle oxygen (VO2), recovery time, and other new use cases.