Nordic-powered ear-worn pulse oximeter enables continuous oxygen monitoring


OxiWear device uses Nordic nRF52840 SoC to process and relay sensor data via low power Bluetooth LE wireless connectivity

U.S.-based health tech startup OxiWear has launched its wireless, non-intrusive, ear-worn pulse oximeter for medical-grade, continuous oxygen monitoring and low oxygen alerts.

The ‘OxiWear’ device is designed to support the more than 10 percent of the global population at risk of hypoxia - a potentially life-threatening disease where tissues in the human body do not receive enough oxygen. Hypoxia is caused by environmental factors, high altitude living and recreation, or chronic medical conditions. The disease can result in various organs, including the brain and heart, to not function properly.

Accurate oxygen level monitoring

Worn on the ear, OxiWear provides an unobtrusive way to accurately monitor a user’s oxygen levels in real time, while offering an alert mechanism if levels drop dangerously low. By using the device, individuals can better manage asymptomatic hypoxia, helping to avoid hospitalizations and unnecessary medical testing.

“We have taken proven pulse oximetry technology and designed it into a miniaturized form factor,” says George Beckstein, Chief Technology Officer, OxiWear. “OxiWear is the only wireless ear-worn pulse oximeter on the market designed for continuous monitoring, which is ideal during physical activity when the user’s hands might otherwise be preoccupied.”

The nRF52840 SoC performs as the primary processor for running OxiWear’s complex DSP algorithms, while also performing a number of housekeeping duties like firmware updates, power management, and storing historical data to Flash
George Beckstein, OxiWear

The OxiWear device features an integrated optical sensor for photoplethysmography (non-invasive technology that uses a light source and a photodetector at the skin’s surface to measure the volumetric variations of blood circulation), and an accelerometer for motion detection and cancellation. These sensors are overseen by the Wafer Level Chip Scale Package (WLCSP) version of Nordic Semiconductor’s nRF52840 SoC, using its powerful 64 MHz, 32-bit Arm® Cortex® M4 processor with floating point unit (FPU).

In addition, the nRF52840 SoC-enabled Bluetooth® LE connectivity allows real-time health data to be relayed wirelessly from the device to the user’s smartphone, from where an accompanying app displays the blood oxygen (SpO2) and heart rate information. The app also collects environmental data that may affect the oxygen intake of an individual, and allows users to list their emergency contacts who will receive a text message alert with the user’s location and vital information during any hypoxic events.

Running complex algorithms

“The Nordic nRF52840 SoC performs as the primary processor for running OxiWear’s complex DSP [Digital Signal Processing] algorithms, while also performing a number of housekeeping duties like firmware updates, power management, and storing historical data to Flash,” adds Beckstein.

OxiWear also employed Nordic’s Power Profiler Kit II (PPK2) to identify parts of the design that were increasing power consumption, allowing the battery life to be optimized and extended. PPK2 enables easy and affordable power measurement during wireless product development providing a simple method for hardware and software engineers to measure average and dynamic power consumption in embedded solutions. The OxiWear device is powered by a rechargeable Li-ion coin cell battery. Even when worn continuously, the device can operate for up to 18 hours, thanks in part to the low power capabilities of the nRF52840 SoC.

“It would be an understatement to say that minimizing power consumption was a high priority during product development – it was absolutely critical,” says Beckstein. “The nRF52840 SoC’s built-in DC/DC regulators eliminated the need for separate regulator ICs while reducing power consumption. The generous amount of Flash and RAM allowed us to run the Bluetooth ‘stack’ and complex DSP algorithms simultaneously, with memory to spare for in-field updates. The hardware-accelerated DSP instructions helped us perform advanced real time sensor data processing while minimizing time spent with the processor awake and, consequently, lowering power consumption.”

OxiWear also opted to use a Nordic solution due to the company’s “industry-leading” support for a tech startup, according to Beckstein. “The technical information Nordic provides is comprehensive and well organized. The reference designs provide excellent starting points for a project, while Nordic’s DevZone forum provides an immense repository of public information.”