Leuven, Belgium-based Ectosense is on a mission to restore sleep for the roughly one billion people that suffer from a sleep disorder. The medtech startup, which was incubated in the imec.istart program, uses microelectronics, biomedical signal processing, and data science to create elegant, effective medical solutions.
Sleep researchers have reported that nearly one billion adults have mild to severe obstructive sleep apnea, which is characterized by interrupted breathing during the night. More than 85% of these patients are undiagnosed. One traditional way to diagnose the condition is through a sleep study performed overnight in a hospital. Ectosense’s founders, however, believe in a less costly, more convenient method for sleep testing. Indeed, with many sleep labs closed due to the COVID-19 pandemic, being able to monitor the condition from home presents a safe option.
The company has created the NightOwl®, a home sleep apnea test consisting of a tiny wearable finger sensor. As the airways collapse and breathing is interrupted—a ‘sleep apnea’ event—the sensor picks up the drop in blood-oxygen levels (SpO2). When the brain arouses the body to resume breathing, the sensor will pick up other important changes in the PPG signal. The device is available in a 3-day rechargeable version and a 10-night disposable option, and comes with a smartphone app that transmits diagnostic data to the prescribing healthcare professional, while providing instructions and other support to the patient. The NightOwl home sleep test recently achieved U.S. Food and Drug Administration (FDA) approval. Since the vital signs measured can also be indicators of pneumonia (or infection), the devices may be of use in remote monitoring of COVID-19 patients.
The NightOwl®, Ectosense’s home sleep apnea test, consists of a tiny wearable finger sensor.
The NightOwl records photoplethysmography (PPG) readings to reveal heart rate and SpO2 levels. To create the device, Ectosense needed, first and foremost, good PPG quality from the biosensor. And to keep its testing device compact enough to fit on a fingertip, the company needed small, low-power components.
Solution and Benefits
After thoroughly evaluating the PPG signals and resulting SpO2 values of leading components on the market, Ectosense chose the MAX30102 pulse oximeter and heart-rate biosensor module. The module includes internal LEDs, photodetectors, optical elements, and low-noise electronics with ambient light rejection. “I’m confident to say, as a user of all present-day alternatives, that Maxim’s components are far ahead of those of alternative suppliers in terms of providing high-quality PPG readings,” said Bart Van Pee, Ectosense’s cofounder and COO.
The MAX30102 is integrated into the reusable NightOwl. The disposable version of the NightOwl is designed with another Maxim biosensor, the MAXM86161 optical data acquisition system. The device’s transmitter side has three programmable high-current LED drivers. Its receiver side has a high-efficiency PIN photodiode and an optical readout channel, which has a low-noise signal-conditioning analog front-end (AFE). The AFE features a 19-bit ADC, an ambient light cancellation circuit, and a “picket fence” detect and replace algorithm.
One of the advantages of the NightOwl, explained Van Pee, is its ability to track sleep apnea parameters over multiple nights to provide a full picture of the patient’s condition. To enable comfortable, multi-night testing at a reasonable pricing model, the Ectosense team needed to keep its device small and long-running. The key to this, Van Pee noted, was to use as small a battery as possible. “We didn't want our device to lose its charm by becoming bulky [due to the battery],” he said. “Maxim's optical sensors offer the best power-quality tradeoff.”
The NightOwl runs on a coin-cell battery. With its low-power operation (< 10µA optical readout channel, 1.6µA shutdown current), the MAXM86161 enables compact, power-efficient wearables. The MAX30102 provides low-power heart-rate monitoring ( <1mW) and low shutdown current (0.7µA). “We couldn’t make our device this small without the Maxim PPG chip because we would’ve needed a larger battery,” said Van Pee. The integration available in the Maxim chips also saved four months of clinical validation time, compared to the effort that would have been required using discrete components.
Having a disposable option reduces handling costs, opens up new channels for sleep apnea testing, and, in this age of COVID-19, reduces the possibility of contamination. Using highly integrated, competitively priced chips such as Maxim’s enabled the company to reduce its design complexity and, in turn, its pricing for a potentially high-volume business.
Working closely with Maxim enabled Ectosense to align its design cycle with Maxim’s roadmap for a more efficient process. “It’s quite amazing that we have FDA approval of a device that houses a Maxim chip that only recently became available,” Van Pee said of the fast validation and design integration process using the MAXM86161.
Looking ahead, Ectosense plans to evaluate other Maxim healthcare ICs as it explores new biometric monitoring capabilities to incorporate into the NightOwl.