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© 2019-2021 Belun Technology

What is the Belun® Ring?

How does the Belun® Ring help?

The Belun® Ring measures

  • Oxygen Saturation (SpO2)

  • Pulse Rate (PR)

  • Apnea Hypopnea Index (bAHI)

  • Sleep Stages

  • Autonomic Nervous System Response (ANS)

  • Motion

Landing_Hand ring

How to use?

Put the ring on before sleep.

A sleep report will be generated automatically in the morning, displaying a sleep apnea risk assessment with apnea hypopnea index (bAHI), autonomous nervous response, and sleep stages.

The Belun Ring helps you discover the quality of your sleep — at home, comfortably, by simply putting on your ring before sleep. You will uncover the mysteries of:

  • Risk of sleep apnea
  • Sleep quality

The Belun Ring equips its users with information that empowers them to change their daily habits — such as activities, exercise, alcohol intake, and medication — to improve their sleep health.

How does the Belun® Ring differ from a traditional pulse oximeter?


The ring is worn at the proximal phalanx instead of the fingertip and will not fall off easily.

Accurate & Reliable

It collects pulse oximetry, pulse rate, heart rate variability and motion. Hence, sleep stages are accurately identified for the calculation of the bAHI.

Easy to use

Based on the measurements, physicians can easily identify the user’s sleep problems.

Sleep Analysis Report

All physiological data, analysis and sleep reports can be viewed and downloaded by people from clinics, health-check centres, respiratory machine vendors, and elderly centres, which provides additional insights to physicians. The Belun® Ring’s report also enables professionals to evaluate how user’s daytime activities affect sleep quality and to review sleep health holistically and scientifically in a way that is unprecedented in the marketplace.

Belun’s AI and cloud-based system will analyze the overnight sleep data using proprietary algorithms. It provides a respiratory event index that has high correlation (0.925), sensitivity (true positive) of 0.88, and specificity (true negative) of 0.859 to the apnea-hypopnea index (gold standard obtained by in-lab polysomnography (PSG)).

Scientific Studies

Gu W., Leung L., “Novel Home Screening Platform for Obstructive Sleep Apnea Through Wearable Ring-Type Pulse Oximeter,” SLEEP, Volume 41, June 2018.

Gu W., Leung L., Chiang A. “A Novel Web-based Ring Device for Sleep Apnea Screening at Home,” SLEEP 2019.

Gu W, et al. “Belun Ring Platform: A Novel Home Sleep Apnea Testing System for Assessment of Obstructive Sleep Apnea,” Journal of Clinical Sleep Medicine, May 2020.


Certifications and Awards


World’s first FDA 510(k) cleared wearable ring for SpO2 measurement


ISO 13485 medical devices quality management system

Technical Specifications

Using spectrophotometric methodology, the Belun® Ring measures blood oxygen saturation by illuminating the skin and measuring changes in light absorption of oxygenated (oxyhemoglobin) and deoxygenated (reduced hemoglobin) blood using two light wavelengths: red and infrared. The ratio of absorbance at these wavelengths is calculated and calibrated against direct measurements of arterial oxygen saturation (SaO2) to establish the pulse oximeter’s measurement of functional oxygen saturation of arterial hemoglobin (SpO2). 

The sensor should be placed on the palmar side of the proximal phalanx of the index finger and along the radial artery such that the accuracy of the device will be minimally affected by the skin color.

International standards

The Belun® Ring complies with the following international standards:

  • IEC 60601-1:2005+AMD1:2012 CSV
  • IEC 60601-1-2:2014
  • IEC 60601-1-6:2013
  • IEC 60601-1-11:2015
  • IEC 62133:2012
  • IEC 62304:2015
  • ISO 10993-1:2009
  • ISO 10993-5:2009
  • ISO 10993-10:2010
  • ISO 14971:2007
  • ISO 80601-2-61:2011

SpO2 Parameter

Range: 0% – 100%
Resolution: 1%
Accuracy: 70%-100%: ±2%, below 70%: unspecified

Pulse Rate Parameter

Range: 30bpm – 250bpm
Resolution: 1bpm
Accuracy: ±2bpm or ±2% whichever is larger

Power Source

Internal Battery: 3.7V rechargeable lithium battery
Charging Input: DC 5V


Ring: 45 x 60 x20mm
Cradle: 60 x 140 x 60mm


Ring: ~13gram
Cradle ~177gram

Sleep Health

A good sleep helps to restore our energy and cognitive function.

Importance of Sleep

The importance of sleep cannot be denied and every sleep stage has its own function. Non-REM sleep helps to repair the body’s cells and ensure we get enough rest to face the challenges in life the next day.

REM sleep, on the other hand, helps us process the information we’ve learnt and reinforces our memory and learning ability.

Therefore, a good sleep can ensure that we are healthy—both physically and psychologically—in order to function optimally and to enjoy stable moods.


The Sleep Cycle

Sleep can be divided into two phases: rapid eye movement sleep (REM Sleep) and non-rapid eye movement sleep (non-REM Sleep).

Non-REM sleep can be divided into four stages: Stage 1, Stage 2, Stage 3 and Stage 4.

Stages 1 and 2 are called “light sleep,” whereas Stages 3 and 4 are called “deep sleep.”

For a typical adult, REM sleep constitutes 20% to 25% of a sleep cycle; the remainder is the non-REM sleep.

The sleep cycle starts with light non-REM sleep, then deep non-REM sleep, followed by REM sleep. A sleep cycle lasts from 90 to 120 minutes. An adult normally has 4 to 6 sleep cycles per night.

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