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Wellue is a company specializing in smart devices and apps that track health-related metrics. The O2 Ring — one of the brand’s best-selling items — is a wearable device that tracks your blood oxygen level and heart rate while you’re asleep. You can check both metrics at any time on the device’s screen display. With the O2 Ring’s ViHealth companion app, you can view additional data points such as your average and lowest overnight oxygen levels.

The O2 Ring is an example of a niche sleep tracker, a device that is optimized to monitor just one or two specific data points. Your blood oxygen level can reflect how well you are breathing, which may be affected by sleep apnea, a disorder characterized by pauses in breathing during sleep. Using the ring can be a convenient way to monitor oxygen saturation, and most people find it significantly more comfortable than traditional duckbill oxygen sensors that either pinch your finger too tightly or can easily become dislodged. 

I tested the O2 Ring for about three weeks. While wearing any device to bed involves an adjustment period, I barely noticed O2 Ring after sleeping with it on my finger for a couple of nights. The tracking capabilities are also impressive. If you want to dive deep into your blood oxygen level, this device should meet your expectations.

In this review, I’ll detail my experience with the Wellue O2 Ring and how it performed.

What Does the Wellue O2 Ring Do?

The O2 Ring tracks two key metrics that are related to your cardiovascular and respiratory systems.

  • Oxygen saturation (SpO2) assesses how much oxygen is in your blood. During waking hours, healthy adults often have an SpO2 of about 95% to 99%, but this may drop by a few percentage points during sleep. When awake, SpO2 levels below 92% may be a sign of insufficient oxygen. Levels below 88% should prompt immediate medical attention.
  • Pulse rate, or heart rate, measures the number of times your heart beats per minute (bpm). The resting heart rate for most healthy adults during the day falls between 60 to 100 bpm, though certain factors may lead to a lower pulse rate without necessarily being a sign of a health problem. During sleep, 40 to 50 bpm is considered a normal range.

When tracked while you sleep, these metrics may be referred to as overnight pulse oximetry (OPO). Most OPO devices, including the O2 Ring, use technology called transmissive pulse oximetry, during which a sensor is placed on your finger or earlobe to obtain a reading of the oxygen levels of the blood in your capillaries. 

Formal sleep studies with polysomnography include OPO measurements, so the O2 Ring tracks a component of your health with equipment that is similar to what is used by a sleep lab. Although a sleep study provides more robust information from sensors to track things like your muscle and brain activity, the O2 Ring can generate useful data that may offer insights into how well you are breathing while you sleep. 

The O2 Ring is engineered to track your data in real time. Using the ViHealth companion app, you can view the following:

  • Total recording time, which corresponds to how long you’ve slept with the ring in place
  • Total time your SpO2 was 90% or higher
  • Number of times your SpO2 dropped by 4% or more
  • Average SpO2 during the night
  • SpO2 drops per hour, which is calculated into a nightly average
  • Lowest SpO2 of the night
  • Average pulse rate during the night

The app also generates a daily O2 Score, which aggregates the frequency, duration, and depth of your SpO2 drops during the night. The score follows a 10-point scale with a corresponding color spectrum. If the score is green, your O2 Score appears to be healthy. A yellow or red score indicates you should speak to your doctor.

Another neat feature of the O2 Ring is the silent vibration. Using the app, you can preset a threshold for SpO2 and a range for your heart rate. For example, you might set an SpO2 threshold of 90% and a bpm range of 50 to 100. If either your SpO2 or heart rate fall outside these ranges, the ring will vibrate. You can also customize the intensity of the vibration. If you prefer, the SpO2 and bpm alerts can be programmed for different vibration settings.

Why Is Blood Oxygen Level Important?

Blood oxygen levels from a device like the O2 Ring are a reflection of the amount of oxygen and carbon dioxide in your blood. We inhale oxygen and exhale carbon dioxide. If there’s an imbalance, this can signify problems with your respiratory system.

Instead of removing a blood sample and measuring how much oxygen and carbon dioxide is present, a pulse oximeter like the O2 Ring uses special sensors to detect how saturated your blood is with oxygen. 

Many factors can affect your blood oxygen level. As I mentioned earlier, a low blood oxygen level may be an indicator of obstructive sleep apnea. This disorder affects up to 30% of adults in the U.S. and has been linked to severe sleep disruptions and excessive daytime sleepiness. Apnea episodes, marked by reductions or pauses in breathing and loud choking or gagging sounds, can occur hundreds of times in a single night. Many people with obstructive sleep apnea also snore heavily, which can affect their own sleep quality and that of their partner. 

In the long term, people with untreated obstructive sleep apnea are at greater risk of developing other health conditions, such as heart disease and type 2 diabetes. You should speak with a doctor if you suspect you’re experiencing sleep apnea symptoms. The Wellue O2 Ring won’t substitute for the traditional polysomnography tests needed to make a sleep apnea diagnosis, but the device may tip you off if your blood oxygen levels are abnormal.

A low blood oxygen level at night may also occur because of sleep-related hypoxemia disorder, a condition characterized by a drop in oxygen concentrations without a corresponding rise in carbon dioxide levels. However, sleep-related hypoxemia disorder usually occurs due to a larger, underlying health problem.

The O2 Ring is not a medical device, so it can’t be used to improve your blood oxygen level if it’s abnormally low. Nevertheless, tracking SpO2 and heart rate data can be a valuable starting point for gathering information, talking with your doctor, and finding or addressing potentially serious medical conditions.

Setting Up and Using the Wellue O2 Ring

Setting up the O2 Ring was a quick, straightforward process. The ring has built-in Bluetooth that is enabled immediately after you turn on the device. Make sure your phone’s Bluetooth is switched on and that the battery is intact before getting started. You’ll also need to download the ViHealth app on your phone prior to setup.

The O2 Ring automatically turns on when you place it on your finger. A red LED light on the inner band illuminates when the device is on, and within a few seconds you’ll be able to view your SpO2 and bpm rates on the screen. Open the ViHealth app on your phone, and everything should automatically sync. To turn off the O2 Ring, simply remove it from your finger. It will automatically power down within 10 seconds or so. 

I didn’t encounter any connectivity issues with my O2 Ring during the three weeks I tested the device, but some people have reported issues. In fact, the ViHealth app has received middling reviews across the board. Software updates to your phone can also affect connectivity. If you run into Bluetooth connectivity problems, try syncing the data to your Mac or PC instead. To do this, download the PC software or Mac app from Wellue’s website, then connect the O2 Ring to your computer using the USB charger that comes with the device.

Other considerations about the Wellue O2 Ring include:

  • Feel: The ring itself is elastic and has a rubbery feel. Since there is only one size for the ring, this helps ensure a comfortable fit for most people. The ring is somewhat bulky, so it might be a hindrance for daily activities like typing or working out, but this is generally a non-issue since the device is designed for nighttime use. 
  • Weight: The O2 Ring weighs about 15 grams, which is on the heavier side for a wearable, ring-style tracker.   
  • Finger choice: Wellue recommends using your thumb or index finger. If the ring is too tight for these digits, try your pinky instead. You should not use your middle finger. The fit should not be loose.
  • Battery: The device’s battery life is 12 to 16 hours. Use the charger included with the device to charge it with any USB port.
  • Memory: The O2 Ring’s built-in memory holds data from up to four sessions of 10 hours or less on the device itself. You can store data on the app to monitor long-term trends.
  • Compatibility: The app is compatible with phones with iOS 9.0 or higher or Android 5.0 or higher, provided they have Bluetooth 4.0 BLE. If you want to use your desktop instead, ViHealth is compatible with Windows 7/8/10 and macOS 10.15 or higher. You can also use the app on an iPad 3 or higher.
  • Cleaning: To clean your O2 Ring, moisten a soft cloth with water or alcohol and gently wipe the device. Don’t use acetone or other volatile cleaners. 
  • Water resistance: Avoid submerging the ring in water or any other liquid.
  • Storage: Do not store the ring in a location with exposure to direct sunlight, high temperature, or excessive moisture.   

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Buying the Wellue O2 Ring

If you’re intrigued by this sleep tracker, I’ll cover the essentials for ordering and purchasing the Wellue O2 Ring.

CostThe O2 Ring currently costs $179, though Wellue offers rotating discounts that knock down the price a bit. The ViHealth app is free to download, as is the desktop software.
Subscription OptionsNo subscription is needed to use the O2 Ring and ViHealth app.
AvailabilityThe O2 Ring is available for purchase on Wellue’s website. You can also buy it from retailers like Walmart and Amazon.com, but keep in mind you’ll defer to the seller’s shipping and return policies.
ShippingShipping is free for all orders of $100 or more, which covers your O2 Ring purchase. A full list of countries Wellue does and does not ship to can be found on the company’s website. 
ReturnsReturns are allowed within 30 days of delivery. Wellue issues full product refunds during this time frame, but you’ll be responsible for return shipping charges.
WarrantyThe O2 Ring is covered under a one-year product warranty against material and workmanship defects.

The Bottom Line

The Wellue O2 Ring may be limited in functionality compared to other sleep trackers I’ve reviewed, but if you’re looking for a device focused on your blood oxygen level, this is probably the tracker for you. The feedback is instantaneous, the data appears to be fairly accurate, and the app is easy to use. An affordable sticker price and no subscription requirement are nice perks as well.

You may need an adjustment period getting used to sleeping with the ring. It’s heavier than other ring-style trackers, and the sensor creates a large and bulky shape. Determining the most comfortable finger for wearing the device may also take a couple of nights. These are small nitpicks, though. The O2 Ring excels at its intended function, and the data you receive from the device could be the push you need to see a doctor about abnormal or problematic blood oxygen levels.

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