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Pulse oximeter: Why SpO2 and blood oxygen will be huge in 2020

Taking a closer look at the tech inside your wearables
Pulse oximeter and SpO2 explained
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There's a new wearable tech metric in town – and it's all about blood oxygen. It might sound complicated and a little pointless, but pulse ox can reveal conditions like sleep apnea – and help athletes recover.

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And pulse ox is starting to appear on the spec sheets of the biggest names in wearables: Fitbit and Garmin already have an SpO2 sensor on most of their devices, and Withings has jumped in too. With 2020 set to be a big year for sleep tracking, you're certain to hear more about blood oxygen.

So why is putting a pulse oximeter inside of a wearable a big deal? We explore what it is, how it works and what it's going to bring to the wearable party.

What is a pulse oximeter?

Sensors explored: Pulse oximeter

When we talk about pulse oximeters or pulse oximetry, we are delving into the realm of medical tech and talking about a device that's able to measure oxygen levels or oxygen saturation in the blood, plus your heart rate. They can also be used to measure pulse rate too.

That tech usually takes form of a clip-on device that you place on your finger, a toe or even on your ear lobe. It uses red and infrared light sensors to detect your oxygen levels, sensing changes in those levels. It measures the volume of oxygen based on the way the light passes through your finger and delivers the data to the device's screen, which will tell you the percentage of oxygen in your blood.

Blood oxygen levels explained

An oxygen saturation percentage greater than 95% is considered to be a normal reading. If you see a score of 92% or less, then it could be time to further investigate and find out whether it's related to an as yet undetected health issue.

John Hopkins Medicine explains how measuring oxygen levels through pulse oximetry can offer insights into a range of health related issues.

It can be used to check whether someone needs assistance with their breathing via a ventilator, measure a person's ability to handle intensive physical activities and it can also check whether breathing stops during sleep.

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This is particularly relevant to sleep apnea, a disorder which if left untreated or undetected could lead to an increase in the risk of high blood pressure, obesity and can even cause a heart attack. It can also be a valuable piece of health data for people suffering from a range of conditions including asthma, pneumonia, heart failure and lung cancer.

The origins of the pulse oximeter

Sensors explored: Pulse oximeter

The first oxygen saturation meter is said to be from as far back as the 1930s, when the exploration of light transmission through skin and the information it could provide really began.

It wasn't until the 1960s and 70s when we began to see the pulse oximeter devices shape into the ones that are now used in hospitals, and which can be purchased to carry out those measurements from your home. Hewlett Packard was the first company to make an ear oximeter, which was largely used inside of clinical sleep labs due to its hulking size.

But it was Japanese bioengineer Takuo Aoyagi, in the early 1970s, who first developed a noninvasive way of using the light transmitted through the ear and went on to develop a pulse oximeter. From then up until today, the size of the tech has become smaller and – crucially – cheaper to build, so more people were able to get their hands on it.

Pulse oximeter and wearables you can buy right now

Pulse oximeters are starting to find their way into some big name wearables and that data is being used in very different ways.

Arguably it started with the Withings Pulse Ox fitness tracker, which measured blood oxygen levels when you placed your finger on the sensor on the back of the device. But things have changed since then, and now the process of taking those measurements happen much more easily from the wrist.

Garmin SpO2 devices

Garmin has introduced pulse ox sensors into a large part of its range, with the Fenix 6X, Fenix 5X, Vivoactive 4 and Forerunner 245/645/945 all using an SpO2 sensor.

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In this instance the on-screen widget will offer a blood oxygen percentage, coupled with data on your altitude, to show the levels of oxygen in the blood. This is particularly useful for anyone that's into hiking, alpine sports and going on big expeditions. With elevation data you can view how oximeter readings are changing relative to your elevation.

However, many wearables use pulse ox for a different reason: sleep apnea. This is a condition that 8/10 suffers do not know they have, where blood oxygen levels dip during sleep. This can cause adverse health effects.

The Garmin Vivosmart 4 able to log blood oxygen levels during sleep, and it's reported in your sleep data. However, the device stops short of alerting you to sleep apnea in particular, and you need to look at the data yourself. What's more, on many devices the pulse ox is turned off by default as it impacts battery life.

Withings

Withings launched the Withings ScanWatch at CES 2020 – and sleep apea is a big new focus. The SpO2 sensor on board will monitor blood oxygen during the night, and alert you to any potential problems. It's still waiting for FDA clearance, however.

Fitbit

We've also mentioned Fitbit's interest in measuring oxygen saturation, but unlike Garmin, it's thinking of the potential for using that data in serious health tracking.

Both its Ionic and Versa smartwatches include a light-based SpO2 sensor, which is a pulse oximeter that measures blood oxygen levels.

We know that Fitbit wants to tackle sleep apnea and the ability to take oxygen measurements from your blood can offer valuable insights relative to exploring a sleep disorder that affects around 18 million Americans.

Right now though, that sensor remains untapped and will do until Fitbit feels it's ready to make use of it.