How do blood oxygen sensors on smart watches work?

The nitty-gritty details of some smart watches’ coolest feature. Join us as we dive in. 

The smartwatch has taken the world by storm. Its convenience and innovation have thousands scrambling for the next and newest model. Not just for the young and hip, the smartwatch is a relevant and potentially life-saving piece of tech for all demographics. With features like blood oxygen sensors, heart monitors and GPS, it’s some of the finest tech available but made small and strapped to your wrist. 

Let’s dive a little deeper into one of the smartwatch’s newest features: the blood oxygen sensor and how you may be able to use it in your daily life.

What is a blood oxygen sensor?

To put bluntly, the blood oxygen sensor or the pulse oximeter is a device used by medical professionals to monitor the amount of oxygen flowing through haemoglobin, the protein particle in your blood that carries oxygen. It is particularly useful device for people suffering from any respiratory illnesses such as asthma.

The device that you’ve probably seen being used in hospitals or doctor’s offices looks a little bit like a small peg. It’s clipped to the end of the index finger and within seconds lights up with a numerical reading indicating your blood oxygen level and heart rate. A healthy reading sits within 95 to 98 per cent. 

How does the tech work and how has it been adapted for the smartwatch?

Blood oxygen sensors use wavelengths of light to target your haemoglobin, the protein particle in your blood that carries oxygen. The haemoglobin will absorb different wavelengths of light depending on how much oxygen it’s carrying. The numerical reading is the percentage of oxygen in your blood. 

For smartwatches, this tech has been miniaturised and placed on the back face of the watch to line up with your wrist. The infrared green, red and infrared LEDs on the back of the watch shine through the blood flowing through the wrist. Photodiodes (devices that convert light into electrical current) then measure the amount of reflecting light. A series of algorithms analyse the data from the photodiodes to determine the colour of the blood, the darker the blood the less oxygen.

What can you use blood oxygen sensors for?

Much like how it’s used in hospitals and doctor’s offices it’s used to monitor your oxygen intake. For people who suffer from respiratory illness such as asthma or people who partake in high altitude hiking, the smartwatch is particularly useful. Here are just a few of the ways the blood oxygen smartwatch capability can be used and who can benefit from it:

Sleep Apnoea 

Sleep apnoea is a sleep disorder characterized by shallow breathing or pauses during sleep, leaving sufferers feeling tired or sleepy during the day. Diagnosing sleep apnoea was previously tricky to do, however, with the advancement of smartwatch blood oxygen technology, monitoring first signs via wearable tech is not only easy but a cost-effective and unobtrusive way of catching the disorder. 

High altitude hiking

For keen mountain climbers, a smartwatch with an in-built blood oxygen sensor can let you know how your body is adjusting to high altitudes. Allowing you to track changes without adding heavy equipment to your pack.

Respiratory illness

For respiratory illnesses such as asthma, a blood oxygen sensor may advise the wearer when they need to slow it down or use an inhaler. Recently, blood oxygen readings have been quite useful for detecting COVID-19 symptoms. However, we suggest seeking medical advice before relying on a wearable for diagnosis.

General wellbeing

The blood oxygen sensor on wearable devices is best used to monitor general health and fitness. For example, if you’re exercising it can track your oxygen levels and analyse your performance. Information essential for professional athletes and those just starting their fitness journey.

Which smartwatches on the market have blood oxygen sensor technology?

Because this technology is quite new, there are only a few watches that house the blood oxygen sensor technology. These are:

• Apple Watch Series 6
• HONOR Band 5
• Realme watch
• Huawei Band 4
• Garmin Forerunner 945 Rubber Watch
• Riversong Wave O2
• Fitbit Sense

If you’re on the hunt for a smartwatch that has blood oxygen sensor capabilities, we’ve got some that will suit your needs. If you want something a little more cost-effective, explore our whole range.