Pulse oximeter and SpO2 explained
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.
Pulse ox is starting to appear on the spec sheets of the biggest smartwatches and fitness devices.
We explore what it is, how it works and what it’s going to bring to the wearable party.
What is a pulse oximeter/SpO2 sensor?
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.
That tech used to take form of a clip-on device that you place on your finger, a toe or even on your ear lobe.
Optical SpO2 sensors use red and infrared light sensors to detect your oxygen levels, sensing changes in those levels by looking at the color of your blood.
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.
Why track blood oxygen?
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 you’re experiencing breathing issues when sleeping.
COVID-19 has put the focus on blood oxygen on the map, but actually, there are many less extreme reasons to keep an eye on blood oxygen levels.
Athletes or people spending time at altitude will want to monitor blood oxygen levels.
However, it’s sleep apnea that really makes SpO2 a worthwhile sensor. It’s 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. And that’s where many health watches and wearables can come in useful.
It’s estimated that 22 million Americans suffer with sleep apnea, but the majority aren’t even aware they have the disorder.
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
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.
Unlike other wearable oximeter rings,CIRCUL includes a pulse oximeter and continuous blood oxygen (SpO2) monitoring.