Best SpO2 Sensor Smartwatches you can Buy!
The term SpO2 sensor is something that has been popping up quite a bit lately and became infamously synonymous with wearable tech like the Apple Watch Series 6. With the advent of the recent covid pandemic, this SpO2 sensor technology on smart devices has proved itself more of a boon rather than just another sensor that has joined the bandwagon of seemingly otherwise unnecessary sensors.
So what is this SpO2 sensor, and what does it do?
For starters, SpO2 is short for Saturation of Peripheral Oxygen. It is the measure of oxygen saturation in the peripheral blood. Peripheral blood is the blood that basically circulates around the body. SpO2 saturation can be measured using what is called a Pulse Oximeter.
There are many different types of oximeters in the medical field and hospitals, ranging from portable handheld monitors to heavier tabletop monitors. The most common forms of Pulse Oximeter is the disposable type that practitioners wrap around the finger in the case of adults above 40Kgs and around the foot or some other body part in the case of children below a specific weight limit.
The Oximeter, featuring an alligator clip that clamps around the finger, uses Transmittance oximetry.
A common Pulse Oximeter works by diodes emitting Infrared and Red light by taking readings from the light. These are allowed to pass through pulsatile blood or the Systematic Arterial System. It is the circulatory system that carries oxygen-rich blood to the other body tissues.
The device basically comes with an emitter and a receiver that work together. The Emitter emits Infrared along with a Red light that passes through the tissue bed and then reaches the receiver that is on the other side.
The fully saturated and desaturated haemoglobin in the blood has the tendency to absorb different spectrums and amounts of light. Fully saturated oxy-haemoglobin absorbs infrared light, meaning the receiver on the other end detects reduced infrared light, while fully desaturated deoxy-haemoglobin absorbs red light, reducing the amount of red light detected by the receiver.
Based upon the information of how much light is absorbed, the device can calculate SpO2 levels available in the blood. Most devices come with an alarm system just in case the SpO2 levels drop beyond recommended levels.
Smartwatches with SpO2 Sensors:
Smartwatches with the heart rate monitor and SpO2 monitor functions run on the same principle. The only difference it exhibits is, it uses the Reflectance Oximetry method rather than the Transmittance Oximetry fount in medical-grade SpO2 monitors.
Smartwatches use a technology called Photoplethysmography or more commonly known as PPG. It’s a noninvasive way to give us health data and provide biometrical information.
It works by the watch’s optical sensor shooting a light onto the surface of the skin. Once it reaches the blood vessel, some of the light is reflected and captured by a photodetector on the watch itself.
If you look closely at the Apple Watch Series 6 or the Samsung Galaxy Watch 3, you notice they have both Red and Green lights on the back. PPG sensors use both Red and Green as they have different wavelengths and hence different levels of light penetration.
Red light has a longer wavelength and therefore has increased depth of penetration properties than the shorter wavelength of Green Light. Apple Watch and the Fitbit use Green light PPG to measure heart rate. Green Light PPG is also resilient to motion, therefore, allowing the device to measure heart rate during exercise.
The Red light PPG has 10 times more penetrative properties than green and therefore can access deeper tissue and the bodies Arterial System. However, redlight is extremely sensitive to movement and environmental noise, explaining why Apple recommends taking the SpO2 measurements while being stationary for much more accurate readings.
As we mentioned earlier, the recent Covid pandemic has shown the tech world how important this little feature can be as the coronavirus enters the body through the respiratory system and is known to cause damage to the lungs by both Pneumonia and inflammation. The damage caused can affect the amount of oxygen transferred to the bloodstream.
There is a wide range of Smartwatches on the market that have PPG sensors and SpO2 monitors. They have recently started becoming a common feature on almost every smartwatch.
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