The blood oxygen sensor featured in Apple Watch Series 6 and 7 is "not intended for medical use," Apple says. That seems odd, considering that low blood oxygen is a critical medical situation. If the watch’s monitor isn't for medical use, then what precisely is it for? On this post, we’ll look at what blood oxygen is, how Apple Watch measures it, how the machine compares to medical-grade alternatives, and what you'll be able to really use it for. What's Blood Oxygen and why does it matter? The Blood Oxygen app on Apple Watch Series 6 and 7 checks your oxygen saturation stage. This is typically informally known as "sats." It’s a measure of how a lot oxygen your blood is carrying from your lungs to the rest of your body. Together with the nutrients you eat, oxygen offers the gasoline that powers literally every little thing your body does: from transferring your muscles, to rising your toenails, and even reading Cult of Mac.
In healthy adults, blood oxygen saturation is generally between 95% and 100%. If it goes below this degree, your physique won’t be getting all of the oxygen it must function appropriately. This condition is known as hypoxemia, and it’s often accompanied by shortness of breath. How does Apple Watch measure blood oxygen saturation? Oxygen is transported in your blood using a protein called hemoglobin in purple blood cells. When there’s plenty of oxygen, it appears to be like brilliant crimson. As the oxygen is used up, it turns purple-blue. This is why your arteries, which carry freshly oxygenated blood from your lungs, look pink. Whereas your veins, which return the blood as soon as the oxygen is used, look blue. It’s additionally why the Apple Watch Blood Oxygen app displays animated purple and blue strains, though these appear to be just for decoration. Apple Watch uses a method generally known as pulse oximetry to estimate how a lot oxygen your blood incorporates. It does this by checking the color of your blood.
To measure this, a red mild shines towards the pores and skin of your wrist and a sensor detects the sunshine reflected back. How accurate is Apple Watch Blood Oxygen sensor? The most correct approach to measure blood oxygen saturation is with a sample of blood out of your arteries. This is known as arterial oxygen saturation or SaO2. But you want a doctor or nurse to take the sample, and a lab to process the results. Apple Watch, like all pulse oximeters, does not take a look at your arteries. Instead, it measures one thing slightly different: BloodVitals SPO2 SpO2. The "p" stands for peripheral, as a result of it appears at capillaries - tiny blood vessels at the periphery of your physique. That is like monitoring automobile site visitors that comes off an exit ramp to figure out how busy the highway is. BloodVitals SPO2 and SaO2 are related metrics, however have completely different medical purposes. SaO2 is used for diagnosing anemic conditions, while SpO2 is used for continuous monitoring, during surgery and emergency care.
Why isn’t Apple Watch’s Blood Oxygen sensor medical-grade? While devices that measure BloodVitals SPO2 have vital medical functions, they are normally clipped onto the tip of a finger, not wrapped around your wrist. Finger-based mostly pulse oximeters shine a gentle by means of your finger to a sensor BloodVitals SPO2 on the opposite facet. This is known as transmissive pulse oximetry. That’s not potential on the wrist, because it’s is simply too thick and bony for gentle to move by means of. So as a substitute, Apple Watch uses reflectance pulse oximetry. It measures light mirrored off the wrist. Recent research discovered "no important differences between the Apple Watch and industrial oximeter gadgets for … SpO2." But research from 2016 discovered that reflectance pulse oximetry "presents challenges with regard to clinical use." Particularly, the precise position of the sensor is necessary. And BloodVitals SPO2 if you progress your wrist, BloodVitals SPO2 it impacts the outcomes. Other elements can also affect the accuracy of pulse oximeters.