Modern smartwatches are gradually acquiring more and more new features. It’s one thing to monitor a person’s activity, but quite another to assess their general physical condition. Apple Watch Series 6 received an interesting and especially relevant function today – measuring the level of oxygen in the blood. This information allows you to know how much oxygen from the lungs is captured by red blood cells for subsequent transportation to other parts of the body.
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In smart watches, this possibility was implemented for the first time. Apple Watch uses LEDs and photodiodes on the inside to non-invasively measure blood oxygen saturation. This sensor works in tandem with Apple’s new Blood Oxygen app.
The data provided by the program cannot be the basis for diagnosis and treatment, however, you can evaluate your general physical condition.
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Why is it important to know the level of oxygen in the blood?
The level of oxygen in the blood directly affects the functioning of the cells of the body. With a lack of oxygen, we begin to feel a breakdown, dizziness, weakness and headache. A low level of oxygen is also accompanied by a decrease in pressure, tachycardia, impaired consciousness, fainting, and a change in skin color.
Today, information is relevant that the lack of oxygen in the blood, or hypoxemia, directly related to COVID-19. Coronavirus affects the lungs, severe tissue damage interferes with the transfer of oxygen from the air to the blood. Doctors use information about the level of oxygen in the blood to assess the severity of the coronavirus disease and choose a treatment. This is an important indicator that determines the need to supply oxygen to the patient through a mask or the choice of ventilation as an urgent measure.
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What is the normal level of oxygen in the blood?
Oddly enough, but there is no clear prescribed norm. On a scale of 100%, it is considered that in a healthy person, oxygen levels in the blood should exceed 95%. This level is enough for the lungs to efficiently transfer oxygen to the blood. A one-time decrease in the level should not be frightening, but the constant shortage of the desired 95% is a reason to see a doctor.
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If the indicator is lower, then everything is bad?
Obviously low rates are not always a reason to sound the alarm. If a person has other chronic lung diseases, the level of oxygen saturation in the blood can drop to 88%. But the body is already used to it and adapted. Low indicators may not be related to the state of health, there are features of measurements both in smart watches (tattoos on the skin) and in pulse oximeters: a cold finger, nail polish, dead batteries. If you feel good even with low blood oxygen levels, then there may be no obvious reason to see a doctor.
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How to check blood oxygen levels on Apple Watch?
Please note that this feature is currently only available for Apple Watch Series 6 and Apple Watch Series 7, not earlier models.
The sensor itself is located on the back of the watch. The beams sent out by the LEDs illuminate the blood vessels on the wrist, and the photodiodes measure the return of the light. The principle of operation of the sensor is that, depending on the oxygen saturation of the blood, red and infrared light are absorbed differently. That is why the study of the reflected rays allows the watch to determine the color of the blood. Bright red blood is saturated with oxygen, while dark red fluid has less. Such blood does not receive enough oxygen from the lungs and cannot deliver it to organs and muscles.
To measure blood oxygen with Apple Watch:
1. Make sure the watch fits snugly on your wrist. In this case, the device should be comfortably placed on the arm – you should not pull the strap.
2. On your Apple Watch, open the “oxygen in the blood“.
Follow the prompts (shown only the first time you launch the app):
3. Stay still and make sure your wrist is level and the watch is pointing up.
4. Press the button “To begin” and hold your hand still for 15 seconds.
The clock will show a timer.
5. After the end of the reading, information about the level of oxygen in the blood will immediately be displayed on the watch screen. You can exit the data window by clicking the “Finish” button.
All blood oxygen readings will be synced to the Health app (tab Overview → Blood oxygen).
For best performance, it is recommended to place your hand on a table or in your lap and make sure the watch is at the same level as your wrist. You can’t clench your hand into a fist. As with any biometric sensor, there are a number of factors that can affect the results. For example, in people with tattoos, the readings may be incorrect – the ink will interfere with the penetration of light into the blood vessels. The volume of blood flowing under the skin can depend on body temperature, environment and varies from person to person, also affecting the sensor readings.
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How do I measure blood oxygen saturation on Apple Watch in the background?
By default, Apple Watch measures hours automatically throughout the day. The watch will take measurements from time to time. This usually happens if the person is not moving. Depending on the activity, the number of readings and the time between them will change.
In addition, you can adjust the measurement of blood oxygen levels in Sleep Focus mode and Theater mode. And since red light is used for measurements, it can be noticeable in the dark.
To enable or disable automatic background blood oxygen measurement:
1. Open the app “Settings” on Apple Watch.
2. Click on an element “Oxygen in the blood”.
3. To enable/disable the background blood oxygen measurement, set the switch of the same name to the required position.
4. To enable/disable background measurements “When Focusing Sleep” and “In theater mode» set the appropriate switches to the desired position.
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Which medical device measures the level of oxygen in the blood?
Measurement of the level of oxygen in the blood is carried out by a medical device pulse oximeter. This is a simple and affordable device that looks like a large clothespin. It is put on the finger and after 10-20 seconds shows not only the level of oxygen in the blood, but also the pulse. The principle of operation of the pulse oximeter sensor is similar to that of the Apple Watch – measurements are made non-invasively by sending and receiving light signals through the skin to the vessels.
Doctors recommend pulse oximeters to patients with chronic lung disease or heart failure to monitor their condition. But this device can also be used simply to monitor your health. However, the Apple Watch and the Blood Oxygen program already seem like a good alternative to the popular medical device.