Apple Watch already allow you to measure blood oxygen saturation with a simple touch. The problem is that specific conditions have to be met in order for a measurement to come out as close to reality as possible. In this article we tell you everything you need to know about this new health feature.
Requirements to perform the measurement
In order to use this function, a series of requirements must be met. For example, that the application is available in the country where you live, something that can be consulted in the initial configuration processes. In addition, you have to have a compatible Apple Watch since not all of them have the necessary sensors. Specifically, the compatible models are the following:
- Apple Watch Series 6 40mm.
- 44mm Apple Watch Series 6.
In addition, in any case, you must have the most recent version of watchOS installed as well as an iPhone 6s or higher with the latest version of iOS available. Added to this is the requirement of being over 18 years of age to be able to use the necessary application, since the algorithm has not been tested on minors.
Initial setup
At the moment that you are configuring your Apple Watch with the sensors to be able to perform the oxygen saturation measurement, a window will appear where they will explain its operation. This is where you can click on ‘Activate’ to download the application to do so. In the event that you have not activated it in the initial configuration, you can simply follow these steps:
- Open the ‘Health’ app on your iPhone with the paired Apple Watch.
- Scroll to the ‘Browse’ tab.
- Follow the path Breathing> Blood oxygen> Set blood oxygen.
At this time you will be asked to make the activation configuration so that the data can be collected. In the event that the application does not appear, you can simply go to the App Store and download the application ‘Blood Oxygen’ to force you to have it. Obviously, this is only possible if you have a watch that supports this functionality.
Measure with Apple Watch
Once you have made sure that you have made the configuration, meeting all the requirements in any case, it is time to perform the measurement. For this you must make sure that the Apple Watch is snug to the wrist but in no case tight. In addition, the fist has to be open and the hand relaxed so that the result is as successful as possible as well as faithful. Once you have taken these indications, you simply have to follow the following steps to perform the measurement:
- Open the ‘Blood Oxygen’ application on your Apple Watch.
- Do not move and keep your wrist in a horizontal position, better supported on a surface such as a table.
- Click on ‘Start’ and wait 15 seconds while the measurement is made.
- Once this measurement has elapsed, you will have access to the result.
The problem that arises is that an interpretation of the results obtained in the measurement is not made. As in the case of ECGs, it is not the case that an assessment is made by the algorithm of whether it is normal or not. That is why these results must always be evaluated with medical knowledge, although it should always be borne in mind that this is not a medical device. If you have any type of symptoms you have to go to a health center to have a measurement done with an oximeter.
It should be noted that the application performs measurements in the background as long as you have it active in the Apple Watch application. The watch intelligently detects when you are not moving to perform the measurement, ideal for when you are sleeping to detect certain pathologies. The problem is that the red light used to measure oxygen saturation can end up annoying or distracting.
Consult data history
All the data that is obtained from the measurements that are carried out are stored for consultation in the Health application. In this way you will be able to consult in a graph the evolution that saturation has had over time. This is ideal especially to be able to check if this has had something to do with a pathological picture that you have suffered. To make this query you simply have to follow the following steps:
- Open the Health app.
- At the bottom, click on ‘Explore’.
- Tap Breathing> Blood Oxygen.
Something extremely interesting that is integrated into this information interface is the possibility of filtering the data obtained by situations. You can always choose if you want to see the measurements that have been taken while you sleep and even at high altitudes.
Common oxygen meter failures
The oxygen saturation measurement is not perfect on the Apple Watch. It should be borne in mind that you are not dealing with a medical section such as an oximeter, despite the fact that it includes very similar sensors, in the end we are not facing the same device. On many occasions, a failed measurement result may occur, which may be because you have moved or the strap is not properly fastened to function properly.
But there are other conditions that can affect having a successful measurement. For example, changes in skin color temporarily or permanently can cause the measurement to be not decisive. This occurs mainly with tattoos that are on the wrist and that can cause the light of the sensor to be blocked, making the light difficult since different photodiodes are used to measure the light that is refracted. Skin perfusion can also vary from person to person, that is, the amount of blood flowing through the skin. As a defense measure, the body can reduce skin perfusion when hypothermic conditions occur, making measurements difficult.
Technical performance
From the Apple Watch Series 6 onwards, heart rate sensors are used to project an infrared light towards the wrist. The light that is reflected at that moment can be read by photodiodes to be interpreted. Thanks to the algorithm included in the software, all the measurements that have been taken can be interpreted to give a result as a percentage. It should be noted that the color of the blood is an indication of oxygen saturation. In the case of highly oxygenated blood, the color is intense red but it darkens as the saturation decreases.
Utility of measuring oxygen saturation
In order to understand the usefulness of this function, you must know what oxygen saturation is. In short, it is the amount of oxygen in the blood associated with red blood cells, and as long as it is at optimal values it is indicative that the cells are receiving enough oxygen to carry out their cellular processes. Although it is repeatedly recalled that this function is not designed for medical use or self-diagnosis, it can give indications to create a pathological picture. Obviously, if the device gives a result lower than 85% and you have some type of respiratory or vertiginous symptoms, it is advisable to go to a medical center. Independently with a point result of low oxygen saturation is not indicative of disease.
Likewise, this function is recommended for those who suffer from a significant ailment or are elderly. In no case does it detect infectious pathologies such as COVID-19, but it can report a symptom that can fit in with numerous diseases such as asthma, bronchitis, COPD, pulmonary edema and endless pathologies. Obviously we repeat that this may be a symptom that must be interpreted with a complete medical history.