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ALL ABOUT: Pulse oximeter – Why is it important, and what does it tell us? (1/2)

31.5.2021 | 5 MIN

A pulse oximeter is a sensor that is making its way into more and more smartwatches. At first, it was a key feature to more expensive smart watches, but now we can also find it in smart bands with pretty low price tags. So the question stands - why should I have a smartwatch with a pulse oximeter, and how does the technology works?

Articles about pulse oximeter:

Why is it important, and what does it tell us?
How does it work, and what is its history?

Pulse oximetry, or SpO2, is a method of measuring the oxygenation of the blood (also called blood oxygen saturation) in peripheral parts of the body such as an earlobe, fingertips, or in the case of a smartwatch - a wrist. Oxygen binds to hemoglobin in the blood and its amount also affects, for example, the color of the blood (the more oxygen, the lighter the blood). Normal blood oxygenation values should be between 94 and 99%.

10.8.2021
ALL ABOUT: Pulse oximeter – How does it work, and what is its history? (2/2)

Insufficient oxygenation can cause organ failure or hypoxia, which is most often associated with staying at high altitudes. To jsou ale ty nejhorší možné scénáře. In the shorter term, a temporary decrease in oxygenation can tell us about an impending illness (for example, COVID-19), the need for regeneration after sports performance, or even poor acclimatization at higher altitudes.

How does altitude relate to oxygenation?

Hypoxia is the biggest risk for climbers or flight personnel as they often stay at high altitudes. Have you ever heard someone say "There's a thinner air up here"? And let me tell you something, the person was not far from the truth.

With higher altitudes, the air pressure and the partial air pressure decreases, which affects the amount of oxygen transported during inhalation. Meaning, if the partial pressure is lower at heights, so-called thinner air is created, and we do not get such an amount of oxygen when we inhale.

If you inhale while being close to the sea, the oxygen pressure is 21.33 kPa. In contrast, at an altitude of 4000 meters above sea level, you get below the critical limit of 4.7 kPa. (Source: Pharmapoint) That is why oxygen devices are needed in altitudes above 4000 meters. At altitudes above 12 kilometers, the pressure drop is opposite (oxygen escapes from the body) and it is necessary to use a pressurized cabin.

However, headaches and similar symptoms can also occur in lower altitude mountains, as there are several factors that affect acclimatization:

the speed of the ascent
time spent in higher altitudes
natural resistance (genetics and so)
physical activity
temperature
low sugar
diet and regime (eg. lack of sleep)
drugs, alcohol, smoking, illness

So for example, if hiking Lysá hora is difficult for you, you smoke, and it is cold outside, you might have low blood oxygenation. The same thing can happen to an athlete, for example, who climbs Lysá hora quickly, and it is too big of physical exertion for him. So what to do at this moment? Acclimatize. Take a break and let your body deal with it. If the problem persists, it is not harmful to give up the climb and rather descend instead.

The same thing happens with proper ascents to four thousand. The body should not be dealing with these changes unnecessarily, and at a lower measured SpO2 value, we should pay attention to acclimatization, which sometimes takes up to two days. After a while, the heart rate frequency should decrease, blood oxygenation increase, and the body should give the same performance as if in lower altitudes.

What does hypoxia look like?

Normal blood oxygenation values should be between 94 and 99%. Lower values might lead to hypoxia (insufficient tissue oxygenation) and might manifest itself like this:

85-94 % – increase in heart rate frequency and breathing
75-84 % – mood improvement, euphoria, increase in self-confidence (similar to mild intoxication)
60-74 % – anxiety, weakness, vomiting (similar to heavy intoxication)
under 60 % – unconsciousness and hypoxic cramps

A decrease in blood oxygenation may indicate various diseases

Decreased blood oxygenation is closely related to hypoxia and altitude, but this does not mean that it may be the only reason why blood oxygen saturation has decreased. So even though this article made it look like it is only convenient for climbers, flight attendants, and mountaineers, it is not the case. So back to the ground.

Decreased blood oxygenation accompanies almost every disease and can therefore serve as a good indicator that there is something wrong with our body.

Insufficient oxygen saturation of the blood can also reveal sleep apnea when the tissues are not sufficiently oxygenated due to repeated interruptions in breathing when asleep.

Currently, oxygenation is also measured in connection with COVID-19 disease, because damaged lungs cause oxygen deficiency.

Why should you monitor blood oxygenation during training?

When performing a sports activity, the oxygen consumption doubles at least and it is important for the body to get used to it and learn how to work with more oxygen. Closely related to this is the VO₂ Max value, the amount of oxygen that an athlete can take in and use when exercising. The higher the value, the better our body can work with oxygen and is able to deliver better and longer performances.

You may have heard about oxygenation and its effect on athletic performance in connection with the Lance Armstrong doping affair. He used EPO (Erythropoietin), a hormone that increases red blood cell production and improves blood oxygenation to improve his performance.

8.4.2021
What is VO2 max?

However, during a hard workout, we may not be able to get that much oxygen and consequently create an oxygen deficit (also known as EPOC). Our body then tries to compensate for this deficit even after the end of sports activity and so the oxygenation values may be lower than normal. What does it mean for us? It means that our body should regenerate because with an oxygenation value below 94%, another strain on the body could be counterproductive and training would not get you anything.

The same thing happens, for example, after a wild party, when you drank alcohol, or when you lack quality sleep. The body is not ok, the oxygenation is lower and should regenerate.

It is ideal to take the measurement right after waking up and then, based on the value obtained, decide whether you will have demanding training, light training or regeneration that day.

So why is it good to have a pulse oximeter in your watch?

If you are an athlete who cares about regeneration or a mountaineer who needs this equipment to acclimatize, the answer is clear. If you are an athlete, who cares about his regeneration, or a mountineer who needs the device to check his acclimatization, the answer is clear. The pulse oximeter is a useful sensor for you. However, it can also be appreciated by ordinary mortals who just want to know their bodies a little better.