General, Research, Technology

What is a pulse oximeter and how to detect coronavirus using blood oxygen levels

One of the most common complications caused by coronavirus COVID-19, is pneumonia. Moreover, according to doctors, many patients who asymptomatically carry the virus begin to suffer from bilateral pneumonia of the lungs long before they feel at least some kind of malaise or experience breathing problems. And if pneumonia reaches its peak, the person immediately has to be connected to a ventilator, although a few days ago he did not have any symptoms of pneumonia. The decision on whether to connect a patient to a ventilator is also made by doctors using an indicator such as the level of oxygen in the blood. And it, in contrast to the same test for antibodies to coronavirus, can be determined independently at home.

Determining blood oxygen levels does require monitoring. And not only because of the coronavirus


  • 1 What is a pulse oximeter
  • 2 How does a pulse oximeter work?
  • 3 How to measure oxygen in blood correctly?
  • 4 Why is it important to know the blood oxygen level in coronavirus?
  • 5 Normal blood oxygen level

What is a pulse oximeter

Pulse oximeter - a device that determines the level of oxygen saturation in the blood.

This sensor is very easy to use: It looks like a large clothespin that you just need to put on your finger, and after 10-15 seconds the device will show the oxygen level in the blood in percent and the pulse in real time.

The pulse oximeter is quite compact, you can take it with you

How does a pulse oximeter work?

For the transfer of oxygen through the blood with the help of redcorpuscles (erythrocytes) are responsible for hemoglobin. Moreover, its amount is different in the veins and arteries, so the venous blood is darker, and the arterial blood is brighter. A pulse oximeter determines the brightness of the blood and, using this parameter, calculates how much hemoglobin in arterial blood is associated with oxygen. This indicator is expressed as a percentage and is called oxygenation of blood.

For example, if the oxygen level in the blood is 98%, this means that 98% of the hemoglobin carries oxygen, and the remaining 2% does not.

In addition, the pulse oximeter also shows the current heart rate, and some models also perfusion index - the intensity of blood flow at the measurement site. But how does a pulse oximeter measure the brightness of the blood and calculate the amount of oxygen?

The pulse oximeter consists of:

  • Sensor for collecting indicators;
  • Microprocessor;
  • Display.

In fact, the principle of operation of the device is quiteplain. The sensor has two LEDs: red and infrared. When you put the oximeter on your finger, the light emitted by the LEDs is captured by the light sensor on the opposite side. How much oxygen is in the blood determines how much light passes through the finger and hits the photosensitive element. Also, with the help of light, the change in the volume of blood vessels with each contraction of the heart is determined.

A pulse oximeter detects how much light has passed through your finger

The data from the sensor is transmitted to the microprocessor, it processes them and displays them on the screen oxygen saturation percentage and pulse.

This is how a pulse oximeter works

The screen allows you to see information about the measurement

Depending on the pulse oximeter model, the device can also measure PI - perfusion index... It shows how intenseblood flow at the measurement site. The sensor detects how much light passes through the vessels and calculates PI from this. As a rule, these are expensive devices, but they can be found cheaper (on the same AliExpress), which measure both the oxygen level, and the pulse, and the perfusion index. It's enough.

PI rate - in the range of 4–7%. If the indicator is lower, then the blood flow is slow, higher - excessive.

How to measure oxygen in blood correctly?

The pulse oximeter is very easy to use, but there are a few guidelines to follow to make the measurement as accurate as possible.

  • Sit or lie down while measuring.
  • Stay calm.
  • Take measurements for 3-4 minutes and calculate the average value.
  • Keep your finger warm.

Why is it important to know the oxygen level in the blood with coronavirus?

Blood oxygen saturation is the main indicatoraccording to which doctors decide on hospitalization for coronavirus. If COVID-19 affects the lungs and causes pneumonia, it can disrupt the transfer of oxygen from the air to the blood. If you determine as early as possible when the oxygen level begins to fall, it will be possible to diagnose lung damage in time, even with asymptomatic coronavirus.

To increase the oxygen level in the blood, a personbegins to breathe faster and deeper, without even realizing it. As a result, this reaction causes more inflammation and pneumonia is aggravated to the point that the oxygen level in the blood begins to drop even more.

Blood oxygen level

In March 2020, the World OrganizationHealthcare recommended that in case of a new coronavirus infection, oxygen should be given to a patient whose indicator is below 90%. Now this indicator has been removed. In accordance with the order of the Moscow Department of Health, if the oxygen level in the patient's blood is less than 93%, he needs hospitalization. In the future, it can be connected to the ventilator.

In a healthy person, the oxygen level in the blood should be 95% and above.

If you have such an indicator, there is nothing to worry about

In fact, the norm may be different. For example, people with chronic lung disease have low blood oxygen saturation levels - up to 88%. Also, the same pulse oximeter may show an incorrect value if you have just returned from frost, and you have a cold finger, or the nail polish is too dark, which will prevent the passage of light through the finger.

Discharged batteries can also distort readings, change them in time

But in any case, a decrease in oxygen levelsrequires attention. Therefore, it is very important to diagnose it in time. Moreover, if you have nasal congestion or pain in the chest, this will once again help you “play it safe” and determine whether you should panic or not, and not look for symptoms on the Internet or in our Telegram chat. In stores, pulse oximeters are not cheap (they are in great demand), but you can always cheat and order one of them on AliExpress. There is a wide choice, the price of the issue is from 500 to 1000 rubles, depending on the design. Worth your peace of mind.

Order a pulse oximeter