What is oxygen saturation and what are normal levels?

We receive many inquiries about blood oxygen saturation . Doubts about normal levels or how and when to take the necessary measurements.

We also answer many questions about oxygen saturation levels when you are at high altitudes . Check out our article dedicated exclusively to this topic.

Normal blood oxygen saturation values

Oxygen saturation is the measure of the amount of oxygen available in the blood. When the heart pumps blood, oxygen binds to the red blood cells and they are distributed throughout the body. Optimal saturation levels ensure that the body's cells receive the proper amount of oxygen.

The adequate and healthy percentage of oxygen in the blood is considered to be between 95% and 100%. For this reason, when the saturation is below 90%, hypoxemia occurs , that is, the level of oxygen in the blood is below normal. And one of its characteristic symptoms is shortness of breath. In addition, when a percentage below 80 is given, it is considered severe hypoxemia.

In these times of pandemic, it is becoming more frequent to notice symptoms such as difficulty breathing , but it is not always due to hypoxemia. It is necessary to differentiate between an oxygen saturation problem and the anxiety generated by confinement and uncertainty or by any other factor.

It is very important to maintain good mental health and to know the difference between a hypoxemia problem and an anxiety problem .

What can cause hypoxemia and what consequences does it have for our body?

Let's not confuse the terms Hypoxemia and Hypoxia. As a clarifying note...

hypoxemia .

We give this name to the decrease in the partial pressure of oxygen in arterial blood below 80 mmHg. It can also be defined as an oxygen saturation below 90.07%.

Having an oxygen level below normal causes a problem in the arteries related to breathing or the circulatory system, generating different symptoms.

Hypoxia .

It is the state of oxygen deficiency in the blood, cells and tissues of the organism with compromise of their function. This is due to an alteration in the phases of alveolar ventilation and/or alveolocapillary diffusion of respiration. In turn, this results in poor delivery of atmospheric oxygen to blood from the pulmonary capillaries, lowering blood oxygen.

Hypoxia affects the largest areas of the brain, such as the cerebral hemispheres. This term is often used to simply mean a lack of oxygen to the brain.

Tissue hypoxia occurs when the oxygen pressure in the capillaries is insufficient to provide the oxygen essential for physiological needs.

Cellular oxygenation is the most important in the production of erythrocytes (red blood cells).

Types of Hypoxia

• Hypobaric hypoxia : When atmospheric pressure decreases.
• Normobaric hypoxia: When atmospheric pressure decreases, reducing the proportion of oxygen in the air.

Focusing now on Hypoxemia...

The decrease in oxygen saturation can be caused by various factors. Some of them are:

• Shallow breathing.
• Reduced oxygen in inhaled air (for example at high altitudes).
• Certain lung or coronary diseases.
• Sleep apnea, among others.

Hypoxemia can cause a decrease in brain performance, producing possible memory loss or difficulty in solving mathematical operations. It can also generate personality alterations and disorders of perception and consciousness.

What can happen if I have hypoxemia?

Hyperventilation (or overbreathing ) is one of the consequences of hypoxemia and is the increase in the frequency of breathing together with the decrease in oxygen levels in the blood. This hyperventilation can be caused by certain states such as anxiety or panic and can also be the product of some pulmonary or coronary disease.
The most common symptoms of hyperventilation are:

• dizziness
• Respiratory problems.
• Abdominal distension.
• Soft spot.
• Confusion.
• Sleep disorders.
• Numbness and tingling in the arms or around the mouth.
• Muscle spasms in the hands or feet.
• Chest pain and palpitations.

What to do if I have low oxygen saturation?

Hypoxemia is a serious condition, and should be treated as such. If you detect that you have a low oxygen saturation, it is essential that you go to your doctor so that he can apply the most appropriate treatment for your situation.

How can I measure blood oxygen saturation?

Oxygen levels are usually measured with a device called a pulse oximeter or saturation meter. The operating principle of the pulse oximeter is based on the different coloration of the blood depending on its level of oxygen saturation , since blood with a higher concentration of this gas is lighter and more vivid in color.

What is a pulse oximeter? How to measure oxygen in blood

The pulse oximeter is placed on a relatively translucent area of ​​the body (such as the fingertip) and emits bursts of light of different frequencies, thus measuring how the arterial blood absorbs each wavelength, thus offering a reading of the oxygen level . 

What is SpO2?

It is the percentage of oxygen saturation that is measured with a pulse oximeter , or pulse oximeter. It is the oxygen saturation of arterial hemoglobin. These meters usually give us two values, the SpO2 , which, as we said before, must be between 95 and 100, to be considered normal. And it will also give us the measurement of the heart rate.

What is an arterial blood gas?

In addition to this meter, there are other types such as arterial blood gases. The test consists of extracting blood from an artery in which the levels of gases it contains (oxygen and carbon dioxide) and its pH or acidity will be measured. This type of measurement is usually done on people with a breathing problem, usually for lung function testing or monitoring in people receiving respiratory therapy. In general, this measurement is carried out in pulmonology and is the best way to measure the correct oxygen dose for the therapy of lung diseases.