Hypoxia happens when the amount of oxygen transported to the cells in the body is insufficient, leading to symptoms like headache, somnolence (sleepiness), cold sweats, blue discoloration of the fingers and around the mouth, and even fainting.

Hypoxia is usually caused by heart problems or lung disease but may also result from other conditions such as anemia or being up at high altitudes.

Treatment for hypoxia depends on cause, severity, and the presence of other health conditions, but will usually involve the administration of oxygen through a mask or an orotracheal tube. Hypoxia can lead to other complications in the body, therefore it is important to seek urgent medical attention at the first signs of hypoxia.

Person checking oxygen level with pulse oximeter — Oxímetro: aparelho que mede a saturação de oxigênio

Common symptoms

The most common symptoms of hypoxia are:

Headache;
Somnolence;
Increased heart rate;
Cold sweats;
Shortness of breath;
Dizziness;
Confusion and fainting;
Blue discoloration of the fingers and mouth (cyanosis).

The body will try to compensate for drops in oxygen in various ways, which can lead to cyanosis or bluish-purple skin. This change in skin color occurs as a result of contraction of the blood vessels, as the body tries to promote blood flow to vital organs to ensure they get enough oxygen. This blood vessel contraction leads to a temporary increase in blood pressure.

However, as oxygen levels continue to drop, blood pressure levels will also start to decrease. This can cause dizziness, fainting, or a loss of consciousness, which require immediate medical attention to reduce the risk for possible complications.

Confirming the diagnosis

The best way to check oxygen levels in the body is with a pulse oximeter (Pulse Ox), which can be purchased at most pharmacies and in some stores.

A pulse oximeter is a small device that you place on the tip of your finger that measures the amount of oxygen in the body and gives a reading in the form of a percentage (oxygen saturation). Read about pulse oximetry.

If you do not have a pulse oximeter at home, make sure to go directly to the clinic or the hospital for an evaluation.

Hypoxia vs hypoxemia

Hypoxemia is defined as a low concentration of oxygen in the blood (below 90% as measured on a pulse oximeter), while hypoxia is reduced oxygenation of the tissues. Symptoms of both conditions are very similar, as hypoxia can happen as a result of hypoxemia.

Possible causes

Hypoxia happens when the amount of oxygen in the tissues is insufficient and may have a variety of causes, such as:

Respiratory insufficiency;
Asthma;
Emphysema;
Acute pulmonary edema;
Pneumonia;
Neurological disorders caused by a traumatic brain injury;
Acute myocardial infarction (heart attack);
High altitudes.

Hemoglobin is a protein in the blood responsible for transporting oxygen throughout the body. Low levels of hemoglobin in conditions like anemia can lead to hypoxia, even if breathing is normal.

Other causes of hypoxia include poisoning from cyanide, carbon dioxide, and psychoactive drugs.

Different types

Types of hypoxia are related to what is causing the lack of oxygen in the body. They include:

Respiratory hypoxia: caused by insufficient delivery of oxygen to the lungs resulting from slowed or absent breathing related to disease or obstruction (blockage) of the airway;
Anemic hypoxia: occurs when hemoglobin levels in the blood are very low, leading to a decrease in oxygen transport in the blood;
Circulatory hypoxia: occurs when low blood flow to the lungs results in poor gas exchange, as with cardiac insufficiency (heart failure);
Hypoxia of specific organs: caused by an arterial obstruction that prevents the flow of blood and oxygen to a particular area, which may happen as a result of atherosclerosis.

Another type of hypoxia exists related to congenital heart malformations, such as tetralogy of Fallot, in which defects in the heart prevent adequate flow of oxygen to the vital organs, such as the brain.

Treatment options

Treatment of hypoxia typically involves the noninvasive administration of oxygen by way of a mask, nasal cannula, or oxygen tent. In more serious cases, however, intubation with an orotracheal tube (through the mouth) is indicated in order to deliver oxygen directly to the lungs.

Supplemental oxygen may not be sufficient in cases of hypoxia caused by anemia, as increasing the amount of oxygen in the blood will not help if there is not enough hemoglobin to transport it to the tissues. A blood transfusion may be necessary in these cases in order to provide more hemoglobin to the body. Learn about how a blood transfusion is performed.

In a similar way, in cases of hypoxia cased by severe heart disease involving circulatory failure, maintaining adequate respiration will not be enough. Correction of the underlying cause (through surgery, for example) will be necessary.

Possible complications

Hypoxia can cause further complications in the body depending on the length of time a person goes without breathing or without adequate oxygenation to maintain vital functions. Damage to the central nervous system is one of the most significant consequences of hypoxia, leading to movement disorders and impairing the ability to walk, talk, eat, and see.

Intubation is necessary in cases of severe hypoxia when the person is unable to breath on their own. A person may be put into an induced coma while machines are helping them to breath.