Hypoxemia: Types, Causes, Symptoms, Diagnosis, Differences, Treatment and Prevention


Hypoxemia is a level of oxygen in the blood below normal, specifically in the arteries. Hypoxaemia is a sign of a problem related to breathing or circulation and can lead to various symptoms, such as difficulty breathing.

Hypoxaemia is determined by measuring the oxygen level in a sample of blood taken from an artery (oxygen in the arterial blood).

It can also be estimated by measuring the oxygen saturation of the blood using a pulse oximeter – a small device that attaches to the finger.

Normal arterial oxygen is approximately 75 to 100 millimeters of mercury (mm Hg). Values ​​below 60 mm Hg usually indicate the need for supplemental oxygen.

Regular pulse oximeter readings generally range from 95 to 100 percent. Values ​​below 90 percent are considered low.

What happens when you have hypoxemia?

Oxygen passes into the blood through the lungs. Blood transports oxygen to all parts of your body. When you have very little oxygen in your blood, your body does not have enough to work with.


With very little oxygen, the heart and other parts of your body do not work very well.

What are the symptoms?

Although they may vary from person to person, the most common hypoxia symptoms are:

  • Changes in your skin color, ranging from blue to cherry red.
  • Confusion.
  • Tos.
  • Rapid heart rate
  • Fast breathing.
  • Difficulty breathing.
  • Perspiration.
  • Wheezing

What are the causes?

Hypoxaemia is usually triggered by respiratory disorders such as:

  • Chronic obstructive pulmonary disease (COPD).
  • Obstruction of the airway.
  • The acute respiratory distress syndrome.
  • Pneumonia.
  • Pneumothorax (pulmonary collapse).
  • Emphysema.
  • Congenital heart defects.
  • Pulmonary embolism (blood clot in the lungs).
  • Pulmonary edema (fluid in the lungs).

The ascent at high altitude could also lead to the low partial pressure of oxygen in the arterial blood. These are some of the conditions that could cause hypoxemia.

In addition, hypoxemia can also be caused as a result of one or a combination of the following:

Hypoventilation: Refers to a condition in which the oxygen content (PaO 2) in the blood decreases and a marked increase in carbon dioxide levels is observed. This lowered PaO2 content can cause hypoxemia.

Under Inspired Oxygen: The FiO2 content in the blood is called the oxygen fraction inspired by the blood.

A decrease in this fraction of inspired oxygen can cause hypoxemia.

Derivation from Right to Left: A right to left derivation refers to a condition in which blood is transferred from the right side of the heart to its left side.

An opening between the atria, ventricles, or blood vessels can occur. A structural defect or a problem in a heart valve can also result in a short circuit from right to left.

Ventilation-perfusion relationship: This is a condition in which an imbalance is seen between the volume of gas expired by the alveoli (alveolar ventilation) and pulmonary capillary blood flow.

This mismatch can cause hypoxemia.

Impairment of diffusion: In this condition, a marked reduction is seen in the movement of oxygen from the alveoli to capillaries. This restricted movement can trigger hypoxemia.

Often, it is challenging to decide on a single cause of hypoxemia in acute diseases. It also becomes almost impossible to determine the degree of contribution of causes of hypoxemia in such cases.

What are the types of hypoxemia that exist?

Nocturnal Hypoxemia

It is a condition where oxygen levels in the blood come down at night when the person is sleeping.

This can be seen in sleep apnea, in which the partial pressure of oxygen in the blood can fall to such a degree that it can lead to the interruption of people’s sleep patterns.

The person can wake up from his sleep due to a lack of air. Nocturnal hypoxemia is observed in patients suffering from chronic bronchitis and hypoxic emphysema. It is also commonly seen in patients with primary pulmonary hypertension.

Refractory hypoxemia

One of the most dangerous types. This is a type of hypoxemia where the patient’s condition does not improve despite oxygen administration.

It is an emergency; the cause of hypoxemia is usually the intra-pulmonary short circuit of the blood, together with the collapse of the respiratory tract.

The oxygen levels in the arterial blood and a chest X-ray help diagnose it.

The inhaled oxygen is not allowed to enter due to the derivation. Thus, the blood with mixed venous oxygen content circulates in the body, which leads to deoxygenated blood reaching the pulmonary veins, thus originating arterial hypoxemia.

Difference between hypoxemia and hypoxia

In a broader sense, hypoxia is the failure of oxygenation at the tissue level, while hypoxemia occurs at the blood level and, therefore, the two should not be considered equal.

 Significant hypoxia can lead to shortness of breath and is commonly experienced at heights where oxygen saturation in the atmosphere is low.


Brain hypoxia is dangerous, and if untreated, it can lead to loss of consciousness and even death. Most commonly, hypoxemia is due to diseases of the lungs and low hemoglobin due to anemia.


Medical hypoxemia is studied by observing the partial pressure of oxygen (mm Hg) in the arterial blood and the amount of oxygen transported by the hemoglobin of the red blood cells.


The oxygen content of the blood is essential since this determines the amount of blood that reaches the cells instead of the pressure of oxygen in the arterial blood.

How is it diagnosed?

Hypoxemia is diagnosed by measuring the amount of oxygen in the blood. This is done by pulse oximetry or by an arterial blood gas test.

Pulse oximetry is performed by a small instrument placed on the finger. The pulse oximeter gives a digital reading of the amount of oxygen in your blood.

During an oxygen test, the doctor will remove a small amount of blood from an artery in the lower part of your wrist. The blood will be analyzed to determine the amount of oxygen it contains.

Which is the treatment?

The treatment will depend on the severity of the hypoxemia.

Oxygen therapy may be necessary for activities, such as exercise. You may need oxygen only when you sleep. Your healthcare provider may have to use oxygen if you have severe hypoxemia.

Pulmonary rehabilitation (RP) can be ordered if the cause of your hypoxemia is related to certain conditions, such as COPD. RP consists of exercise, nutrition, and education about the disease.

You will learn how to conserve (save) your energy and develop a plan of action when breathing. PR also offers advice and support groups.

A simple disposable plastic mask can also be used for controlled low oxygen levels.

This provides an inspired oxygen concentration of approximately 24% with an oxygen flow rate of 1.5 to 2 liters/min; Artificial respiration of carbon dioxide under the mask is negligible.

This mask is a well-tolerated method for short or long-term low oxygen therapy in patients with hypoxemia due to various causes.

The nasal cannula can also be used. It supplies oxygen at a flow rate of 1 to 6 liters per minute (L / min), at concentrations of 24 to 44%.

Hyperbaric oxygen therapy is also recommended in case of prolonged cerebral hypoxia. It mainly works by improving the amount of dissolved oxygen in the plasma and, therefore, increasing the administration of O 2 to the body’s tissues.

Corticosteroids: acute respiratory distress syndrome (ARDS) is a critical hypoxemic state, and inflammation is the crucial factor in the pathophysiology of ARDS.

Corticosteroids are potent anti-inflammatory, antifibrotic and immunomodulatory agents that exert their inhibitory effects on inflammation.

Methylprednisolone is an effective steroid used in the treatment of hypoxemia.

Treatment with positive or continuous pressure in the airway: hypoxemia complicates the recovery of 30% to 50% of patients after abdominal surgery.

Positive or continuous pressure therapy is a better alternative to treat this condition than mechanical ventilation or endotracheal intubation.

Prevention of hypoxemia

To deal with the chronic lack of breathing, try to:

 If you have been diagnosed with COPD or another lung disease, the most important thing you can do is quit smoking.

Avoid passive smoking: Avoid places where others smoke. Secondhand smoke can cause lung damage.

Exercise regularly: It may seem difficult to exercise when you have trouble breathing, but regular exercise can improve your overall strength and endurance.

Deep breathing and coughing techniques help patients effectively clean their airways while maintaining their oxygen levels.

Use of bronchodilators: medications such as bronchodilators effectively relax smooth muscles and open airways in specific disease processes such as COPD.

Oral suction: patients with muscular disorders or those who have suffered a stroke can have ineffective cough reflexes, which could cause hypoxia.

The oral suction administered to these patients can help prevent this condition.

Hypoxic training: Hypoxic training must be administered to maintain good health.

Take medications and use the rescue inhaler when necessary to help prevent rashes.

Stress can trigger many respiratory disorders that lead to hypoxemia and should be avoided.