What Is Hypoxia?
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Hypoxia- Clinical Presentation, Types, and Management

Published on Jan 02, 2023 and last reviewed on Jun 16, 2023   -  5 min read


Hypoxia is a condition that lacks oxygen at the tissue level and requires immediate medical attention. Read the article below to know more.


Hypoxia is defined as a condition in which there is an absence of oxygen at the tissue level. Lung tissues take the oxygen from the inhaled air and combine it with the hemoglobin in the blood. Hemoglobin is an oxygen-binding protein that supplies oxygen to different body parts. Hypoxia and hypoxemia are often confused with one another. Hypoxia is a lack of oxygen at the tissue level, whereas hypoxemia is a lack of oxygen in the blood flow.

What Is the Clinical Presentation of Hypoxia?

Clinical presentation of hypoxia includes

What Are the Types of Hypoxia?

Based on the mechanism of occurrence, there are various types of hypoxia:

  • Hypoxic hypoxia

  • Anemic hypoxia.

  • Stagnant hypoxia.

  • Histotoxic hypoxia.

Hypoxic Hypoxia:

It is the most common type of hypoxia. It is also known as true hypoxia. It is seen when there is a lack of oxygenation of blood in the lungs, which results in low partial pressure of oxygen in the arterial blood. So, a reduced amount of hemoglobin and central cyanosis develops when it exceeds 5 gm %. The peripheral chemoreceptors are stimulated.

Causes of hypoxia include

  • High altitude.

  • Ventilation-perfusion mismatch. Lungs need both airflow (ventilation) and blood flow (perfusion), and whenever there is an imbalance between the two, it will result in a ventilation-perfusion mismatch.

  • Airway obstruction.

  • Depression of the respiratory center.

Anemic Hypoxia:

In this type of hypoxia, the lungs work fine, and there is an average partial pressure of oxygen in the arterial blood. Still, the amount of hemoglobin carrying oxygen is reduced due to anemia. The peripheral chemoreceptors are not stimulated as the dissolved oxygen in the blood plasma is sufficient enough to supply the chemoreceptors.

Causes of hypoxia include

  • Carbon monoxide poisoning.

  • Anemia of all types.

  • Excessive blood loss in the form of hemorrhage.

Stagnant Hypoxia:

In this type of hypoxia, there is reduced blood flow to the tissues. Although the partial pressure of oxygen in the arterial blood and oxygen content is expected, a sufficient amount of blood is not supplied to the tissues. It is also known as ischaemic or hypokinetic hypoxia.

Causes of hypoxia include

  • Sluggishness of blood flow.

  • Circulatory failure like congenital heart defects like the tetralogy of Fallot, ventricular septal defect, patent ductus arteriosus, and congestive heart failure in which the blood pumped by the heart is decreased, which leads to reduced blood flow to the tissues and thereby leading to stagnant hypoxia.

  • Localized stagnant hypoxia-like Raynaud's disease and Buerger's disease, where the blood supply to the extremities is reduced.

  • The shock is due to hypovolemia of blood in the body.

  • A stroke occurs due to a blood clot in the blood vessels, which blocks blood flow and oxygen supply to the brain.

Histotoxic Hypoxia:

In this type of hypoxia, although there is a normal partial pressure of oxygen dissolved in the arterial blood and the oxygen content is also standard, the capability of the tissues to utilize the oxygen is reduced. The peripheral chemoreceptors are stimulated.

The causes of hypoxia are

  • Cyanide poisoning.

  • Sulfide poisoning.

How Is Hypoxia Diagnosed?

Hypoxia can be diagnosed with the help of the following:

  • Arterial Blood Gas (ABG) Analysis: It includes the measurement of arterial oxygen, carbon dioxide, and pH. The calculation can be done with the help of the Henderson-Hasselbach equation, where pH is directly proportional to bicarbonate ions and indirectly proportional to carbon dioxide. The normal partial pressure of carbon dioxide is 35-45 mmHg; more than 45 mmHg is acidosis, whereas less than 35 mmHg is alkalosis. The normal partial pressure of bicarbonate ions ranges between 22-26 mmHg, where more than 26 is considered alkalosis and less than 22 is acidosis.

  • Pulse Oximetry: It is a probe that checks the oxygen saturation level of the blood.

  • Echocardiogram: An ultrasound helps diagnose the reason for hypoxia by checking the heart function.

  • Imaging: Chest X-ray or computed tomography (CT) scan can help diagnose infections or certain lung conditions.

How Is Hypoxia Treated?

Hypoxia is treated with oxygen administration.

  • Supplemental Oxygen Therapy: Oxygen is administered with the help of a cannula, facemask, or tracheostomy depending upon the medical condition and the patient's requirement.

  • Hyperbaric Oxygen Therapy (HBOT): Inhalation of 100 % oxygen at high barometric pressure. This allows the lung to take up three times more oxygen than breathing oxygen at standard pressure. It is indicated in cases of anemic hypoxia, carbon monoxide poisoning, decompression sickness, and air or gas embolism in scuba divers and mountain climbers.

  • Mechanical Ventilation: It is a machine that helps to breathe a critically ill patient who cannot breathe on their own. It is indicated in patients with severe acute hypoxia.

  • Treating the Underlying Cause: It may include the usage of bronchodilators, which may help in opening up the airways, a corticosteroid to subside the inflammation of the lung, or transfusing packed cells in an anemic patient.

What Are the Complications of Hypoxia?

Complications of hypoxia include

  • Brain damage and paralysis.

  • Cardiac arrest.

  • Gangrene.

How to Prevent Hypoxia?

Low oxygen levels in the blood do not have enough oxygen to supply the organs and tissues. This may lead to irreversible and permanent damage to the organs, including death, if it persists over time, specifically the heart and brain, requiring a constant supply of oxygen and nutrients. Acute cases of hypoxia can be fatal. Hypoxia can be prevented by taking certain precautions, such as management of underlying conditions that can lower oxygen levels and asking for any specific precautions if the patient has a compromised lung condition. Mountain climbers and scuba divers must carry oxygen cylinders.


Hypoxia is an emergency condition that requires immediate medical attention. Diagnosing early symptoms like confusion, increased heart rate, breathing, and bluish skin and mucous membrane discoloration requires immediate medical attention. Hypoxia should be treated right away to avoid irreversible organ damage. In some cases, it may require treating the underlying cause; in others, it may require supplemental oxygen therapy or hyperbaric oxygen therapy to resolve the condition.

Last reviewed at:
16 Jun 2023  -  5 min read




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