Oxygen is an essential element that helps to sustain life. It is a requirement for the respiration that human cells and tissues continuously need.

Without oxygen, the human cells can’t produce the energy the body needs to function adequately, nor transform nutrients into Adenosine Triphosphate (ATP).

Lack of oxygen can lead a living organism to death in just a few minutes. And several conditions can significantly reduce the oxygen supply the human body requires.

Some of this respiratory conditions feature hypoxemia as a primary sign or symptom.

Hypoxemia refers to a low pressure of oxygen in the arterial blood. Sometimes people use the term Hypoxia as a synonym of Hypoxemia without realizing they’re two different concepts.

Hypoxia is the abnormal decrease in the amount of oxygen reaching the tissues.

Hypoxemia Vs. Hypoxia

Medical experts define Hypoxemia as the condition in which Arterial Oxygen Tension (PAO2) is below the average level to keep an individual healthy.

The average value of PAO2 that keeps the human body healthy is between 80 and 100 mmHg.

On the other hand, Hypoxia is just a reduced level of tissue oxygenation.

In several cases, both of these clinical manifestations seemingly appear at the same time.

That happens because of the lack of oxygen in the blood resulting in an inadequate supply of oxygen to the tissues.

But sometimes a patient that displays Hypoxemia does not manifest Hypoxia. In these particular cases, a compensatory increase in hemoglobin level and cardiac output keeps the tissues oxygenated.

Patients can also develop Hypoxia without suffering from Hypoxemia.

For example, when people get cyanide poisoning, their cells cannot process oxygen adequately even when the supply from arterial blood is around average levels.

Such thing occurs due to cyanide disrupting cellular respiration. In this case, doctors refer to the resulting condition as Histotoxic Hypoxia.

However, in many cases, Hypoxemia usually leads a patient to develop Hypoxia.



The causes of Hypoxemia are often related to respiratory disorders. But this low level of oxygen in the blood can be the result of other factors, such as the ones listed here below:

  • Hypoventilation: a breathing disorder that consists of insufficient ventilation, which reduces the levels of oxygen in the blood, and increases the levels of carbon dioxide.
  • Left-to-Right Shunt: it refers to abnormal blood flow in the heart caused by a “leak” that allows blood from the left side of the heart to enter the right side without flowing through the systemic circulation.
  • Ventilation-Perfusion mismatch: when the balance between the amount of oxygen that enters the body, and the and the amount of blood sent to the lungs, gets disrupted continuously leading to impaired oxygenation.
  • Lung Diffusion Impairment: it refers to a significant reduction in the capability of transferring the oxygen from the lungs to the blood.


There is a wide variety of factors capable of causing Hypoxia. The common causes of this deficient tissue oxygenation would be the ones listed here below:

  • Cardiac Arrest: it occurs when an irregular heart rhythm causes the heart to suddenly stop pumping blood, which results in a sudden loss of blood flow.
  • Carbon Monoxide Poisoning: it occurs by breathing the poisonous gas. Carbon Monoxide then enters the bloodstream and mixes with hemoglobin, thus making the blood unable to carry oxygen.
  • Cyanide Poisoning: it happens because of cigarette smoking or exposure to chemicals that contain a carbon-nitrogen bond. It may result in tachypnea, tachycardia, hypotension, and even cardiovascular collapse.
  • Suffocation: it refers to the disruption in breathing caused by an obstruction of the airways, resulting in oxygen deprivation.
  • Severe Asthma Attack: it narrows the airways, making it hard for oxygen to enter the body. People require a conscious physical effort (coughing) to clear their lungs, but that consumes more oxygen, which worsens the condition.



The clinical signs that patients display will depend on the severity of the condition.

The patients that suffer from a mild Hypoxemia will likely show symptoms such as restlessness, confusion, anxiety or headaches.

People who suffer from Acute Hypoxemia will display increased blood pressure, apnea or tachycardia.

In the most severe cases, the symptoms of the patient can range from hypotension to ventricular fibrillation. Some may even enter a coma.


The most noticeable symptom of Hypoxia is cyanosis in the affected area.

Other symptoms will depend on the severity of the condition, with the most extreme cases featuring Hypoxia turning into Anoxia, which is a complete lack of oxygen at a tissue level.

Most common symptoms include headaches, fatigue or tiredness, abnormal blood pressure, nausea and vomiting, some cognitive issues, and uncoordinated movement.

In the most severe cases, Hypoxia causes loss of consciousness, seizures or convulsions, coma, and even death.



When it comes to Hypoxemia, healthcare providers will have their patients lying flat on the ground because this increases the supply of oxygen.

In the most severe cases, doctors will likely need to place their patients on mechanical ventilation and reinforce the treatment by putting the patients on oxygen.

Another way to treat people who suffer from Hypoxemia is providing them with packed red blood cells. That will increase the supply of oxygen in the blood.


Since Hypoxia can escalate into something that could threaten the life of the patient, medical experts should treat it as soon as possible.

They often rely on support measures such as intravenous support. Doctors will also prescribe medication to prevent seizures and high blood pressure.