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Hypoxemia Vs. Hypoxia

Chandramita Bora
Hypoxemia is the condition characterized by low partial pressure of oxygen in blood. It can lead to hypoxia or a shortage of oxygen in tissues. The difference between these two conditions are briefly discussed in this story.
The terms 'hypoxia' and 'hypoxemia' may sound similar, but they are two different conditions. Hypoxia is the medical condition characterized by the shortage of oxygen in the tissues. It can be localized or generalized.
Hypoxemia can lead to hypoxia at times, which is known as hypoxemic hypoxia. However, hypoxia can also occur due to other conditions that can restrict the supply of oxygen to tissues. On the other hand, hypoxemia refers to decreased partial pressure of oxygen in arterial blood, or reduced concentration of oxygen in blood.
But in general, hypoxemia is defined in terms of reduced partial pressure of oxygen in arterial blood, as the relevance of oxygen content of blood in determining hypoxemia is a debatable issue.
Here is a brief discussion about hypoxia and hypoxemia, and how these two conditions differ, so that the next time someone gets confused between them, you can correct him or her.

Comparison Between Hypoxemia and Hypoxia

Difference in Causes

As already mentioned in this story, hypoxemia refers to low partial pressure of oxygen in arterial blood, and it can be caused by lung diseases and respiratory disorders. Factors like low oxygen in air or low inspired partial pressure of oxygen, hypoventilation, shunts, and diffusion impairment across the blood gas membrane of the lungs can cause hypoxemia.
The partial pressure of oxygen in the inspired gas can be low due to low barometric pressure. This is the reason why people experience hypoxemia during high altitude ascension.
Hypoxia on the other hand, can be caused by a large number of factors, including a fall in partial pressure of oxygen in arterial blood (hypoxemia), which is known as hypoxemic hypoxia.
Other than hypoxemia, hypoxia can be caused by conditions like cyanide toxicity, carbon monoxide poisoning, ischemic heart disease, choking, suffocation at high altitudes, very low blood pressure, strokes, anemia, and asphyxiation caused by the inhalation of smoke.
Sometimes, one can develop hypoxia while breathing in a mixture of gases having low oxygen content. This usually happens when closed-circuit rebreather systems are used while diving underwater.

Difference in Symptoms

The symptoms of both hypoxia and hypoxemia depend on their severity. In general, the most common symptoms of acute hypoxemia are, shortness of breath, restlessness, an increased rate of breathing, anxiety, and headaches. Chronic hypoxemia can increase pulmonary blood pressure. In extreme cases, hypoxemia may lead to respiratory failure.
The symptoms of hypoxia on the other hand, depend on the severity of oxygen deprivation, as well as the specific type. Some of the symptoms of hypoxia can be similar to those of hypoxemia. The more commonly observed symptoms of generalized hypoxia are, shortness of breath, lightheadedness, nausea, and fatigue.
If there is a shortage of oxygen in the brain, the affected individual can experience confusion, disorientation, changes in consciousness, hallucinations, severe headaches, and uncoordinated movements.
Hypoxia can cause tachycardia and pulmonary hypertension, and eventually lead to cyanosis or bluish discoloration of the skin, bradycardia, seizures, hypotension, and coma. In extreme cases, hypoxia can lead to death as well.

Treatment of Hypoxemia and Hypoxia

Hypoxia can lead to a life-threatening condition, if the supply of oxygen to the vital organs like the brain gets impaired significantly. Therefore, hypoxia is treated promptly by putting the patient on mechanical ventilation. In other words, supplemental oxygen or oxygen therapy is required for the treatment of hypoxia.
For resolving the mild cases of hypoxemia, physicians usually advise their patients to lie down. This can help increase the supply of oxygen. Mechanical ventilation like CPAP is usually required only in severe hypoxemia. Transfusion of packed RBCs is another treatment option available for this condition.
To sum up, hypoxemia refers to low partial pressure of oxygen in arterial blood, while hypoxia is the condition characterized by inadequate supply of oxygen to tissues, which can affect a particular organ or the entire body. Hope this story helped you understand the basic difference between these two conditions, and their causes and symptoms.
Disclaimer: This story is for informative purposes only, and should not be treated as a substitute for professional medical advice.