What is Hypoxemia

What is hypoxemia and how is it different from hypoxia? Read on to know what causes hypoxemia, what are its different types, and also how this condition differs from hypoxia...
Every cell of the human body needs oxygen to carry out its required functions. We breathe in oxygen through the nose, and then it is absorbed through the alveoli in the lungs. There are certain areas where there could be less oxygen in the atmosphere, like at high altitudes. Also, sometimes, a person may be anemic, which could lead to difficulty in breathing. In other words, there are certain conditions where there may be a deficiency of oxygen in the body. When the blood oxygen levels are low enough to lead to decreased partial pressure of oxygen in the body, then it is known as hypoxemia.

As mentioned earlier, when the blood oxygen levels fall, it is known as hypoxemia. The low oxygen levels in the body are often specified as levels that are less than 60 mm of Hg. In other words, a state where the hemoglobin oxygen saturation levels are less than 90%, then it is said to be a case of hypoxemia. There are many different causes of hypoxemia, like inspiration of gas where the partial pressure of oxygen is low, hypoventilation of the alveoli in the lungs, malfunctioning of alveoli leading to decreased diffusion of gases, shunting of blood, etc.

Nocturnal Hypoxemia
Nocturnal hypoxemia is a condition where the blood oxygen levels fall at night when the person is sleeping. This may be seen in sleep apnea wherein the partial pressure of oxygen in the blood may fall to such an extent, that it may lead to disruption of sleep patterns of the individuals. The person may wake up from his sleep due to shortness of breath. Nocturnal hypoxemia is seen in patients suffering from hypoxic chronic bronchitis and emphysema. It is also commonly seen in patients who have primary pulmonary hypertension.

Refractory Hypoxemia
What is hypoxemia that is said to 'refractory' in nature? One of the most dangerous types of hypoxemia is refractory hypoxemia. This is a type of hypoxemia where, despite the administration of oxygen, the condition of the patient does not improve. This is an emergency, the hypoxemia cause is usually intrapulmonary shunting of blood, along with airway collapse. The arterial blood gas levels and a chest X-ray help to diagnose it. The inhaled oxygen is not allowed to enter due to the shunting and so, blood with mixed venous oxygen content circulates in the body, leading to deoxygenated blood reaching the pulmonary veins, and so, resultant arterial hypoxemia.

Difference Between Hypoxia and Hypoxemia
One of the most commonly confused medical terms are hypoxia and hypoxemia. Now that you know what is hypoxemia, let us see what hypoxia is. Hypoxia is a condition where the body is deprived of oxygen supply. Here, it is not the partial pressure of oxygen that is low. Hence, it is possible that a person may be suffering from hypoxia due to anemia, but he may have high partial pressure of oxygen in the blood. Hence, hypoxemia may be one of the causes of hypoxia but a person may also suffer from hypoxia without the presence of hypoxemia. I hope this has made you understand the differences when it comes to hypoxemia vs hypoxia.

This was all about hypoxemia and its different types. This is a serious condition that needs to be dealt with on a prompt basis, especially in cases of refractory hypoxemia. Thus, one needs to be aware of the causes, symptoms and treatment of hypoxemia, so that they can identify and deal with this condition promptly.
By Dr. Sumaiya Khan
Last Updated: 10/5/2011
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