What Is Hypoxemia? - Definition, Symptoms, Causes & Treatment

Instructor: Heather Zonts

Heather has taught in AD and BSN Nursing programs and has a master's degree in nursing.

This lesson will define what hypoxemia is, the symptoms associated with it, and potential causes. Additionally, we will discuss the treatments for this life-threatening disorder.

Oxygen - The Source of Life!

We are going to start with discussing why oxygen is important to the human body. Oxygen provides the fuel for many metabolic processes within our bodies. Without oxygen, cells begin to die, and body processes are altered. It is important for our bodies to maintain a certain level of oxygen to sustain life. Once we are below this level, our body starts to respond adversely due to hypoxemia.

As you can see, the respiratory system handles the exchange of oxygen. This diagram shows how structural changes as well as disease processes increase the likelihood of hypoxemia occurring.
Respiratory System

What is Hypoxemia?

Now let's break down the word hypoxemia, hypo- means 'low', ox- means 'oxygen', and -emia means 'blood.' Therefore, hypoxemia is low oxygen levels in the blood. The oxygen level in the blood is usually determined using a pulse oximeter (quickest route) or blood work. Normal oxygen values would be between 95 and 100. Once the level drops below 90, the patient is considered low and suffering from hypoxemia. Depending on the individual and their symptoms, this can be considered a medical emergency. Now, I want you to start to think about what you would see if someone had low oxygen levels in their blood. And, think about activities or illnesses that can decrease the oxygen levels.

What Causes Hypoxemia?

So, what brings oxygen into the body? The lungs do. Therefore, many of the causes of hypoxemia are associated with this body organ. A basic cause could be a blocked airway not allowing oxygen to enter the body, such as when someone is choking.

Other causes focusing on the respiratory system (lungs) would be chronic obstructive pulmonary disease and emphysema. Both alter the ability to bring oxygen into the body for transfer to the blood. Others include pneumonia, pneumothorax, pulmonary edema, and pulmonary fibrosis, all of which impair the ability for bringing oxygen in and exchanging oxygen in the alveoli (air sacs in the lungs responsible for gas exchange).

Pulmonary embolism (PE) is another cause of hypoxemia. A PE blocks the blood flow to the lungs preventing the exchange of oxygen into the blood.

Sleep apnea is another cause. Sleep apnea means that someone stops breathing when they are sleeping. Many times, this is due to an obstruction, such as the tonsils or tongue blocking the airway. Again, if you block the airway, you cannot get oxygen into the blood.

Now let's shift to the heart, which powers the circulatory (blood) system in the body. Certain congenital heart defects, such as an atrial septal defect, cause the formation of a hole in the wall separating the atrium. This hole will cause deoxygenated blood to mix with oxygenated, decreasing the amount of oxygen circulating through the body. When you decrease these oxygen levels, you increase the likelihood of hypoxemia occurring. Additionally, since the cardiovascular system handles the transportation of blood and oxygen, when the body does not produce enough red blood cells a person is considered anemic. Red blood cells carry oxygen; therefore, less red blood cells mean less oxygen resulting in hypoxemia.

What Symptoms are Associated with Hypoxemia?

We already established that we need oxygen to function and that hypoxemia is low oxygen levels in the blood. Our bodies will work to maintain certain levels of oxygen for delivery to the cells to prevent cell death. Considering this, the body would try to compensate (make up for the low levels by working harder). Therefore, you would start to see the respiratory rate increase (the individual will breath faster) to bring in more oxygen. You would also see the heart rate start to increase. The heart rate increases to try to increase the amount of oxygen delivered to the cells, another compensatory mechanism. The individual will also appear short of breath (like they cannot get enough oxygen).

Depending on the severity of the hypoxemia, they may also be using their abdominal muscles to help them breath. The more severe the hypoxemia is, the more severe the symptoms are. As cells lose oxygen, they start to die. Therefore, you may notice the fingers, toes, lips, and nose turning blue. The blue discoloration is known as cyanosis.

This is an example of a hand that has cyanotic finger tips.

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