Respiratory desaturation, known as hypoxemia in medical terms, is when you have low blood oxygen saturation.

Your blood oxygen saturation is a measure of how much oxygen is in your blood. A normal blood oxygen reading is generally considered to be 95 to 100 percent. A lower reading can indicate an underlying health condition that requires attention.

Many different medical conditions can cause your blood oxygen levels to drop outside of the normal range, including asthma, coronavirus disease 19 (COVID-19), and pneumonia. If you have sleep apnea, you’ll often experience temporary drops in your blood oxygen levels from pauses in your breathing.

Keep reading to learn more about respiratory desaturation, including causes, symptoms, and treatment.

Oxygen saturation is a measure of how many hemoglobin molecules are bound to the oxygen molecules in your body.

Hemoglobin is the iron-containing part of your red blood cells that binds with oxygen. Each red blood cell in your body contains about 270 million hemoglobin molecules, which can each bind with four oxygen molecules.

Respiratory desaturation is when the amount of oxygen bound to your hemoglobin drops below the normal level. Any condition that disrupts your body’s ability to deliver adequate oxygen to your blood can cause respiratory desaturation. This can vary from mild to life-threatening depending on how low your levels drop.

Healthcare professionals can easily measure your oxygen saturation using pulse oximetry. This painless procedure involves attaching a small clip to your finger that passes a beam of light through the blood in your finger. It’s generally accepted that a reading above 95 percent is normal.

Respiratory desaturation can happen suddenly or develop over time. Possible underlying causes of respiratory desaturation include:

  • low levels of oxygen in the air, such as when you’re at a high altitude
  • problems with your lungs’ ability to inhale air
  • problems with your blood’s ability to circulate to your lungs

Specific causes can include:

Respiratory desaturation and sleep apnea

Sleep apnea is a disorder where your breathing repeatedly stops while you’re sleeping.

It’s normal for your blood oxygen levels to drop slightly during sleep, as your breathing rate tends to slow down. Some people with sleep apnea may experience a drop in blood oxygen levels that are outside the normal range. The blood oxygen level of some people with sleep apnea can drop by more than 4 percent when they’re sleeping.

In a 2021 study, researchers found longer and deeper drops in blood oxygen levels to be associated with worsening sleep apnea.

Mildly low levels of oxygen desaturation might not cause any symptoms. Symptoms become more severe as blood oxygen levels drop lower. These symptoms can include:

You may develop cognitive or visual changes at an oxygen saturation of 80 to 85 percent due to low oxygen levels in your brain.

A blue or grayish tint to your skin might develop when your oxygen saturation drops to around 67 to 75 percent. This is more noticeable with light-colored skin. Levels this low are life-threatening and require immediate medical attention.

Treatment aims to increase your blood oxygen to a healthy level and target the underlying condition. You may receive oxygen therapy, which involves breathing in concentrated oxygen through a mask or small tubes.

Other treatment options depend on the reason your blood oxygen levels are low. For example, treatment for sleep apnea may include:

If your blood oxygen levels are consistently low, your organs won’t receive enough oxygen. A lack of oxygen can cause damage to your heart, brain, and other vital organs. Low blood oxygen can be fatal if your levels drop low enough.

People admitted to the hospital with low blood oxygen caused by COVID-19 are usually put on a mechanical ventilator when their oxygen levels drop under 85 percent. Levels under about 70 percent can be life-threatening.

Low oxygen saturation levels during sleep are linked to several health conditions. One study found that an average value below 90 percent while sleeping was linked with double the risk of depression.

In another study, researchers found that sleeping for a period of time with an oxygen saturation rate below 90 percent was a possible predictor of cardiovascular disease mortality, specifically in older men.

Here are some commonly asked questions about respiratory desaturation.

Is respiratory desaturation serious?

Low blood oxygen levels can range from mild to severe. Some conditions such as anemia or asthma can be well managed with proper treatment, whereas a collapsed lung or pulmonary embolism requires immediate emergency medical attention.

What is considered significant desaturation?

Oxygen saturation of 95 to 100 percent is usually considered normal in healthy adults and children. Below 95 percent is considered abnormal.

If your oxygen saturation falls below 89 percent, supplemental oxygen is usually needed.

What is the best way to measure your blood oxygen levels?

The most common way to measure oxygen saturation is with a pulse oximeter.

Researchers are continuing to examine how skin color affects the accuracy of pulse oximetry readings. In one study, researchers found people who identified as Black had three times the frequency of undetected low blood oxygen compared with people who identified as white.

A procedure called arterial blood gas analysis is the most accurate way to measure blood oxygen level. With this procedure, blood is drawn from an artery in your wrist by a trained medical professional. Your blood is sent to a laboratory and results are usually available within a few minutes.

Doctors sometimes administer this test in emergency situations and when testing your lung function.

Respiratory desaturation is when your blood oxygen levels drop below a normal range. Many conditions can cause your blood oxygen levels to drop. Some of these conditions can be easily managed and others are life-threatening.

If you develop symptoms that could indicate low blood oxygen, it’s critical to get prompt medical attention. Developing a blue or gray tint to your skin means your levels are low enough to be life-threatening and a medical emergency.