Low Blood Oxygen Levels and Sleep Apnea

The body regulates the level of oxygen in the blood, ensuring the right amount is delivered around the body to allow our organs to function properly. Hypoxemia is the term for when blood oxygen levels are lower than normal. A disorder which can cause this to happen is sleep apnea. 

Your breathing naturally slows when you sleep. This can result in your blood oxygen level falling to around 90%, which is normal. 

However, when you have sleep apnea, the pauses in breathing can result in blood oxygen levels below 90%. Persistent low blood oxygen levels can be harmful to your health -- and require the underlying cause to be treated.

What Is Obstructive Sleep Apnea?

Obstructive sleep apnea (OSA) is the most common form of sleep apnea. The upper airways narrow or become completely blocked when you sleep as the muscles in the throat relax. This results in breathing pauses which can last up to a minute. The brain reacts to the fall in blood oxygen levels by prompting the body to awake for air.

In the more severe cases, these breathing pauses can happen 30 times or more every hour. Often your partner will be the one who first notices your breathing difficulties when you sleep. 

Symptoms of OSA also include:

  • snoring
  • gasping for air during sleep
  • morning headaches
  • dry mouth in morning
  • poor concentration
  • irritability
  • depression
  • excessive daytime fatigue

Sleep Apnea and Hypoxemia

Each time sleep apnea causes a pause in breathing, it can lead to a fall in blood oxygen levels. Both air and blood flow are key to ensuring there is enough oxygen in the blood to be transported around the body. Therefore, if you have a sleep disorder that affects your breathing and ability to get sufficient oxygen, you are at increased risk from hypoxemia.

One measure of OSA severity is the number of episodes every hour that result in a pause to your breathing. Mild OSA is classified as someone experiencing between 5 to 14 episodes each hour they are asleep. Someone with a severe degree of the disorder can have 30 or more episodes per hour.

The more pauses in breathing, the lower the blood oxygen level. Someone with OSA is at greater risk of high blood pressure because the body increases blood flow to counter the low blood oxygen levels.

Testing with a Pulse Oximeter

Obstructive sleep apnea can be treated and therefore diagnosis is key. Left untreated, the disorder increases the risk of serious health issues such as heart disease, stroke and diabetes. One device used in testing for sleep apnea is a pulse oximeter.

A pulse oximeter simply clips on to your finger and uses infrared sensors to measure your blood oxygen levels. As low blood oxygen results from the breathing pauses, measuring the saturation levels of oxygen in blood is a way of diagnosing OSA. Repeated pauses in breathing and reduction of air inhaled can see a 3% fall in blood oxygen levels.

This painless and non-invasive test can be performed while you sleep in your own bed, with monitoring during a couple of nights. You would then send the test back on completion for analysis.


Treating hypoxemia requires treating the underlying cause. In the case of mild OSA, lifestyle changes may be enough to eliminate the symptoms and return you to uninterrupted sleep. Without the breathing pauses, you will breathe regularly through the night, maintaining normal levels of oxygen in the blood.

For severe cases of OSA, continuous positive airway pressure (CPAP) therapy may be prescribed. This involves a device to deliver pressurized air while you sleep. The air is delivered through a mask worn overnight and helps keep the airways open. This ensures there are no blockages which can disrupt the air you are inhaling, helping maintain normal blood oxygen levels.

Also, some patients benefit from an oral appliance which looks like a mouthguard – and may be an option if you have mild to moderate OSA. As you wear the device while you sleep, it serves to move the jaw forward to help keep the airways clear.

Oxygen Therapy

Oxygen therapy may also be considered for people who have low blood oxygen levels. Symptoms of hypoxemia include:

  • shortness of breath
  • headaches
  • wheezing
  • increased heart rate
  • cough
  • feeling confused

Oxygen therapy provides supplemental oxygen to those who are not getting enough oxygen naturally through their breathing.

For those with hypoxemia resulting from sleep apnea, treating the sleep disorder is usually the means to rectifying their blood oxygen levels. However, not everyone is suited to treatments like CPAP, which can be difficult to adjust to for some people.

One study looked at the use of oxygen therapy in addressing hypoxemia for those with OSA. In this study 43 patients with both conditions were offered oxygen therapy as an alternative to other treatment methods such as CPAP. After 30 days of oxygen therapy there was an improvement in the participants' OSAparticipants OSA symptoms. There also seemed to be an improvement in blood oxygen levels.

However, oxygen therapy did not seem to alter the pauses in breathing. 

Oxygen therapy may seem like an option for people who are unable to adapt to CPAP, but it is only supplementing oxygen -- and does not deliver pressurized air designed to keep your airways clear. 

Final Thoughts

The regular pauses in breathing caused by sleep apnea can result in a drop in the levels of oxygen in the blood. Obstructive sleep apnea left untreated increases the risk from serious health conditions. 

Therefore, if you are displaying symptoms of the disorder, you should consult with your doctor. They can arrange a test for the sleep disorder. If your hypoxemia is caused by sleep apnea, then treating this disorder will help restore your blood oxygen levels – which is best for your overall health and well-being.