An Overview of Transient Nocturnal Desaturation in COPD

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Transient nocturnal desaturation is when your oxygen concentration (the level of oxygen that your blood is carrying) temporarily becomes lower than usual while you are asleep at night. This is a serious problem that is commonly associated with chronic obstructive pulmonary disease (COPD). Though transient nocturnal desaturation does not typically cause immediate symptoms, it can have harmful effects on your health over time.

You may need a sleep study to identify the condition, and nighttime therapeutic oxygen is usually prescribed to help with symptoms.

Woman sleeping in bed
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The typical complaints of people with this condition include:

  • Waking unrefreshed
  • Chronic fatigue
  • Lethargy
  • Impaired quality of life

Beyond those vague symptoms, you probably won't notice any distinct symptoms of transient nocturnal desaturation in COPD.

Rather, the impact of the condition is typically noticed when the slow-progressing, long-term effects on your lung function, blood pressure, heart, and brain health have taken a toll.

Pulmonary Function

The lungs can undergo changes, such as worsening COPD or a condition called pulmonary hypertension, as a result of transient nocturnal desaturation. These pulmonary issues cause fatigue and shortness of breath all day—not just during sleep.

Cardiac Function

Transient nocturnal desaturation is associated with heart conditions such as arrhythmias (heart rate abnormalities) and heart failure. You may experience edema (swelling of your legs), low energy, dizziness, and/or palpitations (a feeling that your heart is racing) with these conditions.

Blood Vessels

Hypertension and arteriopathy are blood vessel conditions that are associated with transient nocturnal desaturation. Neither of these conditions causes noticeable symptoms, but they do increase the risk of serious issues such as heart attack and stroke, which can bring symptoms of their own.

Brain Health

Brain health can be compromised during periods of transient nocturnal desaturation. Ischemic damage, which occurs due to severely low oxygen during a stroke, can be exacerbated when your brain is low in oxygen—worsening the effects of a previous stroke.

Sleep disorders such as sleep apnea (breathing repeatedly stops and starts while you sleep) commonly coexist with COPD, and they may further increase problems and symptoms associated with transient nocturnal desaturation.


COPD is a lung disease, and it causes a decrease in blood oxygen saturation levels during the day and at night.

Oxygen is needed to sustain your organs, and red blood cells carry oxygen from the lungs to the rest of your body. When these cells are full of oxygen, or near full, they are described as saturated. Normal oxygen saturation levels range between 95% and 100%.

When breathing is compromised, as with COPD, the lungs cannot expand as they normally should. Blood vessels often become inflamed, impairing blood flow and oxygen diffusion. This is what causes transient nocturnal desaturation.

Lower daytime oxygen saturation in COPD (below 92%) is commonly associated with transient nocturnal desaturation.


If you have COPD, your healthcare provider may give you screening tests to identify whether you also have transient nocturnal desaturation. At-home, noninvasive tests, as well as long-term overnight tests in a supervised medical setting, can help detect transient nocturnal desaturation.

Home Oximetry

Home oximetry is a test that your healthcare provider may prescribe for you to use on your own. This involves placing a small clip-on device on your finger to measure your oxygen saturation level while you sleep.

Your practitioner will receive a report on the oxygen levels recorded during the device's use. Some home oximeters also have an alarm that sounds when oxygen saturation falls below a certain level.

With transient nocturnal desaturation, your oxygen saturation level would be expected to drop more than 4% below your normal daytime level for at least five minutes while you are asleep.

Sleep Study

Another tool that is useful in identifying transient nocturnal desaturation and other sleep disorders is an overnight polysomnograph (PSG), also called a sleep study.

Sleep studies are performed in a dedicated sleep center, where you'll stay overnight and be monitored by a trained technician. The study equipment simultaneously records various physiological parameters that are related to sleep and wakefulness, including breathing, heart rate, oxygen levels, muscle activity, and eye movements.

Blood Tests

While a pulse oximeter can approximate your blood oxygen saturation, an arterial blood test is more precise. A change in oxygen saturation can be measured with an arterial blood gas sample. This test can be used to detect hypercapnia (too much carbon dioxide) and hypoxemia (too little oxygen). Changes in these levels will occur during sleep if you have transient nocturnal desaturation.


Treatment for transient nocturnal desaturation in COPD usually involves oxygen therapy, which results in the placement of a small plastic tube with two small plastic prongs in your nostrils. The prongs have openings through which oxygen is delivered to your nose. Alternatively, a face mask can be placed over your nose and mouth to deliver oxygen.

This treatment can increase the amount of oxygen that you take in as you inhale, which improves your blood oxygen saturation. If your treatment is effective, you may start to notice an improvement in your daytime energy level.

When you use an oxygen machine at home, you will be given safety instructions. For example, your oxygen source should not be near an open flame.

If you are already using oxygen during the day for your COPD, your healthcare provider may prescribe a higher oxygen concentration for you while you sleep to prevent episodes of transient nocturnal desaturation.

A Word From Verywell

Transient nocturnal desaturation is not an immediately noticeable effect of COPD, but it can have serious health consequences. If you have advanced COPD, your healthcare provider will likely screen you for transient nocturnal desaturation.

Keep in mind that the condition is not curable, and the best way to prevent it from worsening is to avoid factors that exacerbate COPD, such as smoking and exposure to airborne irritants like dust and pollution.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Deborah Leader, RN
 Deborah Leader RN, PHN, is a registered nurse and medical writer who focuses on COPD.