Transient Nocturnal Desaturation in COPD

woman sleeping in bed
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Your blood is responsible for carrying oxygen to your organs and other tissues. However, sometimes at night, it doesn't carry as much oxygen as usual. This problem is called transient nocturnal desaturation, which in simple terms means a temporary drop in your blood's oxygen levels from their normal, daytime levels ("oxygen saturation" is the level of oxygen your blood is carrying).

Transient nocturnal desaturation is a common problem in people with chronic obstructive pulmonary disease — it may affect up to 38% of those with COPD.

Risk Factors

Healthy people with normal lung function usually have oxygen saturation levels of between 95% and 100%. This means their red blood cells are operating close to or at full oxygen carrying capacity.

People with COPD tend to have lower oxygen saturation levels than normal. Some studies have concluded that daytime oxygen saturation levels of less than or equal to 93% can predict a higher risk of transient nocturnal desaturation in people with stable COPD.

Specifically, for someone to be diagnosed with transient nocturnal desaturation, their daytime oxygen saturation level must drop more than 4% from their normal daytime level for at least five minutes while they're asleep.


Transient nocturnal desaturation can occur when your breathing slows during sleep. This is known as hypoventilation.

Hypoventilation may lead to alterations in arterial blood gases such as hypercapnia (too much carbon dioxide) and hypoxemia (too little oxygen) in COPD patients, especially during REM sleep. These alterations may lead to increased episodes of arousal and sleep disruption, pulmonary hypertension and a higher death rate. Additionally, having other sleep disorders such as sleep apnea may further increase problems and symptoms associated with transient nocturnal desaturation.

Transient nocturnal desaturation also can occur due to what's called a ventilation/perfusion mismatch, which means the timing of your breathing is mismatched with the timing of your blood circulating through your lungs. This is another common problem in COPD patients.

Screening Considerations

In people with moderate to severe COPD who are suspected to have transient nocturnal desaturation, home oximetry is an effective tool in screening for this condition.

Overnight home oximeters measure oxygen saturation levels during sleep and are equipped with alarms that sound when oxygen saturation falls below a certain level. They also record your oxygen saturation levels so that your healthcare provider can better evaluate you for transient nocturnal desaturation.

Another tool that is useful in identifying transient nocturnal desaturation and other sleep disorders is a sleep study, also known by the technical term overnight polysomnography (PSG).

Sleep studies are performed in a controlled environment, preferably a sleep center. When you're undergoing a sleep study, you'll 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.


Patients who have severe transient nocturnal desaturation would clearly benefit from prolonged oxygen therapy, particularly if there is evidence of daytime hypoxemia.

Additionally, if you are using oxygen during the day, you should talk to your healthcare provider about the possibility of needing more oxygen during sleep to prevent further desaturation during the night. People with COPD may also find that they get a better night's sleep using oxygen only at night, but, the benefit of this remains unclear.

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