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What is Transient Nocturnal Desaturation?

transient nocturnal desaturation, tnd, copdTransient nocturnal desaturation, also known as nocturnal hypoxemia, is defined as a temporary drop in oxygen saturation during sleep. The condition is a significant problem in COPD, affecting a relatively large number of COPD patients. In fact, one study suggests that 27-70% of COPD patients with daytime oxygen saturation levels of 90-95% experience substantial desaturation at night, particularly during a period of sleep known as rapid eye movement (REM) sleep. In people with severe COPD, desaturation during sleep is even more profound than desaturation during exercise, which is also common.[1]


The primary causes of transient nocturnal desaturation are:[2]

  • Hypoventilation – defined as abnormally slow breathing; a common condition found in people with COPD. Often leads to hypoxemia (low blood oxygen levels) and hypercapnia (high blood carbon dioxide levels).
  • Ventilation/perfusion (VQ) mismatch – also common in COPD; occurs when ventilation (the exchange of air between your lungs and the environment) and perfusion (the passage of blood through the lungs) are not equal. V/Q mismatch also leads to hypoxemia and hypercapnia in COPD patients.

Risk Factors

One study suggests that the only predictor of transient nocturnal desaturation is daytime oxygen saturation levels of less than or equal to 93%.2 Another study suggests that the best predictor of transient nocturnal desaturation is daytime carbon dioxide levels.[3] Another study found that obesity increases the risk and severity of sleep disordered breathing. One thing is certain when it comes to risk factors: updated scientific evidence is lacking on this subject.


To be diagnosed with transient nocturnal desaturation, your normal, daytime oxygen saturation level must drop at least 4% during sleep for at least 5 minutes. Monitoring your oxygen saturation levels at night involves using overnight continuous pulse oximetry.  This is a reliable, cost effective tool that automatically monitors and records information about your saturation levels while you sleep.1  Nocturnal oximetry is recommended to evaluate gas exchange during sleep in COPD patients.[4]


Although it’s been well-established that daytime hypoxemia is treated with long-term oxygen therapy (LTOT), treatment for transient nocturnal desaturation varies among physicians.[5] Developing a clear understanding of how prevalent nocturnal desaturation is in COPD – in the absence of other respiratory conditions – is an important step towards managing it in a standardized way.5

Nocturnal-Only Oxygen Therapy aka Oxygen Therapy During Sleep

At present, there are two groups of COPD patients that may benefit from the use of oxygen therapy during sleep:

  • Patients who normally require oxygen therapy during the day because of daytime hypoxemia.
  • Patients who don’t have daytime hypoxemia or use oxygen therapy during the day, but who experience a drop in their oxygen saturations when they sleep.

NOTE: Medicare will cover nocturnal-only oxygen therapy under certain circumstances. To read more about this and to see if you qualify, read Medicare’s Home Oxygen Therapy Guide.



[1] Owens, Robert L., MD. Supplemental Oxygen Needs During Sleep. Who Benefits? Respiratory Care. January 2013. Vol 58; No 1.
[2] Zanchet, Renata Claudia, & Viegas, Carlos Alberto de Assis. (2006). Nocturnal desaturation: predictors and the effect on sleep patterns in patients with chronic obstructive pulmonary disease and concomitant mild daytime hypoxemia. Jornal Brasileiro de Pneumologia32(3), 207-212. https://dx.doi.org/10.1590/S1806-37132006000300006.
[3] Robert Plywaczewski, MD, et. al. Incidence of Nocturnal Desaturation While Breathing Oxygen in COPD Patients Undergoing Long-term Oxygen Therapy. CHEST. 2000; 117:679–683).
[4][4] Fanfulla F, Cascone L, Taurino AE.Minerva Med. Sleep-disordered breathing in patients with the chronic obstructive pulmonary disease. 2004 Aug;95(4):307-21.
[5] Lacasse Y et. al. Evaluating nocturnal oxygen desaturation in COPD – revised. Respir Med. 2011 May 9.

5 thoughts on “What is Transient Nocturnal Desaturation?”

  1. Avatar moyashi says:

    Thanks, a good read.

  2. Avatar shelley kaiser says:

    I'm interested in getting an Inogen oxygen machine. Is it covered by insurance? I'm on medicare with a supplement.

    Thank You,
    Shelley Kaiser

    1. Inogen Inogen says:

      Hi Shelley, An Oxygen Specialist will contact you shortly.

  3. Avatar Catherine Taylor says:

    I do love my onegin but I wish you you were a Blue Shield provider. I have tried to contact other companies who provide the machine but I would much rather deal with you sincr I have had such good service for so long.

  4. Avatar Cynthia White says:

    Good article. I have used this test process with my pulmonologist. It showed that my levels during the night were stable.

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