Normal Sleeping Pulse Oximeter Tracing Characteristics

Oxygen Saturation During Sleep

Healthy adults have greater variation in oxygen saturation when sleeping than while awake 1
The mean minimum oxygen saturation "nadir" during normal sleep is approximately 90.4% (±3.1%), with a 2SD range of 84.2-96.6% 2
For adults aged 20-30 years, they typically spend 10% of the night with oxygen saturation below 94.8% and half the night below 96.3% 2
For adults aged >60 years, they typically spend 10% of the night below 92.8% and half the night below 95.1% 2
The mean nadir for participants aged >60 years is 89.3% (±2.8%) 2

Older adults (>65 years) typically have lower baseline oxygen saturations than younger adults 3
The mean oxygen saturation for recumbent healthy men and women aged >70 years is approximately 95.0% 3
The 2SD range for recumbent healthy men aged >70 years is 92.5-98.1% 3
The 2SD range for recumbent healthy women aged >70 years is 91.5-98.2% 3

Transient desaturations are common and normal during sleep 2
A single "spot reading" of oxygen saturation on a sleeping person should be interpreted with caution 2
Ideally, oxygen saturation should be observed for a few minutes to differentiate between sustained hypoxemia and transient normal "nocturnal dips" 2

Alcohol and sedative drugs can exaggerate the variation in oxygen saturation during sleep 2
Obese patients with sleep apnea or hypopnea can desaturate to very low levels during sleep (often below 70%), which is abnormal 2
Motion artifacts can affect pulse oximetry readings and should be considered when interpreting unusual patterns 4
The British Thoracic Society recommends using pulse oximeters with a maximum signal averaging time of ≤3 seconds at a heart rate of 80 beats per minute or more for accurate detection of desaturations 4

Most experts emphasize the importance of keeping the oxygen saturation above 90% for most acutely ill patients 2
Sudden exposure to oxygen saturation below about 80% can cause altered consciousness even in healthy individuals 2
Prolonged significant hypoxemia (oxygen saturation <90%) can lead to adverse health outcomes including pulmonary hypertension and cognitive effects 5, 6
Type 1 respiratory failure is defined as PaO₂ <8 kPa or 60 mm Hg (equivalent to oxygen saturation of ~90%) with a normal or low PaCO₂ level 2