What overnight oxygen saturation (SPO2) range creates sleep apnea concerns?

From the Guidelines

Oxygen saturation levels below 90% during sleep are concerning for sleep apnea, with more severe cases showing drops to 85% or lower, and repeated episodes throughout the night. Specifically, if a person's SpO2 drops below 90% for more than 5% of their total sleep time, this is considered clinically significant and may indicate sleep apnea or other sleep-related breathing disorders 1. These oxygen desaturations occur when breathing stops or becomes shallow during apnea events, causing blood oxygen levels to fall. The frequency, duration, and severity of these drops help determine the severity of sleep apnea.

Some key points to consider when evaluating overnight oxygen saturation levels for sleep apnea concerns include:

• A study of healthy participants showed that desaturation routinely occurred with a mean minimum SaO2 ‘nadir’ of 90.4% during the night, with a 2SD range of 84.2–96.6% 1.
• The American College of Physicians guideline defines hypopneas as a ≥30% decrease in nasal flow with a ≥4% oxygen desaturation, and obstructive sleep apnea (OSA) as an apnea-hypopnea index (AHI) ≥5/hr 1.
• Another study used a definition of hypopneas as a ≥50% decrease in nasal flow with a >3% oxygen desaturation 1.
• The body responds to these low oxygen levels by briefly awakening to restore normal breathing, leading to fragmented sleep and daytime symptoms like fatigue and cognitive impairment.

If overnight oxygen monitoring shows concerning desaturations, further evaluation with a comprehensive sleep study is typically recommended to confirm the diagnosis and determine appropriate treatment. It is essential to consider the individual's overall health, medical history, and sleep patterns when interpreting overnight oxygen saturation levels and determining the need for further evaluation or treatment.

From the Research

Overnight SPO2 Range and Sleep Apnea Concerns

• The overnight oxygen saturation (SPO2) range that creates sleep apnea concerns is typically considered to be below 90% 2, 3.
• Oxygen saturation levels below 90% are considered harmful and can lead to intermittent oxygen desaturation associated with periods of apnea or hypopnea 2.
• A study found that severe nocturnal hypoxemia (NH) with a mean SpO2 (MSpO2) < 90% was associated with blunted glomerular filtration rate (GFR) and renal plasma flow (RPF) responses to angiotensin-II, indicating a potential risk for renal damage 3.
• Another study suggested that the time below 90% of SpO2 during sleep (T90%) may be an important marker of wellness in clinical and community-based scenarios, with every 1 SD increase in T90% associated with an adjusted hazard ratio of 1.18 [95% CI: 1.10-1.26] for all-cause mortality 4.
• The American Academy of Sleep Medicine recommends that patients with obstructive sleep apnea (OSA) who experience oxygen saturation levels below 90% for more than 5 minutes should be considered for treatment with positive airway pressure therapy or other interventions 5.

Key Findings

• Oxygen saturation levels below 90% can lead to sleep apnea concerns and potential health risks.
• Severe nocturnal hypoxemia with MSpO2 < 90% is associated with renal damage and increased risk of cardiovascular morbidity and mortality.
• T90% may be a useful marker for predicting sleep apnea-related health risks and guiding treatment decisions.
• Positive airway pressure therapy and other interventions may be effective in reducing sleep apnea-related health risks in patients with oxygen saturation levels below 90%.