Does normal oxygen saturation on a wearable device (such as an Aura Ring) during sleep rule out sleep apnea?

Normal Oxygen Levels on Wearable Devices Do Not Rule Out Sleep Apnea

Normal oxygen saturation readings on wearable devices such as an Aura Ring during sleep do not rule out obstructive sleep apnea (OSA) and should not be used as the sole screening tool to exclude this diagnosis.

Why Wearable Devices Are Insufficient for OSA Diagnosis

Limitations of Oxygen Monitoring Alone

• Polysomnography (PSG) remains the gold standard for diagnosing OSA, measuring multiple parameters beyond just oxygen levels 1, 2
• OSA diagnosis requires measurement of apneas, hypopneas, and respiratory effort-related arousals (RERAs), which cannot be detected by oxygen monitoring alone 1
• The Apnea-Hypopnea Index (AHI) and Respiratory Disturbance Index (RDI) are the established metrics for OSA diagnosis, requiring measurement of airflow, respiratory effort, and arousals 2

Normal Oxygen Variations During Sleep

• Even healthy individuals experience oxygen desaturations during sleep, with studies showing mean minimum SpO2 "nadirs" of 90.4% (±3.1%) in normal subjects 1
• Healthy adults aged 20-30 years typically spend 10% of the night with SpO2 below 94.8%, while those aged 60+ spend 10% below 92.8% 1
• Patients with OSA can have intermittent desaturations that may be missed by spot readings or averaged measurements 1

Sleep Apnea Without Significant Desaturation

• Some patients with OSA may have respiratory events that cause arousals without meeting the threshold for significant oxygen desaturation 1
• The 2007 AASM scoring manual specifically notes that apneas do NOT require associated arterial oxygen desaturation to be scored 1
• RERAs (respiratory effort-related arousals) by definition cause sleep disruption without significant desaturation but still contribute to OSA diagnosis 1

Research on Wearable Devices for OSA Detection

Recent studies have evaluated wearable ring oximeters for OSA detection:

• A 2024 study found that while the Wellue O2 ring showed good accuracy (AUC 0.91) for detecting moderate to severe OSA, it still missed cases, with sensitivity of 87.3% and specificity of 78.7% 3
• A 2022 study of the Circul ring oximeter showed 87% sensitivity and 83% specificity for detecting OSA at AHI ≥5, meaning 13% of OSA cases were missed 4
• Another 2022 study found that combining respiratory effort signals with SpO2 provided better performance than SpO2 alone 5

Proper Diagnostic Approach

Recommended Testing Methods

• In-laboratory polysomnography (Type I) remains the gold standard for OSA diagnosis 2
• Home sleep apnea testing (HSAT) with multiple channels (Type III) measuring airflow, respiratory effort, and oxygen saturation is an acceptable alternative for patients with high pre-test probability of moderate to severe OSA 2
• Type IV testing (oxygen saturation only) has significant limitations and is not recommended as the sole diagnostic tool 2

Risk Factors Requiring Comprehensive Testing

• Patients with cardiorespiratory disease, neuromuscular disease, hypoventilation, opioid use, stroke history, or severe insomnia should undergo full polysomnography rather than limited channel testing 1
• Obesity increases the risk of significant desaturations during sleep, with levels potentially dropping below 70% 1

Clinical Implications

• Relying on normal oxygen readings from wearable devices may lead to missed diagnoses of OSA, delaying treatment and increasing risk of cardiovascular complications 2
• Untreated OSA is associated with increased morbidity (especially cardiopulmonary and metabolic diseases) and increased mortality 1
• If OSA is suspected despite normal oxygen readings on a wearable device, proper diagnostic testing with polysomnography or multi-channel home sleep testing should be pursued 2