Oxygen Saturation (SpO₂)

Monitor blood oxygen levels to assess respiratory and cardiovascular health

What is Oxygen Saturation?

Oxygen saturation (SpO₂) is the percentage of hemoglobin in your blood that's carrying oxygen. It's measured using pulse oximetry (typically via Apple Watch or dedicated devices).

A reading of 98% SpO₂ means 98% of your hemoglobin molecules are saturated with oxygen.

Why Oxygen Saturation Matters

SpO₂ reflects how well your lungs are oxygenating blood and how effectively oxygen is delivered to tissues:

  • Indicates respiratory and cardiovascular function
  • Can detect hypoxemia (low blood oxygen) early
  • Important for monitoring chronic lung conditions (COPD, asthma)
  • Can indicate sleep apnea when measured overnight
  • Useful for high-altitude acclimatization monitoring

Oxygen Saturation Ranges

Normal Range

95-100% - Normal oxygen saturation for most healthy adults

Hypoxemia (Low Oxygen)

<90% - Low oxygen levels requiring medical attention (Mayo Clinic)

Sustained readings below 90% indicate hypoxemia and should be evaluated by a clinician.

Special Considerations

  • Chronic lung disease - Baseline SpO₂ may be 88-92% (consult clinician for target range)
  • High altitude - SpO₂ naturally decreases at elevation (e.g., 90-95% at 8,000-10,000 feet)
  • During sleep - Temporary dips to 88-90% can be normal; sustained low values may indicate sleep apnea

How Cardio Analytics Uses SpO₂ Data

  • Shows SpO₂ trends - Track oxygen saturation over time (daily, weekly, monthly)
  • Alerts for sustained low values - Warnings when readings consistently fall below 90%
  • Overnight monitoring - Identify patterns of nocturnal desaturation (possible sleep apnea)
  • Graceful degradation - If your device doesn't record SpO₂, the card is automatically hidden

⚠️ Not all devices support SpO₂: Apple Watch Series 6 and later support blood oxygen measurement. Older models won't have this data.

HealthKit Data Types

Cardio Analytics reads SpO₂ data from Apple HealthKit using this identifier:

  • oxygenSaturation - Blood oxygen saturation as a fraction (0.0-1.0, displayed as percentage) (Apple Docs)

Learn More About HealthKit Integration

Tips for Accurate SpO₂ Measurement

  • Warm hands - Cold fingers can affect accuracy
  • Stay still - Movement can disrupt the reading
  • Remove nail polish - Can interfere with pulse oximetry sensors
  • Proper watch fit - Apple Watch should be snug but comfortable on your wrist
  • Rest your arm - Place arm at heart level, relaxed on a table

Scientific References

  1. Mayo Clinic. Low blood oxygen (hypoxemia). https://www.mayoclinic.org/symptoms/hypoxemia/basics/definition/sym-20050930

View All References

Track Your Oxygen Saturation with Cardio Analytics

Monitor SpO₂ trends and receive alerts for sustained low oxygen levels.

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