What are the normal ranges for SpO2 (oxygen saturation) as measured by a pulse oximeter?

Normal Pulse Oximetry (SpO2) Ranges

For healthy adults, normal SpO2 ranges from 95-100%, with age-specific variations: younger adults (18-24 years) average 98% (range 96.1-97.7%), while adults ≥65 years average 95.8% (range 92.7-98.3%). 1

Age-Specific Normal Values

Young to Middle-Aged Adults

• Ages 18-24 years: Mean SpO2 98.0%, median 98%, interquartile range 97-99% 1
• Ages 25-34 years: Mean SpO2 97.6%, median 98%, interquartile range 97-99% 1
• Ages 35-44 years: Mean SpO2 97.2%, median 98%, interquartile range 96-99% 1
• Ages 45-54 years: Mean SpO2 96.8%, median 97%, interquartile range 96-98% 1

Older Adults

• Ages 55-64 years: Mean SpO2 96.3%, median 97%, interquartile range 95-98% 1
• Ages ≥65 years: Mean SpO2 95.8%, median 96%, interquartile range 95-98%, with 2SD range of 92.7-98.3% 1, 2

Elderly Patients (>70 years, recumbent position)

• Men: Mean SaO2 95.3% (2SD range: 92.5-98.1%) 1, 2
• Women: Mean SaO2 94.8% (2SD range: 91.5-98.2%) 1, 2

Clinical Target Ranges for Oxygen Therapy

Standard Patients (No COPD/Chronic Respiratory Failure)

Target SpO2: 94-98% 1, 3, 2

• This range ensures adequate oxygenation while avoiding both hypoxemia and hyperoxemia 1
• Patients with SpO2 <94% should be assumed hypoxic until proven otherwise and may require supplemental oxygen 3, 4
• SpO2 <90% represents a clinical emergency requiring immediate intervention 4

COPD or Risk of Hypercapnic Respiratory Failure

Target SpO2: 88-92% 1, 3, 2

• This lower target prevents CO2 retention in patients at risk for hypercapnia 1
• Adjust to 94-98% if PaCO2 is confirmed normal on blood gas analysis (unless history of previous hypercapnic respiratory failure requiring ventilation) 1

Post-Cardiac Arrest Patients

Target SpO2: 94-98% or PaO2 75-100 mm Hg (10-13 kPa) 1

• Avoid both hypoxemia and hyperoxemia in this population 1
• Be aware of increased risk of occult hypoxemia in patients with dark skin pigmentation 1

Important Clinical Considerations

Age-Related Decline

• Oxygen saturation naturally decreases with advancing age, with wider standard deviations in elderly populations reflecting greater physiological variability 1, 2
• The lower limit of normal for elderly patients (92.7%) is significantly below that of young adults (96.1%) 1

Positional Effects

• Recumbent (lying down) values are typically 0.5-1% lower than seated values in elderly patients 2
• During sleep, healthy elderly adults (>60 years) may experience mean nadir saturations of approximately 89.3% (±2.8%) 2

Measurement Accuracy Limitations

• Pulse oximeters have an accuracy of ±2% under optimal conditions 5
• Accuracy deteriorates significantly during hypoxemia, with multiple instances where SpO2 >90% despite actual SaO2 <90% 6
• Motion artifacts and low perfusion degrade performance across all pulse oximeter types 7
• Factors affecting accuracy include anemia, peripheral vasoconstriction, dark skin tone, and skin discoloration 4
• Critical caveat: Patients with dark skin have higher risk of occult hypoxemia (SpO2 >90% while actual arterial saturation <88%) 1

Relationship to PaO2

• SpO2 of 90% corresponds to PaO2 of approximately 60 mm Hg on the oxygen-hemoglobin dissociation curve 5
• Below 90% saturation, small decreases in PaO2 cause large decreases in SpO2, making this a critical threshold 5
• Normal PaO2 ranges: 90-110 mm Hg (12-14.7 kPa) for young adults, declining to 11.89 kPa (89 mm Hg) in adults >64 years 1

Risk of Hyperoxemia

• When oxygen is titrated based solely on SpO2 levels, 40% of patients with hyperoxemia (PaO2 >13.5 kPa) had SpO2 values within or below recommended target ranges 8
• Healthcare providers should be cautious about administering oxygen to patients without clear respiratory compromise, as these patients are at high risk for occult hyperoxia 8