SpO₂ (Peripheral Saturation of Pulmonary O₂) refers to the oxygen saturation level measured in peripheral tissues (usually the fingertips or earlobes) using a pulse oximeter.
Key Points About SpO₂:
- Normal Range: 95–100% (at sea level, in healthy individuals).
- 90–94%: May indicate mild hypoxia (concerning in some patients).
- < 90%: Considered hypoxemia (requires medical attention).
- Measurement Method: Uses light absorption (red & infrared) to estimate oxygen bound to hemoglobin.
- Limitations:
- Less accurate in poor circulation, nail polish, dark skin pigmentation, or motion artifacts.
- Does not measure CO₂ or ventilation efficiency (for that, an arterial blood gas (ABG) test is needed).
Causes of Low SpO₂:
- Respiratory conditions (COPD, pneumonia, asthma, COVID-19).
- Cardiac issues (heart failure, congenital defects).
- High altitude (reduced atmospheric O₂).
- Anemia or carbon monoxide poisoning (misleadingly normal/high SpO₂ in CO poisoning).
