ABG normal values
Here are the normal ABG (Arterial Blood Gas) values:
| Parameter | Normal Range |
|---|---|
| pH | 7.35 - 7.45 |
| PaCO₂ | 35 - 45 mmHg |
| PaO₂ | 80 - 100 mmHg |
| HCO₃⁻ | 22 - 26 mEq/L |
| Base Excess (BE) | -2 to +2 mEq/L |
| SaO₂ | 95 - 100% |
| FiO₂ (room air) | 21% |
Quick memory aids:
- pH: 7.40 is the midpoint (acidic < 7.35, alkalotic > 7.45)
- PaCO₂: "40" is the anchor - respiratory acid/base regulator
- HCO₃⁻: "24" is the anchor - metabolic acid/base regulator
- A-a gradient (on room air): normally < 10-15 mmHg (increases with age)
Interpretation framework:
- Check pH - acidosis or alkalosis?
- Check PaCO₂ - respiratory cause?
- Check HCO₃⁻ - metabolic cause?
- Is there compensation? (partial or full)
- If metabolic acidosis, calculate anion gap: Na⁺ - (Cl⁻ + HCO₃⁻), normal = 8-12 mEq/L
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