Calculates arterial carbon dioxide tension from pH and bicarbonate using Henderson–Hasselbalch.
Overview
Calculates arterial carbon dioxide tension from pH and bicarbonate using Henderson–Hasselbalch.
Clinical Significance
Rearranges the Henderson–Hasselbalch equation and may help check internal consistency of blood-gas values.
When to Use
- Use when the required measurements are available, reliable and clinically relevant.
How It Is Calculated
- PaCO₂ = HCO₃⁻ / [0.03 × 10^(pH − 6.1)].
Interpretation
- Rearranges the Henderson–Hasselbalch equation and may help check internal consistency of blood-gas values.
Worked Example
Enter valid values in the displayed units. MedicalC then applies: PaCO₂ = HCO₃⁻ / [0.03 × 10^(pH − 6.1)].
Limitations
- The result does not establish a diagnosis or mandate treatment.
- Measurement error may be more important than arithmetic precision.
- Published thresholds may differ between populations and settings.
Clinical Pearls
- Document the source values and units with the final result.
- Review trends rather than isolated values where appropriate.
Common Mistakes
- Using the wrong unit.
- Combining values from different time points.
- Applying the result outside the intended measurement or clinical context.
Frequently Asked Questions
What does this calculator provide?
Calculates arterial carbon dioxide tension from pH and bicarbonate using Henderson–Hasselbalch.
What formula is used?
PaCO₂ = HCO₃⁻ / [0.03 × 10^(pH − 6.1)].
Can the result be used alone?
No. It must be interpreted with the full clinical assessment and appropriate investigations.
What is the main limitation?
The result depends on accurate source measurements, correct units and appropriate clinical applicability.
References
- Henderson LJ, Hasselbalch KA. Henderson–Hasselbalch acid–base relationship. — Primary, supporting or authoritative reference for the implemented relationship.
Reviewed by: MedicalC Clinical Editorial Team
Last reviewed: July 2026