Expected HCO3 (respiratory alkalosis)
Expected HCO3 in respiratory alkalosis (Gennari 1972): the appropriate-compensation band vs the measured HCO3.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Measured PaCO2
- 25 mmHg
- Measured HCO3
- 21 mEq/L
- Acute or chronic
- Acute
Result: Expected HCO3 21 mEq/L (acute, -2 per 10 mmHg, floor ~18): the measured 21 mEq/L matches the expected 21 mEq/L (+/-2), consistent with appropriate compensation.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Reading
- a measured HCO3 below the expected band suggests an added metabolic acidosis; above it, an added metabolic alkalosis.
What you enter
- Measured PaCO2
- Measured HCO3
- Acute or chronic
How this is calculated
- Formula
- expected HCO3 = 24 - k x (40 - PaCO2)/10; k = 2 acute, 4 chronic (4-5 range); not below a physiologic floor (~18 acute, ~12 chronic).
Gennari FJ, Goldstein MB, Schwartz WB. The nature of the renal adaptation to chronic hypocapnia. J Clin Invest. 1972;51(7):1722-1730. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.