Arterial blood gas interpreter
Classifies the acid-base disorder, the expected compensation, the anion gap and the delta gap.
When to use
Arterial blood gas where the primary disorder, expected compensation and anion gap reading are wanted.
Pearls and pitfalls
- Bicarbonate decides the metabolic disorder: below 22 is acidosis, above 26 is alkalosis.
- The metabolic acidosis window is 1.5 × bicarbonate + 8, with 2 mmHg on each side.
- The anion gap compares sodium with chloride plus bicarbonate and uses 12 as reference; elevated values suggest a high anion gap acidosis.
- The delta gap checks for another metabolic disorder: values outside minus 6 to plus 6 ask for a second reading of the picture.
Fill in the fields to see the result.
Formula
Metabolic: PaCO2 window from the disorder formula. Respiratory: expected pH when acute and when chronic. Anion gap = Na − (Cl + HCO3). Delta gap = (AG − 12) − (24 − HCO3).
Evidence
Published stepwise approach to blood gas interpretation, with the table of expected compensation per disorder and the anion and delta gap reading.
References
- Muntingh J, Saffari S, Kelly A. Mastering blood gas interpretation: a practical guide for primary care providers. S Afr Fam Pract. 2025;67(1):6058. doi:10.4102/safp.v67i1.6058
Frequently asked questions
What is Arterial blood gas interpreter?
Classifies the acid-base disorder, the expected compensation, the anion gap and the delta gap. Arterial blood gas where the primary disorder, expected compensation and anion gap reading are wanted.
How is the result calculated?
Metabolic: PaCO2 window from the disorder formula. Respiratory: expected pH when acute and when chronic. Anion gap = Na − (Cl + HCO3). Delta gap = (AG − 12) − (24 − HCO3).
How should the result be interpreted?
Published stepwise approach to blood gas interpretation, with the table of expected compensation per disorder and the anion and delta gap reading.
What are the sources?
Muntingh J, Saffari S, Kelly A. Mastering blood gas interpretation: a practical guide for primary care providers. S Afr Fam Pract. 2025;67(1):6058.