An ARCHEMentor Initiative

Advanced ABG Interpreter

Boston-first ABG interpretation with optional Copenhagen and Stewart comparison.

Medical disclaimer: This tool is for educational and clinical decision-support use only. It does not replace clinical judgment or patient-specific assessment.

ABG Inputs

Boston interpretation remains primary. Turn on comparison mode to add Copenhagen and Stewart.

pH Normal 7.35-7.45 PaCO2 (mmHg) Normal 35-45 HCO3 (mEq/L) Normal 22-26 PaO2 (mmHg) Normal 80-100 SaO2 (%) Normal 95-100

Sodium Na+ (mEq/L) Normal 136-145 Chloride Cl- (mEq/L) Normal 98-107 Albumin (g/dL) Normal 3.5-5.0 Albumin correction Apply to anion gap

Compare with Copenhagen and Stewart approaches

When enabled, the app adds a side-by-side comparison. Stewart uses a bedside simplified physicochemical model and lets you override optional analytes if available.

Handy Formulas

Quick bedside formulas commonly used in Boston, Copenhagen and Stewart interpretation.

Boston / Traditional

Anion gap = Na - Cl - HCO3

Albumin-corrected AG = AG + 2.5 x (4.0 - albumin)

Winter's formula = 1.5 x HCO3 + 8 (+/- 2)

Metabolic alkalosis expected PaCO2 = 0.7 x HCO3 + 21 (+/- 2)

Delta ratio = (AG - 12) / (24 - HCO3)

Copenhagen / Base Excess

Standard base excess = 0.9287 x ((HCO3 - 24.4) + 14.83 x (pH - 7.4))

Useful shorthand:

SBE < -2 = metabolic acidosis contribution

SBE > +2 = metabolic alkalosis contribution

Stewart / Simplified Physicochemical

SIDa = Na + K - Cl - lactate

Weak acids = albumin x 10 x (0.1204 x pH - 0.625) + phosphate x (0.309 x pH - 0.469)

SIDe = HCO3 + weak acids

SIG = SIDa - SIDe

Reference Articles

Selected articles relevant to the three acid-base frameworks used in the app.

Boston approach

Kimura S, Shabsigh M, Morimatsu H. Traditional approach versus Stewart approach for acid-base disorders: inconsistent evidence. SAGE Open Med. 2018;6:2050312118801252.

Copenhagen approach

Langer T, Brusatori S, Gattinoni L. Understanding base excess: merits and pitfalls. Intensive Care Med. 2022;48:1308-1310.

Stewart overview

Story DA. Stewart acid-base: a simplified bedside approach. Clin Biochem Rev. 2010;31(2):61-64.

Stewart introduction

Boyle M, Baldwin I. Introduction to an alternate view of acid/base balance: the strong ion difference or Stewart approach. Aust Crit Care. 2002;15(1):14-20.

Base excess reappraisal

Siggaard-Andersen and modern reviews summarized in base excess reloaded literature for metabolic component interpretation in critical care.

Albumin and weak acids

Figge J, Mydosh T, Fencl V. Serum proteins and acid-base equilibria: a follow-up. J Lab Clin Med. 1992;120(5):713-719.

About This Website

Development and academic contributors.

Initiative: An ARCHEMentor Initiative

Developed by: Dr Manjunath J (Dept of Nephrology, FMMC), Aditya M (Student), and Dr Archana S Bhat (Dept of Pathology, FMMC).

Advanced ABG Interpreter

ABG Inputs

Entered Values

Approach Comparison

Boston Details

Handy Formulas

Reference Articles

About This Website