Summary ABG Interpretation Made Easy: Tic-Tac-Toe & R.O.M.E Method (NCLEX/USMLE)

ABG Interpretation Made Easy
The Ultimate Cheat Sheet for Medical & Nursing Exams




1. Normal ABG Values (The Must-Knows)



• pH: 7.35 — 7.45
• PaCO2: 35 — 45 mmHg (Respiratory Acid)
• HCO3 (Bicarb): 22 — 26 mEq/L (Metabolic Base)




2. The R.O.M.E Method

A quick way to remember the relationship:

• R.O: Respiratory Opposite (pH ↑, PaCO2 ↓ = Alkalosis | pH ↓, PaCO2 ↑ = Acidosis)
• M.E: Metabolic Equal (pH ↑, HCO3 ↑ = Alkalosis | pH ↓, HCO3 ↓ = Acidosis)


3. Tic-Tac-Toe Interpretation Method


ACIDOSIS NORMAL ALKALOSIS

pH < 7.35 pH 7.35 - 7.45 pH > 7.45


CO2 > 45 CO2 35 - 45 CO2 < 35


HCO3 < 22 HCO3 22 - 26 HCO3 > 26