Key Concepts
Introduction
Arterial blood gas (ABG) analysis is a bedside diagnostic tool that measures the adequacy of oxygenation, ventilation, and acid-base balance. For NCLEX-RN Canada, ABG interpretation is high-yield — it appears in questions about respiratory distress, COPD, mechanical ventilation, metabolic disorders, and sepsis. Normal ABG values (remember these exactly): - pH: 7.35–7.45 (acidosis < 7.35; alkalosis > 7.45) - PaCO₂: 35–45 mmHg (respiratory component — 'acid tank') - HCO₃⁻: 22–26 mEq/L (metabolic component — 'base buffer') - PaO₂: 80–100 mmHg (oxygenation) - SaO₂: 95–100% - Base excess: –2 to +2 Quick memory tool — ROME: - Respiratory Opposite: pH and PaCO₂ move in opposite directions (↑CO₂ → ↓pH; ↓CO₂ → ↑pH) - Metabolic Equal: pH and HCO₃⁻ move in the same direction (↑HCO₃ → ↑pH; ↓HCO₃ → ↓pH) On the exam, writers often pair stable-sounding options with unstable data—notice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan: breathing work and oxygenation, perfusion and end organs, neuro...