Arterial Blood Gas (ABG) Analysis – Interpretation Guide

This document is a concise study guide on arterial blood gas (ABG) analysis, covering the purpose of ABG (assessing oxygenation, ventilation, and acid-base balance), common arterial puncture sites (radial, brachial, femoral), normal ABG values (pH 7.35–7.45, PaCO₂ 35–45 mmHg, HCO₃ 22–30 mEq/L, PaO₂ 72–104 mmHg, SaO₂ 95–100%), and interpretation of four primary acid-base disorders: respiratory acidosis (pH 7.35, PaCO₂ 45 mmHg – CO₂ accumulation), respiratory alkalosis (pH 7.45, PaCO₂ 35 mmHg – hyperventilation), metabolic acidosis (pH 7.35, HCO₃ 22 mEq/L – tissue hypoperfusion, lactic acid, salicylate/methanol/ethylene glycol/iron toxicity), and metabolic alkalosis (pH 7.45, HCO₃ 26 mEq/L – excessive acid loss from vomiting/NG suction or bicarbonate retention). The guide also includes a compensatory changes table, the “R-O-M-E” mnemonic (Respiratory Opposite, Metabolic Equal) for pH vs. PaCO₂/HCO₃ relationships, and levels of compensation (uncompensated – PaCO₂ or HCO₃ normal; partially compensated – both abnormal, pH abnormal; fully compensated – pH normal but PaCO₂ and HCO₃ abnormal). Suitable for nursing students, medical students, respiratory therapists, and healthcare professionals learning ABG interpretation.