Arterial Blood Gas (ABG) interpretation is a fundamental clinical skill that frequently appears in nursing exams. Understanding ABG values is essential for identifying a patient's acid-base status and determining necessary interventions.
Normal ABG Reference Values
- pH: 7.35 - 7.45 (Below 7.35 = Acidosis, Above 7.45 = Alkalosis)
- PaCO2: 35 - 45 mmHg (Respiratory indicator; high is acidic, low is alkaline)
- HCO3: 22 - 26 mEq/L (Metabolic indicator; high is alkaline, low is acidic)
- PaO2: 80 - 100 mmHg (Oxygenation status)
The ROME Mnemonic
To quickly determine the primary imbalance, remember: Respiratory Opposite, Metabolic Equal (ROME).
- Respiratory Acidosis: pH is Low (↓) and PaCO2 is High (↑) - Opposite directions.
- Respiratory Alkalosis: pH is High (↑) and PaCO2 is Low (↓) - Opposite directions.
- Metabolic Acidosis: pH is Low (↓) and HCO3 is Low (↓) - Equal/same direction.
- Metabolic Alkalosis: pH is High (↑) and HCO3 is High (↑) - Equal/same direction.
Clinical Tip: Always check if the pH is fully compensated (pH returns to normal range), partially compensated (all three values are abnormal), or uncompensated (one parameter remains normal while others are abnormal).
