The 5-Step ROME Method
1
Check pH
Normal
7.35–7.45
↓ Low
< 7.35 = Acidosis
↑ High
> 7.45 = Alkalosis
2
Check PaCO₂
Normal
35–45 mmHg
↓ Low
< 35 = Respiratory Alkalosis
↑ High
> 45 = Respiratory Acidosis
3
Check HCO₃⁻
Normal
22–26 mEq/L
↓ Low
< 22 = Metabolic Acidosis
↑ High
> 26 = Metabolic Alkalosis
4
Match the Culprit
Normal
Which value matches the pH direction?
↓ Low
CO₂ matches → Respiratory
↑ High
HCO₃ matches → Metabolic
5
Check Compensation
Normal
Is the OTHER value trying to correct?
↓ Low
Normal = Uncompensated
↑ High
Abnormal = Partially/Fully compensated
6 Practice ABG Scenarios
| Condition | pH | PaCO₂ | HCO₃⁻ | Interpretation | Compensation |
|---|---|---|---|---|---|
| DKA | 7.28 | 28 | 14 | Metabolic Acidosis | Partially Compensated |
| COPD Exacerbation | 7.32 | 58 | 32 | Respiratory Acidosis | Partially Compensated |
| Anxiety / Hyperventilation | 7.52 | 28 | 24 | Respiratory Alkalosis | Uncompensated |
| Prolonged Vomiting | 7.48 | 42 | 30 | Metabolic Alkalosis | Uncompensated |
| Renal Failure | 7.30 | 32 | 16 | Metabolic Acidosis | Partially Compensated |
| PE with Hypoxemia | 7.50 | 30 | 24 | Respiratory Alkalosis | Uncompensated |
Frequently Asked Questions
What is the ROME method for ABG interpretation?
ROME stands for Respiratory Opposite, Metabolic Equal. In respiratory disorders pH and PaCO₂ move in OPPOSITE directions (pH up = CO₂ down). In metabolic disorders pH and HCO₃ move in the SAME direction (pH down = HCO₃ down).
What are normal ABG values?
pH 7.35–7.45, PaCO₂ 35–45 mmHg, HCO₃ 22–26 mEq/L, PaO₂ 80–100 mmHg, SaO₂ 95–100%.
How do I tell if an ABG is compensated?
Both abnormal + pH normal = fully compensated. Both abnormal + pH abnormal = partially compensated. Only one abnormal = uncompensated.
What ABG pattern occurs in DKA?
Metabolic acidosis: pH <7.35, low HCO₃ (<22), compensatory low PaCO₂ (<35) from Kussmaul breathing. Typical: pH 7.28, PaCO₂ 28, HCO₃ 14.