ABG Interpretation

A guide to understanding Arterial Blood Gases.

ABG Challenge

Test your interpretation skills with a clinical scenario.

"A 68-year-old male with a history of COPD presents to the ER with increased shortness of breath and wheezing. He appears drowsy and is difficult to arouse."

pH

7.28

PaCO2

55

HCO3

24

Normal Values

Reference ranges for ABG components.

ComponentNormal Range
pH7.35 - 7.45
PaCO235 - 45 mmHg
HCO322 - 26 mEq/L

The ROME Mnemonic

A simple way to remember interpretation.

Respiratory = Opposite

If pH is ↑ and PaCO2 is ↓ (or vice versa), it's a respiratory problem.

Metabolic = Equal

If pH is ↑ and HCO3 is ↑ (or vice versa), it's a metabolic problem.

Acid-Base Imbalances

Common causes for the four primary imbalances.

ImbalanceABG ValuesCommon Causes
Respiratory Acidosis↓ pH, ↑ PaCO2, Normal HCO3Hypovoventilation, COPD, pneumonia, drug overdose (opioids, sedatives), atelectasis, respiratory muscle weakness.
Respiratory Alkalosis↑ pH, ↓ PaCO2, Normal HCO3Hyperventilation due to anxiety, fear, pain, hypoxia, fever, mechanical over-ventilation.
Metabolic Acidosis↓ pH, Normal PaCO2, ↓ HCO3Diabetic ketoacidosis (DKA), severe diarrhea, renal failure, shock, sepsis, starvation.
Metabolic Alkalosis↑ pH, Normal PaCO2, ↑ HCO3Severe vomiting, excessive NG suctioning, diuretic therapy (loss of K+), excessive bicarbonate intake.