Interpreting Arterial Blood Gas Results

Introduction to ABG Interpretation

The American College of Physicians recommends using a three-step systematic method to interpret ABG results: first evaluate pH to determine acidemia or alkalemia, then examine PaCO2 to identify the respiratory component, and finally evaluate base excess/bicarbonate to identify the metabolic component 1, 2

pH < 7.35 indicates acidemia, while pH > 7.45 indicates alkalemia, according to the American Thoracic Society 2
PaCO2 > 45 mmHg with low pH indicates respiratory acidosis, and PaCO2 < 35 mmHg with high pH indicates respiratory alkalosis, as stated by the American College of Chest Physicians 2
Base excess < -2 or HCO3 < 22 mmol/L indicates metabolic acidosis, and base excess > +2 or HCO3 > 26 mmol/L indicates metabolic alkalosis, according to the National Institute of Health 2

PaO2 < 60 mmHg indicates significant hypoxemia requiring intervention, and target SpO2 88-92% for COPD and hypercapnic respiratory failure, as recommended by the American College of Cardiology 2, 3
Target SpO2 94-98% for most other patients, according to the American Heart Association 3

Repeat ABG within 60 minutes after starting oxygen therapy or changing FiO2 in COPD patients, as suggested by the European Respiratory Society 3
Perform Allen's test before radial ABG to ensure dual blood supply to the hand, according to the American Society of Anesthesiologists 1, 3
Use local anesthesia for all non-emergency ABG sampling, as recommended by the American Academy of Family Physicians 3
Either arterial or venous blood can measure COHb levels, which are similar, as stated by the American Thoracic Society 4, 5