ABG Interpretation Practice
Clinical SBA questions covering every ABG pattern tested in UKMLA, PLAB, and finals.
← Back to HomeArterial blood gas (ABG) interpretation is a core clinical skill tested in UKMLA AKT, PLAB 1, and medical school finals. Questions typically present a clinical scenario alongside ABG values and ask you to identify the acid-base disorder, degree of compensation, or most appropriate management. Med Qbank covers ABG interpretation within its respiratory, renal, and acute emergency topics.
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Frequently Asked Questions
What is the systematic approach to ABG interpretation?
Step 1 — pH: acidosis <7.35, alkalosis >7.45. Step 2 — pCO₂: if raised, primary respiratory acidosis; if low, primary respiratory alkalosis. Step 3 — HCO₃⁻: if raised, primary metabolic alkalosis; if low, primary metabolic acidosis. Step 4 — Compensation: assess whether the other component is moving in the same direction. Step 5 — pO₂: classify hypoxaemia and determine if Type 1 or Type 2 respiratory failure.
What ABG patterns come up most in exams?
High-yield patterns: Type 1 respiratory failure (low pO₂, normal/low pCO₂ — causes: PE, pneumonia, pulmonary oedema), Type 2 respiratory failure (low pO₂, raised pCO₂ — causes: COPD, neuromuscular disease), DKA (metabolic acidosis, low HCO₃⁻, raised anion gap), aspirin overdose (mixed respiratory alkalosis and metabolic acidosis), and chronic COPD with compensated respiratory acidosis.
What is the difference between Type 1 and Type 2 respiratory failure?
Type 1 (hypoxaemic) respiratory failure: pO₂ <8 kPa with normal or low pCO₂. The lungs cannot oxygenate but can still excrete CO₂. Causes include PE, pneumonia, and pulmonary oedema. Type 2 (hypercapnic) respiratory failure: pO₂ <8 kPa with pCO₂ >6 kPa. There is failure of both oxygenation and ventilation. Causes include COPD, chest wall deformity, and neuromuscular disease.
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