What is the first step in interpreting an ABG?
Identify whether the pH indicates acidaemia or alkalaemia.
After checking pH, what should you assess next?
Determine whether the cause is respiratory or metabolic by analysing PaCO₂ and HCO₃⁻.
What does a raised PaCO₂ suggest in the context of a low pH?
Respiratory acidosis.
What does a low PaCO₂ suggest in the context of a high pH?
Respiratory alkalosis
What does a low HCO₃⁻ suggest in the context of a low pH?
Metabolic acidosis.
What does a raised HCO₃⁻ suggest in the context of a high pH?
Metabolic alkalosis.
What is the difference between respiratory failure type 1 and type 2?
Type 1
* Hypoxemia
* low O2 and normal/low CO2 levels
Type 2
* Hypercapnic
* Low oxygen and high CO2
What clinical signs might prompt ABG analysis?
Altered consciousness, respiratory distress, or unexplained hypoxaemia.
What is the role of ABGs in oxygen therapy decisions?
ABGs help determine the need for and type of oxygen therapy or NIV.
What does partial compensation mean in ABG interpretation?
The body is attempting to correct the pH, but it hasn’t returned to normal.
What does full compensation mean?
The pH has returned to normal, but the underlying abnormality remains.
What might cause respiratory acidosis?
COPD, drug overdose, or neuromuscular weakness affecting ventilation.
What might cause metabolic acidosis?
Diabetic ketoacidosis, renal failure, or sepsis.
What might cause respiratory alkalosis?
Anxiety, pain, or early asthma exacerbation causing hyperventilation.
What might cause metabolic alkalosis?
Vomiting, diuretic use, or excessive bicarbonate intake.
