Blood gas abnormalities

Arterial blood gas interpretation algorithm

Key: (N) normal, ↓ decreased, ↑ increased.

pH	PaCO₂	Bicarbonate (HCO₃-)	Base Excess	Dx
(N)	(N)	(N)	(N)	Normal
(N)	↓	↓	↓	Metabolic acidosis - compensated
(N)	↑	↑	↑	Metabolic alkalosis - compensated
(N)	↑	↑	(N) / ↑	Respiratory acidosis - compensated
(N)	↓	↓	(N) / ↓	Respiratory alkalosis - compensated
↓	↓	(N)	↓	Metabolic acidosis - UNcompensated
↓	↓	↓	↓	Metabolic acidosis - PARTIALLY compensated
↓	(N)	↑	(N) / ↑	Respiratory acidosis - UNcompensated
↓	↑	↑	(N) / ↑	Respiratory acidosis - PARTIALLY compensated
↑	↑	(N)	↑	Metabolic alkalosis - UNcompensated
↑	↑	↑	↑	Metabolic alkalosis - PARTIALLY compensated
↑	(N)	↓	(N) / ↓	Respiratory alkalosis - UNcompensated
↑	↓	↓	(N) / ↓	Respiratory alkalosis - PARTIALLY compensated

Hypoventilation
- Chronic lung disease with CO₂ retention
- Severe acute lung disease (e.g. asthma)
- Respiratory depression (e.g. from drugs)
- Pulmonary oedema