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What is it?
Arterial Blood Gases (or ABG) is a blood test taken from an artery, then analysed to find out the concentrations of various gases disolved in it.
What is measured?
The standard blood gas profile is:
- pH 7.35-7.45
- PaO2 10-13 kPa
- PaCO2 4.5-6 kPa
- HCO3- 22-25 mmol/L
- Base excess -2 to +2
What it means?
- Is the pH high or low? - low pH= acidosis and high pH = alkalosis.
- Is CO2 abnormal? - if so, is this in keeping with the pH change? - i.e. when pH↑, CO2↓ or pH↓, CO2↑. These changes point to a respiratory acidosis/alkalosis. If there is no abnormality in CO2, it may be there has been a compensatory change.
- Is the HCO3- abnormal? - if so, is this in keeping with the pH change? - i.e. (opposite to CO2 changes) when pH↑, HCO3-↑ OR pH↓ HCO3-↓ then the change is metabolic. Otherwise, there may again have been a compensatory change.