Arterial Blood Gases (ABG)

An arterial blood gas (ABG) is a blood test that is performed taking blood from an artery, rather than a vein.  It is performed so that an accurate measurement of oxygen and carbon dioxide levels can be obtained, which then allows the patients oxygen to be delivered appropriately.  It is performed on patients in respiratory distress e.g. asthma attack.  This skill is one you should be familiar with and can be extended to involve the interpretation of blood gas results.

Subject steps

  1. Position the patient’s arm with the wrist extended.

  2. Put on your gloves and attach the needle to the heparinised syringe.

    Also prepare your local anaesthetic and give a small amount over the palpable radial artery.

  3. An extension to this station could be Blood gas interpretation. Before attempting to interpret the results you should know whether the patient was on room air or on oxygen when the sample was taken, and if on oxygen, what concentration.

    It is also useful to know whether the patient has a temperature or not, and this should be clearly written on the sample.

  4. The information below shows the changes in pH, CO2 and bicarbonate concentrations in different situations:

    Metabolic Acidosis

    pH:
    pCO2:
    Bicarbonate:

    Respiratory Acidosis

    pH:
    pCO2:
    Bicarbonate:

    Metabolic Alkalosis

    pH:
    pCO2:
    Bicarbonate:

    Respiratory Alkalosis

    pH:
    pCO2:
    Bicarbonate: