There are a number of indications for capillary blood gas analysis:

• Anyone with an acute exacerbation of a chronic chest condition
• Anyone with impaired respiratory effort
• Patients with a low SpO2 (less than 92%)
• An outpatient non-urgent assessment of blood gases (arterial blood gases commonly used in an emergency department)
• Respiratory failure (acute or chronic)
• Respiratory, metabolic or mixed acid base disturbances, with or without compensatory mechanisms
• Ventilated patients (check sufficient pressures/ volume settings to maintain blood gases)
• Diagnostic test requiring multiple blood gas results, where SpO2 does not give enough information and there is no trained staff to place insert an arterial cannula (e.g. cardiopulmonary exercise testing, long term oxygen therapy, ambulatory oxygen therapy assessment)
• To assess supplementary oxygen requirements
• To identify ketoacidosis or acute poisoning

Capillary sampling should not be performed where there is:

• Inflamed, swollen or oedematous tissue
• Cyanotic or poorly perfused tissues
• Localised areas of infection
• Patient with shock

Relative contra-indications:

• Severe clotting or bleeding disorder
• Anti-coagulation therapy with uncontrolled INR