An earlobe capillary blood gas is a reproducible blood sample that closely approximates an arterial blood sample. It is minimally invasive, taking a small volume of blood from an incision made by an automatic lancet. It can be easily distorted by errors in sampling and analysis, which we will cover later in the course.

What we do know:

• ELCBG’s are no different to ABG’s with regards pH, PaCO₂, SaO₂, HCO₃^– and Base Excess. The PaO₂ only differs significantly when a patient is breathing high flow Oxygen (FiO₂ >20kPa)
• Patients prefer having an ELCBG than an arterial sample.

It is worth reading this systematic review by C Kerry et al from Oxford University (below).

Taking a capillary blood sample is not quick process. It takes a little time to prepare the patient adequately:

• To stabilise the patient in anticipation for the resting measurement
• To adequately warm the ear
• To take the sample and analyse it.

However, when performed well, the results are comparable with an arterial sample, is safer for the patient and less painful. The technique also lends itself well for serial measurements.