Describe how the values for PaO2, PaCO2, pH and bicarbonate are determined on a blood gas sample.
A correct description of the Clarke electrode, Severinghaus and the pH electrode was expected to
attain a pass. Candidates who used correct depictions of these electrodes with annotated
description attracted higher marks. Most candidates didn’t comment on the temperature
correction and standardization to 37 degrees. There was partial understanding on the calculation
of HCO3 by most candidates. In general the question was poorly answered considering the wide
spread use of blood gas analysis