Question 22

Describe how the values for PaO2, PaCO2, pH and bicarbonate are determined on a blood gas sample.

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College Answer

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