Question 9.1 from the second paper of 2008 asks of the bewildered candidates:
"Outline how pH, PCO2 and PO2 are measured in a blood gas analyser and briefly state the underlying principle behind each of those measurements."
The pass rate of 47% was pleasantly surprising, suggesting that many (if not all) of the candidates arose from an intellectually robust anaesthetic background. Judging by the college model answer, the bare minimum of expected knowledge resembles the contents of the following three paragraphs:
LITFL give a good overview, in sufficient detail for the time-poor exam candidate:
The best resource for this sort of stuff is the handbook and user guide for the blood gas machine. The brief brochure for our hometown machine can be found here, at the Radiometer website. There is also a comprehensive operations manual.
If one wishes for more information than LITFL, but less than the 160-page operations manual, one may find the desired level of detail at The Deep Picture; theirs is an excellent professional resource on this topic.
The Radiometer Blood Gas Handbook was once a valuable resource. However, it tried to explain what the parameters mean for clinical decisionmaking, rather than how they are measured. In any case, it is now gone; and the handbook-shaped hole it left in the Radiometer website now generates 404 errors.
If one wants to go to town on this topic, Severinghaus (yes, THE Severinghaus) has published a series of articles on this theme:
Severinghaus, John W., and Paul B. Astrup. "History of blood gas analysis. I. The development of electrochemistry." Journal of clinical monitoring 1.3 (1985): 180-192.
Severinghaus, John W., and Poul B. Astrup. "History of blood gas analysis. II. pH and acid-base balance measurements." Journal of clinical monitoring 1.4 (1985): 259-277.
Severinghaus, John W., and Poul B. Astrup. "History of blood gas analysis. III. Carbon dioxide tension." Journal of clinical monitoring 2.1 (1986): 60-73.
Severinghaus, John W., and Poul B. Astrup. "History of blood gas analysis. IV. Leland Clark's oxygen electrode." Journal of clinical monitoring 2.2 (1986): 125-139.
Severinghaus, John W., and Poul B. Astrup. "History of blood gas analysis. V. Oxygen measurement." Journal of clinical monitoring 2.3 (1986): 174-189.
Severinghaus, John W., and Poul B. Astrup. "History of blood gas analysis. VI. Oximetry." Journal of clinical monitoring 2.4 (1986): 270-288.
Severinghaus, John W., and Yoshiyuki Honda. "History of blood gas analysis. VII. Pulse oximetry." Journal of clinical monitoring 3.2 (1987): 135-138.
Lastly, a digression of truly ridiculous proportions exists in this very website. It is a diverticular sack-like outpouching in the form of a chapter on arterial blood gas interpretation.