If you draw a diagram make it a good one.*
Another rather obvious tip from the cynical anaesthetist you might say. However, every year the same sorts of errors are made by candidates with regards to the use of diagrams.
Some SAQs will specifically ask for a diagram. In this case your diagram must be correct- draw a nice big diagram that takes up at least half the page and label it clearly. Unlike the vivas this is your chance to have axes and units all detailed correctly with the curves or waveforms looking precise. Remember you just have a black pen so practise differentiating multiple curves if that is relevant eg. washin curve for three different agents. If you are not sure about something then best leave it out. There are two good UK exam primer books that deal with every possible diagram you could be asked to do: Graphic Anaesthesia and Physics, Pharmacology and Physiology for Anaesthetists. Of course the diagram must ultimately come from one of the set texts. Many candidates compile a set of diagrams that are examined frequently. Equipment SAQs lend themselves to diagrams.
Most SAQs won’t specifically ask for a diagram but a diagram may enhance your answer. If the diagram is not directly relevant to the question and/or incorrect then it will detract from your response, not enhance it. If your diagram is illustrating just one point or could be replaced with a phrase or line of text then it is probably best to leave it out. Then you don’t detract from your response with a potentially incorrect or poorly drawn diagram that took you two minutes to draw.
A few examples of good and bad use of diagrams from recent papers:
Describe the respiratory response to hypoxaemia in both the awake and anaesthetized patient– a discussion of the hypoxic ventilatory response is clearly relevant here and producing the diagram of PaO2 vs Minute Volume ventilation is a good idea. The diagram is simple, easy to draw and can be used to address the question well- drawing the normal curve and showing how it changes in the presence of anaesthetic agents.
Describe the clinical effects of NSAIDs including mechanisms through which they exert these effects– seems candidates are incapable of answering a SAQ on NSAIDs without producing the generic flow diagram showing the synthetic pathway beginning with membrane phospholipids. Many candidates attempt to produce this diagram which is not relevant to the question and takes up half a page and precious time.
Discuss the potential adverse effects of suxamethonium– please don’t draw the structure of sux. Again, it is not relevant and quite hard to do. Similarly diagrams relating to its mechanism of action are similarly unnecessary and tedious to produce. This SAQ is best addressed by churning out a list of adverse effects with a few lines between each one and then going back filling in detail until your ten minutes are up.
Describe how the large daily volume of glomerular filtrate is altered by the kidney to form a relatively low volume of concentrated urine– while the counter current mechanism is certainly relevant to this question, producing a diagram that explains the mechanism is quite difficult to do. Many candidates attempted drawing nephrons and counter current loops which invariably didn’t enhance their answer. Better to briefly describe the mechanism- you get marks just for writing down the term!
Compare and contrast the action potential from the sinoatrial node and a ventricular myocyte- although it doesn’t explicitly ask for a diagram clearly producing accurate diagrams of the two potentials would go a long way to passing this question. This is a question where if you don’t know the correct diagram you are in a world of pain. Core topics expect and demand a good degree of detail.
Explain the reasons why a pulse oximeter may give incorrect readings– resist the temptation to talk about how a pulse oximeter works. Resist the temptation to trot out the Beer-Lambert law. Resist the temptation to draw the diagram of wavelength vs extinction coefficient or the oxygen dissociation curve or SpO2 vs R value. Although the different absorption spectra of different forms of haemoglobin are very relevant to causing ‘incorrect ‘readings, that is a tough diagram to get right. Better to list the reasons and briefly explain each point than devote yourself to reproducing an unreasonably difficult diagram.
*No diagrams were used (or harmed) in this post.