2008 Second Sitting VIVAs

The initial information given to the candidates was - In this station you will be asked to draw and discuss a capnograph tracing. Draw a graph of partial pressure of CO2 versus time, from a ventilated patient, i.e. a ‘capnograph tracing’. This viva explored the candidates’ knowledge in relation to the following points Capnograph trace and information that can be ascertained from it Methods used to measure partial pressure of CO2 and the underlying principles ETCO2 and PaCO2 relationships and factors that influence it Capnograph and deadspace Examination feedback: General there was a lack of depth in the understanding of the capnograph. Specifically what it measures, principles of measurements and an understanding of deadspace.

The initial information given to the candidates was - What is normal cerebral blood flow? This viva explored the candidates’ knowledge in relation to the following points Cerebral Blood Flow, it’s measurement and factors that alter it Cerebral Blood Flow and acute changes in altitude Morphine, typical dose, CNS effects and metabolites Examination feedback: There was good understanding of cerebral blood flow, and most candidates used figures to good effect during the viva. Areas of weakness were an understanding of the methods of measuring CBF and differential flow to the white and gray matter. Candidates also were less confident with the different CNS effects of morphine. Adapting factual knowledge to define what would happen in states of altered physiology was also handled poorly.

The initial information given to the candidates was - You were asked by an intensive care nurse whether you would like to start some anti- hypertensive treatment for an ICU patient who had a very high arterial blood pressure (systolic 180mmHg, diastolic 60mmHg) displayed on the invasive haemodynamic monitor at the bedside. The ICU nurse said that the non-invasive oscillometric blood pressure monitor (systolic 140mmHg and diastolic 80mmHg) was much lower than the invasive blood pressure. Can you explain how a non-invasive oscillometric blood pressure monitor works? This viva explored the candidates’ knowledge in relation to the following points Principles of oscillometric blood pressure measurements, factors affecting accuracy Principles of invasive blood pressure measurement, factors affecting accuracy, resonance and damping Examination feedback: All candidates had a good understanding of the principles behind oscillometric blood pressure monitoring and its pitfalls. A good understanding on invasive blood pressure monitoring was also essential to pass this viva. The common weaknesses were 1) the effects of the intra-arterial catheter size or bore, catheter length, and compliance of the tubing on resonance and damping; 2) how to assess the damping factor at the bed side; and 3) what is the minimal requirement in terms of natural frequency of the measuring system in relation to the frequency of the blood pressure waveform to prevent resonance. Most candidates found it difficult to convert a heart rate of 60 per minute into frequency in Hz.

The initial information given to the candidates was - This station will explore the pharmacology related to analgesic medications. How will you classify non opioid analgesic agents? This viva explored the candidates’ knowledge in relation to the following points Classification of non opioids, mechanism of actions of non opioids Classification of opioids, mechanism of action, some aspects of their general pharmacology, contrasting fentanyl and morphine, tolerance to opioids Examination feedback: Generally candidates performed better at classifying non opioids in comparison to the opioids. There was also a lack of depth and breadth in knowledge related to opioid receptors

The initial information given to the candidates was - This station is mostly concerned with the pharmacology of drugs acting on the gastrointestinal tract. What is a prokinetic? This viva explored the candidates’ knowledge in relation to the following points Prokinetics, examples of prokinetics, mechanism of action, general pharmacology of metoclopramide GIT secretions Laxatives, mechanism of action of lactulose Octreotide, mechanism of action, general pharmacology, indications for use Examination feedback: This is an important, and potentially overlooked, area of clinical ICU practice. Candidates breadth and depth of knowledge for this important topic was lower than expected. In particular was mechanism of action of prokinetics, laxatives (of which most of the discussion centred around lactulose) and octreotide.

The initial information given to the candidates was - This viva will mostly cover pharmacology and physiology of insulin. Describe the primary function of insulin. This viva explored the candidates’ knowledge in relation to the following points Structure, mechanism of action and physiology of natural insulin Insulin preparations Pathophysiology of re-feeding syndrome Examination feedback: Candidates knowledge in relation to the physiology of insulin was good and much stronger than their knowledge in relation to the pharmacology of the different insulin preparations. It is important that candidates have a good understanding of the pharmacology of insulin preparations as well as remain up to date with changes in those preparations. Candidates also struggled with describing the basic elements, in particular the changes to electrolytes, associated with the re-feeding syndrome.

The initial information given to the candidates was - This station will explore your knowledge of the pharmacology and physiology of noradrenaline. Discuss the pharmacologic effects of noradrenaline on the human heart in-vivo. This viva explored the candidates’ knowledge in relation to the following points Pharmacology of noradrenaline Pressure-Volume Loop of the cardiac cycle Mark on the Pressure-Volume Loop the changes you would expect for an adult patient infused noradrenaline at 10 mcg/min. Explain the consequences of a noradrenaline infusion on myocardial oxygen consumption, work and efficiency. Dobutamine infusion of 5 mcg/kg/min and affect the Pressure-Volume Loop Examination feedback: This viva tested knowledge related to cardiac cycle, P-V loop, inotropes and most importantly a candidates ability to integrate those topics and then discuss them. Generally candidates knowledge in describing the basic P-V loop were sound, but were weaker in explaining how the P-V loop changed with changes in physiology and pharmacological intervention. Candidates were expected to generate discussions relating to the impact in changes to afterload, pre load and contractility as well as concept of potential energy as it elated to the P-V loop.

This station will explore aspects of respiratory physiology and related measurement. This chest X-ray shows complete collapse of the left lung. What pathophysiological processes might contribute to hypoxia in this patient?