2013 Second Sitting SAQs

6 candidates passed (22.2%). Cardiac reflexes are fast-acting reflex loops between the heart and central nervous system that contribute to regulation of cardiac function and maintenance of physiologic homeostasis. It was expected candidates would include within their answer a mention of the stimulus and how it is sensed, the reflex arc and the resultant effect. Thus candidates could have mentioned the Baroreceptor Reflex/Carotid Sinus Reflex, Chemoreceptor, Bainbridge, Cushing, Oculocardiac and Bezold-Jarisch (involves response to ventricular stimuli, sensed by receptors within the LV wall that trigger vagal afferent type C fibers and the resultant triad of hypotension, bradycardia, and coronary artery dilatation) reflexes.

3 candidates passed (11.1%). Candidates should take note of how marks are apportioned to multi part questions and to avoid rewriting the same point more than twice. Generally there was a lack of sufficient breadth in knowledge in responses given for mechanism of action of anti-platelet drugs and sufficient depth of knowledge in relation to aspirin, in particular aspirin pharmacokinetics.

24 candidates passed (88.9%). This question was generally well answered with a good response being in some structured format, e.g. a mention, followed by a description for each function of the liver. For questions asking to outline a particular topic, a general overview of the topic is expected and not merely a “dot-point” list of the functions of the liver without actually delving into the way the liver does those functions. In general candidates should avoid making broad-brush statements, which do not get them any marks like “the Liver is the major organ in the body”. Candidates were expected to list, and provide an overview for each, function of the liver.

18 candidates passed (66.7%). A lack of understanding of the physics behind pulse oximetry was a common area of weakness amongst most candidates. Candidates were expected to mention the underlying principle of the “Beer Lambert” Law, absorption spectra and that the differential absorption of light at different wavelengths by different haemoglobin species is used to determine the fractions of haemoglobin types. Limitations should include mention of errors due to calibration as well as sources of false positive and false negative readings.

5 candidates passed (18.5%). In general, this question was not well answered. In particular candidates did not demonstrate sufficient depth of information. Nunn’s Applied Respiratory Physiology devotes an entire chapter to this topic (Ch. 12, in the 6th edition).

12 candidates passed (44.4%). Basal metabolic rate is the amount of energy liberated by catabolism of food per unit time, under standardised conditions. Knowledge of those conditions (e.g. after a night’s sleep, at rest and with no strenuous activity for at least 1 hour, a relaxed subject at a comfortable ambient temperature, at least 12 hours after a meal) was weak. Factors affecting (e.g. body temperature, various hormones, malnutrition, pregnancy, drugs, disease, etc.) it was often incomplete. Knowledge of measurement was very poor. Candidates were expected to describe the direct (e.g. by using a whole body calorimeter) and indirect (e.g. measuring oxygen consumption) methods.

4 candidates passed (14.8%). This was a straightforward question of core CICM material. Most candidates were able to describe the Fick equation as it related to clearance, and then relate it to Glomerular Filtration Rate (GFR). Formula relating GFR to serum creatinine were often quoted incorrectly, graphs poorly constructed and/or labelled and many answers were very superficially answered. Better candidates were able to relate the graph to functional nephron loss and hence serum creatinine. The non-linear relationship between nephron mass (and function) and the serum creatinine was poorly appreciated by many. The nature of the variability of creatinine production with age, sex, ethnicity etc. was often omitted, as were the factors involved in the variability in an ICU patient.

7 candidates passed (25.9%). The universal gas laws form the basis of oxygen therapy and delivery, pressure and volumetric monitoring as well as a key to understanding the solubility of gases in blood. All the equations and relationship are straightforward so this question provided a good opportunity to score marks. Unfortunately many candidates were aware of the properties of the ideal gases but not the named laws. This led many candidates to omit major sections of the answer and thus scored no marks. Several candidates wasted time with complicated diagrams as well as equations and descriptions (scoring no additional marks). Many candidates were unable to identify Grahams Law (rate of diffusion inversely proportional to the square root of the molecular weight) but included it in an expanded Fick’s Equation.

17 candidates passed (63.3%). In general this question was well answered; however candidates often had difficulty differentiating specifically for a massive blood transfusion (defined as replacement of circulating volume in 24 hours, or greater than 4 units blood transfused in 1 hour of continuing blood loss, or loss of 50% circulating volume in 3 hours). Responses to the first part of the question generally lacked depth. It is suggested that candidates take a systematic approach (e.g. use of categories such as immune, infectious, storage, etc.) when answering these type of questions. Candidates are reminded that when asked to “outline”, that the expectation for them to include a description that reflects understanding, and not just “dotpoints”.

13 candidates passed (48.1%). The skin is the largest organ of the body, accounting for about 15% of the total adult body weight, with a rich, but tightly regulated blood flow. It performs many vital functions, including the protection against external physical, chemical, and biologic threats, the prevention of excess water loss from the body and thermoregulation. It is composed of three principle layers, the epidermis, dermis and subcutaneous tissue, each with their own purpose. In addition candidates were expected to describe those aspects of the skin that play a role in physical protection, immune, sensory, thermoregulatory and water regulation. Candidates lacked a sufficient breath and depth of knowledge in this area and often digressed beyond areas specific to the skin (e.g. thermoregulation not specific to the skin).

3 candidates passed (11.1%). Knowledge of the anatomy of the sympathetic nervous system is important in helping to understand its physiology, and the pharmacology of drugs that affect it. Such information is widely available within most physiology, and even pharmacology texts when mentioning the sympathetic nervous system. In general candidates lacked depth and often were inaccurate in their description. A systematic approach (e.g. spinal levels, pre-ganglionic, post-ganglionic, etc.) was often lacking.

9 candidates passed (33.3%). Understanding the anatomy of the subclavian is essential knowledge in intensive care practice. It was expected that candidates mention where it starts, where it ends, relationship to surrounding structures (in all directions, i.e. medial, lateral, anterior, posterior, etc.) and surface anatomy. In general, relationships and/or surface anatomy was either poorly understood or not mentioned.

4 candidates passed (14.8%). Many candidates' answers included respiratory and other systems (e.g. endocrine) when only cardiovascular changes were asked for. Candidates are reminded to read the questions carefully. Poor candidates lacked detail of the progressive changes through the trimesters. Changes during (and immediately post) labour and delivery were often overlooked. This is listed as a core topic within the syllabus, that is readily covered by most physiology texts and candidates are expected to have a very sound knowledge of it.

In general, knowledge of the ECG changes of hyperkalaemia was lacking. Most candidates could list the
drugs used in hyperkalaemia, but few gave adequate detail of their mechanism of lowering potassium,
dosing, time to onset and duration of action. Many candidates mentioned dialysis or renal replacement
therapy which is not a drug therapy for hyperkalaemia; therefore no points were awarded for this.

11 candidates passed (40.8%). The pain pathways following arterial line insertion involve sensing the stimulus and transmitting the sensation to the central nervous system. It was expected candidates could provide some detail about the major features along this pathway including a description of sensors, nerve types, spinal cord input and decussation with subsequent projection to higher centres. Better answers provided additional details about modulation and descending pathways. The question also required a description of the physiology with some discussion of the mediators involved and explanation of how a stimulus or tissue may result in the perception of pain. Common omissions included insufficient detail of the pain pathway and limited or no discussion of the physiological components.

5 candidates passed (18.5%). This topic required a definition and understanding of airways resistance. It was expected candidates could identify that issues around the nature of flow (turbulent vs. laminar) and airway diameter were central determinants. It was expected candidates would describe the determinants of turbulent flow. The provision of formula and comments about Reynolds number helped demonstrate an understanding of this. Better answers discussed the transitional point in the airway and the paradox about size vs. total cross sectional area and its influence on total resistance. Several candidates confused pulmonary vascular resistance with airways resistance. Using graphs to help illustrate certain concepts would have been helpful. Measurement of resistance (indirectly via measurement of flow and pressure difference by a body plethysmography, spirometry) and detection of flow (spirometry, capnography) was in general poorly understood.

10 candidates passed (37.0%). It was expected candidates would expand on the central role haemoglobin has in oxygen delivery and that in the presence of reduced haemoglobin there are various efforts aimed at maintaining oxygen delivery. Cardiac output is increased, systemic vascular resistance is reduced, modifications are seen in regional circulations and as tissue oxygenation begins to falter then the end products of anaerobic metabolism provide a further stimulus to enhance cardiac out and tissue oxygen delivery. Better answers also included a mention of additional factors that enhance tolerance of chronic anaemia (e.g. angiogenesis).