2014 Second Sitting

2014B 01: 65% of candidates passed this question. This question was generally well answered. The poorer answers suffered for want of a useful classification system that enabled them to separate the various drug classes

2014B 03: 27% of candidates passed this question. Most answers were quite brief and superficial. They simply did not cover enough of the required knowledge base to gain a pass mark. A definition of PEEP is a useful way to start this answer and this was missing in more than half the answers. Deficiencies in knowledge included even the primary respiratory and cardiovascular effects of PEEP. Many candidates incorrectly concluded that PEEP would increase afterload and decrease pulmonary vascular resistance. Some candidates provided description of the cardiovascular effects of Valsalva, which was not part of the question. It was expected candidates would also mention physiological effects on other organ systems such as potential cerebral and renal effects. This topic (Level 1) requires a detailed knowledge and candidates should read widely to gain the depth of understanding required. The core material is covered in texts such as Nunn’s’ Applied Respiratory Physiology and additional applied information can be found in a variety of texts such as Textbook of Critical Care by Fink et al, Irwin and Rippe’s Intensive Care Medicine or Miller’s Anaesthesia.

2014B 04: 0% of candidates passed this question. Generally there was a lack of detailed knowledge, incorrect facts and at times confusion between the sympathetic and parasympathetic nervous system functions. A lack of anatomical detail was common (the origin of preganglionic cell bodies was not described clearly, and parasympathetic ganglia were not often named and located). It was expected an answer would mention the central role of Acetylcholine as a neurotransmitter at preganglionic and post ganglionic neurons in the parasympathetic system. Target organs were identified correctly but the exact action was not specified e.g. pupillary constriction vs. dilatation, GI sphincter/bladder - contraction vs. relaxation. Detail concerning receptor physiology was not required. This is a question covering a core topic that no candidate passed. An overview of the arrangement and function of the autonomic nervous system is provided in several core physiology texts, including Ganong and Guyton.

2014B 05: 8% of candidates passed this question. Very few candidates demonstrated understanding of this core topic. Candidates did not accurately define V/Q inequality and the physiological factors causing this phenomenon. V/Q scatter as well as true shunt (V/Q=0) and dead space (V/Q=∞) needed to be considered. The inability of high V/Q areas to compensate for low V/Q zones owing to the relatively small contribution of blood flow from these high V/Q units was not discussed. The differential effect of FiO2 on true shunt versus V/Q scatter was seldom explained. The shape of the oxy-Hb dissociation curve and CO2-dissociation curve were sometimes mentioned but their effect on arterial gas tensions not well explained. Often graphs were reproduced inaccurately and contradictory statements made, leaving the impression that candidates did not understand the basic concepts. It is core knowledge for Intensive Care Specialists managing respiratory failure. A sophisticated knowledge based on the chapter in Nunn is a minimum standard expected for this topic.

2014B 06: 23% of candidates passed this question. Many candidates did not read the question carefully and misinterpreted what was being asked. Candidates often digressed into a discussion of thermoregulation. Several candidates wrote about body's response to cold and heat rather than mechanisms of heat production and loss as was asked. There was confusion between mechanisms of endogenous heat production and measures to conserve heat. "Behaviour" only attracted marks in relation to voluntary muscle activity for heat production. Changing clothes or seeking a warm environment does not increase heat output by the body. Behaviour can reduce heat loss. Many candidates did not specify ambient or core body temperature. The definitions of Thermoneutral Zone and Interthreshold Range were not clear. Knowledge generally lacked detail and this was most evident when precise definitions were asked.

2014B 07: 15% of candidates passed this question. A structured approach would work well for this question but was often lacking. Many answers were superficial providing short lists of factors affecting NDMRs without reference to mechanism. Candidates failed to differentiate factors which potentiate NDMRs from those which inhibit the action of the drugs. Some confusion also existed confusing speed of onset kinetics with potentiation kinetics. Candidates who structured their answer into pharmacokinetic and pharmacodynamic factors generally scored better marks. Candidates who used pre-post synaptic type structure tended to omit kinetics completely from their answers. Incorrect facts were common.

2014B 08: 0% of candidates passed this question. It was expected candidates would cover all aspects of testing for each test listed. This would include normal, abnormal or therapeutic values, a comment on methods (either laboratory or point of care) and coagulation pathway assessment. General statements about the overall purpose of the test, collection methods, plasma vs whole blood as sample scored additional marks. Diagnoses or errors associated with abnormalities in each test would also have scored marks but were not mentioned in most answers. Overall there was a lack of depth of knowledge and incorrect facts. Many candidates knew about TEG, but did not know details about the other tests.

2014B 09: 8% of candidates passed this question. Triglycerides (TGs) consist of a 3 carbon glycerol backbone with 3 fatty acids attached. It was expected candidates would detail the fate from digestion and absorption, through distribution to storage and metabolism. Most candidates knew the absorptive processes very well but knowledge of TGs fate once it was packaged into a chylomicron was lacking. Some detail was expected on the passage to the liver via the portal circulation, packing and unpacking and distribution to the body. Very few candidates mentioned appropriate hormones and enzymes, target cells or ketogenesis. Some discussion was expected on the possible fate of acetyl Co A. Comment on the synthesis of lipids and the existence of essential fatty acids gained additional marks.

2014B 10: 65% of candidates passed this question. This question was generally well answered. Some candidates did not mention the factors which are peculiar to the coronary circulation and answered in a generic manner, as if for any vascular bed. The coronary circulation has a high O2-ER and flow-dependence. Many candidates seemed to lack a perspective that metabolic demand dominates control of the coronary arterial flow. The phasic nature of flow was best shown with a diagram and whilst "publication-level" graphs are not expected, the graph drawn must be factually correct and convey the principal similarities and differences. While this topic is covered in both Guyton and Ganong, additional detail can be found in the Mosby physiology monograph series: Cardiovascular Physiology, 10th Edition by Pappano and Wier,( the replacement of Berne and Levy).

2014B 11: 54% of candidates passed this question. Asthma involves reversible bronchospasm, inflammation, and airway hyper-responsiveness to inhaled stimuli. The main classes of drugs for acute therapy include sympathomimetics, antimuscarinic agents, corticosteroids, methylxanthines and magnesium. Candidates should have a detailed knowledge of the mode of action of these mainstream drugs. Information about drugs used for prevention and for chronic asthma was not asked for and answers which provided details about long term inhaled steroids or leukotriene antagonists did not gain extra marks. This question was well covered by some candidates in a semi-table format. A structured approach worked well with details about drug class, mechanism of action and example(s).

2014B 12: 27% of candidates passed this question. This is a complex but essential area of physiology for intensive care practice. It was expected candidates would indicate that non-volatile acids are those not able to eliminated by the lungs (lactate, sulphate, phosphate and ketone bodies). The kidney plays a central role via bicarbonate (resorbing filtered bicarbonate and generating “new” bicarbonate = acid excretion). It was expected candidates could detail the processes in various parts of the renal tubules and the role or urinary buffers (dibasic phosphate and ammonia). While a number of candidates were able to provide some of the details of ion transports in the kidney, few showed understanding of the overarching concepts of the proximal bicarbonate reabsorption being necessary to allow the distal acid excretion.

2014B 15: 15% of candidates passed this question. Tolerance is the requirement of higher doses of a drug to produce a given response. When this develops rapidly (with only a few administrations of the drug) this is termed tachyphylaxis. Various mechanisms exist by which tolerance occurs and these include cellular tolerance (e.g. neuronal adaptation to opioids or alcohol), enzyme induction and depletion of neurotransmitters. Few candidates knew a comprehensive list or had a classification system for the different types of tolerance. No candidate had a good definition of tachyphylaxis.

2014B 16: 62% of candidates passed this question. This is a core topic and a detailed knowledge was expected. Baroreceptors are stretch receptors located in the walls of the heart and blood vessels and are important in the short term control of blood pressure. Those in the carotid sinus and aortic arch monitor the arterial circulation. Others, the cardiopulmonary baroreceptors, are located in the walls of the right and left atria, the pulmonary veins and the pulmonary circulation. They are all stimulated by distention and discharge at an increased rate when the pressure in these structures rises. Better answers provided some detail on the innervation for these receptors. It was expected candidates would describe that increased baroreceptor discharge inhibits the tonic discharge of sympathetic nerves and excites the vagal innervation of the heart. This results in vasodilation, venodilation, a drop in blood pressure, bradycardia and a decreased cardiac output. Some candidates had a major misunderstanding around the purpose of "low pressure baroreceptors" with many believing that these are the ones that respond to lower blood pressures, while the "high pressure baroreceptors" respond to higher blood pressures.

2014B 18: 23% of candidates passed this question. Both are globular proteins that bind and deliver O2. Due to myoglobin containing a single globin chain its dissociation curve is hyperbolic in shape. Haemoglobin contains 4 globin chains and is a quaternary structure which exhibits cooperatively resulting in a sigmoid shaped dissociation curve. The differing dissociation curves mean that when the PO2 is high, as in the lungs, both myoglobin and haemoglobin are saturated with oxygen. However, at the lower levels of PO2 in the tissues, haemoglobin cannot bind oxygen as well as myoglobin. Myoglobin can bind the O2 released by haemoglobin, which it stores to meet the demands of muscle contraction. This means haemoglobin (with its higher p50) can offload O2 to myoglobin. Comments on the synthesis and degradation gained additional marks but were a common omission. The physiological relevance was poorly explained. The similarities and differences mean that haemoglobin is the primary means of O2 transport from the lungs to the tissues and myoglobin is the primary O2 carrying pigment of skeletal muscle and acts as local O2 reserve for times of intense muscle activity.

2014B 19: 31% of candidates passed this question. This is a big question and required some structure to cover the material required. A Definition of afterload, factors specific to left ventricle, right ventricle and both were required. The question asked to describe and not merely list factors affecting afterload. Marks were not given for describing pathologies rather than physiological processes that affect afterload. Candidates seemed to lack depth and understanding on this topic.

2014B 22: 23 % of candidates passed this question 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.

2014B 23: 19% of candidates passed this question. This question was generally poorly answered. Total body sodium is regulated within 2% in normal individuals. The vast majority is contained in the extracellular compartment. While any physiological regulation involves a balance of input and output, sodium intake is essentially unregulated in humans. Output is regulated via renal, gastrointestinal and skin losses. Candidates needed to present the renal handling of Na including hormonal control and present factual knowledge about the level of absorption and GFR effects to attain a pass mark. Many candidates focused on osmolality and tonicity and some on the use of diuretics thereby not gaining marks on regulation of sodium. Most candidates didn’t mention either the skin and GIT role in sodium balance. aldosterone = stimulates Na+ reabsorption at the collecting tubules intra renal factors such as interstitial pressure which is lowered during hypovolaemia and reduced renal perfusion, thus promoting Na+ reabsorption gradient sympathetic nervous system – influences interstitial pressure and increases renin production angiotensin II – stimulates reabsorption at proximal tubule Atrial Naturetic Peptide/Factor – inhibits Na+ reabsorption Others – dopamine, cortisol, insulin => increase Na+ reabsorption, but minor factors Syllabus – D1, 2f Reference – Textbook of medical Physiology, Guyton, Chp 28

2014B 24: 23% of candidates passed this question. An understanding of the physiology of gastric emptying has direct relevance to intensive care practice as it influences enteral feed tolerance, helps inform regarding risk of aspiration and has important pharmacologic implications. Candidates’ answers were superficial and the role of intrinsic reflexes and local hormonal responses poorly understood and described. A simple and clear coverage is provided in Principles of Physiology for the Anaesthetist / P. Kam, I. Power – 3rd Ed. VIVAs A. Pharmaceutics B. Pharmacokinetics Dose response curves, renal clearance C. Pharmacodynamics D. Variability in Drug Response E. Cellular Physiology F. Respiratory Resp physio and measurement, Capnography, dead space G. CVS Cariovascular physio and measurement, Caridac pressure waves, alterations with vasopressors, invasive BP monitoring H. Renal I. Body Fluids and Electrolytes IVF, colligative properties, anion gap, frusemide J. Acid Base K. Neuro Cerebral physio + pharm, Vasopressin Nerve action potentials, LA pharm L. Musculoskeletal M. ANS N. Liver Liver physio and blood flow, nutrition, changes with fasting and stress O. GIT P. Nutrition and Metabolism Q. Haematology R. Thermoregulation S. Immunology T. Microbiology U. Endocrine V. Obstetrics Obstetric and neonatal physiology - CV changes, gas exchange across placenta, changes with first breath, humidity W. Measurement and Monitoring X. Procedures