2022 First Sitting SAQs

The effects of critical illness on the physiological factors that influence drug pharmacokinetics was used to analyse the candidates understanding of this core pharmacological principle. Better responses were able to identify the key elements perturbed by critical illness as well as outlining outline the potential cause and effect on the specific PK aspect being discussed. Stronger answers also included specific drug examples. The failure to utilise a structure (absorption, distribution, metabolism, and elimination) with very superficial detail and limited examples limited marks and was common in poorly scoring answers.

This question examined core cellular physiology knowledge. This knowledge is crucial as it underpins much of the electrochemical responses within the syllabus. Mechanisms of diffusion and the role of individual pathways were well presented in many responses. Answers that scored well generally classified the mechanisms of transport into active and passive processes which ensured an appropriate breadth of answer. Many answers failed to provide any examples which was requested. The structure of the Na+/K+ ATPase pump was less well described, however pleasingly most candidates were able to accurately articulate its role and function.

This question covers a core principle of respiratory physiology and would be expected to have a high pass rate. Most candidates were able to provide a concise definition and distinguish between the different types of compliance. The imprecise use of terminology often created the impression of a lack of fundamental understanding of this key concept. Candidates are encouraged to be accurate and concise in their definitions. A lack of detail in describing the relevant components of compliance and the factors that influence it, immediately limited the capacity of some candidates to achieve an adequate score. Most candidates provided less than half of these factors and only provided a list rather than explaining how compliance was impacted. Marks were maximised by dividing the impacts into those that altered lung compliance versus those that impacted on chest wall compliance, and the better candidates explained how and why compliance was affected. Confusion often arose from the imprecise use of arrows with the result that candidates frequently demonstrated an incorrect fact in relation to the direction of the arrow. Candidates are reminded to take care when using abbreviations or arrows to ensure they are not relying on the examiner to interpret a cause and effect relationship.

It was expected that candidates would give a detailed description of the changes that occur throughout pregnancy, labour and post-delivery (a timeline). This should include but not be limited to, cardiac output, total peripheral resistance, blood flow distribution, uterine blood flow and blood volume changes. Better answers were able to relate these changes to the underlying mechanisms (such as progesterone induced vasodilatation etc). A detailed description of aortocaval compression and its importance was also required. Vague and imprecise statements attracted fewer marks (for example simply stating that heart rate increases without discussing the magnitude, time course and influences). This topic is well covered in some of the recommend texts.

It was expected that candidates would define both components of the question, discuss the factors which affect serum creatinine and creatinine clearance and demonstrate their interrelationship. More complete answers described the advantages, disadvantages and limitations of their use in critical illness. In many cases candidates failed to correctly define creatinine clearance. Answers that scored well clearly utilised the above-mentioned breadth of knowledge and linked these to pertinent specific changes that may be associated with critical illness.

etter answers for this question used the “sensor, integrator/controller, effector” structure. They also included appropriate detail relating to the site and mechanism of angiotensin II and the subsequent stimulation of ADH and aldosterone release. A detailed description of ADH was necessary to score well. Lengthy descriptions of body water distribution or renal handling of water did not attract additional marks. Answers that scored less well were often disorganised, with limited structure and incorrect facts.

In the good answers to this question, and there were a number, the candidates included the volumes of the cranium and a correct description of the Monroe Kellie doctrine. A good answer should have included the compensations and consequences of increases in intra-cranial volumes; a discussion of all three components (brain tissue, blood, and CSF) and how they affect intracranial pressure; and then information on intra-ventricular and parenchymal devices in measuring ICP, briefly including their pros and cons. A common issue was writing quite a lot more than was needed on the relationship of cerebral blood flow to cerebral blood volume, and/or on the physiological consequences of raised ICP, which seemed to leave little time for discussion elsewhere. A few candidates did not provide any response for ICP measurement (worth 20% of the marks). Few candidates provided the intra-cranial elastance equation. A significant proportion of candidates missed out a part of the question, either the factors that affect CBV or ICP measurement.

The first part of this question required a description of both the receptor structure and its function. This includes, but is not limited to, its location, the natural ligand, how the channel may be regulated and the results of receptor stimulation. The second part of this question related to ketamine. Marks lost here often related to vague statements and incorrect facts. The examiners also commented that some candidates got confused between the R and S enantiomers. Few candidates commented on the nature of the metabolites and generally the PD section was vaguely answered.

This is a straightforward fact-based and process related question. It is important that candidates take the time to read the entire question prior to starting to write an answer. Unfortunately, many candidates wrote about skeletal muscle contraction which scored no marks. A good answer template included a description of the contractile elements of smooth muscle, the regulatory proteins and the role of calcium, and highlighted how these elements interact. They included descriptions of both the contractile and relaxation processes.

The examiners commented that a well-drawn and labelled diagram was a very useful adjunct to answering this question. Consideration of stimulus, sensors, integrators/processors, and effectors was also useful to ensure that all components of the question were covered by a candidate’s answer. Incorrect facts or a lack of detail about the various receptors and their locations was a common theme in answers that scored poorly. Classes of antiemetics, with specific drugs given as examples, were expected to gain marks.

A good answer was well structured and covered the areas of vasoconstriction, platelet adhesion, activation and aggregation, coagulation, clot retraction and anticlotting mechanisms. Many answers gave an overview of the haemostatic process but revealed insufficient knowledge of the processes involved. It was acceptable to give a classical view of clotting or to describe the cell-based model; or both. However, in several cases answers became confused by mixing up elements of the classical approach and cell-based model approach. Errors concerning details of the cell-based model were frequent. Many candidates did not include how the clot is limited to just the site of injury which happens in parallel with the formation of clot. Candidates should be aware that writing lengthy introductory statements attracted no marks and wastes time.

Sedation reduces body temperature by interfering with heat production and increasing heat loss, along with widening of hypothalamic inter-threshold range. This portion of the question was generally well answered. The question asked to "outline" the answer. Many candidates actually "described" the thermoregulation process in general but were unable to relate those with the impact of sedation. The second part of the question (physiological effect of low body temperature) was answered by most of the candidates with the structure of organ-system wise description. A few candidates scored extra marks by relating these effects with degree of hypothermia and by describing how thermogenesis responses (including shivering) can influence those effects. Some candidates restricted their answers to the effect of thermogenesis in response hypothermia and did not include the overall physiological consequences of low body temperature. Better answers displayed an understanding of core temperature regulation, inter threshold range and the effects of sedatives on thresholds for thermogenic responses, although only a few mentioned gain and maximal response. Better answers included specific detail (mentioned bradyarrhythmia, slow AF, VF, prolonged PR/QRS / J waves rather than just stating arrhythmia) across several organ systems. Marks were not awarded for generic statements such as 'decreased liver function' without some additional detail. Inadequate depth of knowledge was main reason behind overall poor scores.

This question was taken from core syllabus that requires level one (L1) understanding. Physical principles of ultrasound can be illustrated by outlining how ultrasound waves are generated from piezoelectric crystals, how they travel through the tissues, how they interact with different tissue planes and how the reflected waves return to the transducer and create images. Properties of ultrasound transducers include different geometric configurations of transducer probes and frequency-wavelength bandwidth properties of the crystals used in diagnostic ultrasound. Understanding of physical concepts of image resolution including its various aspects (e.g., spatial, temporal, contrast resolution) is required to address the next portion of the question. “Doppler effect” can be illustrated by a definition and equation along with some practical implications. This question was not answered well by majority of the candidates. Lack of knowledge and limited understanding resulted in poor average mark.

An ideal answer includes origin of subclavian vein, its tributaries, course in relation to mediastinal structures and surface anatomy for central line insertion. Vague comments like: “it follows the subclavian artery”, or “it passes between 1st rib and clavicle”, attract minimal marks. Similarly, no marks were awarded for describing technique of central line insertion and complications of procedure. Answers scored poorly due to a combination of the following, a lack of depth to their answers or inaccurate facts and limited structure/approach to an anatomical SAQ. Good answers described the course of the subclavian vein from its origin at the lateral border of the first rib, along the subclavian groove on the upper surface of the first rib, medially to its termination posterior to the sternoclavicular joint at the medial border of the scalenus anterior, where it joined the IJV to form the bracheoceaphalic vein. In addition, high scoring candidates described tributaries (e.g., the thoracic duct, external jugular) where they joined and went on to describe relations in reasonable detail, specifying whether patient is supine or erect.

Candidates who scored well generally defined PaCO2 and proceeded to describe factors in terms of those related to production and elimination. Good answers described the key production factor as being rate of production through aerobic metabolism which is in turn influenced by substrate and BMR. Those who scored well described elimination as being dependent upon minute ventilation, which in turn is influenced by CO2 detection by chemoreceptors, specifically detailing the difference between peripheral and central. Many candidates detailed pathophysiological factors which unfortunately did not gain any marks.

A definition or description of SVR that recognised the importance of radius in small arteries/arterioles as the major determinant attracted marks. Resistance is ΔP/flow; where ΔP is not only MAP and flow is volume/time. The systemic vascular resistance is the resistance of several circuits in parallel, which have both common and independent factors in their regulation. As they are in parallel the sum of reciprocals is used, 1/SVR = 1/R1 + 1/R2 to determine the overall value. A detailed explanation of the Hagen-Pouiselle law was not required, attracted few marks and wasted writing time. The remainder of the answer focus was on the factors that control the radius of these vessels. As a question regarding control, an approach that included sensors, integrators and effectors tended to yield a more comprehensive answer with resultant higher marks. Other useful structures included divisions into intrinsic/local factors (including endothelial input and autoregulation), neural control (reflexes and central controller) and hormonal control. As the question was regarding physiological control, no marks were awarded to pharmacological manipulation of SVR. Given the potential scope of the question, detailed descriptions of how noradrenaline exerts its effect were not required beyond receptor level although stating 'sympathetic nervous system activation results in vasoconstriction' were too simplistic to attract full marks.