Arno M. M. Muijtjens

Velocity profiles of blood platelets and red blood cells flowing in arterioles of the rabbit mesentery.

Velocity profiles were determined in rabbit mesenteric arterioles (diameter 17–32 &mgr;m). A good spatial resolution was obtained by using the blood platelets as small and natural markers of flow, providing for the first time in vivo detailed, quantitative information about the shape of the velocity profiles in microvessels. In some experiments red blood cell velocity profiles were recorded as well. Easy detection of the cells of interest could be achieved by labelling them selectively with a fluorescent dye and visualizing them by intravital fluorescence video microscopy, using flashed illumination. Pairs of flashes were given with a short, preset time interval between both flashes, yielding in one TV picture two images of the same cell displaced over a certain distance for the given time interval. Velocity and mean radial position of cells, flowing within an optical section around the median plane of the vessel, were determined. The shape of the velocity profiles of platelets and red blood cells was similar. The profiles were flattened as compared to a parabola, both in systole and diastole. Vessel diameter did not change measurably during the cardiac cycle. As an index of the degree of blunting of the profiles, the ratio of the maximal and mean velocity of the profile was used, which is 2 for a parabola and 1 for complete plug flow. The index ranged from 1.39 to 1.54 (median 1.50), and increased with vessel diameter. Calculations showed that the blunting of the profiles cannot be explained by an influence of the finite depth of the optical section.

Description of the deformation of the left ventricle by a kinematic model.

A model of left ventricular (LV) kinematics is essential to identify the fundamental physiological modes of LV deformation during a complete cardiac cycle as observed from the motion of a finite number of markers embedded in the LV wall. Kinematics can be described by a number of modes of motion and deformation in succession. An obvious mode of LV deformation is the ejection of cavity volume while the wall thickens. In the more sophisticated model of LV kinematics developed here, seven time-dependent parameters were used to describe not only volume change but also torsion and shape changes throughout the cardiac cycle. Rigid-body motion required another six parameters. The kinematic model employed a deformation field that had no singularities within the myocardium, and all parameters describing the modes of deformation were dimensionless. Note that torsion, volume and symmetric shape changes all require the definition of a cardiac coordinate system, which has generally been related to the measured cardiac geometry by reference to approximate anatomical landmarks. However, in the present study the coordinate system was positioned objectively by a least-squares fit of the kinematic model to the measured motion of markers. Theoretically, at least five markers are needed to find a unique set of parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Workplace-based assessment: effects of rater expertise.

Traditional psychometric approaches towards assessment tend to focus exclusively on quantitative properties of assessment outcomes. This may limit more meaningful educational approaches towards workplace-based assessment (WBA). Cognition-based models of WBA argue that assessment outcomes are determined by cognitive processes by raters which are very similar to reasoning, judgment and decision making in professional domains such as medicine. The present study explores cognitive processes that underlie judgment and decision making by raters when observing performance in the clinical workplace. It specifically focuses on how differences in rating experience influence information processing by raters. Verbal protocol analysis was used to investigate how experienced and non-experienced raters select and use observational data to arrive at judgments and decisions about trainees’ performance in the clinical workplace. Differences between experienced and non-experienced raters were assessed with respect to time spent on information analysis and representation of trainee performance; performance scores; and information processing––using qualitative-based quantitative analysis of verbal data. Results showed expert-novice differences in time needed for representation of trainee performance, depending on complexity of the rating task. Experts paid more attention to situation-specific cues in the assessment context and they generated (significantly) more interpretations and fewer literal descriptions of observed behaviors. There were no significant differences in rating scores. Overall, our findings seemed to be consistent with other findings on expertise research, supporting theories underlying cognition-based models of assessment in the clinical workplace. Implications for WBA are discussed.

Assessing simulated patients in an educational setting: the MaSP (Maastricht Assessment of Simulated Patients)

Context  For more than two decades the Medical School in Maastricht, the Netherlands, has used simulated patients (SPs) to provide students with opportunities to practise their skills in communication and physical examination. In this educational setting a student meets a SP in a videotaped session. Feedback by the SP to the student at the end of the session is considered an important educational feature. We found no instruments to assess individual SP performance during those sessions.

A Comparison of Standard-Setting Procedures for an OSCE in Undergraduate Medical Education.

Purpose To compare four standard-setting procedures for an objective structure clinical examination (OSCE). Methods A 12-station OSCE was administered to 84 students in each of the final (fourth-) year medical classes of 1996 and 1997 at Dalhousie University Faculty of Medicine. Four standard-setting procedures (Angoff, borderline, relative, and holistic) were applied to the data to establish a cutoff score for a pass/fail decision. Results The procedures yielded highly inconsistent results. The Angoff and borderline procedures gave similar results; however, the relative and holistic methods gave widely divergent results. The Angoff procedure yielded results reliable enough to use in decision making for a high-stakes examination, but would have required more judges or more stations. Conclusions The Angoff and borderline procedures provide reasonable and defensible approaches to standard setting and are practical to apply by non-psychometricians in medical schools. Further investigation of the other procedures is needed.

Comparison of a rational and an empirical standard setting procedure for an OSCE

Purpose  Earlier studies of absolute standard setting procedures for objective structured clinical examinations (OSCEs) show inconsistent results. This study compared a rational and an empirical standard setting procedure. Reliability and credibility were examined first. The impact of a reality check was then established.

Comparison of text and video cases in a postgraduate problem-based learning format

Objective  To investigate whether adding a brief video case instead of an equivalent written text improves the cognitive and metacognitive processes (data exploration, theory building, theory evaluation and metareasoning) of residents in problem‐based learning.

Quality of clinical aspects of call handling at Dutch out of hours centres : cross sectional national study

Objective To assess the quality of telephone triage by following the consecutive phases of its care process and the quality of the clinical questions asked about the patient’s clinical condition, of the triage outcome, of the content of the home management advice, and of the safety net advice given at out of hours centres. Design Cross sectional national study using telephone incognito standardised patients. Setting The Netherlands. Participants 17 out of hours centres. Main outcome measures Percentages of clinical obligatory questions asked and items within home management and safety net advice, both in relation to pre-agreed standards, and of care advice given in relation to the required care advice. Results The telephone incognito standardised patients presented seven clinical cases three times each over a period of 12 months, making a total of 357 calls. The mean percentage of obligatory questions asked compared with the standard was 21%. Answers to questions about the clinical condition were not always correctly evaluated from a clinical viewpoint, either by triagists or by general practitioners. The quality of information on home management and safety net advice varied, but it was consistently poor for all cases and for all out of hours centres. Triagists achieved the appropriate triage outcome in 58% of calls. Conclusion In determining the outcome of the care process, triagists often reached a conclusion after asking a minimal number of questions. By analysing the quality of different phases within the process of telephone triage, evaluation of whether an appropriate triage outcome has been arrived at by means of good clinical reasoning or by an educated guess is possible. In terms of enhancing the overall clinical safety of telephone triage, apart from obtaining an appropriate clinical history, adequate home management and safety net advice must also be given.

Effects of conventional and problem‐based learning on clinical and general competencies and career development

Objective  To test hypotheses regarding the longitudinal effects of problem‐based learning (PBL) and conventional learning relating to students’ appreciation of the curriculum, self‐assessment of general competencies, summative assessment of clinical competence and indicators of career development.

Validity of portfolio assessment: which qualities determine ratings?

Context  The portfolio is becoming increasingly accepted as a valuable tool for learning and assessment. The validity of portfolio assessment, however, may suffer from bias due to irrelevant qualities, such as lay‐out and writing style. We examined the possible effects of such qualities in a portfolio programme aimed at stimulating Year 1 medical students to reflect on their professional and personal development. In later curricular years, this portfolio is also used to judge clinical competence.