Cardiovascular consequences of cooling in critical care

This commentary discusses a paper by Filseth and colleagues in a previous issue of Critical Care. The authors describe the cardiovascular effects of induced hypothermia, focusing particularly on post-hypothermic ventricular function. The findings indicate that the treatment resulted in reduced systolic but unchanged diastolic left ventricular function with compensatory effects on heart rate and systemic vascular resistance. The novel aspects of this study are the registration of ventricular function using sophisticated, load-independent indices in a clinically relevant, large animal model during the entire cooling and re-warming trajectory of hypothermia therapy

Weerstand en compliantie

Oratie uitgesproken door Prof.dr. P. Steendijk bij de aanvaarding van het ambt van hoogleraar in de Cardiovasculaire Fysiologie, in het bijzonder Onderzoek van Methoden en Vernieuwingen van het (bio)Medisch Onderwijs aan de Universiteit Leiden op vrijdag 20 oktober 2017Oratie uitgesproken door Prof.dr. P. Steendijk bij de aanvaarding van het ambt van hoogleraar in de Cardiovasculaire Fysiologie, in het bijzonder Onderzoek van Methoden en Vernieuwingen van het (bio)Medisch Onderwijs aan de Universiteit Leiden op vrijdag 20 oktober 2017LUMC / Geneeskunde Repositoriu

Balloon sizing in surgical ventricular restoration: What volume are we targeting?

Cardiolog

Effects of critical coronary stenosis on global systolic left ventricular function quantified by pressure-volume relations during dobutamine stress in the canine heart

AbstractObjectives. In this study we quantified the effects of a critical coronary stenosis on global systolic function using pressure-volume relations at baseline and during incremental dobutamine stress.Background. The effects of coronary stenosis have previously been analyzed mainly in terms of regional (dys)function. Global hemodynamics are generally considered normal until coronary flow is substantially reduced. However, pressure-volume analysis might reveal mechanisms not fully exposed by potentially load-dependent single-beat parameters. Moreover, no systematic analysis by pressure-volume relations of the effects of dobutamine over a wide dose range has previously been presented.Methods. In 14 dogs left ventricular volume and pressure were measured by conductance and micromanometer catheters, and left circumflex coronary flow by Doppler probes. Measurements in control and with left circumflex stenosis were performed at baseline and at five levels of dobutamine (2.5 to 20 μg/kg/min). The end-systolic pressure-volume relation (ESPVR) dP/dtMAX− vs. end-diastolic volume (dP/dtMAX− VED) and the relation between stroke work and end-diastolic volume (preload recruitable stroke work [PRSW]) were derived from data obtained during gradual caval occlusion.Results. In control, dobutamine gradually increased heart rate up to 20 μg/kg/min, the inotropic effect blunted at 15 μg/kg/min. With stenosis, the chronotropic effect was similar, however, contractile state was optimal at approximately 10 μg/kg/min and tended to go down at higher levels. At baseline, the positions of ESPVR and PRSW, but not of dP/dtMAX− VED, showed a significant decrease in function with stenosis. No differences between control and stenosis were present at 2.5 μg/kg/min; the differences were largest at 15 μg/kg/min.Conclusions. Pressure-volume relations and incremental dobutamine may be used to quantify the effects of critical coronary stenosis. The positions of these relations are more consistent and more useful indices than the slopes. The positions of the ESPVR and PRSW show a reduced systolic function at baseline, normalization at 2.5 μg/kg/min and a consistent significant difference between control and stenosis at dobutamine levels of 5 μg/kg/min and higher

Modelling of heat transfer process in condensing unit with titanium alloy tubes

One of the most important units of heat transfer equipment of a nuclear power plant is the condenser. Currently, at the nuclear stations of concern “Rosenergoatom” work is actively underway to replace the tubes of copper containing alloys to various steels or titanium alloys. Also, active work is underway on modernization of heat-exchange equipment of operating units. It is necessary to make the modelling of the parameters of condenser, to ensure that after the upgrade, the unit will continue operating normally. For this purpose, was created the model of module of tube bundle of condenser unit of K-33160 with tubes of titanium alloy. The modelling process is based on the equation of heat balance. In this work were modelled condenser of NPP of K-33160 with WWER-1000 reactor and the tubes of a titanium alloy VT0-1. The calculation was carried out for three presented methods and the error was less than 2%

Making a lecture stick: the effect of spaced instruction on knowledge retention in medical education

IntroductionPoor knowledge retention is a persistent problem among medical students. This challenging issue may be addressed by optimizing frequently used instructional designs, such as lectures. Guided by neuroscientific literature, we designed a spaced learning lecture in which the educator repeats the to-be-learned information using short temporal intervals. We investigated if this modified instructional design could enhance students' retention.Materials and MethodsSecond-year medical students (n = 148) were randomly allocated to either the spaced lecture or the traditional lecture. The spaced lecture consisted of three 15-min instructional periods, separated by 5-min intervals. A short summary of the preceding information was provided after each interval. The traditional lecture encompassed the same information including the summary in the massed format, thus without the intervals. All students performed a baseline knowledge test 2 weeks prior to the lectures and students' knowledge retention was assessed 8 days after the lectures.ResultsThe average score on the retention test (alpha = 0.74) was not significantly different between the spaced lecture group (33.8% 13.6%) and the traditional lecture group (31.8% +/- 12.9%) after controlling for students' baseline-test performance (F(1,104) = 0.566, p = 0.458). Students' narrative comments showed that the spaced lecture format was well-received and subjectively benefitted their attention-span and cognitive engagement.Discussion and Conclusion We were unable to show increased knowledge retention after the spaced lecture compared with the traditional lecture. Based on these findings, we provide recommendations for further research. Ultimately, we aim for optimized spaced learning designs to facilitate learning in the medical curriculum and to help educate health professionals with a solid knowledge base.Immunogenetics and cellular immunology of bacterial infectious disease

Interventional creation of an atrial septal defect and its impact on right ventricular function: An animal study with the pressure-volume conductance system

Background: The aim of our study was to assess the suitability of different interventional techniques to create an atrial septal defect (ASD) and to evaluate the short-term effects of right ventricular (RV) volume overload on RV contractility in the growing swine. Methods: Thirteen ASD and six control animals were studied. An ASD was created by balloon dilatation (BD) of the fossa ovalis (n = 4) or by implantation of a multi-perforated Amplatzer Septal Occluder (n = 4) or a patch-less nitinol device (n = 5). After 4.8 (3.9&#8211;6.0) weeks, the amounts of left-to-right shunting (Qp/Qs) and RV contractility (end systolic elastance &#8212; Ees) were assessed. Results: In the ASD group, a significant left-to-right shunt could be documented (Qp/Qs 1.5 &#177; &#177; 0.4). However, a shunt was absent in the BD subgroup (Qp/Qs 1.1 &#177; 0.1). In animals with devices implanted, a significant relationship between the post-mortem ASD area and Qp/Qs was found (r = 0.68, p < 0.05). Compared to controls, RV contractility was not significantly impaired at rest and during dobutamine in ASD animals (Ees: 0.40 &#177; 0.20 vs 0.54 &#177; 0.12 and 0.75 &#177; 0.29 vs 1.04 &#177; 0.24 mm Hg/mL, p = NS for both). Conclusions: Device implantation is necessary to create a patent ASD resulting in significant left-to-right shunting. In an experimental ASD model, a five week period of chronic RV volume overload does not alter RV contractility significantly. (Cardiol J 2011; 18, 3: 289&#8211;296

An understanding of (mis)understanders: exploring the underlying mechanisms of concept learning using functional magnetic resonance imaging

Obtaining adequate understanding of scientific concepts is considered challenging due to learners' misconceptions about natural phenomena. Misconceptions may coexist with scientific knowledge in the brain. Therefore, misconceptions must be cognitively inhibited in order to select the scientific knowledge. There is, however, lack of substantial neuroscientific evidence supporting this hypothesis. In this study, we sought for this evidence by investigating medical students who solved a cardiovascular conceptual problem in a magnetic resonance imaging scanner. Brain activation was compared between understanders who had the scientific knowledge, and misunderstanders who held a misconception. No significant activation was found in brain areas related to cognitive inhibition in understanders compared with misunderstanders. Therefore, we could not confirm the idea that cognitive inhibition is involved in overcoming a misconception. Instead, we found that the putamen was significantly activated in misunderstanders compared with understanders, suggesting a role for episodic memory in learners holding a misconception.Medical Education Researc

The effect of peer modelling and discussing modelled feedback principles on medical students' feedback skills: a quasi-experimental study

Background Teaching is an important professional skill for physicians and providing feedback is an important part of teaching. Medical students can practice their feedback skills by giving each other peer feedback. Therefore, we developed a peer feedback training in which students observed a peer that modelled the use of good feedback principles. Students then elaborated on the modelled feedback principles through peer discussion. This combination of peer modelling and discussing the modelled feedback principles was expected to enhance emulation of the feedback principles compared to (1) only peer modelling and (2) discussing the feedback principles without previous modelling. Methods In a quasi-experimental study design, 141 medical students were assigned randomly to three training conditions: peer modelling plus discussion (MD), non-peer modelled example (NM) or peer modelling without discussion (M). Before and after the training, they commented on papers written by peers. These comments served as a pre- and a post-measure of peer feedback. The comments were coded into different functions and aspects of the peer feedback. Non-parametrical Kruskall-Wallis tests were used to check for pre- and post-measure between-group differences in the functions and aspects. Results Before the training, there were no significant between-group differences in feedback functions and aspects. After the training, the MD-condition gave significantly more positive peer feedback than the NM-condition. However, no other functions or aspects were significantly different between the three conditions, mainly because the within-group interquartile ranges were large. Conclusions The large interquartile ranges suggest that students differed substantially in the effort placed into giving peer feedback. Therefore, additional incentives may be needed to motivate students to give good feedback. Teachers could emphasise the utility value of peer feedback as an important professional skill and the importance of academic altruism and professional accountability in the peer feedback process. Such incentives may convince more students to put more effort into giving peer feedback.Medical Education Researc