Changes in labial capillary density on ascent to and descent from high altitude

Present knowledge of how the microcirculation is altered by prolonged exposure to hypoxia at high altitude is incomplete and modification of existing analytical techniques may improve our knowledge considerably. We set out to use a novel simplified method of measuring in vivo capillary density during an expedition to high altitude using a CytoCam incident dark field imaging video-microscope. The simplified method of data capture involved recording one-second images of the mucosal surface of the inner lip to reveal data about microvasculature density in ten individuals. This was done on ascent to, and descent from, high altitude. Analysis was conducted offline by two independent investigators blinded to the participant identity, testing conditions and the imaging site. Additionally we monitored haemoglobin concentration and haematocrit data to see if we could support or refute mechanisms of altered density relating to vessel recruitment. Repeated sets of paired values were compared using Kruskall Wallis Analysis of Variance tests, whilst comparisons of values between sites was by related samples Wilcoxon Signed Rank Test. Correlation between different variables was performed using Spearman’s rank correlation coefficient, and concordance between analysing investigators using intra-class correlation coefficient. There was a significant increase in capillary density from London on ascent to high altitude; median capillaries per field of view area increased from 22.8 to 25.3 (p=0.021). There was a further increase in vessel density during the six weeks spent at altitude (25.3 to 32.5, p=0.017). Moreover, vessel density remained high on descent to Kathmandu (31.0 capillaries per field of view area), despite a significant decrease in haemoglobin concentration and haematocrit. Using a simplified technique, we have demonstrated an increase in capillary density on early and sustained exposure to hypobaric hypoxia at thigh altitude, and that this remains elevated on descent to normoxia. The technique is simple, reliable and reproducible

Measurement of functional microcirculatory geometry and velocity distributions using automated image analysis

This study describes a new method for analyzing microcirculatory videos. It introduces algorithms for quantitative assessment of vessel length, diameter, the functional microcirculatory density distribution and red blood-cell (RBC) velocity in individual vessels as well as its distribution. The technique was validated and compared to commercial software. The method was applied to the sublingual microcirculation in a healthy volunteer and in a patient during cardiac surgery. Analysis time was reduced from hours to minutes compared to previous methods requiring manual vessel identification. Vessel diameter was detected with high accuracy (>80%, d > 3 pixels). Capillary length was estimated within 5 pixels accuracy. Velocity estimation was very accurate (>95%) in the range [2.5, 1,000] pixels/s. RBC velocity was reduced by 70% during the first 10 s of cardiac luxation. The present method has been shown to be fast and accurate and provides increased insight into the functional properties of the microcirculation

Online-Anamnesekurs: Chancen und Einschränkungen im Vergleich zum traditionellen Unterricht am Krankenbett

Objective: Obtaining a systematic medical history (MH) from a patient is a core competency in medical education and plays a vital role in the diagnosis of diseases. At the Faculty of Medicine at LMU Munich, students have their first course in MH taking during their second year. Due to the COVID-19 pandemic, the traditional bedside MH taking course had to be transformed into an online course (OC). Our objectives were to implement an online MH taking course, to evaluate its feasibility and to compare the evaluation results to a historic cohort that had undertaken the traditional bedside teaching course (BTC).Methods: 874 second-year students participated in the OC (BTC=827). After teaching the theoretical background via asynchronous online lectures, students participated in a practical exercise with fellow students using the video communication platform Zoom where they were able to practice taking a MH on the basis of fictitious, text-based patient cases. Students were then asked to evaluate the course through a standardized online survey with 31 questions on teaching quality and self-perceived learning success, which had also been used in previous years. The survey results were compared to the results of the historic cohort using the Mann-Whitney U test.Results: A total of n=162 students (18.5%) evaluated the OC. In the historic cohort, n=252 (30.5%) completed the survey. 85.3% of the OC respondents thought that the atmosphere during the practical exercise was productive and 83.0% greatly appreciated the flexibility in terms of time management. Moreover, they appreciated the online resources as well as having the opportunity to undertake a MH taking course during the COVID-19 pandemic. 27.7% of the respondents thought that traditional BTCs should be supplemented through more online activities in the future. With respect to the ability of independently taking a MH upon completion of the course, the OC was rated significantly lower relative to the BTC (mean OC=2.4, SD=±1.1 vs. mean BTC=1.9, SD=±1.1 (1=strongly agree; 5=strongly disagree); p<0.0001).Conclusion: OCs are a feasible format and seem to convey the theory and practical implementation in a peer-exercise format of MH taking to medical students. The theoretical background can be acquired with great flexibility. Nevertheless, the students' self-appraisal suggested that the traditional teaching format was more effective at teaching MH taking skills. Thus, we propose a blended learning concept, combining elements of both formats. In this context, we suggest prospective, randomized trials to evaluate blended learning approaches.Zielsetzung: Die Erhebung einer strukturierten Anamnese (ANA) eines Patienten ist eine Kernkompetenz in der medizinischen Ausbildung und spielt eine wichtige Rolle bei der Diagnose von Krankheiten. An der Medizinischen Fakultät der LMU München belegen die Studierenden im zweiten Studienjahr ihren ersten Anamnesekurs (AK). Aufgrund der COVID-19-Pandemie musste der traditionelle AK am Krankenbett in einen Online-Kurs (OK) umgewandelt werden. Unsere Ziele bestanden darin, einen Online-AK zu implementieren, seine Durchführbarkeit zu bewerten und die Bewertungsergebnisse mit einer historischen Kohorte zu vergleichen, die den traditionellen Unterricht am Krankenbett (UK) absolviert hatte.Methodik: Am OK nahmen 874 Studierende des zweiten Studienjahres teil (UK=827). Nach Vermittlung des theoretischen Hintergrunds mittels asynchronen Online-Vorlesungen nahmen die Studierenden an einer praktischen Übung über die Videokommunikationsplattform Zoom teil, in der sie die Durchführung einer ANA anhand von fiktiven, textbasierten Patientenfällen mit ihren Kommilitonen üben konnten. Anschließend wurden die Studierenden gebeten, den Kurs mittels einer standardisierten Online-Evaluation bestehend aus 31 Fragen zur Lehrqualität und zum selbst wahrgenommenen Lernerfolg zu bewerten. Diese kam auch in den Vorjahren zum Einsatz. Die Evaluationsergebnisse wurden mit den Ergebnissen der historischen Kohorte mit Hilfe des Mann-Whitney-U-Test verglichen.Ergebnisse: Insgesamt bewerteten n=162 Studierende (18,5%) den OK. In der historischen Kohorte beantworteten n=252 (30,5%) die Evaluation. 85,3% der OK-Befragten empfanden die Atmosphäre während der praktischen Übung als produktiv und 83,0% schätzten die Flexibilität bezüglich der Zeiteinteilung sehr. Darüber hinaus schätzten sie die Online-Ressourcen sowie die Möglichkeit, während der COVID-19-Pandemie an einem ANA-Kurs teilzunehmen. 27,7% der Befragten waren der Meinung, dass traditionelle UKs zukünftig durch mehr Online-Aktivitäten ergänzt werden sollten. In Bezug auf die Fähigkeit, nach Abschluss des Kurses selbstständig eine ANA zu erheben, wurde der OK im Vergleich zum UK signifikant schlechter bewertet (Mittelwert OK=2,4, SD=±1,1 vs. Mittelwert UK=1,9, SD=±1,1 (1=trifft voll zu; 5=trifft gar nicht zu); p<0,0001).Fazit: OKs sind ein praktikables Format und scheinen die Theorie und praktische Umsetzung in einem Peer-Übungsformat der ANA-Erhebung an Medizinstudierende zu vermitteln. Der theoretische Hintergrund kann flexibel erworben werden. Die Selbsteinschätzung der Studierenden deutete darauf hin, dass das traditionelle Unterrichtsformat effektiver war, um ANA Erhebungsfähigkeiten zu vermitteln. Daher empfehlen wir ein Blended-Learning-Konzept, das Elemente beider Formate kombiniert. In diesem Zusammenhang schlagen wir prospektive, randomisierte Studien vor, um Blended-Learning-Ansätze zu evaluieren

Platelets contribute to postnatal occlusion of the ductus arteriosus.

The ductus arteriosus (DA) is a fetal shunt vessel between the pulmonary artery and the aorta that closes promptly after birth. Failure of postnatal DA closure is a major cause of morbidity and mortality particularly in preterm neonates. The events leading to DA closure are incompletely understood. Here we show that platelets have an essential role in DA closure. Using intravital microscopy of neonatal mice, we observed that platelets are recruited to the luminal aspect of the DA during closure. DA closure is impaired in neonates with malfunctioning platelet adhesion or aggregation or with defective platelet biogenesis. Defective DA closure resulted in a left-to-right shunt with increased pulmonary perfusion, pulmonary vascular remodeling and right ventricular hypertrophy. Our findings indicate that platelets are crucial for DA closure by promoting thrombotic sealing of the constricted DA and by supporting luminal remodeling. A retrospective clinical study revealed that thrombocytopenia is an independent predictor for failure of DA closure in preterm human newborns, indicating that platelets are likely to contribute to DA closure in humans