Kirsten Wüst

Safety of the combination of chloroquine and methylene blue in healthy adult men with G6PD deficiency from rural Burkina Faso

New drug combinations against falciparum malaria which are both effective and affordable for Sub‐Saharan African populations are urgently needed. The combination of the well‐known drugs chloroquine (CQ) and methylene blue (MB) is such a promising new regimen. However, there is some concern that MB could cause development of haemolysis in patients with glucose‐6‐phosphate dehydrogenase (G6PD) deficiency, a condition which is prevalent in malaria‐endemic regions. Against this background, 74 G6PD‐deficient but otherwise healthy adult men were given a 3‐day oral regimen of a total of 1500 mg CQ and 780 mg MB in the District Hospital of Nouna in north‐western Burkina Faso. Haemolysis did not occur, haemoglobin levels remained stable or even rose in the study participants, and the drug regimen was well tolerated. Therefore, standard dosages of MB appear to be safe in G6PD‐deficient African populations with predominantly class III G6PD deficiency.

The accuracy of the modified Evans blue dye test in detecting aspiration in head and neck cancer patients

The purpose of this study was to determine sensitivity and specificity of the modified Evans blue dye test (MEBDT) in tracheostomised patients after treatment of head and neck squamous cell carcinoma (HNSCC). This was a prospective study with 30 consecutive patients. All individuals underwent a MEBDT and a subsequent fiberoptic endoscopic evaluation of swallowing (FEES) immediately after the MEBDT for reconsidering the validity of the MEBDT. Aspiration was present in 20 patients documented by MEBDT and FEES. One patient was judged to aspirate by FEES but not by MEBDT (1 false-negative result). Nine patients showed no aspiration either by MEBDT or by FEES. The sensitivity of the MEBDT protocol in predicting aspiration among individuals in our cohort was 95.24%, the specificity 100%, respectively. The results of the current investigation suggest that the MEBDT is much more sensitive in tracheostomised HNSCC patients than in tracheostomised neurological patients. The MEBDT for tracheostomised HNSCC patients offers a quick and reliable method to identify aspiration risk in cases of severe dysphagia.

Evaluation des Aspirationsschutzes blockbarer Trachealkanülen

BACKGROUND The aim of the study was to evaluate leakage of liquids in terms of water and artificially produced saliva past low-pressure cuffs of tracheal tubes. METHODS Three different types of tracheal tubes, TRACOE vario, Rüsch Ultra-Tracheoflex, and Portex Blue Line Ultra, were tested in isolated pig tracheas by infusing 6 ml of water or artificially produced saliva over the cuff and measuring the volume of fluid leaking past the cuff after 5, 10, and 15 min. RESULTS The leakage in the saliva experiments was significantly lower than in the water experiments (p < 0.05). The amount of leakage between the three different types of tubes showed statistically significant (p < 0.05) results. There was no statistically significant difference between tracheal tubes of 7 and 8 mm internal diameter. CONCLUSION The present laboratory findings suggest that the three tracheal tubes studied will not guard against aspiration of water but they will prevent the leakage of artificial saliva to a great extent.

Leakage of Fluid in Different Types of Tracheal Tubes

The aim of this study was to evaluate leakage of liquids, i.e., water and saliva, past low-pressure cuffs of tracheostomy tubes. Three different types of tracheostomy tubes, TRACOE® vario (TRACOE Medical GmbH, Germany), Rüsch Ultra-Tracheoflex® (Rüsch GmbH, Germany), and Portex Blue Line Ultra™ (Smiths Medical, UK) were tested in isolated pig tracheas. Sixty samples (10 tubes each of 7- and 8-mm inner diameter of each type) were used. Four different experiments were devised: type 1 (water and artificial ventilation), type 2 (water and no artificial ventilation), type 3 (saliva and artificial ventilation), and type 4 (saliva and no artificial ventilation). Six milliliters of water or artificial saliva were infused over the cuff and the volume of fluid that leaked past the cuff was measured after 5, 10, and 15 min. Intracuff pressure was also measured three times. The saliva experiments resulted in less leakage than the water experiments. Leakage after treatment with water or artificial saliva is higher without artificial ventilation than with ventilation. The amount of leakage among the tubes with respect to manufacturer showed statistically significant results. However, there were no differences among tracheostomy tubes with respect to internal diameter.

Including long- and short-term data in blinded sample size recalculation for binary endpoints

In order to calculate the sample size for a clinical trial with a binary outcome needed to achieve a certain power at a given significance level, one needs to specify the clinically relevant effect as well as the event rate pooled over the treatment groups. However, before conducting the trial the event rates are unknown and the pooled event rate needs to be estimated. A misspecification of this parameter might lead to a study that is either under- or overpowered. In the internal pilot study design the pooled event rate is reestimated during the trial. For this reestimation the current methods only use data of those patients that have concluded the whole study. Instead, a method is proposed that also takes into account data at an earlier point of the trial, a point which, within the internal pilot study, has been passed by a greater number of patients than the trials endpoint. Characteristics of the proposed estimator and the related recalculated sample size are investigated. Analytical computations of the actual type I-error rate are given for small sizes of the internal pilot study. These calculations are completed by simulation studies for larger sample sizes of the internal pilot study. The results show that the inflation of the type I-error rate is often negligible and generally not higher than observed for the fixed sample size design and for the classical recalculation procedure. However, as compared to the conventional approach the proposed procedure may show a considerably lower variability of the resulting sample size and thus an improved ability to achieve the target power.

[Evaluation of aspiration protective-covered tracheal cannulas].

BACKGROUND The aim of the study was to evaluate leakage of liquids in terms of water and artificially produced saliva past low-pressure cuffs of tracheal tubes. METHODS Three different types of tracheal tubes, TRACOE vario, Rüsch Ultra-Tracheoflex, and Portex Blue Line Ultra, were tested in isolated pig tracheas by infusing 6 ml of water or artificially produced saliva over the cuff and measuring the volume of fluid leaking past the cuff after 5, 10, and 15 min. RESULTS The leakage in the saliva experiments was significantly lower than in the water experiments (p < 0.05). The amount of leakage between the three different types of tubes showed statistically significant (p < 0.05) results. There was no statistically significant difference between tracheal tubes of 7 and 8 mm internal diameter. CONCLUSION The present laboratory findings suggest that the three tracheal tubes studied will not guard against aspiration of water but they will prevent the leakage of artificial saliva to a great extent.

Alles nur ein Spiel? - Über die Realitätsnähe von Unternehmensplanspielen

„Eine bedeutende Funktion des erfolgreichen Managers besteht darin zu erkennen, wann das Verhalten der Umwelt so weit von den im Voraus aufgestellten Annahmen abweicht, dass sich Planrevisionen lohnen, und jene Bereiche der gesamten unternehmerischen Tätigkeiten auszuwählen, für die neue Pläne formuliert werden sollen. Die Neuformulierung des Spiels als kontinuierliches Spiel ist ein möglicher Weg zur Schaffung einer Spielumwelt, in der diese Fähigkeiten geübt werden könnten.“ (Cohen/ Rhenman, 1961, S. 44)

Monitoring Continuous Long-Term Outcomes in Adaptive Designs

ABSTRACT Interim analyses offer the possibility to assess the efficacy of a new treatment prior to the originally planned end of a clinical trial. In addition, adaptive designs allow the statistician to modify the study at the time of the interim analysis without inflating the Type I error rate or compromising the overall power of the trial. In studies with the option of early stopping, overrunning occurs when patients have entered the trial but their data was not included in the test decision of an interim analysis while a stopping criterion has been reached. Especially in case of a long-term endpoint, overrunning is hardly avoidable. If overrunning happens, one is interested that the test decision made in the interim analysis remains stable if the delayed observations are included in the evaluation. The available adaptive designs use the data of those patients that have already completed the study for computation of the test statistic at the interim analysis. This approach exhibits a considerable risk of conflicting decisions. In this article, we consider a procedure that takes into account both the data at the endpoint and at an intermediate point of the treatment phase when calculating the test statistic for the interim analysis in an adaptive two-stage design. For known nuisance parameters, the test statistics for the two stages fulfill the p clud condition of a combination test which assures control of the Type I error rate. It is shown analytically that the probability of conflicting decisions in the case of overrunning is considerably reduced if the proposed procedure is used. For unknown nuisance parameters, simulation results demonstrate that the overall Type I error rate is not relevantly inflated and that the reduction of the probability for conflicting test decisions in the case of overrunning is maintained if the sample size in the interim analysis is not too small.

Just a game? How continuous time modelling can ameliorate corporate strategy games

Strategy games are a popular part of todays management training in education and business. Complex economic interrelationships can be illustrated and interdependencies of economic decisions can be more easily understood. Most business games work with a discrete time model, i.e., decisions are made once for an entire time period; usually one fiscal year. Possible drawbacks of the discrete time modelling on the planning and control processes, on the presentation of effect timelines and on the learners comprehension of interrelationships in companies are discussed. The authors hypothesise that a continually-controlled strategy game would greatly increase the simulations applicability to real-world business. Among other advantages of a continually-controlled strategy game, errors in the planning process could be corrected and an early warning system could be implemented. The well-known problem of myopic business decisions at the end of the game could be resolved by linking success in the game with the sustainable development of the simulated company. This articles results are backed by experience as well as the results of a survey at Pforzheim University.

Ökonomische Theorie der Zeit und Psychologie

ZusammenfassungDer Faktor Zeit spielt in der ökonomischen Theorie eine wichtige Rolle — intertemporale Entscheidungen sind in allen Bereichen der Wirtschaftstheorie und -politik relevant. In der überwiegenden Zahl der Fälle stützt man sich dabei auf das sogenannte, ‚Discounted-Utility-Modell‘ (DU-Modell), in dem alle zukünftigen Kosten und Erträge mit einem einheitlichen Zinssatz auf die Gegenwart abgezinst werden. Dieses Modell sieht sich allerdings heftiger Kritik ausgesetzt: So zeigen Experimente, dass viele Verhaltensweisen, die Menschen an den Tag legen, sich nicht mit diesem Modell vereinbaren lassen. Menschen verwenden je nach Entscheidungssituation unterschiedliche Zinssätze, die auch negativ sein können, sie haben eine Vorliebe für steigende Konsumprofile und legen zeitinkonsistentes Verhalten an den Tag. Der vorliegende Beitrag diskutiert diese Anomalien und zeigt auf, welche wirtschaftspolitischen Konsequenzen daraus erwachsen.AbstractThe so-called discounted-utility-model (DU-model) is the gold-standard of economic theory: confronted with intertemporal decicions, people discount future costs and payments with one interest rate and maximise their utility by choosing the option with the highest net present value. In the last decade, however, there has been a lot of empirical research on intertemporal choice, much of it addressing the descriptive validity of the DU-model. It has been shown that the DU-model may not be an adequate description of human behaviour as it can be observed in reality: People discount utility from different sources at different rates, they have a preference for increasing consumption profiles and they show time-inconsistent behaviour. This article discusses some of these anomalies and shows the implications for economic policy and policy-makers.