Simulation study of the Hemopump as a cardiac assist device

A dynamic model was developed for a Hemopump that withdraws blood from the left ventricle and discharges it to the aorta through a miniature axial-flow pump. Incorporation of the Hemopump model in a previously established model for the canine circulatory system enabled the effects of the Hemopump on various haemodynamic variables of the circulatory system to be studied, and the benefit of the Hemopump to the failing heart was investigated. In addition, the influence of the physiological status of the right ventricle on the Hemopump performances was examined, and the synchronous and non-synchronous operations of the Hemopump were compared. Results verified that the Hemopump assists the failing heart by increasing the oxygen supply, while reducing the oxygen consumption of the heart through a reduction in the workload of the left ventricle. These beneficial effects were enhanced when the pump's rotation speed was increased. When pump speed was increased from 17000 to 23000 revolutions min⁻¹, the oxygen supply increased 101%, and the oxygen consumption decreased 60%. However, when the pump rotation speed was too high, the inflow to the pump could be impaired and the pump performance could be negatively affected. Predications from the model were in good agreement with the results previously obtained in animal experiments and in vitro measurements.     

CT模拟定位三维适形放射治疗食管癌的临床研究

目的探讨CT模拟定位三维适形放射治疗食管癌的疗效。方法1997年4月～2002年7月,经病理证实的食管鳞状细胞癌87例患者，其中男性56例，女性31例，年龄42～75岁，平均年龄62.5岁，随机分为2组，两组患者一般情况、性别、年龄及病变部位构成经统计学检验无统计学意义，一组为采用CT模拟定位进行三维适形放射治疗，另一组为常规模拟定位放射治疗，两组的剂量都为64～66Gy／32.33次／6.4～6.6周。结果采用Kaplan—Meier法计算生存率，并用Log—Rank检验其差异性。治疗计划各指标分析采用kolmogorowSmirnov法行正态分布检验，继而行t检验，以P〈0.05为差异有统计学意义。CT模拟定位三维适形放射治疗组和常规模拟定位放射治疗组1、2、3、4年生存率分别为70.1％、55.6％、40.4％、36.3％和65.4％、50.6％、30.6％、20.9％（p〉0.05）。但是对Ⅰ～Ⅱ期患者，CT模拟定位三维适形放射治疗组和常规模拟定位放射治疗组的生存率分别为81.2％、75.5％、67.3％、61.5％和80.1％、65.7％、54.9％、29.7％（P〈0，05），局部控制率分别为75.6％、71.7％、65.5％、59.0％和65.4％、50.6％、33.3％、25.6％（P〈0.05）。而对于Ⅲ～Ⅳ期的患者，两组之间的生存率和局部控制率差异无统计学意义。结论CT模拟定位三维适形放射治疗的疗效明显好于常规模拟定位放射治疗组。特别对Ⅰ-Ⅱ期早期食管癌患者两组之间差异有统计学意义，而对晚期患者差异无统计学意义。     

Modeling of stimulation–secretion coupling in a chromaffin cell

We constructed a chromaffin cell model for analysis of stimulation–secretion coupling in computer simulation studies. The model includes mechanisms involved in the excitatory synapse, voltage-dependent Na⁺, K⁺ and Ca²⁺ channels, Ca²⁺-activated K⁺ channels (SK type), buffered Ca²⁺ diffusion, Ca²⁺ extrusion, fluorescent Ca²⁺ indicators and Ca²⁺-triggered exocytosis. Calculations of the modeled mechanisms were carried out using the NEURON simulation environment (Hines and Carnevale, Neural Computation 9:1179–1209, 1997). A set of parameter values was determined so as to fit basic experimental results reported in the literature. The model was also applied to simulate our experimental results obtained from chromaffin cells in the perfused rat adrenal medulla. Observed profiles of Ca²⁺responses induced by electrically stimulating the splanchnic nerve with various frequencies (1–50 Hz) were adequately simulated with minor readjustments of parameter values for Ca²⁺influx and extrusion. Secretory responses measured at the same time as the Ca²⁺responses were also simulated with consideration of a time constant to detect catecholamines in the experiment. Similarly, model simulations reproduced both Ca²⁺responses and secretory responses evoked by elevations of the extracellular K⁺ concentration for different periods. The results suggest that the presented model provides a useful tool for analyzing and predicting quantitative relations in various events occurring in stimulation–secretion coupling in chromaffin cells.     

Das Magengeschwür als energiebilanzproblem: Entwurf eines cellularen automaten zur simulation von verteilungsstörungen der magenwanddurchblutung

Zusammenfassung Ein cellularer Automat, der eine vereinfachte Abschätzung von Verteilungsmustern der Magendurchblutung erlaubt, wird beschrieben. Die auf der Basis des Energiebedarfs der Säuresekretion und der Morphologie der Magenstrombahn simulierbaren Umverteilungsphänomene stimmen in Form und Lage mit dem menschlichen Magengeschwür überein. Sonderfälle der peptischen' Läsion, wie das lineare Geschwür oder die peptische' Stenose der Speiseröhre, sind mit der Theorie des submucösen Steal-Phänomens zu vereinbaren.

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Gastric ulcer as a problem of energy balance: Design of a cellular automaton for simulation of disorders of blood flow distribution to the stomach wall

Summary A cellular automaton is described, which allows a simple simulation of patterns of gastric blood flow distribution. Effects of redistribution, which can be simulated on the basis of the energy requirements of acid secretion and the morphology of the gastric vascular bed, are isomorph to form and site of gastric ulcer in man. Special forms of the peptic lesion as linear ulcers or peptic stenoses of the oesophagus are consistent with the theory of a submucous steal-phenomenon.

Herrn Prof. Dr. Dr. rer. nat. h. c. Friedrich Stelzner zum 65. Geburtstag gewidmet     

A Bayesian Approach for Incorporating the EQ-5D Visual Analog Scale When Estimating the Health-Related Quality of Life

ObjectivesThe EuroQoL 3-level version of EQ-5D and 5-level version of EQ-5D questionnaires are often used to quantify health states. They include ordinal responses across 5 health dimensions (EQ-5D index) and an EQ-visual analog scale (EQ-VAS) overall health rating. We investigated the value of incorporating the EQ-VAS to update health utility estimates using a Bayesian framework.MethodsWe created a joint bivariate normal EQ-VAS and EQ-5D index utility model and compared this to a univariate normal EQ-5D index utility model. We tested these models for 1026 Sri Lankan patients with chronic kidney disease and 94 Australian patients with wounds. We validated our approach by simulating EQ-VAS and EQ-5D index responses and applying our Bayesian model and then comparing the modeled estimates to our observed data.ResultsThe combined model showed a reduction in estimate uncertainty for all respondents. Compared with the EQ-5D index-only model, the mean utility for Sri Lankan respondents dropped from 0.556 (0.534-0.579) to 0.540 (0.521-0.559) in men and increased from 0.489 (0.461-0.518) to 0.528 (0.506-0.550) in women, with reduced credible interval width by 13% and 23%, respectively. The mean utility in Australian respondents moved from 0.715 (0.633-0.800) to 0.716 (0.652-0.782) in men, and 0.652 (0.581-0.723) to 0.652 (0.593-0.711) in women, with reduced credible interval width by 23% and 17%, respectively. The credible interval width for simulated data also narrowed, ranging from 8.3 to 8.5%.ConclusionsIncluding the EQ-VAS through Bayesian methods can add value by reducing requisite sample sizes and decision uncertainty using small amounts of additional data that is often collected but rarely used.     

Suprachoroidal Injection of Triamcinolone Acetonide Injectable Suspension for the Treatment of Macular Edema Associated With Uveitis in the United States: A Cost-Effectiveness Analysis

ObjectivesSuprachoroidal injection of triamcinolone acetonide is the first Food and Drug Administration–approved treatment for macular edema associated with uveitis. A cost-effectiveness analysis was performed comparing this treatment with best supportive care (BSC) for the management of this indication from US Medicare and commercial payer perspectives.MethodsA patient-level simulation was developed per the patient characteristics and changes in best-corrected visual acuity letter scores observed in a phase III study of triamcinolone acetonide (PEACHTREE). The wholesale acquisition cost of triamcinolone acetonide was $1650/injection; suprachoroidal injection cost was assumed at $200/injection. Healthcare costs were informed by a US claims–based analysis. Mortality risk associated with severe vision loss and blindness was modeled by applying a hazard ratio to all-cause mortality rates of the US general population. Health-related quality of life weights, obtained from a regression model fitted to the Visual Function Questionnaire-25 data from PEACHTREE, were applied based on the best-corrected visual acuity scores of both eyes. Costs (2020 US dollar) and benefits were discounted at 3% annually. Incremental cost-effectiveness ratios were estimated over a 10-year horizon.ResultsIn the base-case, the incremental cost-effectiveness ratio comparing triamcinolone acetonide with BSC was $28 479 per quality-adjusted life-year gained. The wholesale acquisition cost for triamcinolone acetonide for suprachoroidal use was ～68%, ～56%, and ～27% below the willingness-to-pay thresholds of $150 000, $100 000, and $50 000 per quality-adjusted life-year gained, respectively. Results were robust in sensitivity and scenario analyses.ConclusionsTriamcinolone acetonide for suprachoroidal use is cost-effective compared with BSC for patients with macular edema associated with uveitis.     

Using Metamodeling to Identify the Optimal Strategy for Colorectal Cancer Screening

ObjectivesMetamodeling can address computational challenges within decision-analytic modeling studies evaluating many strategies. This article illustrates the value of metamodeling for evaluating colorectal cancer screening strategies while accounting for colonoscopy capacity constraints.MethodsIn a traditional approach, the best screening strategy was identified from a limited subset of strategies evaluated with the validated Adenoma and Serrated pathway to Colorectal CAncer model. In a metamodeling approach, metamodels were fitted to this limited subset to evaluate all potentially plausible strategies and determine the best overall screening strategy. Approaches were compared based on the best screening strategy in life-years gained compared with no screening. Metamodel runtime and accuracy was assessed.ResultsThe metamodeling approach evaluated >40 000 strategies in <1 minute with high accuracy after 1 adaptive sampling step (mean absolute error: 0.0002 life-years) using 300 samples in total (generation time: 8 days). Findings indicated that health outcomes could be improved without requiring additional colonoscopy capacity. Obtaining similar insights using the traditional approach could require at least 1000 samples (generation time: 28 days). Suggested benefits from screening at ages <40 years require adequate validation of the underlying Adenoma and Serrated pathway to Colorectal CAncer model before making policy recommendations.ConclusionsMetamodeling allows rapid assessment of a vast set of strategies, which may lead to identification of more favorable strategies compared to a traditional approach. Nevertheless, metamodel validation and identifying extrapolation beyond the support of the original decision-analytic model are critical to the interpretation of results. The screening strategies identified with metamodeling support ongoing discussions on decreasing the starting age of colorectal cancer screening.     

情景模拟演练在儿科急诊新护士带教中的应用效果研究

目的研究在儿科急诊对新护士展开临床带教中,使用情景模拟演练教学法的实际应用效果。方法选择该院于2018年5月—2019年5月期间于该院儿科急诊中入岗新护士共计70名,设为该次实验对象。设立常规组与实验组后,将其平均分成两组并分别纳入作为对应组观察患者。其中常规组(2018年5—12月期间)的35名实习护士沿用传统带教模式展开教学,实验组(2019年1—5月期间)的35名实习护士沿用情景模拟演练模式展开教学。在两组同时期下收集各100例临床患者,在带教周期一月期间为其提供护理工作评价。并对其护士进科前后综合能力考评情况、护理技术考核成绩、护士带教护理满意度、患者满意度评价进行统计。结果进科前,两组对象综合能力考评能力于组间对比差异无统计学意义(P>0.05)。进科后,实验组新护士综合能力考评成绩相比常规组更高,同时实验组护士的儿科护士护理技术考核明显优于常规组,差异有统计学意义(P<0.05)。相比较常规组,实验组新护士对带教满意度明显更高,同时对应组患者对护理工作的满意性更高,差异有统计学意义(P<0.05)。结论给予儿科急诊中入岗新护士情境教学法,对培养其岗前护理技能操作技能效率较高,同时能改变其患者护理满意性,加强新上岗护士综合能力,拉近护患之间关系,是较好的临床带教方法。     

SARS-CoV-2 Serial Interval Variation,Montana, USA,March 1–July 31, 2020

We report mean severe acute respiratory syndrome coronavirus 2 serial intervals for Montana, USA, from 583 transmission pairs; infectors’ symptom onset dates occurred during March 1–July 31, 2020. Our estimate was 5.68 (95% CI 5.27–6.08) days, SD 4.77 (95% CI 4.33–5.19) days. Subperiod estimates varied temporally by nonpharmaceutical intervention type and fluctuating incidence.