Evaluation of Mechanisms of Postflight Orthostatic Intolerance with a Simple Cardiovascular System Model

A significant fraction of astronauts experience postflight orthostatic intolerance (POI) during 10-min stand tests conducted on landing day. The average time that nonfinishers can stand is about 7 min. This phenomenon, including the delay in occurrence of presyncope, was studied with a five-compartment model of the cardiovascular system incorporating compartments for the heart/lungs, systemic arteries and cephalic, central, and caudal veins. The model included 28 independent parameters, including factors characterizing cardiac performance, vascular resistance, intrathoracic pressure, nonlinear venous compliance and circulating blood volume, and 13 dependent parameters, including cardiac output and cardiac and vascular compartment pressures and volumes. First, a sensitivity analysis of hemodynamic indicators of presyncope to independent parameters was performed. Results demonstrated that both cardiac output and arterial pressure were most sensitive to volume-related parameters, particularly total blood volume, and less sensitive to peripheral resistance. Next, a simulated postflight stand test confirmed that fluid loss due to capillary filtration, particularly from the caudal region where transmural pressure is high during standing, is a plausible mechanism of POI that also explains the delayed onset of symptoms in most astronauts. An accumulated drop in arterial pressure sufficient to compromise cerebral perfusion and, therefore, cause syncope was reached in about 7 min with a fluid loss of 280 mL. Finally, additional simulations showed that a 75% increase in peripheral resistance, similar to finishers of stand tests, was insufficient to overcome the loss of circulating fluid associated with capillary filtration, and extended the time that the modeled astronaut could stand by only about 1 min. It is therefore concluded that capillary filtration may play a key role in producing POI and that development of countermeasures should perhaps focus on reducing postflight capillary permeability or on stimulating volume-compensating mechanisms.     

9. Herzersatz — Künstliches Herz

Zusammenfassung Trotz guter Ergebnisse sind bisher weniger als 600 Herztransplantationen durchgeführt worden. Im gleichen Zeitraum sind rund 150 Millionen an kardialer Insuffizienz gestorben. Geringe Spenderzahl, organisatorischer Aufwand, Auslastung der kardiochirurgischen Abteilungen und immunologische Reaktionen sind die Erklärung. Das künstliche Herz besteht z.Z. aus implantierten Blutpumpen und externem Antrieb. Längste Überlebenszeit eines Versuchstieres: 220 Tage. Klinische Anwendung käme für eine Dauer von 2–3 Monaten bis zu einer Transplantation in Frage. Nächster Schritt: implantierte Blutpumpen, externer transportabler Antrieb.     

Heart rate variability after prolonged spaceflights

Astronauts returning from spaceflight often experience post-flight orthostatic intolerance. This study was designed to determine whether cosmonauts with post-flight syncope could be distinguished from those with no post-flight syncope. The autonomic function was determined in a group of ten subjects, with no previous history of syncope, during a stand test before and after a long-term spaceflight (90 to 198 days). Heart rate (HR) and systolic blood pressure (SBP) were measured beat-by-beat, pre- and post-flight and the spontaneous baroreflex sensitivity and HR variability were studied. Individuals were categorized according to their ability to remain standing for 5 min the day after landing. Three of the ten cosmonauts failed to finish the standing test performed the day after landing (non-finishers). The spontaneous baroreflex slope was reduced in both groups after the spaceflight. The non-finisher group had a lower SBP (P<0.05) at rest in pre-flight tests than the group that completed the test (finisher group). The non-finisher group also had higher indicators of parasympathetic activity when supine, both pre- and post-flight, but this difference disappeared with standing. At the end of the stand test, SBP and HR were lower in non-finisher cosmonauts than the finishers, while HR did not increase compared to early measurements in the stand test of the finisher group. These results suggest an impairment in autonomic control of HR, which might contribute to the fainting response. Electronic Publication     

The impact of symptomatic knee osteoarthritis on overall gait pattern deviations and its association with performance-based measures and patient-reported outcomes

Background

Limited knowledge exists regarding the impact of symptomatic knee osteoarthritis (OA) on the overall gait pattern; and whether gait deviations are associated with performance-based measures (PBMs) and patient-reported outcomes (PROs). This cross-sectional study evaluated overall gait patterns in patients with knee OA using the Gait Deviation Index for kinematics (GDI) and kinetics (GDI-kinetic), and explored associations between gait deviations, PBMs, and PROs.

带膜支架在治疗恶性肿瘤食管狭窄中的应用及护理

目的：总结带膜食管支架在姑息治疗恶性肿瘤食管狭窄中的疗效及护理经验。方法：44例患术前均行X线检查确定病变部位及狭窄程度、范围及与周围组织的关系。在X线电视监视下置入带膜食管支架。结果：支架置放成功率达100％，平均生存期7个月。结论：带膜食管支架治疗食管肿瘤狭窄疗效可靠，并发症少，配合精心护理可改善患生活质量，延长生存期。     

11. Lungentransplantation

Zusammenfassung Die Hoffnungen auf die Lungentransplantation haben sich nicht erfüllt. Bei 37 Transplantationen betrug die längste Oberlebenszeit nur 10 Monate. Probleme ergeben sich durch das Nebeneinander von Transplantat and insuffizienter Lunge. Unterschiedliche Gefäßwiderstände and Elastizität beeinflussen das Durchblutungs- and Belüftungsverhältnis. Gestörter Lymphabfluß kann kurzfristig zu Odemen führen. Offen bleibt der EinfluB der Denervation, ebenso die Annahme, daß die Lunge bei der Abstolßreaktion, immunologischen Behandlung and Infektion ungünstiger reagiert als zum Beispiel die Leber oder Niere.     

MSCT强化度和PET—CTSUV值与肾透明细胞癌病理分级相关性研究

目的 探讨MSCT强化幅度和PET-CT SUV值与肾透明细胞＇癌病理分级相关性.方法 分析肾透明细胞癌Ⅰ、Ⅱ、Ⅲ级各15例患者MSCT增强及PET-CT SUV值的影像数据.结果 三级RCCC在增强皮质期及实质期的最大强化CT值均无统计学意义（P〉0.05）;其SUVmax值有统计学意义（P〈0.05）.随病理分级增高SUVmax值也相应升高.结论 18F-FDG PET-CT的SUV值可以提示RCCC病理分级,为治疗和预后提供更有价值的信息.     

标准曲线变动性的不确定度分量评定

目的:以实时荧光定量PCR检测乙型肝炎病毒核酸载量实验为例,尝试性评定临床实验室中标准曲线变动性的不确定度分量。方法:对4个乙型肝炎病毒脱氧核糖核酸(DNA)定量检测系列标准品重复测定5次,取各标准品的Ct均值对标准品浓度的对数值求回归直线,进而测定并计算高、中、低值血清样本的DNA载量及其标准曲线变动性的不确定度分量。结果:高、中、低值血清样本浓度取对数后的标准曲线变动性的标准不确定度分量分别为0.079、0.040和0.071。结论:标准曲线变动性的不确定度分量和标准品的数量及标准品重复测量次数相关;和待测样本浓度及其重复测量次数相关。     

颈椎疾患颅骨头环牵引卧枕肩背部抬高垫及翻身垫的设计应用

目的探讨颈椎疾患行颅骨头环牵引患者卧枕、肩背部抬高垫及翻身垫在临床的应用效果。方法制作不同身高体型的人体头颈肩背部石膏模,以模为样品制作颅骨头环牵引卧枕、肩背部抬高垫及翻身垫,选择在2007年7月～2010年6月住院的颈椎疾患行颅骨头环牵引治疗患者100例,随机分为对照组和观察组,观察组使用我们设计的卧枕、肩背部抬高垫及翻身垫,对照组使用普通枕,对两组患者持续牵引的有效稳定性、舒适度、头枕部是否出现压疮进行比较。结果观察组患者持续牵引的有效稳定性、舒适度、预防患者头枕部压疮并发症明显优于对照组（P〈0．05）。结论卧枕、肩背部抬高垫及翻身垫应用于颅骨头环牵引患者可明显提高颅骨头环牵引的有效稳定性及患者舒适度、预防压疮发生。