Investigation of the Characteristics of HeartWare HVAD and Thoratec HeartMate II Under Steady and Pulsatile Flow Conditions

The aim of this study was to elucidate the dynamic characteristics of the Thoratec HeartMate II (HMII) and the HeartWare HVAD (HVAD) left ventricular assist devices (LVADs) under clinically representative in vitro operating conditions. The performance of the two LVADs were compared in a normothermic, human blood‐filled mock circulation model under conditions of steady (nonpulsatile) flow and under simulated physiologic conditions. These experiments were repeated using 5% dextrose in order to determine its suitability as a blood analog. Under steady flow conditions, for the HMII, approximately linear inverse LVAD differential pressure (H) versus flow (Q) relationships were observed with good correspondence between the results of blood and 5% dextrose under all conditions except at a pump speed of 9000 rpm. For the HVAD, the corresponding relationships were inverse curvilinear and with good correspondence between the blood‐derived and 5% dextrose‐derived relationships in the flow rate range of 2–6 L/min and at pump speeds up to 3000 rpm. Under pulsatile operating conditions, for each LVAD operating at a particular pump speed, an counterclockwise loop was inscribed in the HQ domain during a simulated cardiac cycle (HQ loop); this showed that there was a variable phase relationship between LVAD differential pressure and LVAD flow. For both the HMII and HVAD, increasing pump speed was associated with a right‐hand and upward shift of the HQ loop and simulation of impairment of left ventricular function was associated with a decrease in loop area. During clinical use, not only does the pressure differential across the LVAD and its flow rate vary continuously, but their phase relationship is variable. This behavior is inadequately described by the widely accepted representation of a plot of pressure differential versus flow derived under steady conditions. We conclude that the dynamic HQ loop is a more meaningful representation of clinical operating conditions than the widely accepted steady flow HQ curve.     

Influence of a Rotational Speed Modulation System Used With an Implantable Continuous‐Flow Left Ventricular Assist Device on von Willebrand Factor Dynamics

We have developed a rotational speed (RS) modulation system for a continuous‐flow left ventricular assist device (EVAHEART) that can change RS in synchronization with a patient's electrocardiogram. Although EVAHEART is considered not to cause significant acquired von Willebrand syndrome, there remains a concern that the repeated acceleration and deceleration of the impeller may degrade von Willebrand factor (vWF) multimers. Accordingly, we evaluated the influence of our RS modulation system on vWF dynamics. A simple mock circulation was used. The circulation was filled with whole bovine blood (650 mL), and the temperature was maintained at 37 ± 1°C. EVAHEART was operated using the electrocardiogram‐synchronized RS modulation system with an RS variance of 500 rpm and a pulse frequency of 60 bpm (EVA‐RSM; n = 4). The pumps were operated at a mean flow rate of 5.0 ± 0.2 L/min against a mean pressure head of 100 ± 3 mm Hg. The continuous‐flow mode of EVAHEART (EVA‐C; n = 4) and ROTAFLOW (ROTA; n = 4) was used as controls. Whole blood samples were collected at baseline and every 60 min for 6 h. Complete blood counts (CBCs), normalized indexes of hemolysis (NIH), vWF antigen (vWF:Ag), vWF ristocetin cofactor (vWF:Rco), the ratio of vWF:Rco to vWF:Ag (Rco/Ag), and high molecular weight multimers (HMWM) of vWF were evaluated. There were no significant changes in CBCs throughout the 6‐h test period in any group. NIH levels of EVA‐RSM, EVA‐C, and ROTA were 0.0035 ± 0.0018, 0.0031 ± 0.0007, and 0.0022 ± 0.0011 g/100 L, respectively. Levels of vWF:Ag, vWF:Rco, and Rco/Ag did not change significantly during the test. Immunoblotting analysis of vWF multimers showed slight degradation of HMWM in all groups, but there were no significant differences between groups in the ratios of HMWM to low molecular weight multimers, calculated by densitometry. This study suggests that our RS modulation system used with EVAHEART does not have marked adverse influences on vWF dynamics. The low NIH and the absence of significant decreases in CBCs indicate that EVAHEART is hemocompatible, regardless of whether it is operated with the RS modulation system.     

What Is the Optimal Setting for a Continuous‐Flow Left Ventricular Assist Device in Severe Mitral Regurgitation?

Excessive left ventricular (LV) volume unloading can affect right ventricular (RV) function by causing a leftward shift of the interventricular septum in patients with mitral regurgitation (MR) receiving left ventricular assist device (LVAD) support. Optimal settings for the LVAD should be chosen to appropriately control the MR without causing RV dysfunction. In this study, we assessed the utility of our electrocardiogram‐synchronized rotational speed (RS) modulation system along with a continuous‐flow LVAD in a goat model of MR. We implanted EVAHEART devices after left thoracotomy in six adult goats weighing 66.4 ± 10.7 kg. Severe MR was induced through inflation of a temporary inferior vena cava filter placed within the mitral valve. We evaluated total flow (TF; the sum of aortic flow and pump flow [PF]), RV fractional area change (RVFAC) calculated by echocardiography, left atrial pressure (LAP), LV end‐diastolic pressure (LVEDP), LV end‐diastolic volume (LVEDV), and LV stroke work (LVSW) with a bypass rate (PF divided by TF) of 100% under four conditions: circuit‐clamp, continuous mode, co‐pulse mode (increased RS during systole), and counter‐pulse mode (increased RS during diastole). TF tended to be higher in the counter‐pulse mode. Moreover, RVFAC was significantly higher in the counter‐pulse mode than in the co‐pulse mode, whereas LAP was significantly lower in all driving modes than in the circuit‐clamp condition. Furthermore, LVEDP, LVEDV, and LVSW were significantly lower in the counter‐pulse mode than in the circuit‐clamp condition. The counter‐pulse mode of our RS modulation system used with a continuous‐flow LVAD may offer favorable control of MR while minimizing RV dysfunction.     

智力障碍青少年工作记忆和加工速度的认知功能缺陷

目的:探讨智力障碍青少年的工作记忆和加工速度是否存在缺陷。方法:在广州市3所智障学校选取13~16岁智力障碍青少年和正常青少年各42例,分别作为研究组和对照组,采用韦氏记忆量表(WMS)中的数字工作广度(顺背、倒背)、空间工作记忆广度(顺背、倒背)和3项加工速度(感觉运动、知觉速度、扫描速度)进行测试。结果:1智力障碍青少年的工作记忆和加工速度得分显著低于智力正常青少年(t=-23.61,-19.35;P0.01);2智力障碍青少年工作记忆和加工速度的性别差异均不显著;3工作记忆和加工速度各变量间均显著相关(P0.05);4智力障碍青少年的工作记忆对加工速度的回归效应显著,预测率为36.00%。结论:智力障碍青少年的工作记忆与加工速度存在缺陷;其工作记忆对加工速度具有预测性。     

Dynamic measurement of the torque-speed characteristics of dental high speed air turbine handpieces*

The first requirement for adequate performance of an air turbine handpiece is sufficient power. Suppliers of such handpieces do not provide data on the power produced by their equipment. A method for determining the torque, speed and hence power during simulated operation is described. Forty-one new and used handpieces were tested. Maximum speeds up to 500 000 rpm, maximum torques up to 2.33 N.mm and maximum power up to 29.6 watt were observed. The maximum power was produced at between 49 and 79 per cent of the free-running speed. A relationship between maximum power and stall torque was noted. The maximum torque is at stall for ball-bearing units. The stall torque can be easily determined by a simple stall torque test which is described. Using this test, the performance of handpieces can be easily checked in the clinic. The one air-bearing handpiece tested performed in a manner similar to the others, except that stall occurred below 60 000 rpm.     

输液所致静脉炎的药物原因分析

目的输液带来的静脉炎等问题是护理工作的难点,药物的渗透压、pH值、刺激性、毒性及输注速度是导致输液性静脉炎的重要原因。文献报道可致输液性静脉炎的药物有多种。     

Recurrent Falls and Dual Task–Related Decrease in Walking Speed: Is There a Relationship?

OBJECTIVES: To determine whether dual task–related changes in walking speed were associated with recurrent falls in frail older adults.
DESIGN: Twelve-month prospective cohort study.
SETTING: Thirteen senior housing facilities.
PARTICIPANTS: Two hundred thirteen subjects (mean age 84.4±5.5).
MEASUREMENTS: Usual and dual-tasking walking speeds (m/s) were calculated on a 10-m straight walkway at baseline. Information on incident falls during the follow-up year was collected monthly, and participants were divided into three groups based on the occurrence of falls (0, 1, and ≥2). Recurrent falls were defined as two or more falls during the 12-month follow-up period.
RESULTS: Twenty subjects (9.4%) were classified as recurrent fallers. The occurrence of recurrent falls was associated with age (crude odds ratio (OR)=1.11, P =.02), number of drugs (crude OR=1.28, P =.002), and walking speed under both walking conditions (crude OR=0.96, P =.002 for usual walking and crude OR=0.60, P =.005 for walking while counting backward). Multiple Poisson regression showed that only walking speed while dual tasking and number of drugs were associated with incident falls (incident rate ratio (IRR)=0.84, P =.045 and IRR=1.10, P =.004).
CONCLUSION: Slower walking speed while counting backward was associated with recurrent falls, suggesting that changes in gait performance while dual tasking might be an inexpensive way of identifying frail older adults prone to falling.     

Factors influencing the fracture of nickel-titanium rotary instruments

AIM: To evaluate the effect of rotational speed and the angle and radius of curvature of root canals on the fracture of two types of nickel-titanium rotary instruments: K3 and ProTaper. METHODOLOGY: A total of 240 root canals of extracted human maxillary and mandibular molars were divided into two groups of 120, according to the angle of the canal curvature (group A: <30 degrees, group B: >30 degrees). Each group was then divided into two subgroups of 60 canals in order to perform instrumentation using K3 and ProTaper rotary instruments at three different rotational speeds: 150, 250 and 350 r.p.m. (20 canals at each rotational speed). Each instrument was used a maximum of 20 times and at one rotational speed only. The angle and radius of canal curvature were measured in the only group in which fractures actually took place (group B). RESULTS: There were a total of 22 instrument fractures; all of these occurred in canals with curves >30 degree. In a multivariate analysis, it was demonstrated that the files used at a rotational speed of 350 r.p.m. were more likely to fracture than those used at 250 r.p.m. (OR: 1113.88; 95% CI: 2.36-526420.05) and than those used at 150 r.p.m. (OR: 13531.33; 95% CI: 5.37-34120254.00). A decrease in the angle of curvature of the canal also significantly reduced the likelihood of fracture (OR: 0.2083; 95% CI: 0.068-0.6502). These relationships remained significant after being adjusted for the potential interactions between the remaining variables. No significant differences were found between the files or the radii of the canals. CONCLUSIONS: Instrument fracture was associated with rotational speed and the angle of curvature of the canal.     

高速离心法和稀释法处理乳糜血对光学法凝血指标检测结果的影响

目的 探讨高速离心法和稀释法处理乳糜血对光学法凝血指标检测结果的影响.方法 以我院检验科2013年4月至2014年4月接收60例正常凝血标本与60例乳糜血凝血标本为对象.正常凝血标本组采用稀释法对PT、APTT和FIB进行检测并对回归方程加以建立.乳糜血凝血标本组根据三酞甘油浓度不同,分为轻度、中度、重度三组;在PT、APTT和FIB的检测上,对稀释法和高速离心法加以采用;同时在回归方程中对稀释后的检测结果加以代人,比较代入后所得结果与高速离心法结果.结果 回归分析正常凝血标本的原血浆与稀释血浆PT、APTT和FIB的检测结果,分别得出PT、APTT和FIB的回归方程(稀释前与稀释后结果分别用Y与X表示).PT:Y=0.305X+4.29,APTT:Y=0.155X+22.607,FIB:Y=2.883X+0.218.PT、APTT和FIB回归方程中r分别为0.860、0.155、0.821,P均为0.000.稀释法与高速离心法对PT、APTT和FIB的检测中,其结果在轻度、中度乳糜血组差异无统计学意义(P＞0.05);在重度乳糜血组检测结果中,稀释法中PT的检测结果及FIB的含量明显比高速离心法高(P＜0.05).结论 当在乳糜血标本的凝血项目检测中应用光学法仪器时,高速离心法比稀释法具有更强的抗干扰能力,适用范围更广,结果也更加准确,更有利于出血性疾病诊断.     

麻仁软胶囊配合步行治疗老年习惯性便秘临床研究

目的 评价麻仁软胶囊配合步行治疗老年习惯性便秘的疗效.方法 将符合入选标准的112例老年习惯性便秘患者采用随机数字表法分为对照A组38例、干预B组38例、干预C组36例,对照A组口服麻仁软胶囊,干预B、C组在对照A组基础上,分别于晚饭后步行30 min、60 min.3组均治疗4周,随访2周.依据治疗前后症状、体征积分变化评价疗效.结果 治疗后4周,干预C组、干预B组便秘症状、体征积分[(4.1±2.0)分、(4.8±2.1)分比(5.3±1.5)分,F=3.886]低于对照A组(P=0.023),干预C组积分低于干预B组(P=0.041).治疗后2周,对照A组总有效率为36.8%(14/38)、干预B组为63.2%(24/38)、干预C组为77.8%(28/36),3组比较差异有统计学意义(χ2=12.741,P=0.005);治疗后4周,对照A组总有效率为47.4%(18/38)、干预B组为76.3%(29/38)、干预C组为86.1%(31/36),3组比较差异有统计学意义(χ2=13.103,P=0.005);随访2周,对照A组总有效率为23.7%(9/38)、干预B组为60.6%(23/38)、干预C组为75.0%(27/36),3组比较差异有统计学意义(χ2=12.904,P=0.015).结论 麻仁软胶囊配合步行可缓解老年习惯性便秘患者临床症状,且步行时间以60 min时疗效最佳.