双模态超燃冲压发动机点火方案对比试验

在来流马赫数2、总温840K的双模态超燃冲压发动机扩张型燃烧室的冷启动工况下,对凹腔上游的煤油横向射流喷雾的三种点火方案(热射流点火、乙烯引导点火、凹腔内局部补氧点火)进行了试验对比研究。采用高速相机拍摄了不同点火方式下的初始火焰生成和发展过程,对比分析了各种点火方案的点火接力过程和压力响应特点。试验研究表明,热射流火焰和喷雾下游掺混燃烧后通过火焰逆传形成凹腔驻留火焰,室压受热射流供应及其与喷雾作用的非定常特性的影响较大；乙烯引导点火受乙烯燃烧强度的影响,在研究的参数范围内,由于生成的乙烯火焰较弱,易被煤油喷雾浇熄,旨在凹腔内形成接力火焰的点火方法未能实现乙烯引导的成功点火；在凹腔内局部补氧能够改善煤油喷雾的点火性能,点火接力过程过渡平稳。      

横向射流起爆爆震波数值研究

采用CFD软件对横向喷射的射流在预先充满丙烷/空气恰当比混合物的爆震室中起爆爆震波的过程和机理进行了数值模拟,并讨论了射流的压力、速度以及温度对爆震波起爆特性的影响。结果表明,对于计算的物理模型,爆震射流不能在爆震室中直接起爆爆震波；射流与壁面的碰撞形成激波反射,激波反射产生的横波、热点和局部爆震引发起爆；能够成功起爆爆震波的横向射流存在最小的射流压力,该射流压力为0.9MPa；较小的射流压力、较小的射流速度或较低的射流温度都不利于横向射流在爆震室中起爆爆震波。      

基于火焰面模型的推力室起动过程仿真

采用计算流体力学的方法,对氢氧火箭发动机推力室的起动过程进行了数值仿真。起动的非定常过程由双时间步方法模拟,燃烧过程由稳态层流火焰面模型模拟,火焰面建库采用6组分8步反应的化学动力学模型。按照地面试车时序进行推力室起动过程仿真,获得了起动过程的建压曲线以及详细的流场建立过程。结果表明,经过点火瞬间压力松弛控制的稳态层流火焰面模型可用于火箭发动机的点火过程动态仿真,仿真得到的压力曲线与试车曲线相比符合良好。      

1026例男性尿流率调查

目的界定排尿正常男性的各项排尿数据。方法将1026例30岁以上志愿者或无下尿路症状性疾病的就诊者，按年龄分为6组，A组30-岁，238例；B组40-岁，329例；C组50-岁，227例；D组60-岁，93例；E组-70。岁，78例；F组80岁以上，61例。分别作尿流率检测，观察其最大尿流率（Qmax）、平均尿流率（Qave）、排尿量、排尿时间和尿流时间。结果各组排尿量间差别无显著性意义（P〉0．05）；Qmax和Oave随年龄的增大而逐渐下降（P〈0．05）。结论初步显示了各年龄组排尿正常男性的各项排尿数据，可作为评价排尿活动的参数。     

不同消毒方法对接台手术间空气质量的影响

目的了解3种消毒方法对接台手术无层流普通手术间空气质量的影响。方法在3个无层流手术间进行连续接台手术270台次，在接台间隙采用3种方法消毒手术间。对照组接台间隙保持动态空气消毒机一直开启，更换手术床单，污物钳夹取地表污物；实验1组在对照组方法的基础上，手术间物表及地表用500mg／L含氯消毒液，按1：100浓度湿拖地面，按1：200浓度湿擦物品表面；实验2组在实验1组方法的基础上，增加紫外线消毒30min。结果第1台手术结束时，三组空气合格率比较，差异无显著性意义（P〉0．05）；第2、3台结束时，三组空气合格率差异有显著性意义（均P〈0．01），但第2台结束时，对照组与实验1、2组比较，差异无显著性意义（均P〉0．0125）；第3台结束时对照组与实验1、2组比较，差异有显著性意义（均P〈0．0125）；实验1组与实验2组比较，差异无显著性意义（均P〉0．0125）。结论无层流手术间随接台手术次数增加，空气质量逐渐下降，行接台手术时空气及物体表面必须进行消毒处理。手术间持续应用动态空气消毒机，接台间隙用含氯消毒液湿擦、湿拖手术间物表及地面，消毒效果好，相对省时。     

心导管室空气培养细菌学分析

目的了解心导管室在连台介入检查与治疗过程中手术间空气污染状况及菌群分布情况,为制定合理可行的感染控制措施提供依据。方法采用平板暴露沉降法,对心导管室手术间术前及连台手术后空气中微生物的污染状态进行五点(即ABCDE五个点位)采集、培养、计数和分析。结果共采集样本255份;手术间各点位细菌浓度随手术台次(即人员流动人数)增加而升高(P0.01);255份空气培养共分离出294株病原菌,以凝固酶阴性葡萄球菌居首,占41.84%;其次为微球菌(占20.75%)和溶血葡萄球菌(占20.07%)。结论连续心脏介入检查及治疗过程中手术间空气微生物污染严重,应限制人员活动,并采取动态空气消毒方法,以减少空气中的微生物。     

湍流燃烧模型对双旋流燃烧室喷雾燃烧的影响

采用数值模拟与试验测量相结合的方法,研究扩展旋涡破碎模型、扩展二阶矩模型和涡团耗散概念模型等三种湍流燃烧模型对双旋流湍流喷雾燃烧流场的影响。在任意曲线坐标系下数值研究双级轴向旋流器环形燃烧室全流程流场,采用粒子图像测速仪测量燃烧流场气流速度分布,热电偶测量燃烧室出口温度分布。计算结果与验证试验数据比较表明:不同湍流燃烧模型对双旋流湍流喷雾燃烧影响较大,所得的回流区形状、速度、温度场以及出口温度分布等都不太相同,其中扩展二阶矩模型所得的结果与试验值符合最好,更适用于模拟双旋流环形燃烧室湍流喷雾燃烧。      

耦合法修复尿道下裂的功能性效果评价

目的 评价口腔黏膜片移植与局部皮瓣耦合组建尿道修复尿道下裂的功能性效果.方法 17例先天性尿道下裂患儿行口腔黏膜片移植与局部皮瓣耦合再造尿道术修复尿道下裂.术前1d和术后1年对患儿进行尿流率测定检查,记录尿流率、尿量、排尿时间等参数,描记尿流曲线.将最大尿流率在Toguri尿流率列线图上进行描点分析.结果 术前17例患儿的最大尿流率为(7.89+2.29) ml/s,其中12例(70.6％)尿流率曲线呈平台形,5例(29.4％)尿流率曲线低平；在Toguri尿流率列线图上描点分析,12例(70.6％)最大尿流率在正常儿童的第5百分位数曲线以下.耦合法再造尿道术后1年随访,17例患儿的最大尿流率为(11.30±3.01) ml/s,其中10例(58.8％)患儿的尿流率曲线接近正常的钟形曲线；7例(41.2％)最大尿流率位于正常儿童的第25百分位数曲线以上,8例(47.1％)位于正常儿童的第25百分位数与第5百分位数曲线之间,2例(11.8％)在第5百分位数曲线以下.结论 耦合法组建尿道修复尿道下裂的功能性效果良好,手术后患者的最大尿流率提高.     

143例肺动脉干下型室间隔缺损外科治疗总结

目的总结肺动脉干下型室间隔缺损手术治疗的经验,了解其特点,探讨本病的手术指征、技巧及术式选择。方法通过1997年1月至2007年8月在我院手术的143例肺动脉干下型室间隔缺损的患者,观察室缺特点及术式选择对预后的影响。结果此类室缺常合并主动脉瓣脱垂和反流,本组为40%;室缺实际大小常大于术前超声报告;此类室缺以补片修补为主,术中处理好主动脉瓣病变。结论肺动脉干下室间隔缺损应及早手术治疗,且以补片修补为主。如合并主动脉瓣脱垂,重视主动脉瓣探查和处理。     

男性原发性膀胱颈梗阻的尿动力学特点

目的 评价原发性男性膀胱颈梗阻的尿动力学表现.方法 回顾性分析23例男性原发性膀胱颈梗阻之尿动力学改变,包括尿流率、残余尿量及多通道尿动力学检查,并结合排尿期膀胱尿道造影、膀胱镜检查进行分析.结果 所有病例尿流率异常,可表现为最大尿流率降低,尿流曲线为钟型达峰时间延长或低平型.压力-流率检查可出现三型:高压-低流、正常压-低流、低压-低流,膀胱颈开放时间延迟在三型中均有出现.结合排尿期膀胱尿道造影、膀胱镜检查分析对确定诊断有重要意义.结论 普通尿动力学检查对原发性膀胱颈梗阻可作出初步诊断,明确诊断需结合排尿期膀胱尿道造影.     

Vasopressor hormone response following mesenteric traction during major abdominal surgery

Background : We investigated the vasopressor hormone response following mesenteric traction (MT) with hypotension due to prostacyclin (PGI₂) release in patients undergoing abdominal surgery with a combined general and epidural anesthesia. Methods : In a prospective, randomized, placebo-controlled study we administered 400 mg ibuprofen (i.v.) in 42 patients scheduled for abdominal surgery. General anesthesia was combined with epidural anesthesia (T4-L1). Before as well as 5, 15, 30, 45, and 90 min after MT we recorded plasma osmolality, hemodynamics and measured 6-keto-PGFlα (stabile metabolite of PGI₂), TXB₂ (stabile metabolite of thromboxane A₂) active renin, and arginine vasopressin (AVP) plasma concentrations by radioimmunoassay. Catecholamine levels were assessed by high-pressure liquid chromatography (HPLC) with electrochemical detection. Results : Following MT, arterial hypotension occurred along with a substantial PGI₂ release. This was completely abolished by ibuprofen administration. Although plasma levels of 6-keto-PGF_1α (1133 (708) vs. 60 (3) ng/L, median (median absolute deviation), P=0.0001, placebo vs. ibuprofen) remained significantly elevated, blood pressure was restored within 30 min after MT in the placebo group. At the same point in time plasma concentrations of TXB² (164 (87) vs. 58 (1) ng/L, P=0.0001), epinephrine (46 (33) vs. 14 (6) ng/L, P=0.001), AVP (41 ± (18) vs. 12 (7) ng/L, P=0.0004), and active renin (27 (12) vs. 12 (4) ng/L, P = 0.001) were significantly higher in placebo-treated patients. Conclusion : Under combined general and epidural anesthesia arterial hypotension following MT due to endogenous PGI₂ release is associated with enhanced release of AVP, active renin, epinephrine and thromboxane A₂, presumably contributing to hemodynamic stability within 30 min after MT.     

A Teaspoon Pump for Pumping Blood with High Hydraulic Efficiency and Low Hemolysis Potential

Abstract: Virtually all blood pumps contain some kind of rubbing, sliding, closely moving machinery surfaces that are exposed to the blood being pumped. These valves, internal bearings, magnetic bearing position sensors, and shaft seals cause most of the problems with blood pumps. The original teaspoon pump design prevented the rubbing, sliding machinery surfaces from contacting the blood. However, the hydraulic efficiency was low because the blood was able to "slip around" the rotating impeller so that the blood itself never rotated fast enough to develop adequate pressure. An improved teaspoon blood pump has been designed and tested and has shown acceptable hydraulic performance and low hemolysis potential. The new pump uses a nonrotating "swinging" hose as the pump impeller. The fluid enters the pump through the center of the swinging hose; therefore, there can be no fluid slip between the revolving blood and the revolving impeller. The new pump uses an impeller that is comparable to a flexible garden hose. If the free end of the hose were swung around in a circle like half of a jump rope, the fluid inside the hose would rotate and develop pressure even though the hose impeller itself did not "rotate"; therefore, no rotating shaft seal or internal bearings are required.     

A comparison of the inhibitory effects of four volatile anaesthetics on the metabolism of chlorzoxazone, a substrate for CYP2E1, in rabbits

Background: Halothane inhibits in vitro and in vivo activity of cytochrome P-450 (CYP) 2E1. There are several fluorinated volatile anaesthetics besides halothane, and most of them are defluorinated by CYP2E1. It is unclear whether other fluorinated anaesthetics inhibit the in vivo activity of CYP2E1.
Methods: We compared the inhibitory effects of therapeutic concentrations of four inhalational anaesthetics, halothane, enflurane, isoflurane, and sevoflurane, on chlorzoxazone metabolism in rabbits receiving artificial ventilation.
Results: All four inhalational anaesthetics decreased arterial blood pressure and increased plasma chlorzoxazone concentration. However, no significant differences in the plasma chlorzoxazone concentration were found between the four anaesthetics. The estimated chlorzoxazone clearance increased after beginning inhalation with all four agents, but no significant difference in clearance was noted between agents.
Conclusions: At therapeutic concentrations, the in vivo inhibitory effect on chlorzoxazone metabolism was similar for all four inhalational anaesthetics examined, even though their chemical characteristics and extent of hepatic metabolism differ considerably.     

Microspheres Based Detoxification System: A New Method in Convective Blood Purification

Abstract: A variety of protein-bound or hydrophobic substances, accumulating as a result of pathologic conditions such as exogenous or endogenous intoxications, are removed poorly by conventional detoxification methods because of low accessibility (hemodialysis), insufficient adsorption capabilities (hemosorption), low efficiency (peritoneal dialysis), or economic limitations (high-volume plasmapheresis). Combining advantages of existing methods with microspheric technology, a module-based system was designed. Major operating parameters of the latter can be modified to allow for adjustment to individual clinical situations. An extracorporeal blood circuit including a plasmafilter is combined with a secondary high-velocity plasma circuit driven by a centrifugal pump. Different microspheric adsorbers can be combined in one circuit or applied in sequence. Thus, a prolonged treatment can be tailored using specially designed selective adsorber materials. Comparing this system with existing methods (high-flux hemodialysis, molecular adsorbent recycling system), results from our in vitro studies and animal experiments demonstrate the superior efficiency of substance removal.     

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background : Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO).
Methods : General hemodynamics and regional blood flows assessed by microsphere technique (15 (μm) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H₂O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg · kg⁻¹ followed by 0.15 mg · kg⁻¹ · h⁻¹, n=8) or verapamil (0.1 mg · kg⁻¹ followed by 0.3 mg · kg⁻¹ · h⁻¹, n=8).
Results : CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase.
Conclusions : The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.     

Bariatric Surgery in Some "Central and East-European (former Eastern bloc)"Countries - Current Status and Prediction for the Next Millennium

Background: Obesity is increasing globallly, including in the formerly "Eastern Bloc" countries. Methods: A survey was made of obesity and bariatric surgery. Results: In the 8 East and Central European countries studied, with total population 300 million, roughly 43% of the population was overweight (BMI 25-30), 23% obese (BMI > 30), with about 15 million people morbidly obese (BMI > 40). From 0-10 morbidly obese individuals/100,000/year undergo bariatric surgery. Conclusion: Most countries were found to provide inadequate treatment for obesity.The majority of the morbidly obese are not treated effectively. However, health-care awareness of obesity and bariatric surgeons are slowly increasing.     

Volatile anaesthetics reduce adhesion of blood platelets under low-flow conditions in the coronary system of isolated guinea pig hearts

Background : Inhibitory effects of volatile anaesthetics on platelet aggregation have been demonstrated in several studies. However, the influence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far.
Methods : Isolated hearts of guinea pigs were perfused with buffer in the absence or presence of volatile anaesthetics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before, during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and reperfusion. The number of platelets sequestered to the endothelium was calculated from the difference between coronary in- and output of platelets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined.
Results : At a flow rate of 5 ml/min only about 3% of the applied platelets did not emerge from the coronary system, in any group. In contrast, 13.1±1.2% (mean±SEM) of infused platelets became adherent in low-flow perfusion in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2±1.2%), sevoflurane (to 4.4±0.9%) or halothane (to 3.2±1.5%) (each P <0.05 vs. control). Volatile anaesthetic, 0.5 MAC, did not inhibit platelet adhesion to a statistically significant extent in any case. Perfusion pressure and metabolic parameters were not statistically different between the control and the hearts exposed to anaesthetics.
Conclusion : Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the coronary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.     

Synergistic interaction between the effects of propofol and midazolam with fentanyl on phrenic nerve activity in rabbits

Background: It has been shown that the depressive effects of both propofol and midazolam on consciousness are synergistic with opioids, but the nature of their interactions on other physiological systems, e. g. respiration, has not been fully investigated. The present study examined the effect of propofol and midazolam alone and in combination with fentanyl on phrenic nerve activity (PNA) and whether such interactions are additive or synergistic. Methods: PNA was recorded in 27 anaesthetised and artificially ventilated rabbits. In three groups, propofol, fentanyl and midazolam were administered intravenously in incremental doses to construct dose-response curves for the depressant effects of each one on PNA. In another two groups, the effect of pretreatment with either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. on the effects of propofol and fentanyl respectively on PNA were studied. Results: Propofol and fentanyl caused a dose-dependent depression of PNA with complete abolition at the highest total doses of 16 mg · kg^?1 i. v. and 32 μg · kg^?1 i. v., respectively. In contrast, midazolam in incremental doses to a total of 0.8 mg · kg^?1 reduced mean PNA by 63%, but approximately 12% of PNA remained at a total dose as high as 6.4 mg · kg^?1. The mean ED₅₀s, calculated from dose-response curves, were 5.4 mg · kg^?1, 3.9 μg · kg^?1 and 0.4 mg · kg^?1 for propofol, fentanyl and midazolam, respectively. Initial doses of either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. acted synergistically with subsequent doses of either propofol or fentanyl to abolish PNA at total doses of 8 mg · kg^?1 and 8 μg · kg^?1, respectively. Conclusion: Fentanyl has a synergistic interaction with both propofol and midazolam on PNA and hence potentially on respiration.     

Influence of dopexamine hydrochloride on haemodynamics and regulators of circulation in patients undergoing major abdominal surgery

Background: Catecholaminergic support is often used to improve haemodynamics in patients undergoing major abdominal surgery. Dopexamine is a synthetic vasoactive catecholamine with beneficial microcirculatory properties. Methods: The influence of perioperative administration of dopexamine on cardiorespiratory data and important regulators of macro- and microcirculation were studied in 30 patients undergoing Whipple pancreaticduodenectomy. The patients received randomized and blinded either 2 μg · kg^?1 · min^?1 of dopexamine (n=15) or placebo (n=15, control group). The infusion was started after induction of anaesthesia and continued until the morning of the first postoperative day. Endothelin-1 (ET-1), vasopressin, atrial natriuretic peptide (ANP), and catecholamine plasma levels were measured from arterial blood samples. Measurements were carried out after induction of anaesthesia, 2 h after onset of surgery, at the end of surgery, 2 h after surgery, and on the morning of the first postoperative day. Results: Cardiac index (CI) increased significantly in the dopexamine group (from 2.61±0.41 to 4.57±0.78 1 · min^?1 · m^?2) and remained elevated until the morning of the first postoperative day. Oxygen delivery index (DO₂I) and oxygen consumption index (VO₂I) were also significantly increased in the dopexamine group (DO₂I: from 416±91 to 717±110 ml/m² · m²; VO₂I: from 98±25 to 157±22 ml/m² · m²), being significantly higher than in the control group. pHi remained stable only in the dopexamine patients, indicating adequate splanchnic perfusion. Vasopressive regulators of circulation increased significantly only in the untreated control patients (vasopressin: from 4.37±1.1 to 35.9±12.1 pg/ml; ET-1: from 2.88±0.91 to 6.91±1.20 pg/ml). Conclusion: Patients undergoing major abdominal surgery may profit from prophylactic perioperative administration of dopexamine hydrochloride in the form of improved haemodynamics and oxygenation as well as beneficial influence on important regulators of organ blood flow.     

Systemic analgesia adapted to the children's condition

A concept of balanced analgesia using nonsteroidal anti-inflammatory drugs (NSAIDs), paracetamol (acetaminophen), opioids, and corticosteroids can also be used in patients with pre-existing illnesses. NSAIDs are the most effective treatment for acute pain of moderate intensity in children; however, these drugs should be avoided in patients at increased risk for serious side effects, e.g. patients with renal impairment, bleeding tendency, or extreme prematurity. NSAIDs can be given with minimal risks to the younger child with mild to moderate asthma, and, in these patients, the use of steroids can be encouraged; in addition to their antiemetic and analgesic action, a beneficial effect on asthma symptoms can be expected. In the non-intubated child with cerebral trauma, exaggerated sedation caused by opioids and increased bleeding tendency caused by NSAIDs must be avoided. In neonates and small infants, the oral administration of sucrose or glucose is helpful to minimize pain reaction during short uncomfortable interventions.