胚胎干细胞转基因治疗甲状旁腺功能低下症

目的　探讨小鼠胚胎干细胞 (TC 1)转基因治疗甲状旁腺功能低下症 (HPT)。方法包装出重组人甲状旁腺素 (PTH )基因的小鼠干细胞病毒 (MSCV) ,以lml重组病毒液加入 poly brene(终浓度 8mg/L)感染TC 1细胞 ,检测基因转导效率 ,PTH分泌情况 ;以及每 1× 10 5个 /mlTC 1细胞注入模型鼠体内各组小鼠血PTH和血钙变化情况。结果　获得滴度为 2× 10 7集落形成单位 (CFU) /ml的重组逆转录病毒 ,其感染TC 1的效率为 70 % ,每 10 6 未分化TC 1每 48h分泌PTH10ng。重组有PTH基因的TC 1细胞注入模型鼠体内后 ,在观察期间实验组动物血PTH和血钙均保持在接近正常值范围内。结论　MSCV介导外源PTH基因可高效转导TC 1并持续分泌PTH ;内环境并不是决定TC 1分化的唯一因素。经基因转导的TC 1可较好的改善模型鼠的症状 ,是未来细胞移植的一种潜在来源。     

造血干细胞基因治疗甲状旁腺功能低下症的实验研究

目的　探讨造血干细胞基因治疗甲状旁腺功能低下症 (HPT)的实验效果。方法　构建重组甲状旁腺素 (PTH)基因的小鼠干细胞病毒 (MSCV)重组质粒 ,转染PA31 7包装细胞 ,G41 8筛选阳性克隆 ,获得的重组病毒液感染造血干细胞 ,静脉注入HPT小鼠血中 ,检测各组小鼠症状改善情况、血PTH及血钙变化情况。结果　获得滴度为 2× 1 0 7CFU(集落形成单位 ) /ml的分泌人PTH的浓缩病毒悬液 ,1× 1 0 6 个细胞培养 48h时PTH的分泌量为 1 5ng。经聚合酶链反应 (PCR)扩增未检测到有野生型病毒存在 ,可以安全应用。感染造血干细胞输注后 ,实验组动物未再出现HPT临床表现 ,而且血钙及血PTH均可长期保持在接近正常值范围内 ,较单纯注射浓缩病毒悬液具有更好的疗效。结论　获得MSCV PTH重组质粒及高滴度的分泌人PTH的浓缩病毒悬液。整合有PTH基因的造血干细胞输注后达到较长期治愈小鼠HPT ,为进一步HPT的临床基因治疗提供了可靠依据。     

转基因造血干细胞移植治疗小鼠甲状旁腺功能低下症的研究

目的　探讨输注整合有甲状旁腺素(PTH)基因的造血干细胞对甲状旁腺功能低下症的治疗效果。方法　将以pcDNA 3.1 PTH 为模板扩增出的PTH 基因插入到逆转录病毒载体MSCV中,得到含PTH基因的重组质粒,并转染PA317 包装细胞,以抗生素Geneticin筛选阳性克隆,获得重组有PTH基因的浓缩病毒悬液,以其感染人脐血造血干细胞,然后注入甲状旁腺功能低下症模型小鼠血中,术后观察小鼠症状的改善情况、血PTH及血钙浓度变化情况。结果　所获得的重组有PTH基因的浓缩病毒悬液,其病毒滴度为2×107 CFU/ml,PTH的分泌量为15 ng/48 h(106个细胞),未检测到有野生型病毒存在。实验组小鼠接受转染有PTH基因的血干细胞后,症状改善,血PTH及血钙浓度逐渐上升,并维持于接近正常水平;仅接受重组有PTH基因的浓缩病毒悬液的小鼠,短期内血PTH及血钙浓度明显升高,以后则呈缓慢下降趋势,并逐渐出现甲状旁腺功能低下症的表现;只接受造血干细胞移植的小鼠术后20 d左右全部死亡。结论　甲状旁腺功能低下症小鼠接受整合有PTH基因的造血干细胞静脉输注可获得较长期的治疗效果。     

甲状旁腺激素基因治疗甲状旁腺功能低下症

目的观察甲状旁腺激素(PTH)基因和蛋白体外表达情况,并评价其基因治疗甲状旁腺功能低下模型鼠的作用。方法(1)以脂质体将质粒pcDPG分别1次和多次转染293细胞,观察绿色荧光蛋白(GFP)的表达并计算转染率;(2)转染24、48、72和96h后real-ti me定量PCR和Western blot法检测PTH基因与蛋白表达,并活性鉴定;(3)建立甲状旁腺功能低下症模型,将pcDPG质粒多次肌肉注射治疗,监测血钙和PTH值、存活时间及各器官病理变化。结果转染后24h即见GFP表达,72h达高峰,96h开始减少;多次转染后GFP表达率可达90%以上;PTHcD-NA拷贝数转染24h为5×103,72h达最高为8×104,多次转染显著增高(P<0.01);Western blot见48h和72h有PTH蛋白表达,其可对抗甲状旁腺切除小鼠抽搐症状;术后第2天血钙与PTH明显低于术前(P<0.05),pcDPG质粒大、中剂量组连续治疗48h后血钙与PTH值均恢复正常。结论重组PTH基因治疗甲状旁腺功能低下模型鼠有较好的疗效。     

病毒白细胞介素-10转基因在造血干细胞中的表达

目的　观察逆转录病毒转病毒白细胞介素 10 (vIL 10 )基因在体内的表达。方法　用MSCVneo vIL 10重组体在体外转导CBA (H 2 K)小鼠的造血干细胞 (HSCs) ,给经致死照射(90 0rads)的 2 0只同基因CBA(H 2 K)小鼠注入经MSCVneo vIL 10转染的HSCs ,2× 10 6HSCs/只。酶联免疫吸附测定 (ELISA)、逆转录 聚合酶链反应 (RT PCR )、Westernblot分析vIL 10的表达。结果　移植MSCVneo vIL 10转染HSCs的 2 0只小鼠 ,移植后 8周用ELISA检测 ,其中 15只小鼠血清的vIL 10浓度为 :2 70～ 13 40ng/L ,5只小鼠血清的vIL 10为阴性。 12周后有 2只小鼠vIL 10测不出 ,13只小鼠长时间表达vIL 10达 6个月。对照组小鼠血清vIL 10均为阴性。RT PCR和Westernblot证实小鼠的器官均有vIL 10的mRNA和蛋白的表达。结论　逆转录病毒能有效地将vIL 10基因导入造血干细胞并在体内长时间表达。     

甲状旁腺素的生物学研究与成骨作用

甲状旁腺素(PTH)是由甲状旁腺主细胞合成分泌的、含有84个氨基酸的碱性单链多肽,是调节血钙、磷水平的主要激素之一,可促使血钙水平升高,血磷水平下降。PTH可精细调节骨的合成、分解代谢,对成骨细胞和破骨细胞的分化、成熟、凋亡发挥重要作用。本文综述了PTH的化学结构、生理作用、生物学研究成果及PTH的临床应用。PTH对Ⅰ型骨质疏松(绝经后骨质疏松症)、Ⅱ型骨质疏松(老年骨质疏松症)、雌激素缺乏的年轻妇女及糖皮质激素所致的骨质疏松症均有治疗作用,能显著升高骨密度,并能降低患者骨质疏松性骨折发生率,加速骨折愈合。甲状旁腺素在临床骨质疏松治疗、骨质疏松性骨折的治疗中都具有重要的应用价值。     

甲状腺术后暂时性甲状旁腺损伤动物模型的建立

目的建立稳定的甲状腺术后暂时性甲状旁腺损伤动物模型。方法 20只新西兰大白兔随机分为全甲状旁腺损伤组(n=10)和下甲状旁腺损伤组(n=10)。下甲状旁腺损伤组结扎双侧下甲状旁腺血管;全甲状旁腺损伤组行甲状腺全切除(含上甲状旁腺切除),然后行双侧下甲状旁腺血管结扎。记录术中甲状旁腺显露情况。测定造模术前以及造模术后1 d、2 d、3 d、5 d、1周、2周、3周及4周的血钙和甲状旁腺激素(PTH)水平,统计造模成功率及动物死亡情况。结果兔有4枚甲状旁腺,双侧下甲状旁腺位于颈总动脉、胸骨甲状肌、胸骨舌骨肌包绕形成的筋膜间隙内,而上甲状旁腺并不能常规显露,病理证实位于甲状腺内。2组造模术前血钙及PTH水平差异无统计学意义(P0.05)。下甲状旁腺损伤组造模术后1 d、2 d及3 d血钙水平显著低于术前(P0.05),全甲状旁腺损伤组造模术后1 d、2 d、3 d及5 d的血钙水平显著低于术前(P0.05),且以造模术后1 d最低。2组造模术后1 d、2 d、3 d、5 d、1周、2周及3周时血PTH水平均显著低于术前(P0.05),4周时血PTH水平与术前比较差异无统计学意义(P0.05),且以术后1 d最低。全甲状旁腺损伤组造模术后1 d、2 d及3 d时血PTH水平显著低于下甲状旁腺损伤组(P0.05),造模术后5 d、1周、2周、3周及4周时全甲状旁腺损伤组的血PTH水平低于下甲状旁腺损伤组,但差异无统计学意义(P0.05)。造模术后血钙及PTH的变化成正相关关系(r=0.771,P=0.000)。全甲状旁腺损伤组造模术后3 d及5 d时成模率高于下甲状旁腺损伤组(P0.05)。结论采用甲状腺全切除+双侧下甲状旁腺血管结扎可建立稳定的甲状腺术后暂时性甲状旁腺损伤动物模型,可用于进一步的研究。     

磷酸盐对PTH分泌和合成的直接调节作用及其机制

甲状旁腺激素(PTH)的分泌和合成受多种因素(如钙、磷酸盐和Vitamin D等)的调节.过去认为,磷酸盐是通过降低血钙和抑制1,25(OH)2D3的合成而间接影响PTH的分泌和合成.近年认为,除上述作用外,更重要的是磷酸盐可直接调节PTH的分泌和合成.磷酸盐对PTH调节作用位于PTH基因表达的转录后水平,并可能是通过蛋白质-RNA与PTH mRNA的3'-非翻译区的结合及甲状旁腺胞浆蛋白对PTH mRNA的降解机制完成的.     

磷酸盐对PTH分泌和合成的直接调节作用及其机制

甲状旁腺激素(PTH)的分泌和合成受多种因素(如钙、磷酸盐和Vitamin D等)的调节.过去认为,磷酸盐是通过降低血钙和抑制1,25(OH)2D3的合成而间接影响PTH的分泌和合成.近年认为,除上述作用外,更重要的是磷酸盐可直接调节PTH的分泌和合成.磷酸盐对PTH调节作用位于PTH基因表达的转录后水平,并可能是通过蛋白质-RNA与PTH mRNA的3'-非翻译区的结合及甲状旁腺胞浆蛋白对PTH mRNA的降解机制完成的.     

人IL-10逆转录病毒载体的构建及对大鼠原位肝移植存活期的影响

目的　探讨人白细胞介素 10 (hIL 10 )逆转录病毒载体的构建及对大鼠原位肝移植存活期的影响。方法　将hIL 10克隆基因片断 ,经双酶切后定向插入到逆转录病毒载体 (MSCV)中 ,用脂质体法转染PT6 7包装细胞 ,以G418筛选阳性克隆。将Wistar对SD大鼠原位肝移植模型分三组 ,组Ⅰ为空白对照组 ,组Ⅱ为MSCV空载体灌洗组 ,组Ⅲ为MSCV hIL 10灌洗组。观察大鼠存活期及肝脏功能变化。结果　hIL 10基因片断插入到MSCV载体中经转染包装后得到 2× 10 7CFU ml的分泌hIL 10的病毒悬液 ,hIL 10分泌量为 12 2 0ng 10 6 细胞 2 4h。组Ⅲ与组Ⅰ、组Ⅱ比 ,大鼠存活期明显延长 (P <0 0 1) ,肝脏功能无明显差异。结论　获得MSCV hIL 10重组质粒 ,获得高滴度的分泌hIL 10的病毒悬液 ,hIL 10的表达可延长大鼠原位肝移植的存活期。     

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.     

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.     

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.     

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.     

Intraoperative autotransfusion is associated with modest reduction of allogeneic transfusion in prosthetic hip surgery

Background: The efficacy of intraoperative salvage and washing of wound blood and the predictors of allogeneic red cell transfusions in prosthetic hip surgery are insufficiently known.
Methods: In 96 patients, undergoing primary or revision surgery, salvaged and washed red cells and, if necessary, allogeneic blood were used to keep haematocrit not lower than 33%. The bleeding of red cells during hospital stay was calculated from the red cell balance. The preoperative red cell reserve (millilitres of red cells in excess of a haematocrit of 33%) was estimated and the difference between this volume and the total bleeding of red cells was retrospectively used to classify patients with regard to the need for red cells. Stepwise regression analysis was used to define patient-related variables associated with allogeneic blood transfusion.
Results: Preoperative knowledge of the type of operation (primary, revision), the preoperative red cell reserve, and the body mass could predict roughly half of the need for banked blood (r²=0.45). Only one-third of the total bleeding of red cells was retransfused. For complete avoidance of allogeneic blood, autotransfusion was most effective in patients with a moderate need (0–4 u). However, 32% of such patients required allogeneic blood.
Conclusions: Autotransfusion has a limited efficacy to decrease the need for allogeneic blood, and other blood-saving methods should be added for this purpose. It is difficult to predict the need for allogeneic blood preoperatively.     

缺氧对肾小管上皮细胞分泌外泌体的影响

目的    观察缺氧对肾小管上皮细胞分泌外泌体的影响,探讨外泌体在缺氧致肾脏损伤中的作用及机制。 方法    （1）常氧（21% O₂）及缺氧（1% O₂）分别处理大鼠肾小管上皮细胞（NRK-52E）48 h,收集细胞上清液并使用高速梯度离心法分离外泌体。采用透射电镜、纳米示踪分析、Western印迹、蛋白浓度定量鉴定并比较两组外泌体的基本特性。（2）在共培养实验中,以不同浓度（1、10、50、100、300 mg/L）的常氧外泌体、缺氧外泌体分别干预脂多糖（LPS）诱导的大鼠原代腹腔巨噬细胞,使用实时荧光定量PCR与酶联免疫吸附试验（ELISA）法分别检测巨噬细胞白细胞介素6（IL-6）、肿瘤坏死因子α（TNF-α）、诱导型氮氧化物合酶（iNOS）水平;使用Western印迹法检测巨噬细胞磷酸化（p）STAT/STAT及细胞因子信号传导抑制蛋白1（SOCS1）的蛋白表达;最后,使用实时荧光定量PCR法检测常氧外泌体与缺氧外泌体中炎性反应相关微RNA（microRNA,miR）的表达差异。 结果    （1）离心得到的囊泡具有外泌体典型的结构,粒径小于150 nm,表达外泌体标志蛋白CD63,说明分离得到外泌体。缺氧对肾小管上皮细胞分泌的外泌体形态、粒径分布比例无明显影响,但提高了外泌体的分泌量。（2）缺氧外泌体相比于常氧外泌体促进了LPS诱导的M1型巨噬细胞IL-6、TNF-α、iNOS 的表达和分泌（均P＜0.01）,同时提高STAT的磷酸化水平并减少SOCS1的蛋白表达（均P＜0.01）;对炎性反应相关microRNA检测发现缺氧外泌体中miR-155、miR-27a表达量较常氧外泌体明显升高（P＜0.05）。 结论    缺氧可改变外泌体的生物学功能,表现为协同促进LPS诱导的M1型巨噬细胞的表型转化,这可能是慢性肾脏病微炎性反应状态持续的原因之一。     

In Vitro Function and Durability Assessment of a Novel Polyurethane Heart Valve Prosthesis

Abstract While flexible-leaflet, central-flow prosthetic heart valves promise relief from anticoagulation therapy, they continue to be restricted by inadequate durability. In consequence, a novel trileaflet valve, made entirely from polyurethane, has been developed. A batch of 6 consecutively manufactured polyurethane valves was subjected to hydrodynamic function and accelerated fatigue testing. Computerized data acquisition and control systems have been introduced to improve valve testing methodologies. In terms of hydrodynamic function, the polyurethane valve demonstrates transvalvular pressure gradients similar to those for a bioprosthetic valve (Carpentier-Edwards) and levels of retrograde flow significantly less than those for either the bioprosthetic valve or a bileaflet mechanical valve (St Jude Medical). The equivalent of 10 years of cycling without failure has been exceeded by all 6 polyurethane valves in accelerated fatigue tests with 2 valves remaining intact after 674 million cycles (equivalent to approximately 17 years) in continuing tests. Highspeed photography revealed considerable differences in leaflet motion between valves cycled at accelerated and physiological rates.     

Negative pressure ventilation vs. spontaneous assisted ventilation during rigid bronchoscopy: A controlled randomised trial

Background: Ventilation during interventional rigid bronchoscopy (IRB) under general anaesthesia (jet ventilation, positive pressure ventilation and spontaneous assisted ventilation) may offer some difficulties. This study compares the effectiveness during IRB of intermittent negative pressure ventilation (INPV) and spontaneous assisted ventilation (SAV). Methods: Thirty-eight patients submitted to IRB were randomised into two groups: SAV or INPV. All patients received a total intravenous anaesthesia; INPV patients were paralysed. Pre-and intra-operative arterial blood gases and O₂ flow through a rigid bronchoscope were assessed. The endoscopist applying a subjective score evaluated the operating conditions. Results: Patients of the INPV group, as compared to the SAV group, required a lower dosage of fentanyl (2.6 ± 1.8 (μg · kg^?1· h^?1 vs. 6.6 ± 4.8 μg · kg^?1· h^?1), a lower O₂ supply (3.3 ± 2.8 1/min vs. 11.6 ± 3.4 1/min), a shorter recovery time (5.4 ± 2.9 min vs. 9.8 ± 7.1 min) and no manually assisted ventilation (0 ± 0 vs. 1 ± 1.1 nd?/procedure). Intraoperative PaCO₂ was higher in the SAV (8.1 ± 1.3 kPa) than in the INPV group (5.0 ± 1.6 kPa) and intraoperative pH differed in the two groups (7.26 ± 0.05, SAV vs. 7.47 ± 0.08, INPV). Operating conditions, as assessed by a subjective score, were considered better with INPV than with SAV (4.9 vs. 4.3). Conclusions: As compared to SAV, INPV in paralysed patients during IRB reduces administration of opioids, shortens recovery time, prevents respiratory acidosis, excludes the need for manually assisted ventilation, reduces 02 need and affords optimal surgical conditions. INPV appears a safe, non-invasive and effective ventilatory management during IRB.