Turbulent stress measurements downstream of three bileaflet heart valve designs in pigs

Objective: Mechanical heart valves can cause thromboembolic complications, possibly due to abnormal flow patterns that produce turbulence downstream of the valve. The objective of this study was to investigate whether three different bileaflet valve designs would exhibit clinically relevant differences in downstream turbulent stresses. Methods: Three bileaflet mechanical heart valves (Medtronic Advantage^®, CarboMedics© Orbis™ Universal and St. Jude Medical^® Standard) were implanted into 19 female 90 kg pigs. Blood velocity was measured during open chest conditions in the cross sectional area downstream of the valves with 10 MHz ultrasonic probes connected to a modified Alfred^® Pulsed Doppler equipment. As a measure of turbulence, Reynolds normal stress (RNS) was calculated at three different cardiac output ranges (3–4, 4.5–5.5, 6–7 L/min). Results: Data from 12 animals were obtained. RNS correlated with increasing cardiac outputs. The highest instantaneous RNS observed in these experiments was 47 N/m², and the mean RNS taken spatially over the cross sectional area of the aorta during systole was between 3 N/m² and 15 N/m². In none of the cardiac output ranges RNS values exceeded the lower critical limit for erythrocyte or thrombocyte damage for any of the valve designs. Conclusions: Reynolds normal stress values were below 100 N/m² for all three valve designs and the difference in design was not reflected in generation of turbulence. Hence, it is unlikely that any of the valve designs causes flow induced damage to platelets or erythrocytes.     

红细胞膜通道力学效应的探讨

在考察红细胞双凹碟形体形成的基础上,讨论了红细胞的输氧功能与红细胞变形的关系,揭示了红细胞膜通道的力学效应:当红细胞呈双凹碟形时,PiPo的地方,红细胞膜通道有释放出氧的现象,其氧的总流率为 J=Lo_2(Pio_2-Poo_2) Lp(Pi-Po) 式中Lo_2为O_2分压差引起的膜通道对氧的流导,PiO_2、Poo_2为膜内外的氧分压;Lp为由于压差引起的膜通道对氧的流导。     

High-frequency ventilation (HFV) in hyaline membrane disease —a preliminary report

Eight premature babies affected by hyaline membrane disease and needing mechanical respiratory support were ventilated by means of a VDR 1 (Bird Space Technology) respirator at 10 Hz during a mean time of 51 h. Before HFV 7 infants had been on conventional mechanical ventilation (CMV) and one on nasal CPAP. The values of mean airway pressure (MAP) and oxygenation index (PaO₂/FIO₂) on CMV and HFV were (mean and range): 1. CMV: MAP 15 (4–29) mm Hg, ox. index 15.47 (5.07–23.19) kPa; 2. HFV after 1 h: MAP 15 (10–19) mm Hg, ox. index 24.13 (9.07–46.12) kPa. Improved oxygenation allowed rapid reduction of FIO₂ in the following hours. Only 3 infants were weaned directly from VDR 1, 5 were switched back to CMV mainly because of technical failures of the respirator. The change from HFV to CMV was associated with a fall of PaO₂/FIO₂ from 35.99 (15.86–74.52) to 22.39 (7.33–31.46) kPa. The mean time of artificial ventilation (CMV+HFV) was 121 h (range 46–166). Except for 1 pneumothorax no medical complications were seen during HFV, and all patients survived. Despite impressive improvements in oxygenation it is cautioned against the use of the VDR 1 because of the high incidence of technical problems.     

Invasive ventilation in the emergency department: Part 2: Implications for patient safety

The use of mechanical ventilation in the Emergency Department requires adequate resources in order to maintain patient safety and avoid potential risks. Moreover, developments in technology require increased knowledge of mechanical ventilation techniques to address the complexity of decision-making involved. Organisational issues and system factors have the potential to negatively impact on the ability of the emergency service to provide optimum care to patients receiving mechanical ventilation. These issues include staffing and skill-mix, demand on emergency services, role-delineation, scope of practice, and current mechanisms for monitoring of quality and safety. Furthermore, in response to advances in ventilator technology, current education programs for both nursing and medical staff require review to ensure that they provide comprehensive information about the types of ventilation techniques now available and the relative risks and benefits associated with their application.This article is the second in a two-part series and explores the educational and organisational factors that impact upon safety and quality of care delivered to patients receiving mechanical ventilation in the emergency department. Recommendations for future policy development, curriculum review and reporting mechanisms to support further research in the application of mechanical ventilation in the emergency department are made.     

无创气道正压通气治疗心力衰竭疗效观察

目的:探讨无创气道正压通气对心力衰竭患者的疗效。方法:将我院住院的86例心力衰竭患者随机分为治疗组(药物常规治疗的基础上运用机械通气)44例和对照组(常规药物治疗组)42例。两组患者性别、年龄、病情情况均无统计学意义。治疗组在药物常规治疗的基础上运用机械通气。结果:两组治疗后,心衰症状、心脏功能指标,血气指标均有改进。但治疗组较对照组改进更明显,与对照组比较差异有显著意义(P<0.01)。结论:无创气道正压通气能增加心脏射血,改善心功能、提高心衰患者生存率。     

Der operierte mechanische Ileus

Zusammenfassung Von 1972 bis 1983 wurden 351 Patienten wegen eines mechanischen Dünndarm- (n = 256) bzw. Dickdarmileus (n = 95) operiert. Die chirurgische Komplikationsrate betrug beim Dünndarmverschluß 28,1 bzw. beim Dickdarmileus 24,3%, wobei am häufigsten Anastomosendehiscen-zen nach Resektionen (17,7% bzw. 53,8%), Enterotomien (5,8%/27,2%), Platzbäuche (3,5%/4,2%) und ein Re-Ileus (5,5%/3,2%) vorlagen. Die internistischen Komplikationen (postop. Pneumonien, Lungenembolien, kardiale Dekompensationen etc.) betrugen 17,9% bzw. 22,1 %. Die perioperative Letalität lag beim Dünndarmileus bei 20,6% und beim Dickdarmileus bei 33,4%. Als Schlußfolgerungen dieser retrospektiven Analyse ergaben sich die frühzeitige, perioperative, intensiv-medizinische Behandlung, die generelle Thrombose-, Pneumonie- und StreBulcusprophylaxe, die exakte, präoperative Röntgendiagnostik, die strenge Indikationsstellung für Enterotomien und Resektionen, das dreizeitige Vorgehen beim linksseitigen Dickdarmileus, die Inkontinuitätsresektion nach Hartmann bei entzündlichen Prozessen im Sigmabereich und die innere Dünndarmschienung bei Peritonitis bzw. ausgedehnten Adhäsionen. Dadurch konnte seit Anfang 1984 die Komplikationsbzw. Letalitätsrate beim Dünndarmileus (n = 64) auf 9,4% bzw. 4,7% und beim Dickdarmileus (n = 20) auf 10% bzw. 5% gesenkt werden.

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Experiences with operations of mechanical ileus

Summary Between 1972 and 1983 a total of 351 patients was operated suffering from mechanical occlusion of the small intestine (n = 256) and of the colon (n = 95). The surgical complication rate amounted to 28.1% in cases of small intestine ileus and to 24.3% in cases of colon ileus; the most frequent complications were anastomotic dehiscences following resections (small intestine 17.7%/colon 33.8%), enterotomies (5.8%/27.2%), abdominal wall ruptures (3.5%/4.2%) and re-ileus (5.5%/3.2%). The medical complication rate (postop. pneumonia, pulmonary embolism, cardial decompensation etc.) amounted to 17.7% resp. 22.1%. All these complications carried a mortality of 20.6% in small intestine ileus and of 30.4% in colon ileus. The consequences of this retrospective analysis resulted in: early intensive care treatment, general perioperative thrombosis-, pneumonia- and stress ulcer prophylaxis, exact preoperative radiological diagnosis, strict indications for enterotomies and resections, sole transversostomy in stage of ileus for the left-sided colon obstruction caused by carcinoma, discontinuity resection by Hartmann in cases of inflammatory or perforated large bowel stenoses and tube decompression of the small bowel in cases of peritonitis or wide-spread adhesions. Since 1984 we could prospectively decrease the complication resp. mortality rate of the small intestine ileus (n = 64) to 9.4% resp. 4.7% and of the colon ileus (n = 20) to 10% resp. 5%.

     

院前紧急气管插管与机械通气24例临床分析

目的总结紧急气管插管与机械通气在院前急救中应用的经验,以期提高院前急救水平。方法回顾性分析24例院前气管插管与机械通气抢救心搏呼吸骤停病人的临床资料。结果24例病人气管内插管均获成功,成功率100%。完成气管内插管的时间是15s～60s,平均时间(25±15)s。心搏、自主呼吸恢复4例(16.7%),心搏恢复8例(33.3%);心搏及自主呼吸均未恢复12例(50.0%)。结论气管插管与机械通气是急诊抢救危重病人的基础,对保证进一步心肺复苏、挽留手术机会以及提高危重患者抢救成功率有重要意义。要加强对抢救人员进行紧急气管插管和机械通气的培训。     

一种新型的声门外通气设备——喉导管

喉导管是一种新型的声门外通气设备.在气道的建立和维持上和喉罩相比有相似的优缺点.喉导管和喉罩总的插管成功率相近,一次插管成功率喉导管要远远高于喉罩.喉导管的气道封闭性更好.喉导管可用于四肢、泌尿、妇科和躯干体表手术以及困难气道的插管.在喉部空间狭小患者和颈髓损伤患者气道的建立上比喉罩更有优势,亦可用于心肺复苏时紧急气道的建立.     

机械通气致下呼吸道黄杆菌感染的临床分析

目的:探讨黄杆菌属致下呼吸道感染的临床特点及对常用抗生素的耐药情况。方法:分析我院六年来机械通气致下呼吸道黄杆菌感染的11例临床资料,平板稀释法测定常用抗菌药物对该菌株的最低抑菌浓度,采用法国生物梅里埃公司API系统进行细菌学鉴定,以美国国家实验室标准化委员会NCCLS的标准判定结果。结果:全部应用广谱抗生素,年龄>60岁者8例,机械通气到发生黄杆菌感染的平均时间为18天,死亡4例;耐药率高,仅对头孢哌酮/舒巴坦、复方磺胺甲恶唑、哌拉西林、左氧氟沙星等较敏感。结论:机械通气致下呼吸道黄杆菌感染常发生在基础状态较差,机械通气时间较长,且长期应用广谱抗生素的老年患者,临床表现常无特征性,细菌耐药严重,病死率高     

BiPAP ViSION 在慢性阻塞性肺疾病Ⅱ型呼吸衰竭的应用和护理

目的 探讨经鼻(面)罩双水平气道内正压通气(BiPAP)ViSION型呼吸机对慢性阻塞性肺疾病(COPD)伴Ⅱ型呼吸衰竭患者疗效及护理特点。方法 应用BiPAP ViSION型呼吸机对21例COPD伴Ⅱ型呼吸衰竭患者采用鼻/面罩连接单向呼气活瓣行双水平气道正压通气,观察其通气前后动脉血气及临床表现变化。结果 通气治疗后19例患者动脉血氧分压(PaO_2)及氧饱和度(SaO_2)明显升高(P<0.01),二氧化碳分压(PaCO_2)显著降低(P<0.05);肺性脑病症状消失,昏迷患者神志转清。2例病情恶化,其中1例改用有创通气后好转,1例拒绝有创通气死亡。结论BiPAP ViSION呼吸机治疗COPD伴Ⅱ型呼吸衰竭的疗效较为肯定,正确的护理对提高其疗效和减少并发症至关重要。