Intravascular Oxygenator: A New Alternative Method for Augmenting Blood Gas Transfer in Patients With Acute Respiratory Failure

A unique hollow fiber membrane oxygenator (IVOX) has been developed, which is inserted into the vena caval blood stream to transfer O2/CO2 to/from circulating blood in an intact subject without involving the natural lungs. Extensive laboratory testing has demonstrated that the device can transfer significant quantities of O2 and CO2 for up to 3 weeks without significant harmful sequelae or complications. Clinical trials are in progress under FDA supervision, in which IVOX has been utilized to date in 56 patients with ARDS. Preliminary findings indicate that risks and hazards from IVOX are nil, and evidence of benefit to the patient has been demonstrated in 86% of the patients. At this time, clinical utilization of IVOX is in the experimental, data collecting mode to determine its proper role or niche as a method for temporary augmentation of blood gas transfer in patients with advanced acute respiratory failure.     

Gas Transport in the Intracorporeal Oxygenator with Woven Tubes

Abstract: The woven tubes membrane oxygenator is a suitable configuration for the intracorporeal membrane oxygenator because of a high gas exchange performance and a compact packing of tubing. In this study the oxygen transfer performance of woven tubes was evaluated by an in vitro experiment with an external perfusion mode; the blood flow is outside of the tubes in order to reveal the feasibility of designing the intravascular oxygenator (IVOX) by the woven tubes. The oxygen transfer efficiency of the external perfusion mode is superior to that with the internal perfusion mode because of the larger convective mixing effect on the external surface of the tubes. Thus the use of the external perfusion mode results in the shorter necessary tube length for the rated condition, which enables making the oxygenator unit more compact. All of these features encourage the adoption of the woven tubes for use in the intravascular oxygenator.     

Improved oxygenation using the prone position in patients with ARDS

Background: The prone position is known to increase oxygen uptake in patients with Adult Respiratory Distress Syndrome (ARDS).
Methods: In this clinical study from 1995–96, 14 ARDS patients with severe respiratory failure were treated for at least 1 h in the prone position. Responders, defined as having more than 10% increase in PaO₂/FiO₂ ratio from baseline after 1 h, were treated at least 6 h in the prone position.
Results: 11 patients responded during the first period of the prone position (primary responders). Two of the 3 non-responders were turned prone a second time with increase in the PaO₂FiO₂ ratio (secondary responders). Mean PaO₂FiO₂ ratio (mean±SEM) in the supine position was 11.7±0.8 kPa, increasing to 16.6±1.8 kPa and 18.0±1.4 kPa after 1 and 6 h respectively ( P =0.009). Mean time spent in the prone position was 69 h (range 3–256 h), and mean ventilatory time was 17 d (3–52 d). The mortality in this subgroup of our patients with ARDS was 42%, compared to 58% in 19 patients not turned prone in the same period.
Conclusions: The prone position together with PEEP appears to improve ventilation-perfusion matching. The prone position is simple, effective and readily available and could be used early in most patients with ARDS.     

重度脑外伤术后并发ARDS治疗分析

目的探讨肺复张技术对重度颅脑外伤后并发急性呼吸窘迫综合征(acute respiratory distress syndrome,ARDS)的治疗效果。方法选取本院2008年1月至2013年9月收治的65例重度颅脑外伤术后并发ARDS的患者为研究对象,根据随机数字表将患者分为对照组32例及观察组33例,对照组给予常规机械通气治疗,观察组在对照组基础上行肺复张技术治疗,对比分析两组治疗前后血气指标、器官功能障碍评分(sepsis-related organ failure assessment,SOFA)、急性生理及慢性健康评分Ⅱ(acute physiology and chronic health evaluationⅡ,APACHEⅡ)、肺损伤评分(Murray评分)、格拉斯哥昏迷评分(Glasgow coma scale,GCS)的差异。结果观察组治疗后48hSOFA评分、APACHEⅡ评分、Murray评分显著低于治疗前及对照组治疗后,而GCS显著升高,差异有统计学意义(P0.05)。观察组治疗后氧合指数(PaO2/FiO2)显著高于对照组,差异有统计学意义(P0.05)。两组患者死亡率、机械通气时间无统计学差异(P0.05),但观察组入住ICU时间显著短于对照组,差异有统计学意义(P0.05)。观察组肺复张时,平均脉压(mean arterial pressure MAP),而心律(heart rate,HR)、中心静脉压(central venous pressure,CVP)上升,与复张前相比,差异有统计学意义(P0.05),而复张结束后120s MAP、HR、CVP逐渐恢复,与复张时相比差异显著(P0.05)。结论肺复张能有效改善氧合指数,改善患者预后,且血流动力学影响短暂,安全有效。     

急性呼吸窘迫综合征患者应用咪达唑仑的疗效观察

目的提高亚急性湿疹疗效。方法对66例亚急性湿疹患者在抗组织胺药物治疗的基础上采用中药离子喷雾局部治疗,连续2个疗程。结果临床治愈44例,占66．67％;显效12例．占18．18％;有效9例．占13、64％;无效1例,占1．51％;总有效率98．48％,未发生不良反应。结论中药离子喷雾治疗亚急性湿疹疗效好．安全;护理中注意充分暴露皮损区及防止烫伤。     

Extracorporeal carbon dioxide removal performed with surface-heparinized equipment in patients with ARDS

To avoid the drawbacks of systemic anticoagulation during prolonged extracorporeal circulation in patients with adult respiratory distress syndrome (ARDS) a heparinization technique has been developed by which partially degraded heparin can be covalently end-point attached to the surface of the equipment constituting the extracorporeal circuit (Carmeda Bio-Active Surface, CBAS) thereby localizing the anticoagulatory effect. Since 1986 we have used extracorporeal circuits and membrane lungs coated with the CBAS for extracorporeal lung assistance (ECLA) in 14 patients suffering from ARDS. The patients were on ECLA for 3 to 55 days with a survival rate of 43%. Our experience so far is that by using equipment coated with CBAS it is possible to perform long-term extracorporeal circulation with a minimum of intravenously administered heparin, thus avoiding the risk of major coagulation defects.     

The effects of multiple small doses of exogenous surfactant on experimental respiratory failure induced by lung lavage in rats

Aim: To test the effect on pulmonary gas exchange and mechanics of multiple small doses of exogenous surfactant as an alternative to bolus delivery in experimental respiratory failure induced by lung lavage.
Methods: After anesthesia, tracheostomy and constant volume ventilation, respiratory failure was induced by lung lavage in 20 rats. Animals were randomly assigned to an untreated control group or two experimental groups. Equal total doses of modified porcine surfactant (200 mg ·kg^-1 body weight,) were given by tracheal instillation, either as a single bolus or in four (50 mg·kg^-1 b.w.) fractional doses at 10-min intervals. Arterial pH and blood gases, and peak inspiratory pressure (PIP) were measured.
Results: After lavage, a rapid decrease in arterial pH and PaO₂, and an increase in PaCO₂ and PIP were observed in all animals. In both surfactant-treated groups, PaO₂ increased after surfactant instillation, and remained significantly higher than controls throughout the experiment. Arterial pH was significantly higher and PaCO₂ significantly lower only in the single bolus group. In the multiple dose group, these levels were similar to those of controls.
Conclusions: In surfactant-depleted rats with respiratory failure, instillation of four fractional surfactant doses did not result in the same enhancement on gas exchange and PIP, in the following 60 min, as same total dose given by a single bolus.     

严重肺挫伤合并急性呼吸窘迫综合征的诊治

目的提高对严重肺挫伤合并急性呼吸窘迫综合征(ARDS)的认识.方法对24例严重肺挫伤合并ARDS患者的临床资料进行回顾性分析.结果本组患者ARDS占同期外科ICU严重肺挫伤患者(47例)的51.1%,全组死亡6例,死亡率25%,24例均给予机械通气;并发肺炎占12例,感染率50%.结论救治严重肺挫伤合并ARDS患者的关键在于对导致ARDS的原发病肺挫伤有充分认识.早期诊断和治疗,正确使用呼吸机,正确治疗多发性损伤是减少ARDS死亡率的有效方法.     

Surfactant inactivation and surfactant replacement in experimental models of ARDS

Lung structure and function, and the effect of surfactant replacement, were studied in three animal models of adult respiratory distress syndrome (ARDS): surfactant depletion by repeated lung lavage, proteinaceous pulmonary edema induced by prolonged exposure to hyperoxia, and inoculation with hybridoma making an antibody to the hydrophobic surfactant-associated protein, SP-B. Surfactant replacement therapy restored normal gas exchange in respiratory failure induced by repeated lung lavage but was ineffective in animals with severe lung parenchymal lesions induced by hyperoxia or antibody to SP-B. Lung edema fluid from animals exposed to hyperoxia inhibited surfactant function in a concentration-dependent manner. These observations indicate that, in experimental ARDS, the effect of surfactant replacement depends on the type of animal model and, especially, on the degree of lung injury present at the time of therapy.     

Methylprednisolone Reduces Vascular Resistance in Hypoxic and Atelectatic Lungs

The effect of pharmacological doses of methylprednisolone (MP) on the pulmonary vasoconstrictor response to hypoxia has been investigated in two groups of isolated rat lung preparations, one consisting of ventilated, and the other of atelectatic lungs. In both groups, MP reduced the vasoconstrictor response to hypoxia in a dose-dependent fashion. At a perfusate concentration of 3 mmol/l of MP, the response was reduced by about 80%. On the contrary, the vasoconstrictor response to injections of standardized doses of angiotensin II, used as an independent vasoconstrictor substance, were not significantly changed by MP, even when administered at a concentration which completely abolished the response to hypoxia. We suggest that MP inhibits the pulmonary vasoconstrictor response to hypoxia without influencing the general reactivity of the pulmonary vascular bed.     

A lung recruitment maneuver immediately before rescue surfactant therapy does not affect the lung mechanical response in immature lambs with respiratory distress syndrome

BACKGROUND: In animals with acquired surfactant-deficiency, a recruitment maneuver by increased tidal volumes enhances the effect of exogenous surfactant. In contrast, in the preterm lamb model, hyperinflation early after birth impairs the effect of surfactant prophylaxis. Here we examined whether a lung recruitment maneuver just before surfactant would affect the response to rescue treatment in immature lambs with established respiratory distress syndrome (RDS). METHODS: Five pairs of preterm twin lambs with gestational age 127 days were delivered by cesarean section and supported by pressure-limited mechanical ventilation for 4 h. At 30 min of age, when all the lambs were in severe respiratory failure, they were treated with porcine surfactant, 200 mg x kg-1. One lamb in each pair was subjected to a lung recruitment maneuver consisting of five sustained inflations of 20 ml x kg-1 just before surfactant instillation. RESULTS: At 10 min after surfactant treatment, all the lambs showed a large improvement in oxygenation and an increase in inspiratory capacity and static compliance. Except for a transiently better oxygenation after surfactant therapy in the recruitment group (P < 0.05), there was no significant between-group differences in gas exchange or lung mechanics at any time point during the study. There was no difference in post mortem intrapulmonary air volume or alveolar expansion in histologic lung sections between groups. CONCLUSION: This small study does not show any positive or negative effect of a lung recruitment maneuver on the response to rescue surfactant therapy in immature animals with RDS.     

Effect of Impeller Design and Spacing on Gas Exchange in a Percutaneous Respiratory Assist Catheter

Providing partial respiratory assistance by removing carbon dioxide (CO₂) can improve clinical outcomes in patients suffering from acute exacerbations of chronic obstructive pulmonary disease and acute respiratory distress syndrome. An intravenous respiratory assist device with a small (25 Fr) insertion diameter eliminates the complexity and potential complications associated with external blood circuitry and can be inserted by nonspecialized surgeons. The impeller percutaneous respiratory assist catheter (IPRAC) is a highly efficient CO₂ removal device for percutaneous insertion to the vena cava via the right jugular or right femoral vein that utilizes an array of impellers rotating within a hollow‐fiber membrane bundle to enhance gas exchange. The objective of this study was to evaluate the effects of new impeller designs and impeller spacing on gas exchange in the IPRAC using computational fluid dynamics (CFD) and in vitro deionized water gas exchange testing. A CFD gas exchange and flow model was developed to guide a progressive impeller design process. Six impeller blade geometries were designed and tested in vitro in an IPRAC device with 2‐ or 10‐mm axial spacing and varying numbers of blades (2–5). The maximum CO₂ removal efficiency (exchange per unit surface area) achieved was 573 ± 8 mL/min/m² (40.1 mL/min absolute). The gas exchange rate was found to be largely independent of blade design and number of blades for the impellers tested but increased significantly (5–10%) with reduced axial spacing allowing for additional shaft impellers (23 vs. 14). CFD gas exchange predictions were within 2–13% of experimental values and accurately predicted the relative improvement with impellers at 2‐ versus 10‐mm axial spacing. The ability of CFD simulation to accurately forecast the effects of influential design parameters suggests it can be used to identify impeller traits that profoundly affect facilitated gas exchange.     

Lung density distribution in dynamic CT correlates with oxygenation in ventilated pigs with lavage ARDS

Background. Fast dynamic computed tomography (dCT) has beenused to assess regional dynamics of lung inflation and deflationprocesses. The aim of this study was to relate ventilation-inducedchanges in lung density distribution, as measured over severalrespiratory cycles by dCT, to oxygenation and shunt fractionin a lavage acute respiratory distress syndrome model. Methods. Six anaesthetized pigs underwent pressure-constantventilation (FI_O2=1.0, inspiratory:expiratory ratio=1:1) beforeand after induction of lung damage by saline lavage. Mean airwaypressure (P     

急性脊髓损伤围手术期急性呼吸窘迫综合征的处理

目的：探讨急性脊髓损伤围手术期急性呼吸窘迫综合征的特点及处理方法，给临床提供参考。方法：对本院1996—2000年收治的急性脊髓损伤患者35例，进行回顾性分析。结果：急性脊髓损伤围手术期急性呼吸窘迫综合征潜伏朋3—15d，发病急骤，进行性低氧血症，死亡率高。抢救不及时容易危及生命，本组抢救成功率88．57％，死亡率11．43％。结论：急性脊髓损伤围手术期急性呼吸窘迫综合征的病因复杂，临床过程凶险，呼吸道的气管前瞻性切开及管理尤为重要。     

Evaluation of a recruitment maneuver with positive inspiratory pressure and high PEEP in patients with severe ARDS

BACKGROUND: To evaluate the effect of a recruitment maneuver (RM) with constant positive inspiratory pressure and high positive end-expiratory pressure (PEEP) on oxygenation and static compliance (Cs) in patients with severe acute respiratory distress syndrome (ARDS). METHODS: Eight patients with ARDS ventilated with lung-protective strategy and an arterial partial pressure of oxygen to inspired oxygen fraction ratio (PaO2/FIO2) < or =100 mmHg regardless of PEEP were prospectively studied. The RM was performed in pressure-controlled ventilation at FIO2 of 1.0 until PaO2 reached 250 mmHg or a maximal plateau pressure/PEEP of 60/45 cmH2O was achieved. The RM was performed with stepwise increases of 5 cmH2O of PEEP every 2 min and thereafter with stepwise decreases of 2 cmH2O of PEEP every 2 min until a drop in PaO2 >10% below the recruitment PEEP level. Data was collected before (preRM), during and after 30 min (posRM). RESULTS: The PaO2/FIO2 increased from 83 +/- 22 mmHg preRM to 118 +/- 32 mmHg posRM (P = 0.001). The Cs increased from 28 +/- 10 ml cmH2O(-1) preRM to 35 +/- 12 ml cmH2O(-1) posRM (P = 0.025). The PEEP was 12 +/- 3 cmH2O preRM and was set at 15 +/- 4 cmH2O posRM (P = 0.025). The PEEP of recruitment was 36 +/- 9 cmH2O and the collapsing PEEP was 13 +/- 4 cmH2O. The PaO2 of recruitment was 225 +/- 105 mmHg, with five patients reaching a PaO2 > or = 250 mmHg. The FIO2 decreased from 0.76 +/- 0.16 preRM to 0.63 +/- 0.15 posRM (P = 0.001). No major complications were detected. CONCLUSION: Recruitment maneuver was safe and useful to improve oxygenation and Cs in patients with severe ARDS ventilated with lung-protective strategy.     

急性胰腺炎并发ALI及ARDS的机制

急性胰腺炎发病急骤,病情变化迅速,可并发急性肺损伤(ALI)及急性呼吸窘迫综合征(ARDS),甚至发生多器官功能障碍综合征,病死率一直居高不下.急性胰腺炎并发ALI及ARDS的机制错综复杂,涉及炎症反应失控、细胞的损伤与凋亡、胰酶的作用、凝血与纤溶失衡等多个层面,而这些层面彼此相互关联形成复杂的网络.深入探讨急性胰腺炎并发ALI及ARDS的机制,将为临床诊治提供更多新的作用靶点.     

急性呼吸窘迫综合征患者适应性支持通气的效果

目的 评价适应性支持通气（ASV）模式与间歇正压通气（IPPV）模式在急性呼吸窘迫综合征（ARDS）患者中的效果。方法 ARDS患者30例，年龄19—46岁，男18例，女12例，ASAⅢ或Ⅳ级。先应用IPPV模式，吸入氧浓度60％，PEEP为0，潮气量（VT）10ml／kg，吸呼比（I：E）1：2，维持8h后随机选择换用ASV或继续IPPV通气模式，通气时依次按0、5、10cm H2O增加PEEP，每一PEEP水平的通气时间为60min，在同样的分钟通气量的设置下，4h后更换另一种通气模式，仍按0,5、10cm H2O增加PEEP，每一PEEP水平的通气时间为60min。每个PEEP水平通气50min时，用Swan-Ganz导管、心电监测仪、呼吸机监测记录血液动力学、呼吸力学和氧代谢数据。结果 与IPPV模式比较，ASV模式下气道峰值压降低，肺动态顺应性（Cdyn）、动脉氧分压（PaO2）和氧供（DO2）增加（P〈0．05）。两种通气模式的血液动力学参数比较差异无统计学意义（P〉0．05）。结论 ASV模式比IPPV模式更有利于ARDS患者的通气治疗。     

The influence of race on the development of acute lung injury in trauma patients

Background

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are sequelae of severe trauma. It is unknown if certain races are at greater risk of developing ALI/ARDS, and once established, if there are racial differences in the severity of lung injury or mortality.

Methods

Retrospective cohort study of 4,397 trauma patients (1,831 Caucasians, 871 African-Americans, 886 Hispanics, and 809 Asian/Pacific Islanders) requiring intensive care unit (ICU) admission between 1996 and 2007 at an urban Level I trauma center.

Results

African-American patients were most likely to present in shock with penetrating trauma and receive a massive transfusion. The incidence of ALI/ARDS was similar by race (P = .99). Among patients who developed ALI/ARDS, there was no evidence to support a difference in partial pressure of oxygen in arterial blood to fraction of inspired oxygen (Pao₂/Fio₂) (P = .33), lung injury score (P = .67), or mortality (P = .78) by race.

Conclusions

Despite differences in baseline characteristics, the incidence of ALI/ARDS, severity of lung injury, and mortality were similar by race.     

肺泡表面活性物质肺灌洗对急性呼吸窘迫综合征PaCO_2及PIP的影响

目的 研究肺泡表面活性物质肺灌洗治疗急性呼吸窘迫综合征(ARDS)的效果.方法 用12 ml/kg 0.0225 N的盐酸注入新两兰白兔气管内,纯氧机械通气1h后,将符合PaO_2/FiO_2≤150mm Hg的动物随机分成五组.每组5只.分别用生理盐水(NS组)、浓度为1 g/L(S_1组)、3g/l(S_3组)、6g/L(S_6组)、12g/L(S_(12)组)的肺泡表面活性物质肺灌洗.灌洗容量为10 ml/kg.观察治疗后的PaCO_2和气道吸气峰压(PIP)变化,并对肺标本行病理切片检查.结果 S_3组、S_6组、S_(12)组肺灌洗后PaCO_2明显改善,但效果不能持久.S_3组、S_6组、S_(12)组中肺泡间质允血水肿较NS组、S_1组明显减轻.结论 采用浓度为3g/L以上的外源性肺泡表而活性物质对盐酸诱导的ARDS行肺灌洗治疗可以改善肺通气,但效果不能持久.