急性呼吸窘迫综合征小潮气量肺保护通气策略的预后分析

目的：探讨急性呼吸窘迫综合征应用小潮气量肺保护性通气策略的预后情况。方法：急性呼吸窘迫综合征患者80例根据入住病床单双号分为治疗组40例与对照组40例,两组都给予常规治疗,治疗组采用小潮气量辅助/控制机械通气治疗,对照组采用肺复张/机械通气治疗。结果：两组治疗前Pa02、Pa02/Fi02和PaC02对比无明显差异,治疗后各时间点Pa02和Pa02/Fi02值明显上升,PaC02值显下降(P<0.05),同时组间对比无统计学差异。治疗组的机械通气时间与住院时间都明显少于对照组,差异有统计学意义(P<0.05)。两组都无死亡患者,治疗组呼吸机相关肺炎、恶心呕吐和肺出血并发症发生率明显低于对照组(P<0.05)。结论：小潮气量肺保护性通气策略应用于呼吸窘迫综合征的治疗能有效保持动脉血气的稳定,加快患者的恢复,减少并发症,值得推广应用。     

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??Abstract??Mechanical ventilation is still one of the main treatment measures of acute respiratory distress syndrome (ARDS).From the traditional high tidal volume ventilation (10 ~ 15 mL/kg) to the current use of lung protective ventilation strategies??low tidal volume ventilation (VT)??positive end-expiratory pressure (PEEP)??airway pressure release ventilation (APRV)??bilevel positive airway pressure(BIPAP)??considerable progress has been made.In addition to the well-known conventional mechanical ventilation modes and methods??there are many non-standard mechanical ventilation modes and methods??such as prone position ventilation??neurally adjusted ventilatory assist (NAVA)??extracorporeal membrane oxygenation (ECMO)??high-frequency ventilation and etc.All these measures produce unique effects on the treatment of ARDS.     

An Update on Interventional Lung Assist Devices and Their Role in Acute Respiratory Distress Syndrome

In recent years, pumpless arteriovenous systems for extracorporeal gas exchange have become a new therapeutic option for the treatment of patients suffering from acute respiratory failure. Experiences with the pumpless extracorporeal membrane lung in animal experiments and in patients with adult respiratory distress syndrome published in the current literature are reviewed. In addition this article presents a case of varicella pneumonia with persistent hypoxemia and hypercapnia under mechanical ventilation that showed a significant improvement with treatment with a pumpless extracorporeal lung assist using an arteriovenous shunt for eight days. The patient made a complete recovery. This is the first report of a patient with a life-threatening varicella pneumonia successfully treated with pumpless extracorporeal lung assist device. This review provides an update on interventional lung assist devices and a critical discussion of their advantages and limitations.     

Extrakorporale Lungenunterstützungsverfahren in der Intensivmedizin 2014

Background

In recent years a rapid expansion of extracorporeal devices for support of severe lung failure has been witnessed. Systems for veno-venous extracorporeal membrane oxygenation (VV-ECMO) or for extracorporeal carbon dioxide elimination are distinguished depending on the indications.

Objectives

The state of the art of extracorporeal lung support is presented with an overview of the different systems, the indications, efficiency and potential side effects.

Methods

By means of a selective literature research and based on personal experience, the principles and techniques, efficiency and potential side-effects of the new modalities are described.

Results

The VV-ECMO systems may be indicated in severe, refractory and predominantly hypoxemic lung failure (p_AO₂/F_IO₂ Conclusion Modern extracorporeal lung support devices allow an effective extracorporeal gas exchange and have become an inherent component of intensive care treatment of critically ill patients. Due to potentially severe complications the use should be restricted to specialized centers with experience in the treatment of severe acute respiratory distress syndrome (ARDS).     

急性呼吸窘迫综合征家兔肺不同区域有效血流灌注变化及肺保护性通气对其的影响

目的 通过观察家兔急性呼吸窘迫综合征(ARDS)模型肺不同区域有效血流灌注变化及肺保护性通气对其的影响,探讨ARDS所致严重低氧血症的发生机制。方法 采用静脉注射油酸的方法建立家兔ARDS模型,应用PIM-Ⅱ激光多普勒血流灌注扫描仪观察不同肺通气模式[(大潮气、小潮气 外源性呼气末正压(PEEP)、大潮气 俯卧位、俯卧位 小潮气 PEEP]下肺不同区域(肺上区、肺下区腹侧和肺下区背侧)局部有效血流灌注及动脉血气指标的变化。结果 家兔静脉注射油酸后,(1)肺不同区域氧合指数明显下降,应用肺保护性通气(小潮气 PEEP,俯卧位 小潮气 PEEP)后氧合指数明显改善;(2)肺不同区域局部有效血流灌注均有不同程度的下降,以肺下区背侧最为明显,肺下区腹侧次之,肺上区变化最小,应用肺保护性通气后,小潮气 PEEP对改善肺下区背侧胸膜下肺局部有效血流灌注的效果不如俯卧位 小潮气 PEEP。结论小潮气 PEEP、俯卧位 小潮气 PEEP均可良好改善肺局部有效血流灌注,其中俯卧位 小潮气 PEEP效果尤为明显;右-左分流导致的肺内分流可能是ARDS发生严重进行性低氧血症的主要原因之一。     

肺复张手法与单纯小潮气量机械通气治疗急性呼吸窘迫综合征

目的观察肺复张手法对急性呼吸窘迫综合征（ARDS）患者的治疗作用,并与小潮气量辅助／控制通气方式比较。方法20例ARDS患者,平均年龄（58±8）岁。分为两组：（1）试验组10例：采用肺复张手法机械通气;（2）对照组10例：采用小潮气量辅助／控制通气（潮气量设为6ml／kg,体重为标准体重）。分别观察两组患者上机后0、48和72h的氧合指数、中心静脉压、镇静药物的用量以及28d的病死率和并发症等。结果试验组与对照组比较,氧合指数48h分别为（297±15）及（211±12）cmH20,72h为（305±18）及（247±16）cmH2O;带机时间缩短为（15±2）及（21±2）d;48h中心静脉压分别为（14．1±0．5）及（19．2±1．0）cmH2O,72h分别为（11．3±0．8）及（17．1±1．1）cmH2O。28d病死率和并发症的发生率两组比较差异无统计学意义（P〉0．05）。结论肺复张手法比单纯小潮气量容量控制／辅助通气具有改善氧合迅速、带机时间短、血流动力学稳定及所用镇静药物少等优点。     

The effect of hypopnea on low-pressure pulmonary edema

The effects of the mechanical factors involved in ventilation on pulmonary edema are only partially understood. To clarify the effect of ventilation on the adult respiratory distress syndrome (ARDS), we examined the effect of reducing rate and tidal volume on oleic acid-induced low-pressure pulmonary edema in dogs, hypothesizing that hypopnea would reduce lung edema. We placed the experimental animals on venous-venous extracorporeal membrane oxygenation (ECMO) for CO2 clearance and oxygenation 1 h after the injury. This allowed reduction of the ventilatory rate from 17.2 +/- 4.8 to 3.3 +/- 0.8 breaths/min and tidal volume from 20 to 16 ml/kg, effectively resting the injured lung. After 5 h of hypopnea there was no reduction in edema by gravimetric or extravascular thermal volume measurements. The ECMO-facilitated hypopnea reduced airway pressure and pulmonary artery pressure while improving arterial oxygen saturation but increased venous admixture. These results suggest that there may be a supportive role for ECMO-assisted hypopnea, but there was no direct beneficial effect of hypopnea on edema.     

The role of CT-scan studies for the diagnosis and therapy of acute respiratory distress syndrome

CT has provided new insights on the pathophysiology of acute respiratory distress syndrome (ARDS), demonstrating that ARDS does not affect the lung parenchyma homogeneously. These findings suggest that lung edema, as assessed by CT scan, should be included in the definition. Lung CT findings may provide a firm rationale for tailoring tidal volume during mechanical ventilation. Ideally, tidal volume should be proportional to the portion of the lung open to ventilation, as assessed by CT scan, rather than to the body weight. CT assessment of lung recruitability seems to be a prerequisite for a rational setting of positive end-expiratory pressure.     

Extrakorporale Lungenunterstützungssysteme

In severe acute lung failure, which cannot be handled by conventional therapeutic options, pump-driven systems (veno-venous extracorporeal membrane oxygenation, ECMO) or pumpless systems (interventional lung assist, iLA) can be used for extracorporeal lung assist. A veno-venous ECMO is indicated in refractory hypoxaemia and/or in severe respiratory acidosis with a pH <7.2. Survival rates of more than 50% have been reported with the use of vv-ECMO in severe ARDS. Veno-venous extracorporeal systems can supply about 50–80% of the necessary gas exchange. Thus, a more protective ventilation is possible and the extent of the ventilator-induced lung injury is limited. Pumpless devices with an arteriovenous cannulation are well suited for carbon dioxide elimination. Therefore, their primary indication is for refractory hypercapnia with respiratory acidosis. As the blood flow is generated exclusively by the arteriovenous pressure difference, a reduced cardiac pump function or a low mean arterial pressure must be considered a contraindication. Because many complications can potentially occur with the use of extracorporeal systems, close surveillance of the patient and device is essential.     

Mechanical ventilation in an airborne epidemic

With the increasing threat of pandemic influenza and catastrophic bioterrorism, it is important for intensive care providers to be prepared to meet the challenge of large-scale airborne epidemics causing mass casualty respiratory failure. The severe acute respiratory syndrome outbreak exposed the vulnerability of health care workers and highlighted the importance of establishing stringent infection control and crisis management protocols. Patients who have acute lung injury and acute respiratory distress syndrome who require mechanical ventilation should receive a lung protective, low tidal volume strategy. Controversy remains regarding the use of high-frequency oscillatory ventilation and noninvasive positive pressure ventilation. Standard, contact, and airborne precautions should be instituted in intensive care units, with special care taken when aerosol-generating procedures are performed.     

Tidal volume reduction in patients with acute lung injury when plateau pressures are not high

Use of a volume- and pressure-limited mechanical ventilation strategy improves clinical outcomes of patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS). However, the extent to which tidal volumes and inspiratory airway pressures should be reduced to optimize clinical outcomes is a controversial topic. This article addresses the question, "Is there a safe upper limit to inspiratory plateau pressure in patients with ALI/ARDS?" We reviewed data from animal models with and without preexisting lung injury, studies of normal human respiratory system mechanics, and the results of five clinical trials of lung-protective mechanical ventilation strategies. We also present an original analysis of data from the largest of the five clinical trials. The available data from each of these assessments do not support the commonly held view that inspiratory plateau pressures of 30 to 35 cm H2O are safe. We could not identify a safe upper limit for plateau pressures in patients with ALI/ARDS.     

机械通气策略在体外膜肺氧合过程中的应用

体外膜肺氧合是一种为常规治疗(机械通气)难以治愈的呼吸衰竭患者提供了临时体外呼吸循环支持的技术,在静脉-静脉体外膜肺氧合的过程中,血液从患者的静脉系统进入人工膜肺,进行氧合与二氧化碳的去除,随之再从静脉系统回输至患者体内。为了避免正常肺功能的丧失,机械通气在体外膜肺氧合的过程中仍然有必要,但如何设置体外膜肺氧合过程中的机械通气参数,至今没有明确的指南。因此,本文将简述体外膜肺氧合期间气体交换的病理生理学机制,并就现有证据和文献总结体外膜肺氧合过程中的机械通气策略。     

Management of oxygenation in pediatric acute hypoxemic respiratory failure.

The prognosis for patients with acute respiratory distress syndrome (ARDS) in adults and children has improved since its formal acceptance as a clinical entity in 1967. Because acute hypoxemic respiratory failure is the hallmark of acute lung injury and ARDS, the management of oxygenation is crucial. Physicians managing pediatric patients with acute lung injury or ARDS are faced with a complex array of options influencing oxygenation. Certain treatment strategies can influence clinical outcomes, such as a lung-protective ventilation strategy that specifies a low tidal volume (6 mL/kg) and a plateau pressure limit (30 cm H(2)O) (Acute Respiratory Distress Network, N Engl J Med 2000;342:1301-1308). Other lung-protective strategies such as different levels of positive end-expiratory pressure, altered inspiratory:expiratory ratios, recruitment maneuvers, prone positioning, and extraneous gases or drugs may impact clinical outcomes but require further clinical study. This paper reviews state-of-the-art strategies on the management of oxygenation in acute hypoxemic respiratory failure and attempts to guide pediatric pulmonologists in managing children with respiratory failure.     

Management des akuten Lungenversagens

Acute pulmonary failure by definition excludes cardiac insufficiency as the pathogenetic mechanism involved in the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). The systemic inflammatory reaction underlying acute pulmonary failure has many etiological causes. One of the most important trigger mechanisms is sepsis. In the realm of cardiac intensive care medicine, the systemic inflammatory reaction is observed in conjunction with assist systems, during extracorporeal circulation, or in the course of cardiogenic shock. In the end, even mechanical ventilation itself can elicit an inflammatory reaction and result in pulmonary failure through ventilator-associated lung injury. Knowledge of the mechanisms has led to the concept of protective ventilation, which exerts both prophylactic and therapeutic effects. Protective ventilation is an integral part of a bundle of therapeutic intensive care measures. Both constitute the essence of management of acute pulmonary failure.     

Randomized controlled trial of volume-targeted synchronized ventilation and conventional intermittent mandatory ventilation following initial exogenous surfactant therapy

We set out to evaluate the impact of volume-targeted synchronized ventilation and conventional intermittent mandatory ventilation (IMV) on the early physiologic response to surfactant replacement therapy in neonates with respiratory distress syndrome (RDS). We hypothesized that volume-targeted, patient-triggered synchronized ventilation would stabilize minute ventilation at a lower respiratory rate than that seen during volume-targeted IMV, and that synchronization would improve oxygenation and decrease variation in measured tidal volume (V(t)). This was a prospective, randomized study of 30 hospitalized neonates with RDS. Infants were randomly assigned to volume-targeted ventilation using IMV (n = 10), synchronized IMV (SIMV; n = 10), or assist/control ventilation (A/C; n = 10) after meeting eligibility requirements and before initial surfactant treatment. Following measurements of arterial blood gases and cardiovascular and respiratory parameters, infants received surfactant. Infants were studied for 6 hr following surfactant treatment. Infants assigned to each mode of ventilation had similar birth weight, gestational age, and Apgar scores at birth, and similar oxygenation indices at randomization. Three patients were eliminated from final data analysis because of exclusionary conditions unknown at randomization. Oxygenation improved significantly following surfactant therapy in all groups by 1 hr after surfactant treatment (P < 0.05). No further improvements occurred with time. Total respiratory rate was lowest (P < 0.05) and variation in tidal volume (V(t)) was least in the A/C group (P < 0. 05). Minute ventilation (V(')(E)), delivered airway pressures, respiratory system mechanics, and hemodynamic parameters were similar in all groups. We conclude that volume-targeted A/C ventilation resulted in more consistent tidal volumes at lower total respiratory rates than IMV or SIMV. Oxygenation and lung mechanics were not altered by synchronization, possibly due to the volume-targeting strategy. Of the modes studied, A/C, a fully-synchronized mode, may be the most efficient method of mechanical ventilator support in neonates receiving surfactant for treatment of RDS.     

Different modes of assisted ventilation in patients with acute respiratory failure.

The aim of the present study was to verify that the patient/ventilator interaction is similar, regardless of the mode of assisted mechanical ventilation (i.e. pressure- or volume-limited) used, if tidal volume (VT) and peak inspiratory flow (PIF) are matched. Therefore, the authors compared the effects of three different modes of assisted ventilation on the work of breathing (WOB) and gas exchange in patients with acute respiratory failure. For Protocol 1, in seven patients, the authors compared pressure support, assist pressure control and assist control (with square and decelerating wave inspiratory flow pattern) set to deliver the same VT and PIF. For Protocol 2, in another 10 patients, the authors compared pressure support and assist control with high (0.8 L x s(-1)) and low (0.6 L x s(-1)) PIFs set to deliver the same VT. In Protocol 1, there was no difference in WOB and gas exchange between the three modes of assisted ventilation tested. In Protocol 2, the decrease of PIFs during assist control significantly increased WOB. In conclusion, different modes of assisted ventilation similarly reduce work of breathing and provide adequate gas exchange at fixed tidal volume and peak inspiratory flow only. During assist control, tidal volume and peak inspiratory flow (set by the physician) are the main determinants of the patient/ventilator interaction.     

Mechanical ventilation in acute lung injury and acute respiratory distress syndrome

Mechanical ventilation provides life-sustaining support for most patients with acute lung injury and acute respiratory distress syndrome; however, traditional approaches to mechanical ventilation may cause ventilator-associated lung injury, which could exacerbate or perpetuate respiratory failure caused initially by conditions such as pneumonia, sepsis, and trauma. This article reviews the theory, laboratory data, and results of recent clinical trials that suggest that modified ventilator strategies can reduce ventilator-associated lung injury and improve clinical outcomes.     

Extrakorporale Lungenunterstützung beim hyperkapnischen Lungenversagen

In recent years the use of extracorporeal lung assist devices has rapidly increased in intensive care medicine. While venovenous extracorporeal membrane oxygenation (vv-ECMO) is applied as rescue therapy in patients with severe hypoxemic respiratory failure, extracorporeal CO₂ removal (ECCO₂R) can be applied in patients with hypercapnic respiratory failure. Especially in patients with acute on chronic hypercapnic respiratory failure treated with invasive mechanical ventilation, ventilator-associated side effects can lead to a poorer outcome. In these patients extracorporeal lung assist often enables lung protective ventilation and potentially ameliorates ventilator-associated side-effects. Moreover, by reducing the load on the respiratory muscle pump ECCO₂R may facilitate weaning from the ventilator and in individual patients with failure of non-invasive ventilation (NIV) may even help to avoid intubation. In selected patients with chronic lung disease listed for lung transplantation, the avoidance of invasive mechanical ventilation for acute decompensation by means of extracorporeal lung support may help to maintain the option for transplantation. The potential advantages of ECCO₂R must be weighed against the risks and complications.     

Reducing acute respiratory distress syndrome occurrence using mechanical ventilation

The standard treatment for acute respiratory distress syndrome (ARDS) is supportive in the form of low tidal volume ventilation applied after significant lung injury has already developed. Nevertheless, ARDS mortality remains unacceptably high (> 40%). Indeed, once ARDS is established it becomes refractory to treatment, and therefore avoidance is key. However, preventive techniques and therapeutics to reduce the incidence of ARDS in patients at high-risk have not been validated clinically. This review discusses the current data suggesting that preemptive application of the properly adjusted mechanical breath can block progressive acute lung injury and significantly reduce the occurrence of ARDS.