Prone position in acute respiratory distress syndrome.

In the last few years prone positioning has been used increasingly in the treatment of patients with acute respiratory distress syndrome (ARDS) and this manoeuvre is now considered a simple and safe method to improve oxygenation. However, the physiological mechanisms causing respiratory function improvement as well as the real clinical benefit are not yet fully understood. The aim of this review is to discuss the physiological and clinical effects of prone positioning in patients with ARDS. The main physiological aims of prone positioning are: 1) to improve oxygenation; 2) to improve respiratory mechanics; 3) to homogenise the pleural pressure gradient, the alveolar inflation and the ventilation distribution; 4) to increase lung volume and reduce the amount of atelectatic regions; 5) to facilitate the drainage of secretions; and 6) to reduce ventilator-associated lung injury. According to the available data, the authors conclude that: 1) oxygenation improves in approximately 70-80% of patients with early acute respiratory distress syndrome; 2) the beneficial effects of oxygenation reduce after 1 week of mechanical ventilation; 3) the aetiology of acute respiratory distress syndrome may markedly affect the response to prone positioning; 4) extreme care is necessary when the manoeuvre is performed; 5) pressure sores are frequent and related to the number of pronations; 6) the supports used to prone and during positioning are different and nonstandardised among centres; and 7) intensive care unit and hospital stay and mortality still remain high despite prone positioning.     

Ventilatory strategies in patients with sepsis and respiratory failure

Patients with sepsis may require mechanical ventilation due to the acute respiratory distress syndrome (ARDS). It has become increasingly accepted that mechanical ventilation can contribute to lung injury in these patients. The modern concept of ventilator-induced lung injury is described in the context of alveolar over-distention (volutrauma), alveolar de-recruitment (atelectrauma), and biochemical injury and inflammation to the lung parenchyma (biotrauma). To avoid over-distention lung injury, the tidal volume should be set at 6 mL/kg predicted body weight and plateau pressure should be limited to 30 cm H₂O. This has been shown to afford a survival benefit. Although setting positive end-expiratory pressure (PEEP) to zero is likely harmful during mechanical ventilation of patients with ARDS, evidence is lacking for a survival benefit if a high PEEP level is set compared with a modest level of PEEP. Although adjunctive measures such as recruitment maneuvers, prone position, and inhaled nitric oxide may improve oxygenation, evidence is lacking that these measures improve survival.     

Intensive care management of life-threatening avian influenza A (H5N1)

A large proportion of patients with avian influenza A (H5N1) develop life-threatening manifestations, often including ARDS, acute renal failure and multiple organ failure that requires aggressive intensive care management. The pace of development of respiratory failure is often rapid and can occur in previously healthy hosts, mandating close observation and timely intervention of infected individuals. Use of standard, contact, droplet and airborne isolation precautions is recommended to protect healthcare workers. Key components of ARDS management encompass appropriate mechanical ventilation including limiting tidal volume to ≤6 mL/kg of predicted body weight, maintaining transpulmonary pressures ≤30 cm H₂O, and utilizing positive end–expiratory pressure to limit alveolar deflation and to improve oxygenation. Additional strategies include conservative fluid management and using nutrition supplemented with antioxidants. Use of corticosteroids is controversial for both early and late ARDS and although often used for avian influenza, beneficial effects on outcomes have not been demonstrated for corticosteroids. Prone positioning can improve oxygenation temporarily and might be useful as rescue therapy for severe hypoxemia. Administration of inhaled nitric oxide and high frequency oscillatory ventilation can improve oxygenation but have not been demonstrated to improve survival in ARDS—their role in avian influenza is uncertain and availability limited. Management of multiple organ failure may include vasopressor support for septic shock and renal replacement therapy for acute renal failure.     

Mechanical ventilation in ARDS: a state-of-the-art review

Mechanical ventilation is an essential component of the care of patients with ARDS, and a large number of randomized controlled clinical trials have now been conducted evaluating the efficacy and safety of various methods of mechanical ventilation for the treatment of ARDS. Low tidal volume ventilation (相似文献   

Evidencias de la posición en decúbito prono para el tratamiento del síndrome de distrés respiratorio agudo: una puesta al día

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) have high incidence and mortality rates. Most of the recently introduced treatments have failed to improve the prognosis of patients with ALI or ARDS or to reduce mortality. Several studies have shown improved oxygenation in the prone position during mechanical ventilation in patients with ARDS. However, current evidence strongly suggests that placing ARDS patients in prone position does not improve survival or reduce the duration of mechanical ventilation. Therefore, though in clinical practice this position may improve refractory hypoxemia in patients with ARDS, there is no evidence to support its systematic use.     

Successful treatment of a critically ill patient with acute respiratory distress syndrome from COVID-19 using mechanical ventilation strategy with low levels of positive end-expiratory pressure: A CARE-compliant case report

Introduction:Acute respiratory distress syndrome (ARDS) secondary to COVID-19 is different from the ARDS caused by other infections. Conventional mechanical ventilation strategies using high levels of PEEP may not be beneficial and can even be harmful to patient with ARDS from COVID-19. So the ventilation strategies should be adjusted in order to improve the pulmonary ventilation function and oxygenation status, and outcomes of the patient.Patient concerns:Herein, we present a 76-year-old male patient with ARDS secondary to COVID-19. We describe our experience with mechanical ventilation strategy and the changes in respiratory mechanics in the patient during treatment.Diagnosis:The patient had tested positive for coronavirus (COVID-19) in nucleic acid test. Chest CT showed multiple ground glass shadows in both lungs.Interventions:The patient received mechanical ventilation with low tidal volume and low PEEP.Outcomes:After treatment, the patients condition, as well as oxygenation status was improved, and he tested negative for the coronavirus several times.Conclusion:This case demonstrated that the low tidal volume with low levels of PEEP ventilation strategy may be more suitable for ARDS from COVID-19.     

Lung recruitment maneuvers in acute respiratory distress syndrome

In the experimental setting, repeated derecruitments of the lungs of ARDS models accentuate lung injury during mechanical ventilation, whereas open lung concept strategies can attenuate the injury. In the clinical setting, recruitment manuevers that use a continuous positive airway pressure of 40 cmH2O for 40 secs improve oxygenation in patients with early ARDS who do not have an impairment in the chest wall. High intermittent positive end-expiratory pressure (PEEP), intermitent sighs, or high-pressure controlled ventilation improves short-term oxygenation in ARDS patients. Both conventional and electrical impedance thoracictomography studies at the clinical setting indicate that high PEEP associated with low levels of pressure control ventilation recruit the collapsed portions of the ARDS lungs and that adequate PEEP levels are necessary to keep the ARDS lungs opened allowing a more homogenous ventilation. High PEEP/low tidal volume ventilation was seen to reduce inflammatory mediators in both bronchoalveolar lavage and plasma, compared to low PEEP/high tidal volume ventilation, after 36 hours of mechanical ventilation in ARDS patients. Recruitment maneuvers that used continuous positive airway pressure levels of 35-40 cmH2O for 40 secs, with PEEP set at 2 cmH2O above the lower inflection point of the pressure-volume curve, and tidal volume < 6 mL/kg were associated with a 28-day intensive care unit survival rate of 62%. This contrasted with a survival rate of only 29% with conventional ventilation (defined as the lowest PEEP for acceptable oxygenation without hemodynamic impairment with a tidal volume of 12 mL/kg), without recruitment manuevers (number needed to treat = 3; p < 0.001). In the near future, thoracic computed tomography associated with high-performance monitoring of regional ventilation may be used at the bedside to determine the optimal mechanical ventilation of the ARDS keeping an opened lung with a homogenous ventilation.     

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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.     

Respiratory system mechanics in acute respiratory distress syndrome

Respiratory mechanics research is important to the advancement of ARDS management. Twenty-eight years ago, research on the effects of PEEP and VT indicated that the lungs of ARDS patients did not behave in a manner consistent with homogenously distributed lung injury. Both Suter and colleagues] and Katz and colleagues reported that oxygenation continued to improve as PEEP increased (suggesting lung recruitment), even though static Crs decreased and dead-space ventilation increased (suggesting concurrent lung overdistension). This research strongly suggested that without VT reduction, the favorable effects of PEEP on lung recruitment are offset by lung overdistension at end-inspiration. The implications of these studies were not fully appreciated at that time, in part because the concept of ventilator-associated lung injury was in its nascent state. Ten years later. Gattinoni and colleagues compared measurements of static pressure-volume curves with FRC and CT scans of the chest in ARDS. They found that although PEEP recruits collapsed (primarily dorsal) lung segments, it simultaneously causes overdistension of non-dependent, inflated lung regions. Furthermore, the specific compliance of the aerated, residually healthy lung tissue is essentially normal. The main implication of these findings is that traditional mechanical ventilation practice was injecting excessive volumes of gas into functionally small lungs. Therefore, the emblematic low static Crs measured in ARDS reflects not only surface tension phenomena and recruitment of collapsed airspaces but also overdistension of the remaining healthy lung. The studies reviewed in this article support the concept that lung injury in ARDS is heterogeneously distributed, with resulting disparate mechanical stresses, and indicate the additional complexity from alterations in chest wall mechanics. Most of these studies, however, were published before lung-protective ventilation. Therefore, further studies are needed to refine the understanding of the mechanical effects of lung-protective ventilation. Although low-VT ventilation is becoming a standard of care for ARDS patients, many issues remain unresolved; among them are the role of PEEP and recruitment maneuvers in either preventing or promoting lung injury and the effects of respiratory rate and graded VT reduction on mechanical stress in the lungs. The authors believe that advances in mechanical ventilation that may further improve patient outcomes are likely to come from more sophisticated monitoring capabilities (ie, the ability to measure P1 or perhaps Cslice) than from the creation of new modes of ventilatory support.     

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.     

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。     

Rechtsherzfunktion bei ARDS und maschineller Beatmung

The right ventricle is the stepchild of intensive care medicine. In diseases of the lung mainly when the relationship between ventilation and perfusion is disturbed, assisted respiration with positive end-expiratory pressure (PEEP) is essential to improve oxygenation. The serious damage to the lung parenchyma as seen in adult (acute) respiratory distress syndrome (ARDS) and pneumonia has considerable consequences for cardiac function. Whereas left ventricular function remains almost completely unaffected well into late stages of the disease, the right ventricle is subjected early to stress from the underlying disease and mechanical ventilation. The effects of therapeutic measures aimed at maintaining oxygenation and ventilation partially have negative consequences for right ventricular function and encourage the development of acute cor pulmonale. They can be the cause of right-sided heart failure.     

肺开放策略治疗急性呼吸窘迫综合征的临床研究

目的探讨压力控制法进行肺开放治疗急性呼吸窘迫综合征(ARDS)的临床疗效。方法 52例ARDS患者在肺保护通气的基础上采用压力控制法进行肺开放,将呼吸机调整到压力支持模式,个体化使用PEEP和支持压力水平,PEEP15～25 cm H2O,支持压力15～20 cm H2O,气道峰压不超过45 cm H2O,维持1分钟,肺开放后继续进行肺保护通气。动态观察肺开放策略实施前后氧合指标、呼吸力学指标及血流动力学指标的变化。结果 52例ARDS患者共进行164次肺开放,肺开放前后氧合功能障碍明显改善。结论肺开放策略治疗重症ARDS明显改善了肺的氧合功能和顺应性,对血流动力学影响小,相对安全,有效地提高了抢救成功率。     

Bronchialobstruktion in der Intensivmedizin

Bronchial obstruction due to one of the major pulmonary diseases asthma, COPD, or emphysema are a common problem in intensive care medicine as the leading cause or as comorbidity. While in pharmacological therapy no major changes have occurred during the last few years, two major advances have been reached in ventilation therapy which are in the focus of this review. First the non invasive ventilation (NIV) has been shown to prove efficient in treating acute on chronic respiratory failure in COPD patients and is capable of shortening the duration of hospital stay. In addition NIV can be used successfully in weaning after long time ventilator therapy and improve prognosis in COPD patients. Secondly the strategy of invasive ventilation therapy has changed significantly. “Permissive hypercapnia” is unequivocally established in severe bronchial obstruction in situations of limited ventilation. When intrinsic PEEP and elevated airway resistance are present PEEP may be useful and the upper limit of airways peak pressure that we are used to in “protective ventilation” of ARDS patients can be necessary and useful to exceed.     

Bronchial obstruction in intensive care

Bronchial obstruction due to one of the major pulmonary diseases asthma, COPD, or emphysema are a common problem in intensive care medicine as the leading cause or as comorbidity. While in pharmacological therapy no major changes have occurred during the last few years, two major advances have been reached in ventilation therapy which are in the focus of this review. First the non invasive ventilation (NIV) has been shown to prove efficient in treating acute on chronic respiratory failure in COPD patients and is capable of shortening the duration of hospital stay. In addition NIV can be used successfully in weaning after long time ventilator therapy and improve prognosis in COPD patients. Secondly the strategy of invasive ventilation therapy has changed significantly. "Permissive hypercapnia" is unequivocally established in severe bronchial obstruction in situations of limited ventilation. When intrinsic PEEP and elevated airway resistance are present PEEP may be useful and the upper limit of airways peak pressure that we are used to in "protective ventilation" of ARDS patients can be necessary and useful to exceed.     

Adjunctive therapy to mechanical ventilation: surfactant therapy, liquid ventilation, and prone position

Acute lung injury and acute respiratory distress syndrome are associated with significant morbidity and mortality in critically ill patients. Although lung protective mechanical ventilation is the only therapy shown to reduce mortality and development of organ failure, several biologic pathways have been identified and provided an opportunity for therapeutic interventions. No pharmacologic or adjunctive treatments are available. Clinical studies demonstrated that prone position results in significant and clinically relevant improvement in oxygenation and ventilation, which persist when patients are returned to supine position; the beneficial response is not limited to patients turned early in disease course. Few complications are associated with prone ventilation. Clinical experience suggests that prone ventilation may protect the lung from potential detrimental effects of mechanical ventilation. Further studies are needed.     

ARDS患者仰卧位通气与俯卧位通气的对比

目的通过ARDS患者仰卧位通气与俯卧位通气血流动力学指标和血气指标，探讨俯卧位通气在ARDS肺保护作用。方法对19例ARDS患者按机械通气时体位分两组，仰卧位通气组（11例）和俯卧位通气组（8例），分别检测机械通气开始时（0h时）、2h时、24h时的血流动力学及血气的改变。结果两组对改善血流动力学方面作用不大，两组间MBP、CVP差异无明显性（P〉0．05），而俯卧位通气对HR的改善在24h时较明显，与仰卧位通气比较差异有显著性（P〈0．05）。仰卧位通气与俯卧位通气均能较好改善PO2、PaO2／FiO2，俯卧位通气与仰卧位通气比较能更好的改善PO2、PaO2／FiO2，在24h时最明显。差异有显著性（P〈0．05）；两组对PCO2改善不显著。结论俯卧位通气较仰卧位通气能明显改善ARDS患者的氧合，对血流动力学改变不明显。俯卧位通气可能通过改善通气／血流比例失调来促进ARDS患者氧合，纠正缺氧。     

The efficacy and safety of prone positioning in adults patients with acute respiratory distress syndrome: a meta-analysis of randomized controlled trials

Background

Prone positioning for acute respiratory distress syndrome (ARDS) has no impact on mortality despite significant improvements in oxygenation. However, a recent trial demonstrated reduced mortality rates in the prone position for severe ARDS. We evaluated effects of prone position duration and protective lung strategies on mortality rates in ARDS.

Methods

We extensively searched MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials to identify randomized controlled trials (RCTs) reporting on prone positioning during acute respiratory failure in adults for inclusion in our meta-analysis.

Results

Eight trials met our inclusion criteria, Totals of 1,099 and 1,042 patients were randomized to the prone and supine ventilation positions. The mortality rates associated with the prone and supine positions were 41% and 47% [risk ratio (RR), 0.90; 95% confidence interval (CI), 0.82-0.98, P=0.02], but the heterogeneity was moderate (P=0.01, I²=61%). In a subgroup analysis, the mortality rates for lung protective ventilation (RR 0.73, 95% CI, 0.62-0.86, P=0.0002) and duration of prone positioning >12 h (RR 0.75, 95% CI, 0.65-0.87, P<0.0001) were reduced in the prone position. Prone positioning was not associated with an increased incidence of cardiac events (RR 1.01, 95% CI, 0.87-1.17) or ventilator associated pneumonia (RR 0.88, 95% CI, 0.71-1.09), but it was associated with an increased incidence of pressure sores (RR 1.23, 95% CI, 1.07-1.41) and endotracheal dislocation (RR 1.33, 95% CI, 1.02-1.74).

Conclusions

Prone positioning tends to reduce the mortality rates in ARDS patients, especially when used in conjunction with a lung protective strategy and longer prone position durations. Prone positioning for ARDS patients should be prioritized over other invasive procedures because related life-threatening complications are rare. However, further additional randomized controlled design to study are required for confirm benefit of prone position in ARDS.     

有创呼吸支持技术的进展与挑战

有创呼吸支持技术作为挽救危重症患者生命的重要生命支持手段之一,临床上通过动态观察反映肺应力的驱动压和跨肺压指标,评价肺的应变。并应用新的监测手段,如重症超声、电阻抗等,建立个体化动态评价有创呼吸支持的临床解决方案,指导肺保护性通气、呼气末正压(PEEP)滴定、肺复张、俯卧位通气、体外膜肺氧合等呼吸支持技术,在有效改善危重症患者有效氧合的同时尽量减少有创通气的副作用。