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??Abstract??Ventilation with low tidal volume (Vt)normalized to ideal body weight (IBW) has become a doctrine for the ventilation of patients with ARDS since the end of last century and mortality of ARDS has decreased to some extent.However??it is still highly debatable about how to choose a suitable tidal volume.Recently??with better insights into ARDS’ pathophysiological changes and its respiratory mechanics??especially with the more popular use of EIT??critical ultra sound and lung stress and strain??it is feasible to choose tidal volume individually according to the lung compliance of ARDS patients.     

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??Abstract??Acute respiratory distress syndrome (ARDS) is the most commonly-seen clinical acute respiratory failure.After half a century of clinical exploration and practice??great progress has been made in the diagnosis and treatment of ARDS.Despite this intense research progress??there are very few effective therapies for ARDS other than the use of lung protection strategies.With the development of medical technology??new modes of mechanical ventilation and gene therapy for ARDS have been widely concerned.     

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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.     

New modalities of mechanical ventilation: high-frequency oscillatory ventilation and airway pressure release ventilation

Management of acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) is largely supportive, with the use of mechanical ventilation being a central feature. Recent advances in the understanding of ALI/ARDS and mechanical ventilation have revealed that lung-protective ventilation strategies may attenuate ventilator-associated lung injury and improve patient morbidity/mortality. High-frequency oscillatory ventilation and airway pressure release ventilation are two novel alternative modes of ventilation that theoretically fulfill the principles of lung protection and may offer an advantage over conventional ventilation for ALI/ARDS.     

肺保护性通气改善急性呼吸窘迫综合征预后的机制

肺保护性通气策略（lung protective ventilation strategy，LPVS）的提出是近年来在急性呼吸窘迫综合征（ARDS）治疗方面的最主要进展，LPVS在临床的应用是ARDS病死率降低的重要原因。最初认为LPVS是通过降低ARDS机械通气过程中的机械性损伤而改善ARDS预后的，但目前研究显示LPVS还可通过降低肺和全身炎症反应、改善肺氧化一抗氧化失衡和细胞凋亡异常等多个机制改善ARDS预后。     

The Basics of ARDS Mechanical Ventilatory Care for Cardiovascular Specialists

The ongoing COVID-19 pandemic has placed pressure on health care systems and intensive care unit capacity worldwide. Respiratory insufficiency is the most common reason for hospital admission in patients with COVID-19. The most severe form of respiratory failure is acute respiratory distress syndrome (ARDS), which is associated with significant morbidity and mortality. Patients with ARDS are often treated with invasive mechanical ventilation according to established evidence-based and guideline recommended management strategies. With growing strain on critical care capacity, clinicians from diverse backgrounds, including cardiovascular specialists, might be required to help care for the growing number of patients with severe respiratory failure and ARDS. The aim of this article is to outline the fundamentals of ARDS diagnosis and management, including mechanical ventilation, for the nonintensivist. In the absence of mechanical ventilation trials specifically in patients with COVID-19-associated ARDS, the information presented is on the basis of general ARDS trials.     

High-frequency ventilation for acute lung injury and ARDS

In patients with acute lung injury (ALI) and ARDS, conventional mechanical ventilation (CV) may cause additional lung injury from overdistention of the lung during inspiration, repeated opening and closing of small bronchioles and alveoli, or from excessive stress at the margins between aerated and atelectatic lung regions. Increasing evidence suggests that smaller tidal volumes (VTs) and higher end-expiratory lung volumes (EELVs) may be protective from these forms of ventilator-associated lung injury and may improve outcomes from ALI/ARDS. High-frequency ventilation (HFV)-based ventilatory strategies offer two potential advantages over CV for pateints with ALI/ARDS. First, HFV uses very small VTs, allowing higher EELVs with less overdistention than is possible with CV. Second, despite the small VTs, high respiratory rates during HFV allow the maintenance of normal or near-normal PaCO(2) levels. In this review, the use of HFV as a lung protective strategy for patients with ALI/ARDS is discussed.     

Ventilator-associated lung injury

Mechanical ventilation is indispensable in support of patients with respiratory failure who are critically ill. However, use of this technique has adverse effects, including increased risk of pneumonia, impaired cardiac performance, and difficulties associated with sedation and paralysis. Moreover, application of pressure to the lung, whether positive or negative, can cause damage known as ventilator-associated lung injury (VALI). Despite difficulties in distinguishing the effects of mechanical ventilation from those of the underlying disorder, VALI greatly assists patients with the most severe form of lung injury, acute respiratory distress syndrome (ARDS). Moreover, modification of mechanical ventilation so that VALI is kept to a minimum improves survival of patients with ARDS. Here, we outline the effects of mechanical ventilation on injured lungs and explore the underlying mechanisms.     

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.     

Adenovirus Pneumonia Complicated With Acute Respiratory Distress Syndrome: A Case Report

Severe adenovirus infection in children can manifest with acute respiratory distress syndrome (ARDS) and respiratory failure, leading to the need for prolonged mechanical support in the form of either mechanical ventilation or extracorporeal life support. Early extracorporeal membrane oxygenation (ECMO) intervention for children with ARDS should be considered if selection criteria fulfill.We report on a 9-month-old boy who had adenovirus pneumonia with rapid progression to ARDS. Real-time polymerase chain reaction tests of sputum and pleural effusion samples confirmed adenovirus serotype 7. Chest x-rays showed progressively increasing infiltrations and pleural effusions in both lung fields within 11 days. Because conventional ARDS therapies failed, we initiated ECMO with high-frequency oscillatory ventilation (HFOV) for 9 days. Chest x-rays showed gradual improvements in lung expansion.This patient was subsequently discharged after a hospital stay of 38 days. Post-ECMO and adenovirus sequelae were followed in our outpatient department.Adenovirus pneumonia in children can manifest with severe pulmonary morbidity and respiratory failure. The unique lung recruitment by HFOV can be a useful therapeutic option for severe ARDS patients when combined with sufficient lung rest provided by ECMO.