Seminars in respiratory and critical care medicine
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Acute respiratory distress syndrome (ARDS) is a syndrome of acute respiratory failure caused by noncardiogenic pulmonary edema. Despite five decades of basic and clinical research, there is still no effective pharmacotherapy for this condition and the treatment remains primarily supportive. It is critical to study the molecular and physiologic mechanisms that cause ARDS to improve our understanding of this syndrome and reduce mortality. ⋯ First, we will describe how pulmonary edema fluid accumulates in ARDS due to lung inflammation and increased alveolar endothelial and epithelial permeabilities. Next, we will review how pulmonary edema fluid is normally cleared in the uninjured lung, and describe how these pathways are disrupted in ARDS. Finally, we will explain how clinical trials and preclinical studies of novel therapeutic agents have further refined our understanding of this condition, highlighting, in particular, the study of mesenchymal stromal cells in the treatment of ARDS.
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Semin Respir Crit Care Med · Feb 2019
ReviewDefinitions, Epidemiology, Clinical Risk Factors, and Health Disparities in Acute Respiratory Distress Syndrome.
Acute respiratory distress syndrome (ARDS) is a syndrome of inflammatory lung injury currently defined as the rapid onset of hypoxemia and radiographic opacities from a recent direct or indirect insult that is not explained by other causes. While the diagnostic criteria used to define ARDS are helpful in the clinical setting, they are not entirely specific for the characteristic pathophysiology of diffuse alveolar lung damage. ⋯ Within these limitations, ARDS appears to be a condition that is relatively rare within the general population but common within the context of the intensive care unit. Furthermore, the frequency and outcomes of ARDS seem to vary between populations, with no clearly discernible temporal trends in incidence or case fatality that are uniform across studies.
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Semin Respir Crit Care Med · Feb 2019
ReviewOptimal Ventilator Strategies in Acute Respiratory Distress Syndrome.
Mechanical ventilation practices in patients with acute respiratory distress syndrome (ARDS) have progressed with a growing understanding of the disease pathophysiology. Paramount to the care of affected patients is the delivery of lung-protective mechanical ventilation which prioritizes tidal volume and plateau pressure limitation. Lung protection can probably be further enhanced by scaling target tidal volumes to the specific respiratory mechanics of individual patients. ⋯ Airway pressure release ventilation offers an alternative approach to maximize lung recruitment and oxygenation, but clinical trials have not demonstrated a survival benefit of this mode over conventional ventilation strategies. Rescue therapy with high-frequency oscillatory ventilation is an important option in refractory hypoxemia. Despite a disappointing lack of benefit (and possible harm) in patients with moderate or severe ARDS, possibly due to lung hyperdistention and right ventricular dysfunction, high-frequency oscillation may improve outcome in patients with very severe hypoxemia.
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Semin Respir Crit Care Med · Feb 2019
ReviewExtracorporeal Strategies in Acute Respiratory Distress Syndrome.
Despite the breadth of life-sustaining interventions available, mortality in patients with acute respiratory distress syndrome (ARDS) remains high. A greater appreciation of the potential iatrogenic injury associated with the use of mechanical ventilation has led clinicians and researchers to seek alternatives. Extracorporeal life support (ECLS) may be used to rescue patients with severely impaired gas exchange and provide time for injured lungs to recover while treating the underlying disease. ⋯ VV-ECLS can be configured as a system that uses higher blood flows with extracorporeal membrane oxygenation (VV-ECMO) or as one that uses lower blood flows for extracorporeal carbon dioxide removal (VV-ECCO2R). Recent studies support the use of VV-ECMO in patients with severe ARDS who present with refractory gas exchange despite the use of lung-protective mechanical ventilation, positive end-expiratory pressure optimization, neuromuscular blockade, and prone positioning. The optimal management of patients during ECLS (i.e., anticoagulation, transfusions, mechanical ventilation) and the role of ECCO2R in the management of ARDS remain to be determined.
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Semin Respir Crit Care Med · Feb 2019
ReviewPathophysiology and Management of Acute Respiratory Distress Syndrome in Obese Patients.
A rising prevalence of obesity is reported over time and throughout the world. At the same time, the acute respiratory distress syndrome (ARDS) remains an important public health problem, accounting for approximately 10% of intensive care unit admissions and leading to significant hospital mortality. Even in the absence of acute illnesses, obesity affects respiratory mechanics and gas exchange in the setting of a restrictive disease. ⋯ Then the diagnostic challenges due to obesity-related artifacts of the different imaging techniques will be presented. A subsequent, detailed description of the altered respiratory anatomy and physiology of obesity will provide help in selecting an optimal, individually tailored strategy of support. Furthermore, we will discuss how esophageal manometry should be used to adjust the settings of positive end-expiratory pressure and tidal volume; the challenges of prone positioning and extracorporeal support; and the optimal strategies for weaning from mechanical ventilation, including when and how to perform a tracheostomy.