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KEY POINTS

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KEY POINTS

  1. Acute respiratory distress syndrome (ARDS) is characterized by a severe inflammatory process, which causes diffuse alveolar epithelial and capillary damage.

  2. A number of medical and surgical conditions have been associated with the development of ARDS, with pneumonia and sepsis being the two most common predisposing conditions.

  3. The Berlin definition of ARDS includes four diagnostic criteria: (1) bilateral opacities on chest radiograph or computed tomography, (2) PaO2/FiO2 300 mm Hg or less with 5 cm or more H2O PEEP, (3) respiratory failure not fully explained by cardiogenic edema or volume overload, and (4) 7 days or less from predisposing clinical insult.

  4. Severity of ARDS is classified by the Berlin definition according to PaO2/FiO2: mild (201-300), moderate (101-200), and severe (< 100).

  5. Management strategies for ARDS are centered on treatment of the underlying clinical disorder while providing supportive care that minimizes ventilator-induced lung injury.

  6. Current clinical practice guidelines for reducing lung injury include low tidal-volume ventilation, application of PEEP (while maintaining plateau pressures < 30 cm H2O), and reduction of FiO2 to lowest necessary value to maintain a goal oxygen saturation of 88% to 95%.

  7. A number of novel therapies and ventilation strategies are currently under investigation.

  8. Despite significant advancements in the diagnosis and management of ARDS over the last two decades, mortality estimates remain more than 30% with significant morbidity among survivors.

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INTRODUCTION

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The acute respiratory distress syndrome (ARDS) was first described in 1967 by Dr David Ashbaugh and colleagues.1 ARDS is a life-threatening lung condition characterized by acute onset and rapidly progressive dyspnea, tachypnea, and hypoxemia. Several clinical precipitants are associated with the development of ARDS, including sepsis, pneumonia, aspiration, and transfusion of blood products. Pathogenesis is through a severe inflammatory process, which causes diffuse alveolar damage and alveolar capillary leakage, resulting in a ventilation-perfusion mismatch and poor lung compliance. A significant amount of basic and clinical research has resulted in a greater understanding of ARDS and subsequent improvement in outcomes through improved ventilatory strategies and supportive care of other organ systems. Morbidity and mortality, however, remain high. This chapter discusses the current understanding of the epidemiology, pathophysiology, management approaches, and prevention of ARDS.

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Epidemiology

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Accurate estimation of the incidence of ARDS is limited due to variations in diagnostic criteria over the last two decades. In 2005, a prospective cohort study estimated the incidence of acute lung injury (ALI) and ARDS to be approximately 190,600 cases annually in the United States.2 Additional cross-sectional studies demonstrated that patients with ARDS represent approximately 5% of hospitalized, mechanically ventilated patients.3 Over the last decade, there has been a decrease in the incidence of hospital-acquired ARDS, which has been attributed to overall improvements in the care of critically ill patients. However, it appears the incidence of community-acquired ARDS is unchanged.4...

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