What Is the Best Mechanical Ventilation Strategy in ARDS?

Abstract

Acute respiratory distress syndrome (ARDS) is the catastrophic response of the lung to an injury that results in severe respiratory failure. It has been recognized as a clinical entity in adults for more than 40 years 1 and affects more than 100,000 adults in the United States every year. 2 Despite intensive management, outcomes remain poor. Reported mortality rates in observational studies persist at between 40% and 50%, and long-term morbidity affects most survivors. 3,4 PATHOPHYSIOLOGY AND CLINICAL FEATURES OF ARDSThe damage to the lungs in ARDS can occur after a direct insult to the lung (pulmonary ARDS) or due to indirect damage through the alveolar epithelium (extrapulmonary ARDS). Patients with ARDS generally share several constant characteristics that identify the condition. First, ARDS typically develops after exposure to at least one of a well-known list of risk factors (Table 15-1). 5 Second, ARDS has an acute onset and is persistent over time. One of the most relevant clinical features is the presence of bilateral pulmonary airspace opacities in the chest radiograph. Severe impairment of gas exchange with hypoxemia and decrease of pulmonary compliance are also hallmarks of ARDS. The underlying cause of ARDS is extremely complex and to date is incompletely understood. It appears to involve the initiation of an inflammatory cascade within the alveolar-capillary endothelium or epithelium, and a wide range of inflammatory cells, cytokines, and chemokines have been implicated in this process. At least in its early stages, ARDS represents the pathologic state of diffuse alveolar damage (DAD). 6-8