肺脏病理生理学精品.ppt

* Clinical conditions Associated with ARDS Condition Frequently associated with ARDS Description Incidence: Infection Viral pneumoniae, Pneumocystis carinii pneumonia, gram negative pneumonia or sepsis Shock All types, especially septic shock Major trauma Long-bone fractures, pulmonary contusions, head trauma, fat emboli, burns Hypertransfusion Gastric aspirations 正常成人呼吸频率：12～18次/每分钟； 潮气量：～900ml；pH ： 7.35～7.45。 * Mortality: 30-40%; survivors: respiratory function recovers within 6-12 months. Background: Ashbaugh and colleagues first described acute respiratory distress syndrome (ARDS) in 1967. They described the syndrome as acute onset of severe respiratory distress, cyanosis (hypoxemia) refractory to oxygen therapy, diffuse abnormalities on chest radiographs (CXRs), and decreased lung compliance. In 1994, the American-European Consensus Conference (AECC) on ARDS formulated their definition of ARDS as follows: Acute onset of symptoms Ratio of PaO2 to the fraction of inspired oxygen (FIO2) of 200 mm Hg or less Bilateral infiltrates on CXRs Pulmonary arterial wedge pressure of 18 mm Hg or less or no clinical signs of left atrial hypertension The radiographic abnormalities of ARDS reflect the leakage of fluid with a high protein content into the alveolar spaces because of alveolar epithelial injury, or diffuse alveolar damage. ARDS is a syndrome defined by its clinical features. It may result from intrathoracic or extrathoracic events of various etiologies, such as inflammatory, infectious, vascular, or traumatic etiologies. Determining the causative event may be clinically important for proper treatment. ARDS is a syndrome that commonly begins after exposure to a known risk factor. Why some people develop ARDS and others do not is still unknown. The risk factors for ARDS include primary pulmonary etiologies (eg, aspiration, pneumonia, toxic inhalation, pulmonary contusion) and extrapulmonary etiologies (eg, sepsis, pancreatitis, multiple blood transfusi