Acute lung injury is a critical illness syndrome consisted of acute hypoxemic respiratory failure with bilateral pulmonary infiltrates that are not attributed to left atrial hypertension. The severity of the hypoxemia differentiates these two entities, with a ratio of partial pressure of oxygen in arterial blood (PaO2) to inspired fraction of oxygen (FIO2) of less than 200 mm Hg for ARDS and of less than 300 mm Hg for ALI. Although ARDS initially was reported in 1967 by Ashbaugh and colleagues, it was not until 1992 that the American-European Consensus Conference (AECC) on ARDS developed a standardized definition for ARDS and ALI. There are many epidemiologic researches about the incidence and mortality of the ALI/ARDS.[3-6] Gorden D  reported that a total of 1113 King County residents undergoing mechanical ventilation met the criteria for acute lung injury and were 15 years of age or older. On the basis of this figure, the crude incidence of acute lung injury was 78.9 per 100,000 person-years and the age-adjusted incidence was 86.2 per 100,000 person-years. The in-hospital mortality rate was 38.5 percent. In our country, Yueming Lu  reported in-hospital and 90-day mortalities of ARDS patients were 68.5 and 70.4% in Shanghai ICU in 2004.
In recent years, significant progress has been made in the diagnosis and treatment of the ALI/ARDS, such as the application of the lung protective ventilation strategy and the CRRT, which may prove the symptoms and the prognosis of the ALI/ARDS. However, controversies still remained. Ventilation drive pressure, early application of neuromuscular blockade, strategy of PEEP level are frequently met questions in routine practice. In our country, a guideline for the treatment and diagnosis of ALI/ARDS was developed in 2006 . So the incidence and the mortality of this disease are unknown in our country now. Therefore, the investigators will perform a prospective, multi-center study to survey the incidence, risk factors and outcome of ALI/ARDS in 13 adult ICU in Shanghai.