Definition of ALI/ARDS
Section snippets
Importance of defining ALI/ARDS
A precise definition of ARDS is necessary to facilitate research into the pathogenesis and standardize treatment modalities. There is broad recognition that ALI/ARDS has many predisposing risk factors, and the definition merely represents a functional indicator of the severity of the lung injury. Should we be studying individual risk factors/disease that led to this syndrome, such as aspiration-induced lung injury, lung contusion, transfusion-related acute lung injury (TRALI), or lung injury
The American-European Consensus Conference Definition
The American-European Consensus Conference (AECC) on ARDS in 1994 defined ALI as respiratory failure of acute onset with a PaO2/FiO2 ratio of less than 300 mm Hg (regardless of the level of positive end-expiratory pressure, PEEP), bilateral infiltrates on frontal chest radiograph, and a pulmonary capillary wedge pressure of 18 mm Hg or less (if measured) or no evidence of left atrial hypertension.8 ARDS was defined identically except for a lower limiting value of less than 200 mm Hg for PaO2/FiO
Accuracy of current ALI/ARDS definitions
The diagnostic accuracy of the ALI/ARDS definitions currently in use has been critically examined. A comparison of the AECC definition with autopsy findings of DAD in a series of 382 patients found the sensitivity (75%) and specificity (84%) to be only moderate.12 Of interest, the AECC definition was more accurate for patients with extrapulmonary risk factors than for patients with pulmonary risk factors. The AECC definition has performed poorly in limited reliability testing.23, 24
Is the severity of hypoxemia important?
The traditional thinking with ARDS is that it is the multiorgan dysfunction and not hypoxemia that is responsible for mortality. This assumption was based on several ARDS network trials in which hypoxia was well tolerated (up to saturations of 88%)2 and improvements in oxygenation did not translate into a survival advantage. A detailed discussion of such studies is provided in the chapter by Thompson and Bernard elsewhere in this issue.
It must be pointed out that some studies after the adoption
Is it time to change the definition of ALI/ARDS?
Over the past few years many different study groups have raised doubts about the validity of the current ALI/ARDS definitions and have recommended a change.30, 31 The authors believe strongly that it is time to change the definition after 17 years of the predominant use of the AECC definition for ALI/ARDS. Based on available data with various validity studies, it is suggested that the new definition should be standardized as follows. (a) Risk factors: direct (pulmonary) or indirect
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