Current American-European Consensus Conference (AECC) definitions for ALI and ARDS are inadequate for inclusion into clinical trials due to the lack of standardization for measuring the oxygenation defect. We questioned whether an early assessment of oxygenation on specific ventilator settings would identify patients with established ARDS (persisting over 24h).

We designed this study to determine whether standard ventilator settings applied on the day ARDS is identified (Day 0) or 24 hours (Day 1) later: (1) would have an impact on the reclassification of patients into ALI or ARDS, and (2) would identify groups with different clinical outcomes. Our hypothesis was that the assessment of PaO2/FiO2 on standard ventilator settings 24 hours after patients originally met the AECC definition of ARDS would identify patients with established ARDS (persisting over 24 h) from others with different degrees of lung injury. If this hypothesis is supported, it would suggest that patients with a better outcome could have been preferentially entered into one group of previously conducted clinical trials, resulting in a viable therapy being proved useless or useless therapy proven viable.

Inclusion Criteria:

• All patients meeting American-European Consensus Conference (AECC) ARDS criteria were approached for enrollment regardless of their current status or past medical history.

Exclusion Criteria:

• The only patients excluded were those in which >24 hrs had pasted after initially meeting the AECC ARDS criteria before consent and results of initial standard ventilator settings could be obtained.