Although mechanical ventilation is life saving, it is associated with a number of severe complications collectively referred to as ventilator induced lung injury (VILI). VILI contributes to the high morbidity and mortality associated with the acute respiratory distress syndrome (ARDS). Within the context of a randomized study evaluating the feasibility of conducting a study comparing high frequency oscillation to conventional lung protective ventilation in early severe ARDS, we are evaluating the effect of both ventilator strategies on biological markers of VILI.

Specific objectives:

To measure known biomarkers conventionally associated with VILI and biotrauma To measure potential novel biomarkers of VILI and biotrauma To identify the best time point for biomarker measurement To collect and store samples for differential expression and genomic analysis

Inclusion Criteria:

Informed consent previously obtained for enrollment in the OSCILLATE study:

1. Acute onset of respiratory failure
2. Endotracheal intubation or tracheostomy
3. Hypoxemia (P:F <200 mmHg)
4. Bilateral alveolar consolidation

Exclusion Criteria:

1. Refusal of consent to participate in this biomarkers substudy

Subset of patients enrolled in the parent study (OSCILLATE- #NCT00474656) Patients enrolled in the parent study have early severe acute respiratory syndrome and will be recruited from a critical care environment