Definitions

ARDS was defined by the Berlin criteria including bilateral diffuse pulmonary infiltrates on chest X-ray or CT scan (without evidence of heart failure); there are three categories of ARDS based on degree of hypoxemia: grade 1 mild (200 < PaO₂/FIO₂ ≤ 300), grade 2 moderate (100 < PaO₂/FIO₂ ≤ 200), and grade 3 severe (PaO₂/FIO₂ ≤ 100), all with positive end expiratory pressure (PEEP) ≥ 5cmH₂0 [14]. Worst PaO₂/FIO₂ ratios were calculated on a daily basis starting from day 1 after trauma.

Acute hypoxic respiratory failure (AHRF); hypoxemia divided in three categories similar to ARDS, but without classical bilateral diffuse pulmonary infiltrates on X-ray.

Multiple organ dysfunction syndrome (MODS) was defined by Denver multiple organ failure (MOF) scores of greater than 3, occurring more than 48 h after injury [9]. Denver MOF score was chosen over sequential organ failure assessment (SOFA) to avoid difficulties by including the Glasgow coma scale (GCS) in the organ failure score. GCS can be challenging to obtain in the trauma patient in ICU, because they are often sedated and intubated for extended periods. This could negatively influence the CNS organ failure score [21].

Urgent laparotomy was defined as a laparotomy that was performed in patients who were transported from ED directly (or via CT scan) to the operating room (OR).

Pneumonia was defined as the development of purulent sputum (with positive cultures of sputum) in conjunction with radiological evidence of a new or progressive pulmonary infiltrate.