Potential Effects of Corticosteroids on Physiological Dead-Space Fraction in Acute Respiratory Distress Syndrome

BACKGROUND: Increased dead-space fraction is common in patients with persistent acute respiratory distress syndrome (ARDS). We evaluated the changes in the oxygenation and dead-space fraction in patients with persistent ARDS after corticosteroid therapy. METHODS: This was a non-randomized non-placebo, controlled observational study including 19 patients with persistent ARDS treated with corticosteroids. We measured P-aO2/F-IO2 and dead-space fraction at days 0, 4, and 7 after corticosteroids treatment (methylprednisolone) initiation. Patients were classified in intermediate group when corticosteroids were initiated between days 8-14 after ARDS onset, and in late group when initiated after 14 days. RESULTS: Mean time from the diagnosis of the ARDS to methylprednisolone treatment was 11 +/- 2 days in the intermediate group (10 patients) and 21 +/- 8 days in the late group (9 patients). When comparing days 0, 4, and 7 after methylprednisolone treatment, we found an increase in the P-aO2/F-IO2 (145 +/- 64 mm Hg, 190 +/- 68 mm Hg, and 226 +/- 84 mm Hg, respectively, P < .001) and a decrease in the physiological dead-space fraction (0.66 +/- 0.10, 0.58 +/- 0.12, and 0.53 +/- 0.11, respectively, P < .001). No differences were found between the intermediate and late groups. CONCLUSIONS: In patients with persistent ARDS, the increase in oxygenation was accompanied by a decrease in the dead-space fraction after a few days of corticosteroid treatment. To confirm potential benefit of corticosteroids on physiological parameters and mortality will require a powered randomized placebo controlled trial.