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(aO(2))/F(IO(2)) 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(aO(2))/F(IO(2)) (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.

Prognostic value of the pulmonary dead-space fraction during the early and intermediate phases of acute respiratory distress syndrome.

BACKGROUND: Little is known about the alveolar dead-space fraction after the first week of acute respiratory distress syndrome (ARDS). We measured the dead-space fraction in the early phase (first week) and the intermediate phase (second week) of ARDS, and evaluated the association of dead-space fraction with mortality. METHODS: We prospectively measured dead-space fraction and other variables in 80 intubated patients during the early phase of ARDS and in 49 patients during the intermediate phase. We used multiple logistic regression analysis to evaluate data. The primary outcome was in-hospital mortality. RESULTS: In the early and intermediate phases the dead-space fraction was higher in patients who died than among those who survived (dead-space fraction 0.64 +/- 0.09 vs 0.53 +/- 0.11, P < .001, and 0.62 +/- 0.09 vs 0.50 +/- 0.10, P < .001, respectively). In both the early and intermediate phases the dead-space fraction was independently associated with a greater risk of death. For every dead-space-fraction increase of 0.05 the odds of death increased by 59% in the early phase (odds ratio 1.59, 95% confidence interval 1.18-2.16, P = .003) and by 186% in the intermediate phase (odds ratio 2.87, 95% confidence interval 1.36-6.04, P = .005). Age and Sequential Organ Failure Assessment score were also independently associated with a greater risk of death in both phases. CONCLUSIONS: Increased alveolar dead-space fraction in the early and intermediate phases of ARDS is associated with a greater risk of death.