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.