Increased ratio of dead space to tidal volume in subjects with inhalation injury

Abstract

BACKGROUND: Inhalation injury increases morbidity and mortality in burn patients. Patients with inhalation injury present with large differences between end-tidal CO2 pressure and PaCO2, an indirect measure of dead space. We aimed to investigate the relationships between increased dead space and inhalation injury outcomes. METHODS: This retrospective study included 51 adult subjects with burns and inhalation injuries. Demographics, size of burns, length of stay, ventilator days, blood gas results, end-tidal CO2 pressure, presence of ventilator-associated pneu-monia, and mortality data were collected. Modified Baux scores and ratios of alveolar dead space to alveolar tidal volume (VDalv /VTalv) were calculated. Independent t tests were used to com-pare mean VDalv /VTalv of survivors to that of subjects who died and between subjects with and without pneumonia. The relationships between VDalv /VTalv and ventilator days or modified Baux score were assessed with bivariate correlation analysis. RESULTS: Our population had a mean age of 52 y and an average burn size of 17.5%. The average length of stay and ventilator days were 12 d and 3.8 d, respectively. The mean modified Baux score was 87. The mean VDalv /VTalv was 0.38. Ten subjects died, and 6 subjects had pneumonia. The VDalv /VTalv of survivors was significantly smaller for survivors than for subjects who died (0.34 vs 0.52, P 5 .03). No significant difference was observed between subjects with and without pneumonia (0.36 vs 0.47, P 5 .26). VDalv /VTalv correlated significantly with modified Baux score (r 5 .524, P