The association between the end tidal alveolar dead space fraction and mortality in pediatric acute hypoxemic respiratory failure

Objective: To investigate the relationship of markers of oxygenation, PaO(2)/FIO(2) ratio, SpO(2)/FIO(2) ratio, oxygenation index, oxygen saturation index, and dead space (end tidal alveolar dead space fraction) with mortality in children with acute hypoxemic respiratory failure. Design: Retrospective. Setting: Single-center tertiary care pediatric intensive care unit. Patients: Ninety-five mechanically ventilated children with a PaO(2)/FIO(2) ratio <300 within 24 hrs of the initiation of mechanical ventilation. Interventions: None. Main Results: The end tidal alveolar dead space fraction, PaO(2)/FIO(2) ratio, SpO(2)/FIO(2) ratio, oxygenation index, and oxygen saturation index were all associated with mortality (p < .02). There was a small correlation between the end tidal alveolar dead space fraction and decreasing PaO(2)/FIO(2) (r(2) = .21) and SpO(2)/FIO(2) ratios (r(2) = .22), and increasing oxygenation index (r(2) = .25) and oxygen saturation index (r(2) = .24). In multivariate logistic regression modeling, the end tidal alveolar dead space fraction was independently associated with mortality (p < .02). Oxygenation index, oxygen saturation index, and the end tidal alveolar dead space fraction were all acceptable discriminators of mortality with receiver operating characteristic plot area under the curves >= 0.7. Conclusions: In pediatric acute hypoxemic respiratory failure, easily obtainable pulmonary specific markers of disease severity (SpO(2)/FIO(2) ratio, oxygen saturation index, and the end tidal alveolar dead space fraction) may be useful for the early identification of children at high risk of death. Furthermore, the end tidal alveolar dead space fraction should be considered for risk stratification of children with acute hypoxemic respiratory failure, given that it was independently associated with mortality. (Pediatr Crit Care Med 2012; 13:11-15)