Despite advances in the understanding of the pathophysiology in ARDS and identification of improved strategies that prevent further ventilator-induced lung injury (VILI), mortality in ARDS remains high. This inefficiency in CO 2 elimination is caused by increased physiologic dead space as microvascular injury reduces perfusion of ventilated alveoli. ConclusionĪrterial to end-tidal CO 2 (ETCO 2) difference is an independent predictor of mortality in patients with ARDS.Īcute Respiratory Distress Syndrome (ARDS) is an acute inflammatory process which leads to protein-rich, non-hydrostatic pulmonary edema with reduced lung compliance, refractory hypoxemia, and impaired ability to eliminate carbon dioxide.

In the validation cohort, substitution of the arterial-ET difference for the modified Enghoff equation showed similar results. By multivariable analysis, the arterial-ET difference continued to be predictive of mortality ( P = 0.031).

The University of Chicago cohort found arterial-ET difference, age, ventilator mode, vasopressor requirement, and APACHE II to be associated with mortality in a univariate analysis. In a separate analysis, the modified Enghoff equation ((P aCO 2–P ETCO 2)/P aCO 2) was used in place of the arterial-ET difference and did not alter the results. By multivariable analysis, only the arterial-ET difference remained significant ( P = 0.047). The ARDS Network derivation cohort demonstrated arterial-ET difference, vasopressor requirement, age, and APACHE III to be associated with mortality by univariable analysis. We then performed a separate retrospective analysis of patients with ARDS using University of Chicago patients ( N = 302) as a validation cohort. We first used publicly available databases from the ALTA, EDEN, and OMEGA ARDS Network trials ( N = 124) as a derivation cohort to test our hypothesis. We performed two separate exploratory analyses. We hypothesized that early measurement of the difference between arterial and end-tidal CO 2 (arterial-ET difference), a surrogate for dead space fraction, would predict mortality in mechanically ventilated patients with ARDS. In acute respiratory distress syndrome (ARDS), dead space fraction has been independently associated with mortality.

Dead space vs shunt CO2