Background: Acute respiratory distress syndrome (ARDS) is associated with high ventilation-perfusion heterogeneity and dead space ventilation. However, whether the degree of dead-space ventilation correlates with outcomes is uncertain.

Aims and objectives: In this systematic review and meta-analysis, we evaluated the ability of measures of dead-space ventilation to predict mortality in patients with ARDS.

Methods: We systematically searched MEDLINE, CENTRAL, and Google Scholar databases. We included studies of adults with ARDS reporting a measure of dead-space ventilation and mortality. We performed a meta-analysis of unadjusted and adjusted results using a random effects model. We assessed heterogeneity using the I² statistic. Risk of bias was assessed using the quality in prognostic studies tool.

Results: We included 28 studies in our review, 21 of which were included in our meta-analysis. All but one study had a low risk of bias. The two most commonly studied indices were pulmonary dead-space fraction (V_D/V_T) and ventilatory ratio (VR). A high V_D/V_T was associated with increased mortality (n=3,660; OR, 3.52; 95% CI, 2.22-5.58; p<0.001; I²=84%). Every 0.05 increase in V_D/V_T is independently associated with increased odds of death (n=6,265; OR, 1.23; 95% CI, 1.13-1.34; p<0.001; I²=57%).  A high VR was also associated with increased mortality (n=7,363; OR, 1.55; 95% CI, 1.33-1.80; p<0.001; I²=48%). The association between every 1 unit increase in VR and death is independent of confounding variables (n=7,015; OR, 1.33; 95% CI, 1.12-1.58; p=0.001; I²=66%).

Conclusion: Elevated dead-space ventilation indices independently predict mortality in adults with ARDS.