The dead space fraction as a prognostic death indicator in patients with ARDS: a systematic review and meta-analysis.

Objective:   Acute respiratory distress syndrome (ARDS) is a systemic disease with high morbidity and mortality. Dead space fraction (Vd/Vt) represents the volume of air that does not participate in gas exchange and accurately depicts the pathophysiology of ARDS due to ventilation and perfusion mismatch. In this study, we aim to conduct a systematic review and meta-analysis regarding its usefulness for predicting mortality.

Materials and methods: We performed a systematic literature search identifying comparative studies meeting the above criteria from four databases: MEDLINE, clinicaltrials.gov, CENTRAL, and Google Scholar. A statistical meta-analysis was conducted utilizing the "meta" package in R software, with the included studies assessed based on the Newcastle-Ottawa scale.

Results: A total of twelve studies were included and data from over 1,700 patients was collected. Patients with higher levels of Vd/Vt were more likely to not survive with an OR=1.27 [95% CI (1.09, 1.48), I2=93%, p<0.01]. In addition, non-survivors of ARDS had higher mean value levels of Vd/Vt than survivors with an MD=0.07 [95% CI (0.02, 0.11), I2=82%, p<0.01]. Furthermore, a leave-one-out meta-analysis was performed in order to assess the effect of each individual study on the overall outcome, which led to the lowering of heterogeneity to 0.

Conclusions: The Vd/Vt ratio is an accurate index for determining the mortality of ARDS, reflecting the severity of the disease.