Physiologic and alveolar dead space fractions' utility in mechanically ventilated children: a systematic review

Abstract

Objective: Assess and synthesize the prognostic value of both physiologic (VD/VT) and alveolar (AVDSf) dead space fraction measurements in mechanically ventilated children (MVC). Data Sources: MEDLINE, SCOPUS and Web of Science databases were searched. Study Selection: All studies investigating the utility of dead space measurements in MVC without congenital heart disease were included. Data Extraction: Of 692 screened articles, 9 were selected for qualitative synthesis. Data Synthesis: VD/VT was the parameter studied in 6 of the studies: 3 evaluated VD/VT's ability to predict extubation success, 2 evaluated VD/VT's correlation with gas exchange variables and time on mechanical ventilation and 1 evaluated the effect of lung injury in VD/VT. Mixed results regarding VD/VT ability to predict extubation outcome and time on mechanical ventilation were found between the studies, but VD/VT was well correlated with lung injury and gas exchange variables. In the remaining 3 studies, AVDSf's elevation was consistently associated with mortality. Conclusions: AVDSf may be a significant bedside tool in risk stratification and outcome prediction in MVC, particularly in those with respiratory failure. The variability of the studied outcomes, the lack of uniformity in the context and timing of measurements between studies, as well as the lack of established conditions requiring the use of volumetric over time-based capnography (or otherwise) for dead space measurements, requires confirmation of the presented results by future studies.