High PEEP Increases Airway Dead Space and Decreases Alveolar Ventilation: A New Technique for Volumetric Capnography

Background/Objectives: Identifying the optimal positive end-expiratory pressure (PEEP) is a major challenge in implementing strategies to prevent ventilator-induced lung injury in newborns. In this study, we assessed the validity of volumetric capnography based on the neonatal patient monitor (V_cap,PM) technique and investigated the impact of PEEP on newborns. Methods: Analysis 1 evaluated the validity of the V_cap,PM technique with data from pediatric patients receiving invasive respiratory support. Linear regression and Bland-Altman analyses were performed on V_cap,PM and HAMILTON-C1 data. Analysis 2 evaluated the impact of PEEP on newborns. The PEEP level was increased from mild to high (the incremental phase) and then decreased from high to mild (the decremental phase) while performing the V_cap,PM technique on term and preterm infants. Results: Analysis 1 included 31 children (age, 9 [interquartile range (IQR), 0-36] months; weight, 6.0 [IQR, 3.8-10.5] kg). Regression and Bland-Altman analyses demonstrated the accuracy of V_cap,PM. Analysis 2 included 28 term (mean gestational age, 38 [IQR, 38-40] weeks; weight, 2924 [IQR, 2725-3109] g) and 21 preterm (mean gestational age, 33 [IQR, 31-34] weeks; weight, 1918 [IQR, 1356-2186] g) newborns. Despite no difference in tidal volume, high PEEP significantly increased airway dead space and decreased alveolar tidal volume compared to mild PEEP in each phase in term and preterm neonates. Conclusions: High PEEP induced airway dilation in newborns, as determined using a novel V_cap technique. This technique, which requires no special equipment, has the potential for wider clinical application in neonatal care.