Detecting regional overdistention during mechanical ventilation using 4-dimensional computed tomography

Mechanical ventilation (MV) is a critical intervention for managing respiratory compromise and acute respiratory conditions. However, MV can also cause ventilator-induced lung injury (VILI) through mechanisms such as volutrauma, atelectrauma, and biotrauma. Conventional global pressure-volume (PV) loop analysis cannot capture regional mechanical heterogeneity within the lungs, which is central to amplifying VILI, particularly in the context of pre-existing lung injury. In this study, we employed four-dimensional computed tomography (4DCT) combined with propagation-based phase-contrast X-ray imaging to evaluate regional lung mechanics (overdistention and cyclic collapse) in a mouse model subjected to four MV protocols with varying peak inspiratory pressure and positive end-expiratory pressure. Regional PV loop analysis revealed significant overdistention in low tidal volume ventilation settings, which was not apparent in global PV loops, particularly in the group that was ventilated with a low tidal volume and zero PEEP (LVZP). Although global and regional collapse metrics showed no significant differences, regional overdistention indices were markedly higher than global measurements in LVZP, underscoring the limitations of global assessments. These findings highlight the utility of 4DCT for detecting subtle regional mechanical stress and support the integration of regional metrics into MV strategies to enhance lung protection and reduce the risk of VILI.