Mapping Regional Differences of Local Pressure-Volume Curves With Electrical Impedance Tomography.

Objectives: Lung-protective mechanical ventilation aims to prevent alveolar collapse and overdistension, but reliable bedside methods to quantify them are lacking. We propose a quantitative descriptor of the shape of local pressure-volume curves derived from electrical impedance tomography, for computing maps that highlight the presence and location of regions of presumed tidal recruitment (i.e., elastance decrease during inflation, pressure-volume curve with upward curvature) or overdistension (i.e., elastance increase during inflation, downward curvature). Design: Secondary analysis of experimental cohort study. Setting: University research facility. Subjects: Twelve mechanically ventilated pigs. Interventions: After induction of acute respiratory distress syndrome by hydrochloric acid instillation, animals underwent a decremental positive end-expiratory pressure titration (steps of 2 cm H2O starting from >= 26 cm H2O). Measurements and Main Results: Electrical impedance tomography-derived maps were computed at each positive end-expiratory pressure-titration step, and whole-lung CT taken every second steps. Airway flow and pressure were recorded to compute driving pressure and elastance. Significant correlations between electrical impedance tomography-derived maps and positive end-expiratory pressure indicate that, expectedly, tidal recruitment increases in dependent regions with decreasing positive end-expiratory pressure (p = 0.72; p

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