Analysis of regional compliance in a porcine model of acute lung injury

Lung protective ventilation in Acute Lung Injury (ALI) focuses on using low tidal volumes and adequate levels of positive end-expiratory pressure (PEEP). Identifying optimal pressure is difficult because pressure-volume (PV) relations differ regionally. Precise analysis demands local measurements of pressures and related alveolar morphologies. In a porcine model of surfactant depletion (n = 24), we combined measuring static pressures with endoscopic microscopy and electrical impedance tomography (EIT) to examine regional PV loops and morphologic heterogeneities between healthy (control group; CON) and ALI lungs ventilated with low (LVT) or high tidal volumes (HVT). Quantification included indices for microscopy (Volume Air Index (VAI), Heterogeneity and Circularity Index), EIT analysis and calculation of regional compliances due to generated PV loops.We found that: (1) VAI decreased in lower lobe after ALI, (2) electrical impedance decreased in dorsal regions and (3) PV loops differed regionally.Further studies should prove the potentials of these techniques on individual respiratory settings and clinical outcome.

► Acute lung injury leads to regional differences in morphology and alveolar dynamics. ► Imaging techniques are necessary to evaluate the lung state. ► Quantification was done by Volume Air Index, Heterogeneity Index and Circularity Index. ► EIT helps to identify regional heterogeneities and to estimate regional compliance. ► Analysis of regional pressure-volume-curves contribute to a clinical evaluation of ARDS.