Electrical impedance tomography
EIT measurements were performed with the Dräger PulmoVista 500 (Dräger Medical Deutschland GmbH, Lübeck, Germany). The 16-electrode belt was placed between the 3rd and 5th intercostal spaces. Ventilation data were continuously recorded by the EIT device via a serial interface (Medibus, Dräger Medical Deutschland GmbH, Lübeck, Germany).The following EIT parameters were stored during the measurement phases: EIT tidal images, global impedance curves, regional impedance curves and tidal variation of regions of interest (ROI) 1–4, change in end-expiratory lung impedance (ΔEELI) and ventilator flow curve.