An apparatus for determining functional lung characteristics of a patient comprising an electrical impedance tomography (EIT) imaging device adapted to record the impedance distribution within a plane of the thorax of the patient, the EIT imaging device including a control and analysis unit for performing the impedance measurement and deriving the impedance distribution within the plane of the thorax, characterised in that the control and analysis unit is further arranged to automatically perform the following steps:
- determining a global impedance change, defined as the impedance change with respect to an earlier measured reference impedance distribution integrated over the electrode plane, and recording the global impedance change curve as a function of time,
- performing breath detection in order to identify a breathing cycle,
- subdividing each breathing cycle to define a plurality of intratidal intervals,
- subdividing an EIT image from each interval into a plurality of regions of interest and calculating for each region of interest the ratio of the integrated impedance change within this region of interest to the global impedance change of this EIT image,
- for each intratidal interval presenting indications of the ratios determined for the regions of interest to provide an intratidal gas distribution representation for each interval.