A simulation study on the ventilation inhomogeneity measured with Electrical Impedance Tomography

Electrical Impedance Tomography (EIT) is a medical imaging modality which is mainly used in mechanically ventilated patients to monitor the regional distribution of ventilation. Recently, the potential of EIT has also been demonstrated as additional tool for diagnosis in spontaneously breathing patients with obstructive lung diseases, such as cystic fibrosis or chronic obstructive lung disease. Besides the generation of images depicting lung ventilation in real-time, EIT also provides quantitative measures to numerically describe the inhomogeneity of ventilation. In this work the impact of ventilation inhomogeneity and lung obstruction on the reconstructed EIT images is evaluated using three dimensional simulation models with different severities of obstruction. Simulation results reveal that the ventilation inhomogeneity determined with EIT raises for increasing and more severe obstructions. For obstructions affecting less than 25% of lung tissue the ventilation inhomogeneity in EIT images underestimates the disease state.