Regional ventilation in cystic fibrosis measured by electrical impedance tomography

BackgroundThe feasibility of electrical impedance tomography (EIT) as an alternative examination tool in cystic fibrosis (CF) was examined.Methods14 CF patients and 14 healthy volunteers were studied. Spirometry and EIT measurements were performed simultaneously. The global inhomogeneity (GI) index was applied to assess the degree of ventilation homogeneity at different levels of maximum inspiratory volume. Ratios of maximum expiratory flow at 25% and 75% of vital capacity (MEF25/MEF75) were calculated for both global lung and regional areas in EIT images.ResultsSignificant differences among GI values at various lung volumes were found in CF patients (P < 0.01) but not in healthy subjects. Global MEF25/MEF75 measured with spirometry and with EIT were highly correlated for all subjects (r2 = 0.69, P < 0.01). Significant difference in global MEF25/MEF75 was found between CF patients and healthy volunteers with both spirometer (CF: 0.15 ± 0.09; healthy: 0.46 ± 0.15; P < 0.001) and EIT (CF: 0.14 ± 0.09; healthy: 0.42 ± 0.08; P < 0.001). Regional airway obstruction was identified in the MEF25/MEF75 maps in CF patients.ConclusionsCompared to the global parameters provided by spirometry, EIT is able to deliver both global and regional information to assess the airway obstruction in CF patients.