Assessment of Cystic Fibrosis Lung Disease Using Electrical Impedance Tomography.

INTRODUCTION Electrical impedance tomography (EIT) is a non-invasive, effort-independent imaging technique for measurement of regional lung ventilation and function that does not utilize ionizing radiation. There are limited data on the use of EIT to assess lung disease in people with CF (PwCF).

Methods

This was a cross-sectional observational cohort study. Study participants performed EIT, multiple breath washout (MBW) and spirometry in a single session. We analyzed EIT results to calculate the global inhomogeneity index (GII) and regional ventilation delay at 40% of maximal inspiratory impedance (RVD40). We used pairwise Spearman correlations to compare EIT measurements with the lung clearance index (LCI) and percent predicted forced expiratory volume in 1 s (FEV1pp). We generated receiver operator characteristic (ROC) curves to assess specificity and sensitivity for GII and RVD40 to predict an abnormal LCI.

Results

31 participants ranging in age from 6 to 65 years performed EIT and spirometry; 23 performed research-quality MBW. The median GII and RVD40 were 39.1 and 5.52, respectively. The median LCI was 8.9. RVD40 correlated moderately with LCI (r = 0.49, p = 0.02) and negatively correlated with FEV1pp (r = -0.36, p = 0.04). There was a weak positive correlation between GII and LCI (r = 0.27, p = 0.21). GII demonstrated a significant negative correlation with FEV1pp (r = -0.44, p = 0.01).

Discussion

We found that EIT measurements correlated with spirometry and MBW. RVD40 was more sensitive and specific for ventilation inhomogeneity as compared to GII. Our data suggest that EIT measurements made during tidal breathing could be a useful clinical test in the evaluation of CF lung disease, though further investigations are needed.