Current standards for conducting spirometry examinations recommend that the ventilation manoeuvres needed in pulmonary function testing are carried out repeatedly during the sessions. Chest electrical impedance tomography (EIT) can determine the presence of ventilation heterogeneity during such manoeuvres which increases the information content derived from such examinations. The aim of this study was to characterise regional lung function in patients with chronic obstructive pulmonary disease (COPD) during repetitive forced full ventilation manoeuvres. Regional lung function measures derived from these manoeuvres were compared with quiet tidal breathing.
60 hospitalised patients were examined during up to three repeated ventilation manoeuvres. 53 patients (12 women, 41 men; age: 68±17 years (mean±SD)) exhibited acceptable spirometry manoeuvres and EIT recordings suitable for analysis. Pixel values of tidal volume, forced full inspiratory and expiratory volume in 1s, forced inspiratory and expiratory vital capacity were calculated from the EIT data. Spatial ventilation heterogeneity was assessed using the coefficient of variation, global inhomogeneity index, centres and regional fractions of ventilation. Temporal inhomogeneity was examined by pixel expiration times needed to exhale 50% and 75% of regional forced vital capacity.
All EIT-derived measures of regional lung function showed reproducible results during repetitive examinations. Parameters of spatial heterogeneity obtained from quiet tidal breathing were comparable with the measures derived from the forced manoeuvres.
Measures of spatial and temporal ventilation heterogeneity obtained in COPD patients by EIT provide comparable findings during repeated examinations within one testing session. Quiet tidal breathing generates similar information on ventilation heterogeneity as forced manoeuvres that require high patient effort.

© 2020 Institute of Physics and Engineering in Medicine.

Author