Regional lung function determined by electrical impedance tomography in lung-healthy adults

Abstract

Introduction: Electrical impedance tomography (EIT) is able to determine regional ventilation distribution during PFT. Reliable data on regional lung function in healthy subjects are needed as reference data for correct assessment of regional lung function deterioration in patients with lung diseases.

Methods: We examined 177 allegedly lung-healthy adults (63 non-smokers (48±19 yr, mean age± SD), 68 ex-smokers (55±16)and 46 current smokers (47±15)) using EIT during a forced expiration manoeuvre. EIT data were acquired in one thoracic plane using the Goe-MF II EIT device (CareFusion, Höchberg, Germany) at 33 images/s. In each of the 912 EIT image pixels, we identified the beginning and the end of forced expiration and determined the times needed to expire 50, 75 and 90% of the pixel vital capacities (t₅₀, t₇₅, t₉₀). Next, we calculated the median regional t₅₀, t₇₅, t₉₀ in each subject and created histograms of pixel ventilation distribution in all 3 study groups. Finally, we determined the coefficient of variation (CV) of t₅₀, t₇₅, t₉₀ to characterize the heterogeneity of ventilation.

Results: The frequency distributions of pixel values of t₅₀, t₇₅, t₉₀ showed a significant effect of smoking. The median t₉₀ discriminated the 3 groups (p<0.0001). The histograms changed their shapes in the course of expiration depending on the smoking history; the narrowest histograms' shapes were found in non-smokers. The CV distinguished the non-smokers from the other 2 groups (p<0.0001).

Conclusion: EIT reveals differences in regional ventilation distribution between lung-healthy non-smokers and allegedly lung-healthy smokers and ex-smokers.