Regional lung function in nonsmokers and asymptomatic current and former smokers

Abstract

Electrical impedance tomography (EIT) is able to detect rapid lung volume changes during breathing. The aim of our observational study was to characterise the heterogeneity of regional ventilation distribution in lung-healthy adults by EIT and to detect the possible impact of tobacco consumption.A total of 219 nonsmokers, asymptomatic ex-smokers and current smokers were examined during forced full expiration using EIT. Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC were determined in 836 EIT image pixels for the analysis of spatial and temporal ventilation distribution. Coefficients of variation (CVs) of these pixel values were calculated. Histograms and medians of FEV1/FVCEIT and times required to exhale 50%, 75%, 90% of FVCEIT (t50, t75 and t90) were generated.CV of FEV1/FVCEIT distinguished among all groups (mean±sd: nonsmokers 0.43±0.05, ex-smokers 0.52±0.09, smokers 0.62±0.16). Histograms of FEV1/FVCEIT differentiated between nonsmokers and the other groups (p<0.0001). Medians of t50, t75 and t90 showed the lowest values in nonsmokers. Median t90 separated all groups (median (interquartile range): nonsmokers 0.82 (0.67–1.15), ex-smokers 1.41 (1.03–2.21), smokers 1.91 (1.33–3.53)).EIT detects regional ventilation heterogeneity during forced expiration in healthy nonsmokers and its increase in asymptomatic former and current smokers. Therefore, EIT-derived reference values should only be collected from nonsmoking lung-healthy adults.

Distribution of regional lung function in upright healthy subjects determined by electrical impedance tomography in two chest examination planes

“…This finding has some practical implications regarding the interpretation of the EIT studies performed in the past and the planning of EIT applications in the future. In most of the EIT studies carried out in upright human subjects so far, the EIT electrodes were located below the nipples (Coulombe et al 2005, Zhao et al et al 2013, Vogt et al 2019, Milne et al 2019, Haris et al 2021, i.e. in a plane rather corresponding to the caudal plane in the present study.…”

“…However, EIT is gradually starting to be applied also in patients with chronic lung diseases who are typically examined by EIT in the sitting position while breathing spontaneously or performing specific ventilatory manoeuvres (Zhao et al 2013, Frerichs et al 2016, Vogt et al 2019, Lasarow et al 2021, Ma et al 2022. In these subjects, the breathing pattern is far less uniform than in ventilated patients and the EIT electrode plane is perpendicular to the gravity vector.…”