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.

Background: Pulmonary function is not routinely assessed in patients without respiratory disease and symptoms before surgery, even if they are smokers. We aimed to check whether the new spirometric reference values of the worldwide Global Lung Initiative (GLI) affected the preoperative assessment of lung function in allegedly lung-healthy patients compared with the still commonly used old predicted values. Methods: Two hundred nineteen allegedly lung-healthy non-smokers, past and current smokers were examined by spirometry before elective surgery. The obtained values of forced expiratory volume in 1 second (FEV 1 ), forced vital capacity (FVC) and FEV 1 /FVC were transformed into z-scores according to the GLI guidelines. A comparison between the new and old reference values was performed. FEV 1 was used for the grading of airway obstruction. Results: One hundred eighty-three subjects performed the ventilation manoeuvre according to the GLI recommendations and were analysed. Most non-smokers and past smokers met the new references ranges for spirometric values. Only z-scores of FEV 1 /FVC distinguished among all three patient groups, FEV 1 between smokers and the other two groups and FVC did not discriminate the groups, irrespective of the reference values used. Airway obstruction was identified in 24% of asymptomatic smokers by z-scores of FEV 1 /FVC but in only 14% by the old predicted values. In elderly smokers (>60 years), the corresponding values rose to 50% and 30%. Old predicted values of FEV 1 underestimated the degree of airway obstruction mainly in middle-aged smokers. Conclusion: Allegedly lung-healthy current smokers showed a higher proportion of preoperatively reduced lung function when z-scores were used, especially in elderly subjects. K E Y W O R D Spreoperative, pulmonary function, smoking, spirometry, visit, z-scores 240 | VOGT eT al.How to cite this article: Vogt B, Hennig V, Deuß K, Balke L, Weiler N, Frerichs I. Performance of new spirometry reference values in preoperative assessment of lung function. Clin Respir J.