Electrical impedance tomography of the lungs – does biological sex affect the findings?

<bold>Background:</bold> The impact of biological sex on chest electrical impedance tomography (EIT) findings has hardly ever been studied. <bold>Objective:</bold> The aim of our study was to determine if the spatial distribution of ventilation determined by EIT during quiet breathing was influenced by biological sex. <bold>Methods:</bold> 219 lung-healthy adults were examined by EIT in sitting position with the EIT electrodes placed around the lower chest (6th intercostal space). The study was approved by the local Ethics Committee (D492/13) and all subjects consented to participate. EIT data was recorded at 33 images/s during quiet breathing for 60 s. 218 data sets were analyzed (120 men, 98 women) (age: 53±18 vs 50±16 yr (p=0.2607), body mass index: 26.4±4.0 vs 26.4±6.6 kg/m² (p=0.9158), mean±SD). Regional tidal volumes were calculated in all EIT image pixels and their spatial distribution determined using the EIT measures of centre of ventilation in ventrodorsal (CoV_vd) and right-to-left direction (CoV_rl), the dorsal and right fraction of ventilation. <bold>Results:</bold> Highly significant differences in ventilation distribution were identified between men and women between the right and left chest sides (CoV_rl: 47.0±2.9 vs 48.8±3.3% of chest diameter (p<0.0001), right fraction of ventilation: 0.573±0.067 vs 0.539±0.071 (p=0.0004)) and less significant in the ventrodorsal direction (CoV_vd: 55.6±4.2 vs 54.5±3.6% of chest diameter (p=0.0364), dorsal fraction of ventilation: 0.650±0.121 vs 0.625±0.104 (p=0.1155)). <bold>Conclusion:</bold> Biological sex needs to be considered when EIT findings acquired in a rather caudal EIT examination plane are interpreted. Sex differences in chest anatomy and thoracoabdominal mechanics may explain the results.