Immediate effects of body lateralization on pulmonary ventilation distribution and aeration in spontaneously breathing healthy individuals

<bold>Background:</bold> Body lateralization is used in critically ill patients to improve gas exchange, positioning the thoracic region in a direction that is not dependent on gravity. <bold>Objectives:</bold> Investigate the immediate effects of body lateralization on aeration and distribution of lung ventilation in healthy, spontaneously breathing individuals. <bold>Methods:</bold> Eighteen healthy individuals were evaluated in supine and lateral positions at 30°, with the right hemithorax non-gravity-dependent (Clinical Trials <ext-link>NCT06044896</ext-link>). The Multicare bed (Linet) adjusted the body position, while pulmonary ventilation was monitored using electrical impedance tomography (EIT) Enlight1800 (Timpel). The acquired images were segmented into four Regions of Interest (ROIs): upper right (UR), upper left (UL), lower right (LR), and lower left (LL). One-way ANOVA tests for pulmonary aeration and two-way ANOVA ventilation-position interaction (p<0.05) <bold>Results:</bold> Lateral positioning overall increased lung aeration by 54.4 ml (95% CI: 34.0-74.8) (p < 0.001). In the ROIs UR, LR and LL, specific increases of 186.7 ml (95% CI: 158.0 - 215.4), 135.8 ml (95% CI: 101.2 - 170.4) and 41.0 ml (95% CI: 25.5 - 56.6), respectively. However, only the UL region showed a reduction of -145.9 ml (95% CI: -171.2 to -120.1) (p < 0.001 for all). Ventilation distribution varied (p=0.023 for ROIs-position interaction). <bold>Conclusions:</bold> Lateralization enhances lung aeration in non-dependent regions, implying gravity's influence on transpulmonary pressure and ventilation distribution modulation. This study offers insights for future critical population studies.