Effects of Resting Posture on End-Expiratory Lung Impedance and Regional Ventilation Distribution, Assessed Using...

Electrical impedance tomography (EIT) provides a noninvasive means of assessing posture-related end-expiratory lung impedance and the regional distribution of ventilation. However, the physiological effects of specific bedside postures, including the hands-on-knees and tripod positions, have not been fully characterized using EIT in spontaneously breathing individuals. We aimed to compare the end-expiratory lung impedance and regional ventilation distribution of healthy volunteers across a range of postures as a physiological proof-of-concept to inform future clinical investigations.

The regional end-expiratory lung impedances (ΔEELI) of 20 healthy male subjects who adopted the 6 following postures were compared: supine, prone, sitting, tripod, hands-on-knees, and standing. The distribution of ventilation between the dorsal and ventral lung regions was also analyzed for each posture. The Wilcoxon test with the Holm-Bonferroni correction was used to compare the datasets.

Compared with the supine posture, the hands-on-knees posture was associated with the highest global ΔEELI (3.58 units, 95% CI: 2.81-4.58, P < .001), followed by the tripod position (2.16 units, 95% CI: 1.69-3.47, P < .001). With respect to the regional ventilation, dorsal ventilation was significantly better for all other postures versus the supine posture, particularly for the hands-on-knees and tripod position (ΔEELI in the dorsal region 2.77 units, 95% CI: 2.02-3.33, and 2.02 units, 95% CI: 1.35-2.64, respectively; both P < .001).

In healthy men, the hands-on-knees and tripod postures were associated with greater global and dorsal end-expiratory lung impedance and a more dorsal ventilation distribution. Whether these physiological observations might translate to clinically meaningful improvements in patients with respiratory disease warrants further investigation in clinical studies.