BODY position reshapes ventilation distribution in healthy lungs, with lateral positioning producing the strongest gravity-dependent shifts.
Ventilation Distribution Changes With Posture
Researchers used electrical impedance tomography to examine how regional ventilation changed across five body positions in 10 healthy male volunteers. Measurements were taken during quiet breathing while participants were supine, prone, sitting, and lying in right and left lateral decubitus positions.
Electrical impedance tomography is a noninvasive, radiation-free technique that continuously measures breathing-related changes in thoracic impedance. This allowed the investigators to assess regional ventilation in real time and compare within-person changes relative to the supine position.
Lateral positioning produced the clearest ventilation redistribution. In both lateral decubitus positions, ventilation shifted toward the dependent lung regions and away from the nondependent regions, reflecting the influence of gravity. The effect was more asymmetric when participants lay on their right side.
Subtle Changes Detected Beyond Lateral Positioning
Overall dorsoventral ventilation patterns appeared broadly similar between the supine, prone, and sitting positions. However, an analysis of changes from the supine baseline identified smaller but statistically significant shifts during prone positioning and sitting.
The findings indicate that proportional ventilation measurements alone may overlook subtle redistribution. Measuring within-person changes against a common baseline may therefore provide a more sensitive method for characterizing position-related respiratory physiology.
Researchers also investigated factors that could explain why ventilation distribution varied between individuals. Redistribution during lateral positioning was associated with body mass index and cardiothoracic ratio, suggesting that body composition and thoracic morphology may influence the effect of gravity on the lungs.
Changes during sitting were associated with diaphragmatic excursion, indicating that diaphragm movement may contribute to ventilation redistribution when gravitational loading changes.
Potential Relevance for Respiratory Care
These exploratory findings establish a physiological framework for quantifying how posture affects regional ventilation. This could support future research into positioning strategies, respiratory rehabilitation, and ventilation monitoring in people with respiratory disease or those receiving mechanical ventilation.
However, the study included only 10 healthy male volunteers with a relatively narrow body mass index range. The results may not be generalizable to women, older adults, or people with cardiopulmonary disease, and larger studies are required before the findings can guide clinical positioning decisions.
Reference
Tsuji H et al. Posture-related ventilation redistribution and associated factors in healthy subjects assessed by electrical impedance tomography. Respir Physiol Neurobiol. 2026;doi:10.1016/j.resp.2026.104619.
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