# Physiology of body lateralization on regional lung ventilation and lung volumes in healthy subjects: Within-subjects design

## TL;DR

This study examines how lying on one's side affects lung ventilation and volume in healthy individuals, finding that it improves ventilation in dependent lung regions.

## Contribution

The study provides new insights into the acute effects of lateral positioning on regional lung function in healthy adults.

## Key findings

- Left-lateral positioning increased ventilation in dependent lung regions and decreased it in nondependent regions.
- End-expiratory lung volumes increased in nondependent and posterior dependent regions during lateral positioning.
- Bilateral positioning showed no significant changes in regional ventilation but significant changes in lung volumes.

## Abstract

Lateral positioning improves pulmonary mechanics and lung volumes, but its effects in healthy adults remain unclear due to individual variability.

To analyze the acute effects of lateral body positioning on regional lung ventilation and lung volumes in healthy adults.

This within-subject study included two protocols: supine and left-lateral position (unilateral) with repeated measures and supine, left, and right-lateral positions (bilateral). All positions were performed at 30° for 5 minutes on an automated rotation bed. Electrical Impedance Tomography measured regional lung ventilation (%) and end-expiratory lung volumes (EELV) across four lung regions: (anterior right [AR] and left [AL]; posterior right [PR], and left [PL]). Linear mixed models assessed the influence of body position and individual variability on regional ventilation and lung volumes, while the Restricted Maximum Likelihood method compared between right- and left-lateral positioning.

In the unilateral protocol (n = 29; 58.6% male; 22.8 ± 4.0 years), left-lateral positioning decreased regional ventilation in nondependent regions (AR: −0.96%, PR: −1.63%) and increased it in dependent regions (PL: 1.17%, AL: 1.42%) versus supine (p < 0.001). EELV increased in PL (+ 0.7 mL/kg PBW), PR (+2.0), and AR (+2.8), but decreased in AL (−2.3) (p < 0.001). In the bilateral protocol (n = 10, 70% male; 23.6 ± 3.2 years), regional ventilation showed no significant effects of position, ROI, or interaction (p > 0.05). However, EELV varied significantly with body position (p < 0.001), with no isolated ROI effect (p = 1.000).

Lateral positioning improves regional ventilation in dependent lung regions and increases EELV in nondependent and posterior dependent lung regions, regardless of side.

ClinicalTrials.gov [NCT06044896]