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. 2022 Dec 9;12(1):21315.
doi: 10.1038/s41598-022-25865-0.

Comparison of inspiratory and expiratory airway volumes and luminal areas among standing, sitting, and supine positions using upright and conventional CT

Yoshitake Yamada  1 , Minoru Yamada  2 , Shotaro Chubachi  3 , Yoichi Yokoyama  2 , Shiho Matsuoka  4 , Akiko Tanabe  4 , Yuki Niijima  5 , Mitsuru Murata  6 , Takayuki Abe  7   8 , Koichi Fukunaga  3 , Masahiro Jinzaki  9
Affiliations

Comparison of inspiratory and expiratory airway volumes and luminal areas among standing, sitting, and supine positions using upright and conventional CT

Yoshitake Yamada et al. Sci Rep. .

Abstract

Upright computed tomography (CT) provides physiologically relevant images of daily life postures (sitting and standing). The volume of the human airway in sitting or standing positions remains unclear, and no clinical study to date has compared the inspiratory and expiratory airway volumes and luminal areas among standing, sitting, and supine positions. In this prospective study, 100 asymptomatic volunteers underwent both upright (sitting and standing positions) and conventional (supine position) CT during inspiration and expiration breath-holds and the pulmonary function test (PFT) within 2 h of CT. We compared the inspiratory/expiratory airway volumes and luminal areas on CT among the three positions and evaluated the correlation between airway volumes in each position on CT and PFT measurements. The inspiratory and expiratory airway volumes were significantly higher in the sitting and standing positions than in the supine position (inspiratory, 4.6% and 2.5% increase, respectively; expiratory, 14.9% and 13.4% increase, respectively; all P < 0.001). The inspiratory and expiratory luminal areas of the trachea, bilateral main bronchi, and average third-generation airway were significantly higher in the sitting and standing positions than in the supine position (inspiratory, 4.2‒10.3% increases, all P < 0.001; expiratory, 6.4‒12.8% increases, all P < 0.0001). These results could provide important clues regarding the pathogenesis of orthopnea. Spearman's correlation coefficients between the inspiratory airway volume on CT and forced vital capacity and forced expiratory volume in 1 s on PFT were numerically higher in the standing position than in the supine position (0.673 vs. 0.659 and 0.669 vs. 0.643, respectively); however, no statistically significant differences were found. Thus, the airway volumes on upright and conventional supine CT were moderately correlated with the PFT measurements.

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Conflict of interest statement

Masahiro Jinzaki received a grant from Canon Medical Systems. However, Canon Medical Systems was not involved in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, and approval of the manuscript. The remaining authors (Y.Yamada, M.Y., S.C., Y.Yokoyama, S.M., A.T., Y.N., M.M., T.A., and K.F.) have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Upright CT examination in the standing position (A), upright CT examination in the sitting position (B), and conventional CT examination in the supine position (C). Upright CT examinations in the standing position (A) and sitting position (B) were performed with the subject’s arms down during both deep inspiration breath-hold and expiration breath-hold. Conventional CT in the supine position (C) was performed with the subject’s arms raised during both deep inspiration breath-hold and expiration breath-hold. CT computed tomography.
Figure 2
Figure 2
Representative volume rendering airway images in a 39-year-old man acquired in the standing, sitting, and supine positions.
See this image and copyright information in PMC

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