Frontiers in Physiology (Mar 2023)

Relationships of computed tomography-based small vessel indices of the lungs with ventilation heterogeneity and high transfer coefficients in non-smokers with asthma

  • Kaoruko Shimizu,
  • Hirokazu Kimura,
  • Naoya Tanabe,
  • Shotaro Chubachi,
  • Susumu Sato,
  • Masaru Suzuki,
  • Kazuya Tanimura,
  • Hiroaki Iijima,
  • Akira Oguma,
  • Yoichi M. Ito,
  • Nobuyasu Wakazono,
  • Michiko Takimoto-Sato,
  • Machiko Matsumoto-Sasaki,
  • Yuki Abe,
  • Nozomu Takei,
  • Hironi Makita,
  • Hironi Makita,
  • Masaharu Nishimura,
  • Masaharu Nishimura,
  • Satoshi Konno,
  • Hi-CARAT investigators

DOI
https://doi.org/10.3389/fphys.2023.1137603
Journal volume & issue
Vol. 14

Abstract

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Background: The mechanism of high transfer coefficients of the lungs for carbon monoxide (Kco) in non-smokers with asthma is explained by the redistribution of blood flow to the area with preserved ventilation, to match the ventilation perfusion.Objectives: To examine whether ventilation heterogeneity, assessed by pulmonary function tests, is associated with computed tomography (CT)-based vascular indices and Kco in patients with asthma.Methods: Participants were enrolled from the Hokkaido-based Investigative Cohort Analysis for Refractory Asthma (Hi-CARAT) study that included a prospective asthmatic cohort. Pulmonary function tests including Kco, using single breath methods; total lung capacity (TLC), using multiple breath methods; and CT, were performed on the same day. The ratio of the lung volume assessed using single breath methods (alveolar volume; VA) to that using multiple breath methods (TLC) was calculated as an index of ventilation heterogeneity. The volume of the pulmonary small vessels <5 mm2 in the whole lung (BV5 volume), and number of BV5 at a theoretical surface area of the lungs from the plural surface (BV5 number) were evaluated using chest CT images.Results: The low VA/TLC group (the lowest quartile) had significantly lower BV5 number, BV5 volume, higher BV5 volume/BV5 number, and higher Kco compared to the high VA/TLC group (the highest quartile) in 117 non-smokers, but not in 67 smokers. Multivariable analysis showed that low VA/TLC was associated with low BV5 number, after adjusting for age, sex, weight, lung volume on CT, and CT emphysema index in non-smokers (not in smokers).Conclusion: Ventilation heterogeneity may be associated with low BV5 number and high Kco in non-smokers (not in smokers). Future studies need to determine the dynamic regional system in ventilation, perfusion, and diffusion in asthma.

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