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

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

JOURNAL=Frontiers in Physiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2023.1137603

DOI=10.3389/fphys.2023.1137603

ISSN=1664-042X

ABSTRACT=<p><bold>Background:</bold> 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.</p><p><bold>Objectives:</bold> 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.</p><p><bold>Methods:</bold> 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; V<sub>A</sub>) to that using multiple breath methods (TLC) was calculated as an index of ventilation heterogeneity. The volume of the pulmonary small vessels &lt;5 mm<sup>2</sup> 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.</p><p><bold>Results:</bold> The low V<sub>A</sub>/TLC group (the lowest quartile) had significantly lower BV5 number, BV5 volume, higher BV5 volume/BV5 number, and higher Kco compared to the high V<sub>A</sub>/TLC group (the highest quartile) in 117 non-smokers, but not in 67 smokers. Multivariable analysis showed that low V<sub>A</sub>/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).</p><p><bold>Conclusion:</bold> 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.</p>