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. 2025 Feb 24;15(1):6670.
doi: 10.1038/s41598-025-91060-6.

Air trapping in patients with idiopathic pulmonary fibrosis: a retrospective case-control study

Taehun Kim  1 , Mi-Ae Kim  2 , Seong Hwan Youn  2 , Yongshik Kwon  2 , Hyun Jung Kim  2 , Jae Seok Park  2 , Sun Hyo Park  2
Affiliations

Air trapping in patients with idiopathic pulmonary fibrosis: a retrospective case-control study

Taehun Kim et al. Sci Rep. .

Abstract

Idiopathic pulmonary fibrosis (IPF) is characterised by progressive worsening of lung function. In some cases, IPF is accompanied by air-trapping and emphysema. This study aimed to evaluate air trapping quantified with RV/TLC in patients with IPF. This retrospective study included 122 patients diagnosed with IPF in South Korea between January 2011 and December 2020. Air trapping was defined as RV/TLC ≥ 0.40. Increased RV/TLC was found in 34.4% of all patients. The RV/TLC negatively correlated with lung function (forced expiratory volume in 1 s and functional vital capacity [FVC]) and showed consistent results after 1 year of follow-up. After propensity score matching, FVC and diffusion capacity between the groups showed no statistical difference. No difference in lung function decline was found between the increased and not increased RV/TLC groups. Regarding univariable analysis, the patients in the increased RV/TLC group had a lower risk of all-cause mortality (hazard ratio 1.753, P = 0.034). Using multivariable analysis, age, pirfenidone treatment, and FVC were significant factors for survival but not increased RV/TLC. Increased RV/TLC was related to emphysema and demonstrated a negative relationship with lung function. Although increased RV/TLC might relate to poor clinical outcome, it was not independent prognostic factor for IPF.

Keywords: Air trapping; Idiopathic pulmonary fibrosis; Mortality; Pirfenidone; Pulmonary function tests; RV/TLC ratio.

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Conflict of interest statement

Declarations. Competing interests: The authors declare no competing interests. Ethics approval: The study protocol was reviewed and approved by the Institutional Review Board of the Keimyung University College of Medicine (approval no. 2023-07-087-001). The study conformed to the tenets of Declaration of Helsinki (revised edition 2013). The requirement for informed consent was waived by IRB of Keimyung University College of Medicine because of the retrospective nature of the study.

Figures

Fig. 1
Fig. 1
Dot plot between various parameters. (A) between baseline RV/TLC ratio FEV1. (B) between RV/TLC ratio and FVC. (C) between RV/TLC ratio and FEF 25–75%. (D) between baseline RV/TLC ratio and follow-up RV/TLC after 1 year. FEF Forced expiratory flow, FEV1 Forced expiratory volume in 1 s, FVC Forced vital capacities, RV/TLC Residual volume/total lung capacities ratio.
Fig. 1
Fig. 1
Dot plot between various parameters. (A) between baseline RV/TLC ratio FEV1. (B) between RV/TLC ratio and FVC. (C) between RV/TLC ratio and FEF 25–75%. (D) between baseline RV/TLC ratio and follow-up RV/TLC after 1 year. FEF Forced expiratory flow, FEV1 Forced expiratory volume in 1 s, FVC Forced vital capacities, RV/TLC Residual volume/total lung capacities ratio.
Fig. 2
Fig. 2
Kaplan–Meier curve according to RV/TLC ratio.
Fig. 3
Fig. 3
Kaplan–Meier curve according to pirfenidone.
Fig. 4
Fig. 4
Flow diagram of the study population.
See this image and copyright information in PMC

References

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