J Clin Med. 2020;9(5):jcm9051512.

Decline in Carbon Monoxide Transfer Coefficient in Chronic Obstructive Pulmonary Disease.

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제1저자 김연욱 · 교신저자 이창훈

PMID 32443426 PMC7290811 DOI 10.3390/jcm9051512 IF 3.3 호흡기내과

소속 (8)

Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam 13620, Korea.
Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, Seoul 03080, Korea.
Department of Medicine, Soonchunhyang University Gumi's Hospital, Asan 39371, Korea.
Department of Internal Medicine, Chonnam National University Hospital, Gwangju 61469, Korea.
Seoul Metropolitan Government-Seoul National University Boramae Medical Center (SMG-SNU Boramae Medical Center), SNU, Seoul 07061, Korea.
Division of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea.
Department of Internal Medicine, Eunpyeong St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul 03312, Korea.
Department of Internal Medicine, Pusan National University School of Medicine, Busan 49241, Korea.

Abstract

BACKGROUND Although a reduced carbon monoxide transfer coefficient (Kco) is an important feature in chronic obstructive pulmonary disease (COPD), how it changes over time and its relationship with other clinical outcomes remain unclear. This study evaluated longitudinal changes in Kco and their relationship with other clinical outcomes.

METHODS We evaluated patients with COPD from the Korean Obstructive Lung Disease cohort, followed up for up to ten years. Random coefficient models were used to assess the annual change in Kco over time. Participants were categorized into tertiles according to Kco decline rate. Baseline characteristics and outcomes, including changes in FEV1 and emphysema index, incidence of exacerbations, and mortality, were compared between categories.

RESULTS A decline in Kco was observed in 92.9% of the 211 enrolled participants with COPD. Those with the most rapid decline (tertile 1) had a lower FEV1/FVC% (tertile 1: 43.8% ± 9.7%, tertile 2: 46.4% ± 10.5%, tertile 3: 49.2% ± 10.4%, p = 0.008) and a higher emphysema index at baseline (27.7 ± 14.8, 22.4 ± 16.1, 18.1 ± 14.5, respectively, p = 0.001). Tertile 3 showed a lower decline rate in FEV1 (16.3 vs. 27.1 mL/yr, p = 0.017) and a lower incidence of exacerbations (incidence rate ratio = 0.66, 95% CI = 0.44-0.99) than tertile 1. There were no differences in the change in emphysema index and mortality between categories.

CONCLUSION Most patients with COPD experienced Kco decline over time, which was greater in patients with more severe airflow limitation and emphysema. Decline in Kco was associated with an accelerated decline in FEV1 and more frequent exacerbations; hence, this should be considered as an important outcome measure in further studies.

Keywords

carbon monoxide transfer coefficientchronic obstructive pulmonary diseaseexacerbationlung function decline

Figures

**Figure 1** Flow diagram of the study design.

**Figure 2** Distribution of estimated annual rates of change in Kco (n = 211). Footnotes: Best Linear Unbiased Prediction (BLUP) of the annual change in Kco was calculated for each patient using the random-coefficient model, and the data are shown as a histogram. Mean ± SD = −0.04 ± 0.03 (mmol/min/mmHg/L per year).

**Figure 3** Comparison of annual rates in change of (A) post-bronchodilator FEV1, (B) emphysema index, and (C) SGRQ score by annual rates of decline in Kco. Comparisons of the risk of acute exacerbations and mortality in COPD according to changes in Kco over time.

**Figure 4** Comparison of the incidence rate of acute exacerbation according to annual rates of decline in Kco. Footnotes: All statistical analyses were adjusted for age, sex, body mass index, smoking status, pack-years smoked, baseline post-bronchodilator FEV1, exacerbation history at baseline, and use of inhaled corticosteroid/long-acting β-agonists (ICS/LABA), or inhaled long-acting muscarinic antagonists (LAMA), * p-value < 0.05.

**Figure 5** Comparison of mortality risk by annual rates of decline in Kco. Footnotes: All statistical analyses were adjusted by age, sex, body mass index, smoking status, pack-years smoked, baseline post-bronchodilator FEV1, exacerbation history at baseline, and use of inhaled corticosteroid/long-acting β-agonists (ICS/LABA), or inhaled long-acting muscarinic antagonists (LAMA).

그림 출처: PubMed Central 공개 논문 (PMC7290811)

Conflict of interest statement

The authors declare no competing interests.

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