A new approach to assess COPD by identifying lung function break-points

Abstract

Purpose

COPD is a progressive disease, which can take different routes, leading to great heterogeneity. The aim of the post-hoc analysis reported here was to perform continuous analyses of advanced lung function measurements, using linear and nonlinear regressions.

Patients and methods

Fifty-one COPD patients with mild to very severe disease (Global Initiative for Chronic Obstructive Lung Disease [GOLD] Stages I–IV) and 41 healthy smokers were investigated post-bronchodilation by flow-volume spirometry, body plethysmography, diffusion capacity testing, and impulse oscillometry. The relationship between COPD severity, based on forced expiratory volume in 1 second (FEV ₁), and different lung function parameters was analyzed by flexible nonparametric method, linear regression, and segmented linear regression with break-points.

Results

Most lung function parameters were nonlinear in relation to spirometric severity. Parameters related to volume (residual volume, functional residual capacity, total lung capacity, diffusion capacity [diffusion capacity of the lung for carbon monoxide], diffusion capacity of the lung for carbon monoxide/alveolar volume) and reactance (reactance area and reactance at 5Hz) were segmented with break-points at 60%–70% of FEV ₁. FEV ₁/forced vital capacity (FVC) and resonance frequency had break-points around 80% of FEV ₁, while many resistance parameters had break-points below 40%. The slopes in percent predicted differed; resistance at 5 Hz minus resistance at 20 Hz had a linear slope change of −5.3 per unit FEV ₁, while residual volume had no slope change above and −3.3 change per unit FEV ₁ below its break-point of 61%.

Conclusion

Continuous analyses of different lung function parameters over the spirometric COPD severity range gave valuable information additional to categorical analyses. Parameters related to volume, diffusion capacity, and reactance showed break-points around 65% of FEV ₁, indicating that air trapping starts to dominate in moderate COPD (FEV ₁ =50%–80%). This may have an impact on the patient’s management plan and selection of patients and/or outcomes in clinical research.

Journal

Journal ID (nlm-ta): Int J Chron Obstruct Pulmon Dis

Journal ID (iso-abbrev): Int J Chron Obstruct Pulmon Dis

Journal ID (publisher-id): International Journal of COPD

Title: International Journal of Chronic Obstructive Pulmonary Disease

Publisher: Dove Medical Press

ISSN (Print): 1176-9106

ISSN (Electronic): 1178-2005

Publication date Collection: 2015

Publication date (Electronic): 14 October 2015

Volume: 10

Pages: 2193-2202

Affiliations

[1 ]Respiratory Medicine and Allergology, Department of Clinical Sciences, Lund University, Lund, Sweden

[2 ]Regional Cancer Center South, Skåne University Hospital, Lund, Sweden

Author notes

Correspondence: Göran Eriksson, Respiratory Medicine and Allergology, Department of Clinical Sciences, Lund University, 221 84 Lund, Sweden, Tel [phone], Email goran.eriksson@ 123456med.lu.se

[*]

These authors contributed equally to this work

Article

Publisher ID: copd-10-2193

DOI: 10.2147/COPD.S86059

PMC ID: 4610777

Copyright statement: © 2015 Eriksson et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License

License:

The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

Categories

Subject: Original Research