University of Tasmania
Johns et al Improved detection of small airway narrowing - concavity Int J COPD 2017.pdf (1.05 MB)

Improved spirometric detection of small airway narrowing: concavity in the expiratory flow–volume curve in people aged over 40 years

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journal contribution
posted on 2023-05-19, 14:17 authored by Johns, DP, Das, A, Toelle, BG, Abramson, MJ, Marks, GB, Wood-Baker, R, Eugene WaltersEugene Walters

Background and objective: We have explored whether assessing the degree of concavity in the descending limb of the maximum expiratory flow–volume curve enhanced spirometric detection of early small airway disease.

Methods: We used spirometry records from 890 individuals aged $40 years (mean 59 years), recruited for the Burden of Obstructive Lung Disease Australia study. Central and peripheral concavity indices were developed from forced expired flows at 50% and 75% of the forced vital capacity, respectively, using an ideal line joining peak flow to zero flow.

Results: From the 268 subjects classified as normal never smokers, mean values for postbronchodilator central concavity were 18.6% in males and 9.1% in females and those for peripheral concavity were 50.5% in males and 52.4% in females. There were moderately strong correlations between concavity and forced expired ratio (forced expiratory volume in 1 second/ forced vital capacity) and mid-flow rate (forced expiratory flow between 25% and 75% of the FVC [FEF25%–75%]; r=-0.70 to -0.79). The additional number of individuals detected as abnormal using the concavity indices was substantial, especially compared with FEF25%–75%M, where it was approximately doubled. Concavity was more specific for symptoms.

Conclusion: The inclusion of these concavity measures in the routine reports of spirometry would add information on small airway obstruction at no extra cost, time, or effort.


Publication title

COPD: journal of chronic obstructive pulmonary disease








Tasmanian School of Medicine


Taylor & Francis Inc.

Place of publication

United States

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Copyright 2017 Johns et al. Licensed under Creative Commons Attribution-NonCommercial 3.0 Unported (CC BY-NC 3.0)

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  • Open

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Clinical health not elsewhere classified

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