The association of tidal EFL with exercise performance, exacerbations, and death in COPD

Aarli, Bernt Boegvald, Calverley, Peter MA, Jensen, Robert L, Dellaca, Raffaele, Eagan, Tomas ML, Bakke, Per S and Hardie, Jon A
(2017) The association of tidal EFL with exercise performance, exacerbations, and death in COPD. INTERNATIONAL JOURNAL OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE, 12. pp. 2179-2188.

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<h4>Background</h4>Tidal expiratory flow limitation (EFL<sub>T</sub>) is frequently found in patients with COPD and can be detected by forced oscillations when within-breath reactance of a single-breath is ≥0.28 kPa·s·L<sup>-1</sup>. The present study explored the association of within-breath reactance measured over multiple breaths and EFL<sub>T</sub> with 6-minute walk distance (6MWD), exacerbations, and mortality.<h4>Methods</h4>In 425 patients, spirometry and forced oscillation technique measurements were obtained on eight occasions over 3 years. 6MWD was assessed at baseline and at the 3-year visit. Respiratory symptoms, exacerbations, and hospitalizations were recorded. A total of 5-year mortality statistics were retrieved retrospectively. We grouped patients according to the mean within-breath reactance [Formula: see text], measured over several breaths at baseline, calculated as mean inspiratory-mean expiratory reactance over the sampling period. In addition to the established threshold of EFL<sub>T</sub>, an upper limit of normal (ULN) was defined using the 97.5th percentile of [Formula: see text], of the healthy controls in the study; 6MWDs were compared according to [Formula: see text], as normal, ≥ ULN < EFL<sub>T</sub>, or ≥ EFL<sub>T</sub>. Annual exacerbation rates were analyzed using a negative binomial model in the three groups, supplemented by time to first exacerbation analysis, and dichotomizing patients at the ULN.<h4>Results</h4>In patients with COPD and baseline [Formula: see text] below the ULN (0.09 kPa·s·L<sup>-1</sup>), 6MWD was stable. 6MWD declined significantly in patients with [Formula: see text]. Worse lung function and more exacerbations were found in patients with COPD with [Formula: see text], and patients with [Formula: see text] had shorter time to first exacerbation and hospitalization. A significantly higher mortality was found in patients with [Formula: see text] and FEV<sub>1</sub> >50%.<h4>Conclusion</h4>Patients with baseline [Formula: see text] had a deterioration in exercise performance, more exacerbations, and greater hospitalizations, and, among those with moderate airway obstruction, a higher mortality. [Formula: see text] is a novel independent marker of outcome in COPD.

Item Type: Article
Uncontrolled Keywords: forced oscillation technique, reactance, COPD, exacerbations, 6-minute walk test, mortality
Depositing User: Symplectic Admin
Date Deposited: 13 Aug 2019 09:10
Last Modified: 19 Jan 2023 00:31
DOI: 10.2147/COPD.S138720
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