Author(s): Aarli B.B.; Eeagan T.M.L.; Bakke P.S.; Hardie J.A.; Calverley P.M.A.; Jensen R.L.; Dellaca R.
Source: International Journal of COPD; Jul 2017; vol. 12 ; p. 2179-2188
Publication Date: Jul 2017
Publication Type(s): Article
Available in full text at International Journal of Chronic Obstructive Pulmonary Disease – from National Library of Medicine
Available in full text at International Journal of COPD – from Directory of Open Access Journals
Abstract:Background: Tidal expiratory flow limitation (EFLT) 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-1. The present study explored the association of within-breath reactance measured over multiple breaths and EFLT with 6-minute walk distance (6MWD), exacerbations, and mortality. Methods: 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 (DELTA(Formula Presented.)), measured over several breaths at baseline, calculated as mean inspiratory-mean expiratory reactance over the sampling period. In addition to the established threshold of EFLT, an upper limit of normal (ULN) was defined using the 97.5th percentile of DELTA(Formula Presented.) of the healthy controls in the study; 6MWDs were compared according to DELTA(Formula Presented.), as normal, >= ULN T, or >= EFLT. 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. Results: In patients with COPD and baseline DELTA(Formula Presented.) below the ULN (0.09 kPa.s.L-1), 6MWD was stable. 6MWD declined significantly in patients with DELTA(Formula Presented.) >= ULN. Worse lung function and more exacerbations were found in patients with COPD with DELTA(Formula Presented.) >= ULN, and patients with DELTA(Formula Presented.) >= ULN had shorter time to first exacerbation and hospitalization. A significantly higher mortality was found in patients with DELTA(Formula Presented.) >= ULN and FEV1.50%. Conclusion: Patients with baseline DELTA(Formula Presented.) >= ULN had a deterioration in exercise performance, more exacerbations, and greater hospitalizations, and, among those with moderate airway obstruction, a higher mortality. DELTA(Formula Presented.) is a novel independent marker of outcome in COPD.
Copyright © 2017 Aarli et al.