Relationships Between Forced Oscillatory Impedance and 6-minute Walk Distance After Pulmonary Rehabilitation in COPD

Abstract

Rationale

Pulmonary rehabilitation for chronic obstructive pulmonary disease (COPD) reduces dyspnoea and improves exercise capacity and quality of life. The improvement in exercise capacity is variable and unpredictable, however. Respiratory system impedance obtained by forced oscillation technique (FOT) as a measure of ventilatory impairment in COPD may relate to improvement in exercise capacity with pulmonary rehabilitation. We aimed to determine if baseline FOT parameters relate to changes in exercise capacity following pulmonary rehabilitation.

Methods

At the start of rehabilitation, 15 COPD subjects (mean(SD) 75.2(6.1) years, FEV1 z-score −2.61(0.84)) had measurements by FOT, spirometry, plethysmographic lung volumes and 6-minute walk distance (6MWD). Respiratory system resistance (Rrs) and reactance (Xrs) parameters as the mean over all breaths (R _mean, X _mean), during inspiration only (R _insp, X _insp), and expiratory flow limitation (DeltaXrs = X _insp−X _exp), were calculated. FOT and 6MWD measurements were repeated at completion of rehabilitation and 3 months after completion.

Results

At baseline, Xrs measures were unrelated to 6MWD. X _insp improved significantly with rehabilitation (from mean(SD) −2.35(1.02) to −2.04(0.85) cmH ₂O.s.L ⁻¹, p=0.008), while other FOT parameters did not. No FOT parameters related to the change in 6MWD at program completion. Baseline X _mean, DeltaXrs, and FVC z-score correlated with the change in 6MWD between completion and 3 months after completion of rehabilitation (r _s=0.62, p=0.03; r _s=−0.65, p=0.02; and r _s=0.62, p=0.03, respectively); with worse ventilatory impairment predicting loss of 6MWD. There were no relationships between Rrs parameters, FEV1 or FEV1/FVC z-scores and changes in 6MWD.

Conclusion

Baseline reactance parameters may be helpful in predicting those patients with COPD at most risk of loss of exercise capacity following completion of pulmonary rehabilitation.

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): COPD

Journal ID (pmc): copd

Title: International Journal of Chronic Obstructive Pulmonary Disease

Publisher: Dove

ISSN (Print): 1176-9106

ISSN (Electronic): 1178-2005

Publication date (Electronic): 21 January 2020

Publication date Collection: 2020

Volume: 15

Pages: 157-166

Affiliations

[1 ]The Woolcock Emphysema Centre, Woolcock Institute of Medical Research, The University of Sydney , Glebe, NSW 2037, Australia

[2 ]The Northern Clinical School, Faculty of Medicine and Health Sciences, The University of Sydney , Camperdown, NSW 2006, Australia

[3 ]Department of Respiratory Medicine, Royal North Shore Hospital , St Leonards, NSW 2065, Australia

[4 ]School of Life Sciences, Faculty of Science, University of Technology Sydney , Ultimo, NSW 2007, Australia

Author notes

Correspondence: Sabine C Zimmermann The Woolcock Institute of Medical Research , 431 Glebe Point Road, Glebe, NSW2037, AustraliaTel [phone]Fax [phone] Email [e-mail]

Article

Publisher ID: 225543

DOI: 10.2147/COPD.S225543

PMC ID: 6982450

Copyright statement: © 2020 Zimmermann et al.

License:

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Page count

Figures: 4, Tables: 3, References: 51, Pages: 10

Funding

SCZ was supported by a NHMRC Postgraduate Scholarship. This research did otherwise not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Categories

Subject: Original Research