Sensory-Mechanical Responses to Eucapneic Voluntary Hyperventilation, Hypertonic Saline, and Mannitol in Individuals with Cough Variant Asthma and Chronic Cough
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Authors
Korovina, Maria
Date
2024-08-30
Type
thesis
Language
eng
Keyword
Asthma , Chronic Cough , Cough Variant Asthma , Indirect Inhallation Challenges , Eucapneic Voluntary Hyperventilation , Mannitol , Hypertonic Saline , Methacholine
Alternative Title
Abstract
Introduction: Chronic cough is the most common reason to seek primary care. Some individuals with asthma have cough as their sole or predominant symptom, termed cough variant asthma (CVA). Previously, Lougheed et al. identified individuals suspected of CVA who tested negative to methacholine (MCh) challenge, termed COUGH. Following a high-dose MCh challenge, those with COUGH developed dynamic hyperinflation, gas trapping, and small airway obstruction, which partially resolved after a deep inspiration (DI) and a cough. The clinical relevance of the COUGH phenotype is unclear.
Purpose: This study investigated sensory-mechanical response among CVA, COUGH, and healthy individuals (CONTROL) during MCh, eucapneic voluntary hyperventilation (EVH), mannitol, and hypertonic saline (HS) challenges.
Methods: Individuals 18-65 years of age were recruited to attend three visits, with an optional fourth. Following the first visit (MCh challenge), participants were randomized to perform either EVH or mannitol challenge (visits 2/3), with some participants completing the optional HS challenge (visit 4). During each visit, exhaled nitric oxide, spirometry, plethysmography, and impulse oscillometry (IOS) were assessed.
Results: 10 CONTROL, 9 CVA, and 1 COUGH attended all three mandatory visits. CVA and CONTROL had increases in cough counts following the mannitol challenge (p= 0.021 and p= 0.003, respectively). CVA developed dynamic hyperinflation (ΔIC: -0.31 ± 0.34 L) and gas trapping (ΔRV/TLC: 0.05 ± 0.04 L) exclusively during MCh, coinciding with increased dyspnea (p = 0.041). At MAX, CVA had a preserved bronchodilation effect in MCh, borderline preservation in EVH, and no DI effect in mannitol challenge. IOS showed significant increases in total resistance in CVA during each challenge, but the increase during mannitol was exclusively due to increases in peripheral resistance. Among CONTROL participants, two reacted to EVH and two reacted to mannitol, while two from CVA did not react to EVH and four did not react to mannitol.
Conclusion: This study highlights differences in sensory-mechanical responses between CONTROL and CVA using indirect inhalation challenges and IOS. Inconsistencies in airway sensitivity between challenges highlight the limitations of relying solely upon airway sensitivity to MCh when evaluating suspected CVA, and the merits of examining responses to indirect inhalation challenges in COUGH.
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Attribution-NonCommercial-NoDerivatives 4.0 International
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.