Respiratory Duty Cycles in Individuals With and Without Airway Hyperresponsiveness

Christianne M Blais; Beth E Davis; Brian L Graham; Donald W Cockcroft

doi:10.1016/j.chest.2019.09.005

Respiratory Duty Cycles in Individuals With and Without Airway Hyperresponsiveness

Chest. 2020 Feb;157(2):356-362. doi: 10.1016/j.chest.2019.09.005. Epub 2019 Sep 19.

Authors

Christianne M Blais¹, Beth E Davis¹, Brian L Graham¹, Donald W Cockcroft²

Affiliations

¹ Division of Respirology, Critical Care and Sleep Medicine, Department of Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
² Division of Respirology, Critical Care and Sleep Medicine, Department of Medicine, University of Saskatchewan, Saskatoon, SK, Canada. Electronic address: don.cockcroft@usask.ca.

PMID: 31542451
DOI: 10.1016/j.chest.2019.09.005

Abstract

Background: The respiratory duty cycle (T_i/T_tot) can influence bronchoprovocation test results and nebulized drug delivery. The T_i/T_tot has not yet been examined in individuals with airway hyperresponsiveness (AHR) in typical bronchoprovocation test conditions. This study investigated the mean T_i/T_tot in participants with and without AHR and whether the T_i/T_tot changes with increasing bronchoconstriction.

Methods: Fifteen participants with AHR and fifteen participants without AHR completed this randomized crossover study. An ultrasonic spirometer was used for continuous measurement of the T_i/T_tot as participants inhaled room air or aerosolized solution. Each participant completed two methacholine challenges, one using a continuous-output vibrating mesh nebulizer/ultrasonic spirometer and one with the nebulizer only. Prior to each methacholine challenge, participants inhaled room air and aerosolized saline through the nebulizer/spirometer setup to record baseline T_i/T_tot data.

Results: The mean T_i/T_tot findings [95% CIs] during room air inhalation were 0.392 [0.378-0.406] and 0.447 [0.426-0.468] in participants with and without AHR, respectively (P < .001). The mean T_i/T_tot during saline inhalation were 0.389 [0.373-0.405] and 0.424 [0.398-0.450] in participants with and without AHR (P = .040). The T_i/T_tot showed a nonsignificant downward trend with progressive methacholine-induced bronchoconstriction.

Conclusions: The mean T_i/T_tot in participants with AHR closely resembles the assumed T_i/T_tot of 0.40 recommended for standard use when calculating methacholine challenge results. Since the T_i/T_tot did not change significantly over the course of a methacholine challenge, the same T_i/T_tot can be used to calculate the dose of methacholine inhaled, regardless of the level of bronchoconstriction.

Trial registry: ClinicalTrials.gov; No.: NCT03505489; URL: www.clinicaltrials.gov.

Keywords: aerosols; airway hyperresponsiveness; provocation test; pulmonary function test.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adolescent
Adult
Bronchial Provocation Tests / methods*
Bronchoconstrictor Agents
Case-Control Studies
Cross-Over Studies
Female
Forced Expiratory Volume / physiology
Humans
Inhalation / physiology
Male
Methacholine Chloride
Middle Aged
Random Allocation
Respiratory Hypersensitivity / diagnosis
Respiratory Hypersensitivity / physiopathology*
Spirometry / methods*
Time Factors
Young Adult

Substances

Bronchoconstrictor Agents
Methacholine Chloride

Associated data

ClinicalTrials.gov/NCT03505489