The Effect of Deep Inhalation on Mannitol Responsiveness

The study will assess how the inhalation technique used (deep inhalations versus tidal breathing) influences the results of a mannitol challenge test and a methacholine challenge test, if at all.

This study will look at airway responsiveness to inhaled methacholine and mannitol administered with and without deep inhalation. This study will also investigate the role of airway inflammation on these responses, using sputum differential cell counts and fractional exhaled nitric oxide. This is a single center, open label, randomized study. Individuals with stable asthma will be eligible for enrollment. The study will consist of two parts, screening and testing. Part 1: Screening Participants will undergo consent procedures and assessments of fractional exhaled nitric oxide levels, airway responsiveness to methacholine and sputum induction. If participants show airway responsiveness to methacholine (i.e. methacholine PC20 16mg/mL), they will be scheduled to undergo the testing part of the study. Part 2: Testing Participants will be randomized to undergo two methacholine or two mannitol challenges. Further randomization will occur with respect to whether the standard challenge method or the modified challenge method is performed first.

Mannitol challenge performed per standard mannitol challenge procedure with deep inhalation technique

Mannitol challenge performed per standard mannitol challenge procedure except with tidal breathing technique

Methacholine challenge performed per standard 2-minute tidal breathing challenge procedure except with deep inhalation technique

Methacholine challenge performed per standard 2-minute tidal breathing challenge procedure (tidal breathing technique)

Effect of deep inhalation (versus tidal breathing) on mannitol provocative dose causing a 15% fall in forced expiratory volume in one second (FEV1)

Effect of airway inflammation on methacholine and mannitol challenge results-fractional exhaled nitric oxide

Collection of fractional exhaled nitric oxide at screening - analysis of resulting measurement indicative of degree of baseline airway inflammation

Collection of sputum at screening - analysis for differential cell counts indicative of degree of baseline airway inflammation

Inclusion Criteria: signed informed consent men and women between 18 and 75 years of age FEV1 at first measurement of greater than or equal to 65% predicted methacholine provocative concentration causing a 20% in FEV1 at screening that is less than or equal to 16mg/ml generally good health stable asthma Exclusion Criteria: respiratory infection within 4 weeks of screening visit worsening of asthma within 4 weeks of screening visit lung disease other than asthma significant medical comorbidity current smoker or ex-smoker with significant smoking history currently pregnant or breastfeeding

Blais CM, Davis BE, Cockcroft DW. The effect of deep inhalation on mannitol responsiveness. Clin Exp Allergy. 2020 Mar;50(3):308-314. doi: 10.1111/cea.13543. Epub 2019 Dec 14.

Blais CM, Davis BE, Graham BL, Cockcroft DW. 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.