Evaluating the Feasibility and Reliability of Using Handheld Nebulizers to Conduct Cough Sensitivity Testing With Citric Acid

Objective cough reflex sensitivity testing is typically restricted to specialized research laboratories due to reliance on expensive dosimeter-controlled aerosol delivery systems. This study evaluates the feasibility and reliability of a low-cost alternative method using a handheld nebulizer for citric acid cough challenge testing. Healthy adult participants will complete cough reflex sensitivity testing using both a standard dosimeter-controlled nebulizer system (Cosmed QuarkSpiro) and a handheld nebulizer (DeVilbiss 45). The study will compare cough threshold outcomes between methods to determine whether handheld nebulizer-based testing produces comparable and reproducible measurements.

Cough reflex sensitivity testing is widely used in respiratory research to quantify airway sensory responsiveness. Traditional testing protocols use dosimeter-controlled nebulizer systems to deliver precise concentrations of aerosolized tussive agents such as citric acid. However, these systems are costly and require specialized laboratory infrastructure, limiting access to objective cough testing in outpatient and community-based settings. This study investigates the feasibility and reliability of using a commercially available handheld nebulizer as a low-cost alternative for cough reflex sensitivity testing. Healthy adult volunteers will undergo standardized cough challenge testing using citric acid delivered through two aerosol delivery systems: a laboratory dosimeter-controlled nebulizer (Cosmed QuarkSpiro) and a handheld nebulizer (DeVilbiss 45). The primary outcomes will be cough threshold measures (e.g., C2 and C5), defined as the citric acid concentration that elicits two or five coughs. Participants will complete testing sessions using both delivery methods under controlled conditions. Findings from this proof-of-concept study will inform future research aimed at expanding access to objective cough assessment in clinical and community settings.

Inclusion Criteria: * Healthy adults at least 18 years of age * Consent to audio/video recording of the research sessions for research purposes * Spirometry testing results obtained by study team on same day of first testing session with FEV1/FVC ratio and FEV1 percent predicted values of at least 0.70 Exclusion Criteria: * Pregnant or trying to become pregnant (if capable of becoming pregnant- a urine pregnancy test will be provided onsite and a negative result must be obtained prior to the first testing session) * Smoking of any substance in the last six months * Diagnosed or suspected pulmonary disease (e.g., asthma, COPD) * History of chronic cough * History of head or neck cancer * History of neurological disease (e.g., cerebrovascular accident) * History of dysphagia (swallowing difficulty) * Current complaint of a voice problem * Current upper respiratory infection