Group allocation and blinding
cough, cough hypersensitivity, urge-to-cough
RECRUITMENT, BLIND
The final author created a list of random numbers a-priori using a random number generator. Even numbers were assigned to the CDT group while odd numbers were assigned to the sham group. All participants were enrolled by either the first or second author. Each newly enrolled participant was allocated to the next number on the randomized participant number list. Participants were told the purpose of the study was to investigate efficacy of an inhaled substance to reduce cough hypersensitivity. The informed consent form for each group differed slightly in relation to stated treatment risks and treatment session descriptions in order to reduce risk of unblinding. Placebo participants were told only that the experimental substance was designed to reduce cough sensitivity. They were not told the experimental substance would cause an urge-to-cough (UTC) or that they would be asked to report UTC after each dose. Participants were informed the full treatment was 12 sessions across six weeks, but they would be assessed for progress after six sessions (i.e., midpoint). If no clinically meaningful progress was made on at least one measure at midpoint, they would be eligible to switch to the active treatment (if they were receiving sham) or to end treatment (if they were receiving CDT). The purpose of setting a stopping-criteria was to reduce participant burden and maximize recruitment.Participants were blind to group assignment. It was not possible for researchers administering the treatment to be blinded because procedures for each treatment varied slightly (described below). Furthermore, there is an obvious difference in participant response when giving capsaicin versus saline. Assessors were not blinded due to budgeting and personnel constraints. To reduce risk of assessor bias, all researchers were given strict training in cough challenge testing procedures and the other outcome measures were collected via an electronic survey without involvement from the assessor other than setup assistance.