Cough Desensitization Therapy: Pilot 2

The study will be a randomized, placebo-controlled, blinded study. It will take place in three phases, across 10 weeks.

WEEK 1: BASELINE TESTING AND TRAINING (approximate time = 1 hour).

Cough sensitivity testing: Standardized procedures that have been established and approved by the FDA will be used to determine cough sensitivity. Participants will inhale capsaicin vapor (a known cough stimulant) through a nebulizer with dosimeter, that delivers a specific dose of capsaicin in a mist form. They will inhale doubling doses of capsaicin mist from .49 micromolar to 1000 micromolar. The testing will be stopped when the investigators find the dose that causes five coughs or after giving the 1000 micromolar dose, whichever comes first. This testing will take approximately 30 minutes.

Urge-to-cough (UTC) testing: Participants be asked to report their UTC on a scale from 0 (no UTC) to 10 (maximum UTC) after each mist of capsaicin and after being presented with the following stimulants/tasks that cause some people to cough: perfume, bleach, vinegar, wood chips, laundry soap, cleaning wipe, deep and fast breath through the mouth, sustained voicing, reading a 55 word passage, and yelling a short phrase). This testing will take about 10 minutes.

Cough-related quality of life: Participants will complete the Leicester Cough Questionnaire which is a 23-item validated questionnaire designed to measure cough-related quality of life. It will take about 5 minutes.

Visual analogue cough severity (VAS): Participants will rate their cough severity on a visual analogue scale by placing a tick mark on a 100 mm line where 0 mm indicates "no cough" and 100 mm indicates "worst possible cough".

WEEKS 2-7: TREATMENT. Participants will attend treatment sessions twice per week for up to six weeks. Participants will use the breathing strategies following inhalation of either the active substance (experimental condition) or repeated exposures to an inactive substance (placebo condition). Participants will do this no more than twelve times per session. Each session will take 45-60 minutes. If a participant misses a treatment session, the investigators will attempt to re-schedule that session. Each participant must complete at least 10 treatment sessions to remain in the study.

WEEKS 8 AND 10: POST-TREATMENT TESTING. Outcome measures, as in the baseline phase, will be taken at one-week and three-weeks post-treatment. The LCQ will be measured again at three-months post-treatment.

Inclusion criteria

• At least 18 years of age
• Currently suffering from a cough that started at least 8 weeks ago
• Have seen at least one physician for the cough and have received medical treatment without success
• Normal chest x-ray, pulmonary function testing (completed by your physician or a qualified speech-language pathologist).
• Completion of a laryngoscopy (by ENT physician or qualified speech-language pathologist) with no evidence of an anatomical abnormality (i.e., masses or lesions such as nodules, cysts, or cancer) that could contribute to cough.
• Willing to take a pregnancy test before enrollment (if applicable)
• Willing to use contraception during the study (if applicable; we will not be able to supply you with contraceptive methods)
• If you are diagnosed with asthma, you may enroll in the study if you are regularly followed by a pulmonologist who will verify, in writing, that your asthma symptoms are well-controlled (apart from cough symptoms) with your current medication protocol, which would not be altered when you are in the study. In order to remain in the study, your forced expiratory volume (FEV1), which will be measured during baseline lung function testing with spirometry, must be no less than 60% of predicted values given age, height, and weight. You must also carry a rescue inhaler with you when participating in all assessment and treatment sessions.
• Willing to sign an informed consent form

Exclusion criteria

• Under 18 years of age
• Positive for COVID-19 or presenting with any of the following symptoms of COVID- 19: fever or chills, sputum, difficulty breathing, fatigue, muscle or body aches, headache, loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting, diarrhea.
• Have not followed current local, state, and CDC COVID-19 mitigation guidance, especially regarding travel.
• Unwilling to comply with COVID-19 precautions (see below)
• Currently a smoker of any substance
• Pregnant or attempting to become pregnant
• Diagnosed with a respiratory or pulmonary condition (other than asthma) that commonly contributes to cough (e.g., chronic obstructive pulmonary disease, emphysema, lung cancer, bronchitis)
• Diagnosed with asthma that is not well managed and/or do not have the necessary written consent by a pulmonologist to be in the study.
• Suffering from any signs of upper respiratory illness
• Taken any of the following medications within the past month:

• lisinopril/Prinivil/Zestril
• captopril/Capoten
• enalapril/Epaned/Asotec, ramipril/Altace
• benazepril/Lotensin
• fosinopril/Monopril
• moexipril/Univasc
• perindopril/Aceon
• quinapril/Accupril
• trandolapril/Mavik