Investigating the Role of ATP Production by Airway Epithelium in Patients With Refractory and Unexplained Chronic Cough (RCC/UCC).

Inclusion Criteria for RCC/UCC: * Patients with a history of RCC/UCC. * Normal Chest X-ray in the last 5 years. * No Evidence of Airflow Obstruction (FEV1/FVC ratio above LLN) * Cough Severity VAS ≥ 40 mm at screening. Inclusion Criteria for Healthy Controls: * No history of chronic cough, asthma, COPD, or clinical history of bronchiectasis or interstitial lung disease * No current smokers or those with \>10 pack year history. * No evidence of airflow obstruction ( FEV1/FVC ratio above LLN). * Able to understand and give written informed consent. Exclusion Criteria: * Participants who are currently established on treatment and their chronic cough is well controlled. * Unable to perform acceptable and reproducible spirometry. * Participants with a positive covid-19 test within 2 weeks of screening. * Current smoker or ex-smoker with ≥20 pack year smoking history and abstinence of ≤6 months * Symptoms of upper respiratory tract infection in the last 1 month which have not resolved * Lower respiratory tract infection or pneumonia in the last 1 month * Asthma exacerbation in the previous month requiring an increase or start of an inhaled corticosteroid (ICS) or oral corticosteroid (OCS) * Significant other primary pulmonary disorders in particular; pulmonary embolism, pulmonary hypertension, lung cancer, cystic fibrosis, significant radiologically proven emphysema, interstitial lung disease or bronchiectasis. * History of psychiatric illness, drug or alcohol abuse which may interfere in the participation of the trial. * Allergy or intolerance to sedation medication including fentanyl and midazolam, or a history of complications during procedural sedation * Severe coagulopathy, bleeding disorder, or medical need for anti- coagulation that would increase the risk of endobronchial biopsy as determined by the investigator