Neurophysiology of Cough Reflex Hypersensitivity

Inclusion criteria

Healthy volunteers inclusion:

• Over 18 years
• Measurable cough reflex sensitivity - required as is the primary end-point
• No current or past history of chronic cough or chronic respiratory disease

Chronic Cough Patients inclusion:

• Over 18 years
• Chronic persistent cough (> 8 weeks) despite investigation and/or treatment trials for cough variant asthma/post-nasal drip and gastro-oesophageal reflux
• Normal chest radiograph - primary respiratory cause for cough excluded
• Normal lung function - primary respiratory cause for cough excluded Measurable cough reflex sensitivity - required as primary end-point

Exclusion criteria

• Recent upper respiratory tract infection (<4 weeks) - this can lead to increased sensitivity of the cough reflex which resolves as the infection settles
• Pregnancy/breast-feeding - unknown effects of oesophageal acid infusion
• Current smokers or ex-smokers with < 6 month abstinence or history > 20 pack years - smoking can alter the sensitivity of the cough reflex
• Opiate or ACE inhibitor use or centrally acting medication - can alter the cough reflex sensitivity
• Symptomatic gastro-oesophageal reflux, post-nasal drip or asthma (chronic cough cohort may have been treated for these in the past but cough did not resolve) - these conditions are known to cause cough and alter cough reflex sensitivity
• Significant ongoing chronic respiratory/cardiovascular/gastro-intestinal/haematological/ neurological/psychiatric illness. We are aiming to recruit healthy volunteers and chronic cough patients who are otherwise healthy