Cough Responses to Tussive Agents in Health and Disease
Condition: Chronic Obstructive Airway Disease; Asthma; Chronic Cough
MeSH terms: Cough; Lung Diseases, Obstructive; Pulmonary Disease, Chronic Obstructive
Study type: Observational

Summary: 
      The sensitivity of a persons cough reflex can be measured by getting them to breath in
      (inhale) irritant chemicals. The purpose of this clinical research study is to test the
      sensitivity of the cough reflex to a variety of chemicals that can be inhaled to see if
      coughing responses are different between healthy people and people with respiratory problems
      that make them cough.
    

Detailed description: 
      Coughing is a distressing symptom which has a major impact on quality of life. It has been
      estimated that cough costs the UK economy £1 billion each year. Currently there are no
      effective anti-tussive agents to treat subjects with cough. Although drugs such as morphine
      may have some anti-tussive effect, side effects unacceptable.

      Currently our understanding of the mechanisms which lead to coughing in different diseases is
      poor. Many mechanistic studies rely on testing the sensitivity of the cough reflex by
      inhalation of capsaicin (chilli-pepper extract) or citric acid. These challenges do not
      differentiate well between health and disease or between different disease states. Other
      agents such as prostaglandins and bradykinin are known to stimulate a coughing but responses
      to these agents have rarely been used as a measure of cough reflex sensitivity and not been
      compared to standard challenges.

      It is clear that patients with common airway diseases such as COPD and asthma cough
      significantly more than healthy subjects. Moreover subjects presenting with chronic cough
      have cough rates an order of magnitude higher than most patients with airway disease. These
      differences are poorly represented by the differences in current cough challenge tests.

      The investigators hypothesize that patterns of cough responses to different tussive agent may
      better differentiate between health and different disease states. These patterns may also
      suggest the different mechanisms leading to cough in different diseases.
    

Intervention name(s): Cough Challenge Tests; ambulatory cough recording; Cough questionnaires
Intervention type(s): Other; Other; Other
Intervention description(s): Inhalational cough challenge tests with capsaicin, bradykinin, Citric acid and prostaglandin E2; Cough recording with a portable device to capture cough sounds; Questionnaires designed to study cough. These include Leicester cough questionnaire, cough visual analogue score and cough quality of life questionnaire.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Adults aged 18 and over who are healthy non smokers, or are current smokers with no
        respiratory conditions and normal spirometry, or have a diagnosis of asthma, chronic cough
        or COPD.
      
Biospecimen description: 
      Sputum.
    
Keywords: Cough; Inhalational cough challenges; Cough reflex sensitivity; Chronic cough.