A Comprehensive Evaluation of the Impact of ATP on Laryngeal Symptoms, Hypersensitivity and Function

OBJECTIVES

* To deliver a comprehensive model of laryngeal assessment, evaluating both the sensory and motor components of upper airway control and to relate this to symptom disturbance.
* Determine if laryngeal control is altered by coughing and the impact of repeated coughing on overall laryngeal control and relaxation to its baseline state.
* Evaluate if cell damage and tissue inflammation (including exposure to ATP) modulates laryngeal hypersensitivity and function, by using a comprehensive array of test modalities.

AIM To utilise state-of-the-art comprehensive assessment tools to evaluate laryngeal hypersensitivity and function in a cohort of individuals with chronic refractory cough and control subjects. The test modalities utilise direct stimulation of the laryngeal adductor reflex, measurement of laryngeal EMG and assessment of functional laryngeal response to an inhalational challenge with laryngoscopic techniques.

HYPOTHESIS Physiological markers of laryngeal hypersensitivity and dysfunction are highly prevalent in patients with chronic refractory cough and manifestations are driven by ATP stimulation.

OUTCOME MEASURES Measurements of laryngeal symptomatology will be measured over a run-in period and during challenge testing. Laryngeal relaxation will be studied using our novel tracking software capability, combining endoscopic imaging and physiological measurements of diaphragm activation.


Eligibility Criteria:
Inclusion criteria (controls)

* Age ≥ 18 years
* Healthy - with no history of any medical conditions
* No history of asthma / allergies
* Normal spirometric indices
* Non smoker

Inclusion criteria (patients)

* Age ≥ 18 years
* Chronic cough as per ATS definition (\>8 weeks duration)
* High symptom burden (i.e. Cough VAS \>= 40 mm at the screening visit)
* Chest radiograph or CT within 3 years of the screening visit with no abnormalities considered to contribute to chronic cough
* For patients with asthma: a confirmed diagnosis of asthma on the basis of asthma symptoms and reversible airflow obstruction (BDR 200mls + 12% change post bronchodilator and/or positive bronchoprovocation test).

Exclusion criteria

* Current smoker or a smoking history of \>10 pack years
* Asthma that is not well-controlled, as per international asthma guidelines as specified by Global Initiative for Asthma (GINA)
* Recent exacerbation of cough or asthma within 4 weeks of inclusion
* Pregnancy or childbearing potential and no contraceptive treatment
* Respiratory tract infection within 4 weeks of inclusion
* Currently taking any of the following medications:

  * ACE inhibitors and within 3 months of inclusion
  * Antitussives (opioids, pregabalin, gabapentin, amitriptyline, nortriptyline or over-the-counter medications) within 2 weeks of inclusion
  * Medical treatments for GORD, eosinophilic bronchitis or other cough related conditions, initiated or changed (i.e. not in a stable regimen) for 4 weeks prior to inclusion.
* Medical history of COPD or chronic bronchitis
* Medical conditions/history or other circumstances which, in the judgement of the investigator, could increase the risk of adverse events or bias the study results