The Efficacy of Capsaicin Sensitivity Testing in Patients With Irritable Larynx Syndrome

Study Overview
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Brief Summary
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Irritable larynx syndrome (ILS) is a hyperkinetic laryngeal dysfunction that is characterized by a persistent cough, voice changes, or breathing difficulties, which are often triggered by an irritant. Diagnosis of ILS is difficult and typically made via a thorough review of the clinical history and, occasionally, the patient's reaction to an odor-provocation test. Standard treatment for ILS is behavioural therapy with a speech language pathologist (SLP), which provides symptom improvement for most patients. However, currently, there are no objective measures of the upper airway hyper-responsiveness in this condition to assist in diagnosing and monitoring disease severity. Since the cough is irritant-based, it is anticipated that patients with ILS will have a hypersensitivity to the irritant capsaicin. Capsaicin is the active component of chili peppers and is what makes them hot. The capsaicin cough challenge is a well recognized test that involves inhaling different concentrations of capsaicin solutions to determine a cough reflex sensitivity. The purpose of this research study is to confirm that ILS patients have a hypersensitivity to capsaicin compared to healthy volunteers. If a hypersensitivity is observed in ILS patients, the second objective of this study will be to see if behavioural therapy improves the cough reflex sensitivity in this patient population.

Detailed Description
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The proposed study has two purposes; the first is to utilize capsaicin cough challenge to demonstrate an increased efferent receptor sensitivity level in ILS subjects as compared to a control group. The second is to determine if there is an objective change in capsaicin cough challenge results after behavioral therapy, and whether it correlates to the subjective improvement. Self-reporting measures include two validated cough quality of life (QoL) questionnaires collected at the same intervals as the capsaicin testing.

Official Title
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The Efficacy of Capsaicin Sensitivity Testing in Patients With Irritable Larynx Syndrome

Conditions
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Cough, Larynx

Intervention / Treatment
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* Other: Capsaicin cough challenge test


Participation Criteria
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Eligibility Criteria
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ILS Participants: Inclusion Criteria: Diagnosis of ILS as per the St Michael's voice clinic consultation Methacholine test performed Negative/borderline result for methacholine test and/or negative/incomplete response for asthma treatment Negative test result for gastroesophageal reflux or negative/incomplete response to reflux treatment Allergy test has been completed with negative result or does not account for all symptoms Agreed to behavioural therapy in SMH Voice Disorders Clinic Exclusion Criteria: Active smoker Active respiratory disease (e.g., COPD, pulmonary fibrosis, lung malignancy.) Taking an ACE inhibitor Pregnant and/or breastfeeding Impaired liver and/or renal function Neurological disorder Psychiatric condition (outside of depression or anxiety) Healthy Volunteers: Exclusion Criteria: Active smoker Active respiratory disease (e.g. COPD, asthma) ILS diagnosis Chronic cough diagnosis Known hypersensitivity to capsaicin

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Healthy Volunteers<br>Capsaicin cough challenge test. The ILS participants will be asked to attend two study visits at the pulmonary function laboratory at SMH; one before behavioural therapy and one after. The healthy volunteers will be asked to attend one study visit. At each of these study visits, the ILS participants will complete the Leicester Cough Questionnaire (LCQ) (Appendix B) and the Dyspnea Index (DI) Questionnaire (Appendix C). The LCQ is a valid assessment tool for evaluating the impact of cough on QoL.19 The DI is a short, validated questionnaire used to quantify a patient's symptoms of dyspnea.20 Following completion of the questionnaires, participants will complete a capsaicin cough challenge test, which is discussed in the following section. | Other: Capsaicin cough challenge test<br>* The capsaicin cough challenge testing will be conducted in the pulmonary function laboratory at SMH by a pulmonary function technologist. The test involves having the participant inhale increasing concentrations of capsaicin solutions and assessing their response. The tidal breathing method and solution preparation presented by Nejla, et al. 12 will be used to conduct this testing. The tidal breathing method is preferred to the alternative dosimeter method as it produces similar results with lower capsaicin concentrations thereby resulting in less throat irritation for the participant. The technique is detailed in the following sections.<br>|
| Irritable Larynx Syndrome Patients<br>Capsaicin cough challenge test. The ILS participants will be asked to attend two study visits at the pulmonary function laboratory at SMH; one before behavioural therapy and one after. The healthy volunteers will be asked to attend one study visit. At each of these study visits, the ILS participants will complete the Leicester Cough Questionnaire (LCQ) (Appendix B) and the Dyspnea Index (DI) Questionnaire (Appendix C). The LCQ is a valid assessment tool for evaluating the impact of cough on QoL.19 The DI is a short, validated questionnaire used to quantify a patient's symptoms of dyspnea.20 Following completion of the questionnaires, participants will complete a capsaicin cough challenge test, which is discussed in the following section. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| cough reflex sensitivity | measured via the capsaicin cough challenge test | measured before and after behavioural therapy for ILS participants (approximately 5 month time frame); measured once for healthy volunteers |