The Effect of Odors on Asthma Symptoms

Study Overview
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Brief Summary
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An extended replication of Jaen & Dalton (2014), the investigators aim to investigate the role of odors and associated trigger beliefs on symptom perception and airway inflammation in individuals with asthma

Detailed Description
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Participants with asthma are randomly assigned to a 15-min (phenylethyl alcohol) odor inhalation, accompanied by either an asthmogenic suggestion (nocebo), or a therapeutic suggestion (placebo). Airway inflammation, lung function, and asthma symptoms are measured in response to the odor/suggestion, up to 24 hours after odor inhalation. The investigators are also measuring worry and heart rate variability as potential mediators of the response.

Official Title
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The Effect of Suggestion of Harmful/Beneficial Effects of Odors on Asthma Symptoms

Conditions
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Asthma

Intervention / Treatment
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* Behavioral: Therapeutic Suggestion
* Behavioral: Asthmogenic Suggestion
* Other: Phenylethyl Alcohol odor


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: A physician diagnosis of asthma Exclusion Criteria: FEV1 lower than 60% predicted clinical condition other than asthma

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Odor+ Positive belief<br>Participants receive 15 minute odor presentation (Phenylethyl Alcohol odor) accompanied by the suggestion that this odor improves asthma symptoms (therapeutic suggestion) | Behavioral: Therapeutic Suggestion<br>* suggestions about potential beneficial effects of the odor are given<br>* Other names: positive treatment belief induction;Other: Phenylethyl Alcohol odor<br>* Over the course of 15 minutes, participants, receive 15 short sniffs of Phenylethyl Alcohol odor<br>|
| Experimental: Odor + Negative belief<br>Participants receive 15 minute odor presentation (Phenylethyl Alcohol odor) accompanied by the suggestion that this odor worsens asthma symptoms (asthmogenic suggestion) | Behavioral: Asthmogenic Suggestion<br>* suggestions about potential negative effects of the odor are given<br>* Other names: negative treatment belief;Other: Phenylethyl Alcohol odor<br>* Over the course of 15 minutes, participants, receive 15 short sniffs of Phenylethyl Alcohol odor<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from Baseline Exhaled Nitric Oxide to 24 hours after odor induction | Fraction of exhaled nitric oxide | baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| asthma symptoms | measured using the Asthma Symptom Checklist | baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction | 
| Forced Expiratory Volume at one second (FEV1) | Measured using Jaeger Masterscreen Spirometer, according to ERS-ATS guidelines | baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction | 
| Worry | measured using worry Visual Analog Scales | baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction | 
| Cortisol | cortisol awakening response (AUC), and changes in cortisol (AUC) will be measured using saliva sampling | baseline, immediately after odor induction, 2 hours after odor induction, at awakening, 30 min after awakening, 24 hours after odor induction | 
| Change in Heart rate and Heart Rate Variability (HRV) | 24 hour heart rate data will be recorded using an ambulatory ECG monitor, and analyzed in 1 hour epochs, extracting mean of successive differences (MSD) as a variable of interest. | change from baseline to 24 hours after odor induction | 
| Change in Respiratory rate | respiratory rate (breaths/min) is recorded continuously, and changes between baseline and odor presentation periods will be analysed | change from baseline to 15 min odor presentation | 
| change in Fraction of end-tidal carbon dioxide (FetCO2) | FetCO2 (plateau %CO2 in exhaled air) is recorded continuously, and changes between baseline and odor presentation periods will be analysed | change from baseline to 15 min odor presentation | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Odor, trigger, inflammation, nocebo