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
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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
48
suggestions about potential beneficial effects of the odor are given
suggestions about potential negative effects of the odor are given
Over the course of 15 minutes, participants, receive 15 short sniffs of Phenylethyl Alcohol odor
UZ Leuven
Leuven, Belgium
Change from Baseline Exhaled Nitric Oxide to 24 hours after odor induction
Fraction of exhaled nitric oxide
Time frame: baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction
asthma symptoms
measured using the Asthma Symptom Checklist
Time frame: 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
Time frame: baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction
Worry
measured using worry Visual Analog Scales
Time frame: 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
Time frame: 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.
Time frame: change from baseline to 24 hours after odor induction
Change in Respiratory rate
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respiratory rate (breaths/min) is recorded continuously, and changes between baseline and odor presentation periods will be analysed
Time frame: 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
Time frame: change from baseline to 15 min odor presentation