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Change in Forced Expiratory Volume in 1 Second After Sham Bronchoconstrictor in Suggestible but Not Suggestion-Resistant Asthmatic Subjects

A Pilot Study

From the Firestone Institute for Respiratory Health (R.L., F.E.H.) and the Brain Body Institute (G.M., G.T., J.B.), St. Joseph’s Healthcare, McMaster University, Hamilton, Ontario, Canada.

Address reprint requests to: John Bienenstock, McMaster University, HSC Room 3N26H, Department of Medicine, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5. Email: bienens{at}mcmaster.ca

OBJECTIVE: Randomized controlled trials in asthma often demonstrate a benefit from placebo interventions, although no study has yet characterized this group of placebo responders. Literature points to the importance of suggestion in asthma, and we reasoned that patients’ level of suggestibility might influence their likelihood of responding to placebo-like suggestion.

METHODS: To determine whether suggestion differentially influenced airway tone in preselected suggestible compared with suggestion-resistant asthmatics, we performed a prospective, double-blind, crossover pilot study in which subjects were identified as being suggestible or suggestion-resistant using the Creative Imagination Scale. Responses to inhaled saline were assessed using FEV₁ and a modified Borg scale after the suggestion that the saline was a bronchoconstrictor and subsequently a bronchodilator.

RESULTS: Five of eight suggestible subjects compared with one of nine suggestion-resistant subjects demonstrated a fall in FEV₁ greater than 150 ml in response to inhaled saline and suggestion of bronchoconstriction (p = .027). Fourteen subjects experienced dyspnea in response to sham bronchoconstrictor, but none reported increased dyspnea after sham bronchodilator.

CONCLUSIONS: This is the first time that subjects with asthma have been categorized as suggestible or nonsuggestible with this distinction then used to predict response to an intervention. The results of this pilot study suggest that a subgroup of suggestible asthmatic patients is more likely to respond to a placebo-like sham bronchoconstriction challenge. The data support earlier observations that psychological factors may influence asthma, and provide insights into the placebo response.

Key Words: asthma, • suggestion, • placebo response.

Abbreviations: CIS = Creative Imagination Scale;; FEV₁ = forced expiratory volume in 1 second;; PC₂₀ = provocative concentration of methacholine causing a 20% fall in FEV₁.

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