The impact of harmfulness information on citric acid induced cough and urge-to-cough

Abstract

Purpose: The cough reflex is an automatic protective reflex, which can be modulated by conscious effort or other forms of top-down control. In this experiment, we investigated whether information about harmfulness of a cough-inducing substance would augment cough reflex sensitivity and associated urge-to-cough.

Methods: Healthy participants (N = 39) were randomized to receive information that they were to inhale a harmless substance (natural citric acid), or a potentially harmful substance (a potent agro-chemical acid). Using dosimeter-controlled inhalations, the dose of citric acid eliciting at least three coughs (C3) was determined. Next, participants received 4 blocks of randomized presentations of citric acid at the C3 dose, a sub-threshold dose of citric acid and saline control.

Results: C3 was reached for 27/39 participants, and C3 thresholds were not influenced by harmfulness information. During repeated citric acid presentations, framing the cough-inducing substance as a potentially harmful chemical resulted in a greater urge-to-cough compared to information framing it as natural citric acid (p < .01). The experimental manipulation did not influence cough frequencies.

Conclusions: Our findings show that harmfulness information influences urge-to-cough, corroborating the role of cortical mechanisms in modulating the urge-to-cough and suggesting that cognitive manipulations may contribute to cough treatment.

Keywords: Citric acid; Cough; Environmental exposure; Environmental intolerance; Perceived harmfulness; Urge-to-cough.