The Effect of Attentional Manipulation on Cough Reflex Sensitivity in Individuals with Refractory Chronic Cough and Healthy Controls

Background: Cough reflex sensitivity during cough challenge testing has been found to be modifiable with distraction in groups of healthy individuals. The purpose of this study was to examine this phenomenon in healthy controls and patients with refractory chronic cough (RCC) to advance our understanding of the role attention plays in cough modulation and shed light on avenues for therapeutic advances for RCC. Methods: Thirteen adults with RCC (mean age = 60, 12 women) and twelve healthy controls (mean age = 60, 11 women) participated in this study. The participants completed cough challenge testing with nebulized capsaicin doses tailored to their individual cough reflex sensitivity under distraction and no-distraction conditions. The distraction condition consisted of cough challenge testing while completing a cognitive (visual memory) task on a tablet. Capsaicin doses included the dose that elicited two coughs (C2), and up to three doubling doses above C2. Capsaicin doses were administered in serial order with a placebo dose randomized into the order to control for an anticipation effect during each condition. For each dose administered, the participants were instructed to cough if they needed to. Cough frequency within 15 s and maximal urge-to-cough with each dose were recorded. The order of conditions (distraction or no distraction) was alternated, and all testing was completed within one session. Results: There were no meaningful differences in the dose–response rate parameters for cough frequency or urge-to-cough, respectively, when comparing the results from the RCC group in the condition without distraction to the condition with distraction (p = 0.647, 95% CI = −2.25, 1.15; p = 0.783, 95% CI = −1.94, 0.84), and to the healthy control group without distraction (p = 0.921, 95% CI = −2.11, 2.73, p = 0.887, 95% CI = −1.40, 0.80), and with distraction (p = 0.970, 95% CI = −2.16, 3.36), p = 0.808, 95% CI = −1.49, 0.89). Conclusions: Distraction with the cognitive task chosen in this study did not influence cough reflex sensitivity in either group, which is contrary to studies on healthy volunteers and anecdotal evidence reported by RCC patients. Attentional resources may not have been sufficiently taxed, or too few capsaicin doses were administered to capture an effect as there was high individual variability in cough frequency and urge-to-cough. Additional research is needed to tailor the difficulty of the cognitive task to each participant and incorporate a real-world distraction scenario that may better reveal how attentional manipulation could be harnessed to optimize the effectiveness of behavioral cough suppression therapy for patients with refractory chronic cough.