Abstract
One previous study has demonstrated that cough reflex sensitivity to inhaled capsaicin is transiently enhanced during acute viral respiratory tract infection (URI) by comparing single cough reflex sensitivity measurements at baseline and during URI (O'Connell F, et al. Respir Med 1996;90:279-286). To our knowledge, no one has performed multiple measurements of cough reflex sensitivity during acute URI to evaluate presence or absence of stability during the acute viral illness. To date, we have evaluated 37 otherwise healthy adult nonsmokers with acute URI. Subjects underwent capsaicin cough challenge testing, as previously described in the ERS guidelines (Morice et al. Eur Respir J 2007;29:1256-1276), on 2 consecutive days within the first 8 days of their illness, and again after 4-8 weeks (post-recovery). Briefly, subjects inhaled single, vital-capacity breaths of nebulized capsaicin, administered in incremental doubling concentrations, until the concentration inducing 5 or more coughs (C5) was attained. All 37 subjects had serial C5 measurements within 1 doubling concentration during the acute illness. Post-recovery mean log C5 was significantly higher than during illness (0.84±0.08 [SEM] vs. 0.50±0.08; p=0.000004). Our results demonstrate that cough reflex sensitivity remains stable in the acute phase of URI, and confirm previous findings of a transient increase of cough reflex sensitivity during URI compared to healthy baseline levels. The demonstration of stability of cough reflex sensitivity during the early stages of URI is relevant to potential investigators planning to evaluate the effect of a pharmacological intervention on cough reflex sensitivity during URI.
- © 2011 ERS
