Airway hyperresponsiveness and cough-receptor sensitivity in children with recurrent cough.

Abstract

In children, recurrent cough is a common presenting symptom that may represent asthma. We tested the hypotheses that children with recurrent cough have increased cough-receptor sensitivity (CRS) or airway hyperresponsiveness (AHR). Skin prick testing, the capsaicin CRS test, and hypertonic saline (HS) challenge were performed in 44 children (median age: 8.9 yr) with recurrent dry cough (> or = 2 episodes of cough, each lasting > or = 2 wk, within a period of 12 mo) and 44 controls. Measures of CRS were the concentration of capsaicin required to stimulate > or = 2 coughs (Cth) and > or = 5 coughs (C5). During the coughing period, Cth (mean log: 0.62 [95% CI: 0.43 to 0.81]) and C5 (mean log: 1.15 [95% CI: 0.86 to 1.44]) of the subjects without AHR were significantly lower (p = 0.0026, 0.027, respectively) than Cth (mean log: 1.27 [95% CI: 0.88 to 1.66]) and C5 (mean log: 1.79 [95% CI: 1.21 to 2.37]) of the subjects with AHR and those of the controls (p = 0.0002 and 0.0001). During the cough-free period, there was no difference in CRS among the groups. In subjects who demonstrated AHR, the provocation dose causing a > or = 15% fall in FEV1 (PD15) during the cough period was significantly lower (p = 0.005) than that during the cough-free period. We conclude that AHR or increased CRS is present during the coughing phase in children with recurrent cough.

Bronchodilator responsiveness and atopy in 5–10-yr-old coughers

“…It is possible that rhinovirus infection could be responsible for persistent cough and BDR in susceptible subjects. This study has shown that, in addition to the observations of others of increased BHR and CRS at the time of coughing [17,23], there is also increased BDR. If BDR returns to normal when cough resolves, then a common reason for both BDR and cough would be suggested.…”

“…In population studies, coughers without reported wheeze are no more likely to demonstrate BHR than controls [1,2]. However, coughers demonstrate BHR to hypertonic saline at the time of coughing [17], possibly reflecting epithelial damage and the priming of airway smooth muscle with inflammatory mediators, rendering them more sensitive to bronchoconstricting agents. There is little known about the relationship of the properties of airway smooth muscle, such as contractility and phenotype, to BHR, and nothing known about their relationship to BDR [18].…”

“…Rhinovirus replication persists for up to 3 weeks, long enough to cause persistent symptoms, at least in some subjects. It has been shown that children with persistent cough have increased cough receptor sensitivity (CRS) at the time of the cough, which could be related to increased sensitivity of parasympathetic reflexes [17]. It is possible that rhinovirus infection could be responsible for persistent cough and BDR in susceptible subjects.…”

The diagnosis and management of chronic cough

“…A problem with followup data is selection bias as a result of selective loss-to-followup in asymptomatic children [35]. It seems that coughing children have similar airway responsiveness than controls, but may have temporarily increased airway responsiveness during cough episodes [36].…”

Chronic cough in children: bronchoalveolar lavage findings

“…A noninvasive and specific marker of eosinophilic airway inflammation would be a valuable tool to study this, and exhaled nitric oxide may be useful in this regard. Others have tried to distinguish different causes of chronic cough using some feature of the bronchial responsiveness plot [8] or cough receptor sensitivity to capsaicin in children [26]. However, both of these techniques appear to have little value in distinguishing which children with chronic cough will respond to antiasthma therapy.…”