COUGH RECEPTOR SENSITIVITY IN CHILDREN WITH ACUTE AND NONACUTE ASTHMA

Background - Cough is a major symptom in some children with asthma. Th e relationship between cough and the severity of asthma is ill defined . A study was undertaken to test the hypotheses that, in children with asthma who cough as a major part of their asthma symptoms, cough rece ptor sensitivity (CRS) is heightened during an acute severe exacerbati on of asthma but not in the non-acute phase and airway calibre or its change correlates with CRS. Methods - Spirometric measurements and the capsaicin CRS test were performed on children admitted to hospital fo r an acute severe exacerbation of asthma. Nasal secretions were tested for viruses. The children were grouped into those who usually cough w ith asthma episodes and those who do not. The tests were repeated 7-10 days and 4-6 weeks later. The CRS outcome measure used was the concen tration of capsaicin required to stimulate two (Cth) and five coughs ( C5). Results - The CRS of the group who coughed (n=15) was significant ly higher than those who did not cough (n=16) (mean difference log Cth 0.77 mu mol (95% CI 0.35 to 1.18), C5 0.72 mu mol (95% CI 0.26 to 1.1 8)) during acute asthma but not after the exacerbation. CRS was not si gnificantly different between groups based on the presence of a viral infection. Neither forced expiratory volume in one second (FEV1) nor i ts change correlated with CRS nor its change. Conclusions - In childre n with asthma CRS is heightened in acute severe asthma in the subgroup of children who have cough as a significant symptom with their asthma episodes. In acute and non-acute asthma CRS does not correlate with F EV1.