New knowledge about the neural aspects of cough has revealed
a complex network of pathways that initiate cough. The effect of
inflammation on cough neural processing occurs at multiple
peripheral and central sites within the nervous system. Evidence
exists that direct or indirect neuroimmune interaction induces
a complex response, which can be altered by mediators released
by the sensory or parasympathetic neurons and vice versa. The
aim of this study was to clarify changes of cough reflex sensitivity
– the activity of airway afferent nerve endings - in asthmatic
children. 25 children with asthma and 15 controls were submitted
to cough reflex sensitivity measurement - capsaicin aerosol in
doubling concentrations (from 0.61 to 1250 µmol/l) was inhaled
by a single breath method. Concentrations of capsaicin causing
two (C2) and five coughs (C5) were reported. Asthmatic children'
(11 boys and 14 girls, mean age 9 ± 1 yrs) cough reflex sensitivity
(geometric mean, with the 95 % CI) for C2 was 4.25 (2.25-8.03)
µmol/l vs. control C2 (6 boys and 9 girls, mean age 8 ± 1 yrs) was
10.61 (5.28-21.32) µmol/l (p=0.024). Asthmatic children' C5 was
100.27 (49.30-203.93) µmol/l vs. control C5 56.53 (19.69-162.35)
µmol/l (p=0.348). There was a statistically significant decrease of
C2 (cough threshold) in the asthmatic patients relative to controls
(p-value for the two-sample t-test of log(C2) for the one-sided
alternative, p-value = 0.024). The 95 % confidence interval for the
difference of the mean C2 in asthma vs. control, [1.004, 6.207].
For C5, the difference was not statistically significant (p-value =
0.348). There was a statistically significant decrease of cough
reflex sensitivity (the activity of airway afferent nerve endings) -
C2 value in the asthmatic children relative to controls.