Laboratory research of cough reflex utilizes almost exclusively
male guinea pigs – a practice that represents a significant obstacle
in the successful translation of results into clinical practice. Chronic
hypersensitivity cough syndrome affects mostly postmenopausal
women and it represents significant decrease in patient’s quality
of life. No cause for such exaggerated cough can be found,
therefore this condition cannot be treated appropriately. One of
the reasons leading to the lack of relevant data about mechanisms
responsible for hypersensitivity of cough related pathways is
nowadays widely discussed gender bias, which is present in nearly
all branches of biomedical research. Since gender differences in
cough reflex physiology do exist in humans, it would be reasonable
to study cough-related phenomena on both sexes of laboratory
animals. In this study, we focused on detailed characterization of
cough response of female guinea pigs to aerosols of commonly
used tussive agents (capsaicin, distilled water, allyl isothiocyanate,
cinnamaldehyde, citric acid). In pooled data from multiple
challenges we found no statistical difference in number of cough
and cough latency between sexes. Based on our results we
conclude that the utilization of female guinea pigs model does not
lead to messy data and can be used in basic cough research.
Obesity is characterized by chronic, low-grade systemic inflammation. Obesity may also be associated with chronic cough. The aim of this pilot study was to clarify relation of cough reflex sensitivity and body mass index (BMI) in children with chronic cough. Altogether 41 children having symptoms of chronic cough were submitted to cough reflex sensitivity measurement. We assessed the relation of cough reflex sensitivity (CKR) due to BMI. Cough reflex sensitivity was defined as the lowest capsaicin concentration which evoked two (C2) or five (C5) coughs. Capsaicin aerosol in doubling concentrations (from 0.61 to 1250 µmol/l) was inhaled by a single breath method (KoKo DigiDoser; nSpire heath Inc, Louisville, CO, USA), modified by the addition of an inspiratory flow regulator valve (RIFR; nSpire heath Inc, Louisville, CO, USA). BMI was calculated. Pulmonary function was within normal range. Concentrations of capsaicin causing two (C2) and five coughs (C5) were reported. Children' (22 boys and 19 girls, mean age 6.8 years) cough reflex sensitivity (median, with the InterQuartile Range) for C2 was 19.5 (73.4) µmol/l; for C5 it was 78.1 (605.5) µmol/l. We have noticed statistically significant relation of the cough reflex sensitivity (C5) and body mass index (P<0.0001); however, the effect size was small, R2 =0.03. Increase of body mass index in one unit is associated with -34.959 µmol/l decrease of C5. We did not find a statistically significant relation between C2 and BMI (P=0.41). The median value of CKR (C2) in boys is not statistically significantly different than the median value of CKR (C2) in girls (P-value 0.5). The median value of CKR (C5) in boys is not statistically significantly different than the median value of CKR (C5) in girls (P-value 0.5). Increase of body mass index in children suffering from chronic cough relates to decrease of cough reflex sensitivity (C5 value).
Cough is one of the most important defensive reflexes. However,
extensive non- productive cough is a harmful mechanism leading
to the damage of human airways. Cough is initiated by activation
of vagal afferents in the airways. The site of their convergence is
particularly the nucleus of the solitary tract (nTS). The secondorder neurons terminate in the pons, medulla and spinal cord and
there is also the cortical and subcortical control of coughing. Upper
airway cough syndrome (UACS) – previously postnasal drip
syndrome - is one of the most common causes of chronic cough
together with asthma and gastroesophageal reflux. The main
mechanisms leading to cough in patients with nasal and sinus
diseases are postnasal drip, direct irritation of nasal mucosa,
inflammation in the lower airways, upper airway inflammation and
the cough reflex sensitization. The cough demonstrated by UACS
patients is probably due to hypersensitivity of the upper airways
sensory nerve or lower airways sensory nerve, or a combination of
both. Further studies are needed to clarify this mechanism.