Cough reflex sensitivity and fractional exhaled nitric oxide in children with asthma

Individual studies have suggested the utility of fractional exhaled nitric oxide (FeNO) measurement in detecting cough-variant asthma and eosinophilic bronchitis in patients with chronic cough. The aim of this study was to clarify a correlation of cough reflex sensitivity and fractional exhaled nitric oxide 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 micromol/l) was inhaled by a single breath method. Concentrations of capsaicin causing two (C2) and five coughs (C5) were reported. Fractional exhaled nitric oxide (FeNO) measurement was included. Asthmatic children' (11 boys and 14 girls, mean age 9+/-1 years) and control group (unconfirmed diagnosis of asthma) (6 boys and 9 girls, mean age 8+/-1 years) were included into the study. FeNO vs. C2 in asthma (Spearman´s rank correlation: -0.146, p=0.49); FENO vs. C5 in asthma (Spearman´s rank correlation: -0.777, p=0.71). We found that there is no correlation between cough reflex sensitivity and fractional exhaled nitric oxide either in children with asthma or in the control group.

Cough Reflex Sensitivity in Asthmatic Children

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.

Relationship between cough reflex sensitivity and body mass index in children with chronic cough - a pilot study

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 micromol/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 Inter-Quartile Range) for C2 was 19.5 (73.4) micromol/l; for C5 it was 78.1 (605.5) micromol/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 micromol/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).

Vagus Nerves Provide a Robust Afferent Innervation of the Mucosa Throughout the Body of the Esophagus in the Mouse

The vagal afferent nerves regulate swallowing and esophageal motor reflexes. However, there are still gaps in the understanding of vagal afferent innervation of the esophageal mucosa. Anatomical studies found that the vagal afferent mucosal innervation is dense in the upper esophageal sphincter area but rare in more distal segments of the esophagus. In contrast, electrophysiological studies concluded that the vagal afferent nerve fibers also densely innervate mucosa in more distal esophagus. We hypothesized that the transfection of vagal afferent neurons with adeno-associated virus vector encoding green fluorescent protein (AAV-GFP) allows to visualize vagal afferent nerve fibers in the esophageal mucosa in the mouse. AAV-GFP was injected into the vagal jugular/nodose ganglia in vivo to sparsely label vagal afferent nerve fibers. The esophageal tissue was harvested 4-6 weeks later, the GFP signal was amplified by immunostaining, and confocal optical sections of the entire esophagi were obtained. We found numerous GFP-labeled fibers in the mucosa throughout the whole body of the esophagus. The GFP-labeled mucosal fibers were located just beneath the epithelium, branched repeatedly, had mostly longitudinal orientation, and terminated abruptly without forming terminal structures. The GFP-labeled mucosal fibers were concentrated in random areas of various sizes in which many fibers could be traced to a single parental axon. We conclude that the vagus nerves provide a robust afferent innervation of the mucosa throughout the whole body of the esophagus in the mouse. Vagal mucosal fibers may contribute to the sensing of intraluminal content and regulation of swallowing and other reflexes.

The infusion of menthol into the esophagus evokes cold sensations in healthy subjects but induces heartburn in patients with gastroesophageal reflux disease (GERD)

Recent studies in animal models have reported that some afferent fibers innervating the esophagus express the cold receptor TRPM8. In the somatosensory system the stimulation of TRPM8 leads to cold sensations and in certain circumstances alleviates pain. It is therefore hypothesized in this paper that the esophageal infusion of the TRPM8 activator menthol evokes cold sensations from the esophagus and alleviates heartburn in humans. The esophageal infusion of menthol (3 mM, 20 min) evoked cold sensations in 11 of 12 healthy subjects. In striking contrast, the esophageal infusion of menthol evoked heartburn in 10 of 10 patients with gastroesophageal reflux disease (GERD). In healthy subjects the cold sensation evoked by menthol was perceived only as a minor discomfort as evaluated by the visual analog scale (VAS score 1.9 ± 0.3 on the scale 1-10). However, in patients with GERD the menthol-induced heartburn was perceived as painful (VAS score 5.6 ± 0.6, P < 0.01 compared to healthy subjects). It is concluded that the sensations evoked by esophageal infusion of menthol change from relatively nonpainful cold sensations in healthy subjects to painful heartburn sensations in patients with GERD. These qualitative and quantitative changes indicate substantial alterations in afferent signaling mediating sensations from the esophagus in patients with GERD.

The effect of adenoidectomy on cough reflex sensitivity in atopic children

The aim of this study was to determine whether cough sensitivity is changed after adenoidectomy in atopic children with chronic cough. 21 Children having symptoms of chronic cough and adenoid hypertrophy verified by nasal fiberoptic endoscopy were submitted to cough sensitivity measurement before and after adenoidectomy. Their pulmonary function was within normal range. Concentrations of capsaicin causing two (C2) and five coughs (C5) were reported. Children' (14 boys and 7 girls, mean age 6,52 yrs) cough sensitivity (geometric mean, with 95% CI) for C2 was preoperatively (before adenoidectomy) 19.95 (9.95-39.98) micromol/l vs. children' C2 postoperatively 14.04 (7.16-27.55) (P = .083 for Wilcoxon paired two sample test). Children' C5 was preoperatively 86.26 (39.25-189.57) micromol/l vs. C5 postoperatively 95.23 (46.33-195.75) micromol/l (P = .794 for Wilcoxon paired two sample test). We conclude that cough sensitivity for C2 and C5 was not significantly changed after adenoidectomy in atopic children with chronic cough.

Structure of vagal afferent nerve terminal fibers in the mouse trachea

The structure of primary afferent nerve terminals profoundly influences their function. While the complex vagal airway nerve terminals (stretch receptors, cough receptors and neuroepithelial bodies) were thoroughly characterized, much less is known about the structure of airway nerves that do not form distinct complex terminals (often termed free nerve fibers). We selectively induced expression of GFP in vagal afferent nerves in the mouse by transfection with AAV-GFP virus vector and visualized nerve terminals in the trachea by whole organ confocal imaging. Based on structural characteristics we identified four types of vagal afferent nerve fiber terminals in the trachea. Importantly, we found that distinct compartments of tracheal tissue are innervated by distinct nerve fiber terminal types in a non-overlapping manner. Thus, separate terminal types innervate tracheal epithelium vs. anterolateral tracheal wall containing cartilaginous rings and ligaments vs. dorsal wall containing smooth muscle. Our results will aid the study of structure-function relationships in vagal airway afferent nerves and regulation of respiratory reflexes.

Impact of Air Pollution on Age and Gender Related Increase in Cough Reflex Sensitivity of Healthy Children in Slovakia

BACKGROUND

Numerous studies show higher cough reflex sensitivity (CRS) and cough outcomes in children compared to adults and in females compared to males. Despite close link that exists between cough and environment the potential influence of environmental air pollution on age- and gender -related differences in cough has not been studied yet.

PURPOSE

The purpose of our study was to analyse whether the effects of exposure to environmental tobacco smoke (ETS) from parental smoking and PM10 from living in urban area are implied in age- and gender-related differences in cough outcomes of healthy, non-asthmatic children. Assessment of CRS using capsaicin and incidence of dry and wet cough was performed in 290 children (mean age 13.3 ± 2.6 years (138 females/152 males).

RESULTS

CRS was significantly higher in girls exposed to ETS [22.3 μmol/l (9.8-50.2 μmol/l)] compared to not exposed girls [79.9 μmol/l (56.4-112.2 μmol/l), p = 0.02] as well as compared to exposed boys [121.4 μmol/l (58.2-253.1 μmol/l), p = 0.01]. Incidence of dry cough lasting more than 3 weeks was significantly higher in exposed compared to not exposed girls. CRS was significantly higher in school-aged girls living in urban area [22.0 μmol/l (10.6-45.6 μmol/l)] compared to school-aged girls living in rural area [215.9 μmol/l (87.3-533.4 μmol/l); p = 0.003], as well as compared to teenage girls living in urban area [108.8 μmol/l (68.7-172.9 μmol/l); p = 0.007]. No CRS differences were found between urban and rural boys when controlled for age group. No CRS differences were found between school-aged and teenage boys when controlled for living area.

CONCLUSIONS

Our results have shown that the effect of ETS on CRS was gender specific, linked to female gender and the effect of PM10 on CRS was both gender and age specific, related to female gender and school-age. We suggest that age and gender related differences in incidence of cough and CRS might be, at least partially, ascribed to the effect of environmental pollutants. The role of age and gender in the effect of air pollution on cough strongly suggest some interplay of development with biological and behavioral factors.

Relationship between variation of seasonal temperature and extent of occupational exposure to phthalates

Spot urine samples were collected in summer and winter season to examine the association between temperature variation and phthalate concentration in an occupationally exposed group. We analysed samples by high-performance liquid chromatography with mass spectrometry (HPLC-MS/MS) to determine the concentrations of four phthalate metabolites: mono (2-ethylhexyl) phthalate (MEHP), monobutyl phthalate (MnBP), monoethyl phthalate (MEP), and monoisononyl phthalate (MiNP). We observed significantly higher urinary concentrations of all monitored phthalate metabolites collected during the summer in occupationally exposed group (MEP p < 0.0015, MiNP p < 0.0001, MnBP p < 0.00019, and MEHP p < 0.05); however, in general, population was noticed this difference only for MEHP (p < 0.05) in winter season. We conclude that increasing indoor and outdoor temperature is related to phthalate exposure in specific types of work environment.

Growth and obesity and its association with plasma level of steroid hormones and insulin-like growth factor-I (IGF-I) in Slovak female students

The aim of the present study was to examine the possible role of steroid hormones and insulin-like growth factor 1 (IGF-I) in the control of human growth and obesity. We measured plasma level of progesterone, testosterone, estradiol and IGF-I in 301 young women at different stages of their ovarian cycle, and compared them to the standard morphometric indexes of their growth and obesity - body height, body weight, abdomen circumstance and waist to hip ratio (WHR). The ovarian cycle-dependent changes in plasma progesterone and estradiol, but not in testosterone and IGF-I level were found. Young women with higher body height had significantly higher plasma level of estradiol, testosterone and IGF-I, but not of progesterone, compared to subjects with lower body height in both follicular and luteal phases of the ovarian cycle. Subjects with a higher body weight had significantly higher plasma estradiol and progesterone, but not testosterone and IGF-I than subjects with lower body weight in both follicular and luteal phases of ovarian cycle. Women with a higher abdomen circumference had significantly lower plasma estradiol, but not the other hormones than the subjects with lower abdomen circumference. Women with higher WHR index had significantly higher plasma level of estradiol, but not other hormones than subjects with lower WHR index in both follicular and luteal phases of ovarian cycle. The present observations suggests: (1) that luteal phase of the women ovarian cycle is characterised by a dramatically increase in both progesterone and estradiol, but not in testosterone and IGF-I release, (2) that in human females growth can be up-regulated by testosterone, estradiol and IGF-I, but not by progesterone, (3) that body mass can be up-regulated by progesterone and estradiol, but not by testosterone or IGF-I, and (4) that women obesity (high WHR, but not abdomen circumference) can be promoted by estradiol, but not by other steroid hormones or IGF-I (Tab. 1, Fig. 4, Ref. 45).

Distinction of cough from other sounds produced by daily activities in the upper airways

OBJECTIVES

The aim of this study was to validate the successfulness of our developed system for distinction between cough and other sounds which are present in daily human activities from the upper airways.

BACKGROUND

To date, methods used for monitoring of cough sound were primarily subjective. A reliable measure of cough is needed so that the severity of cough in various patients and the effectiveness of treatment can be assessed.

METHODS

Sounds of induced cough and sneezing, voluntary throat and nasopharynx clearing, forced ventilation and laughing, snoring, eructation, loud swallowing, and nasal blowing were studied. Characteristics of the sound events in 20 volunteers were calculated using the time-domain, spectral and non-linear analysis. The classification tree was constructed for classification between cough and non-cough sounds. We have validated the usefulness of our developed algorithm against subjective cough counts, which were performed by two trained observers.

RESULTS

The value of sensitivity for distinction between cough and other sounds was 86% and the value of specificity was 91%. The value of sensitivity for distinction between voluntary and induced cough sounds was 96% and specificity was 43%. The value of sensitivity between cough sounds and voluntary throat clearing was 96% and specificity was 85%. The value of sensitivity between cough sounds and induced sneezing was 95% and specificity was 93%.

CONCLUSION

We have developed an algorithm for distinction between cough and other sounds with a relatively high degree of accuracy (Tab. 1, Fig. 5, Ref. 15).