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Biomedical subjects

A B Chang

Publications and source records attributed to A B Chang.

65 records · Page 4Linked to original sources
PubMed1997

Cough receptor sensitivity in children with acute and non-acute asthma.

BACKGROUND: Cough is a major symptom in some children with asthma. The 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 receptor sensitivity (CRS) is heightened during an acute severe exacerbation 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 for an acute severe exacerbation of asthma. Nasal secretions were tested for viruses. The children were grouped into those who usually cough with 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 concentration of capsaicin required to stimulate two (Cth) and five coughs (C5). RESULTS: The CRS of the group who coughed (n = 15) was significantly higher than those who did not cough (n = 16) (mean difference log Cth 0.77 mumol (95% CI 0.35 to 1.18), C5 0.72 mumol (95% CI 0.26 to 1.18)) during acute asthma but not after the exacerbation. CRS was not significantly different between groups based on the presence of a viral infection. Neither forced expiratory volume in one second (FEV1) nor its change correlated with CRS nor its change. CONCLUSIONS: In children 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 FEV1.

Acute Disease↗
PubMed1997

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

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.

Adolescent↗
PubMed1997

A new use for an old Holter monitor: an ambulatory cough meter.

Cough is commonly used as an outcome measure in clinical studies, although the subjective reporting of cough is unreliable when compared to objective measures. We describe an inexpensive new ambulatory cough meter that is based on a disused Holter monitor. The cough meter consists of a Holter monitor and a cough processor, designed on a computer to select the most appropriate filters. The cough meter was then validated against the overnight tape recorder on 21 occasions in 18 children (aged 6-15 yrs). The agreement between the cough meter and the tape recorder was good (mean difference of -0.3 coughs x h(-1); limits of agreement -2.2 to 1.7 coughs x h(-1)). We conclude that our newly described ambulatory cough meter provides a valid and inexpensive method of objectively monitoring cough for up to 24 h.

Adolescent↗
PubMed1996

Capsaicin cough receptor sensitivity test in children.

Capsaicin has been used as a tussive agent in studies in adults to determine cough receptor sensitivity. The aim of this study was to determine the tolerance, repeatability and influence of inspiratory flow on the capsaicin cough receptor sensitivity test in children. Thirty children (mean age 11 yrs; range 6-16 yrs) were tested on two different days, to determine the lowest concentration of capsaicin required to stimulate two or more coughs (cough threshold (Cth)), 2-4 coughs (C2), and five or more coughs (C5). Capsaicin was nebulized through a dosimeter, with an arrangement that allowed the subjects to visualize and regulate their inspiratory flow. Using a constant inspiratory flow of 20 L x min(-1), tests were reproducible for C2, C5 and Cth (doubling dose changes of 1.13, 1.03 and 1.08, respectively). An increase in the inspiratory flow from 20 to 60 L x min(-1) significantly increased C2 (19.5 to 46.8 microM; p=0.016) and C5 (46.8 to 128.8 microM; p=0.008). We conclude that in children, the capsaicin cough challenge test: 1) is well-tolerated; 2) is highly repeatable; and that 3) the inspiratory flow significantly influences cough receptor sensitivity and repeatability of the test and should, thus, be regulated.

Adolescent↗
PubMed1983

An anterograde HRP study of the retinotectal pathways in albino and pigmented guinea pigs.

An uncrossed retinotectal projection was observed in albino guinea pigs using the anterograde HRP method, suggesting that the retinal projection in these animals, similar to that in the pigmented strain, is not strictly crossed as reported previously. It was also noted that a small retinal projection terminated in a restricted region in the most medial portion of the contralateral inferior colliculus, implying that it might be influenced directly by fibers arising from the contralateral eye.

Animals↗