Abstract
Through a questionnaire, we examined the major onset time of asthmatic attack worsening at night (so-called nocturnal asthma (NA)) in 34 allergic asthmatic children in our hospital. All of them had been shown to have frequent episodes of NA before admission. As a result, it was shown that NA frequently developed early in the evening (5-8pm)in the majority of study subjects (56%). In these children, it was suggested that asthmatic attacks in the evening, or in other words, worsened lung function in the evening might be one of the causes for the development of NA. It was thus considered that it would be important for the treatment of NA to study exacerbating factors on lung function at the time in these children.
To study the relationship between exacerbation of lung function in the evening and the degree of cholinergic tone at the time, eight NA children with such characteristics were examined by beat-to-beat variation of the heart rate (BVHR) at 9am, 2pm, and 7pm. The PEFR at 7pm was shown to be significantly lower than at 9am and 2pm in these children. BVHR was quantitatively measured as a coefficient of variation of the R-R interval (CVR-R, see ref 14). As a result, CVR-R in these children was significantly increased at 7pm, while it was not in those of asthmatic children who did not have any diurnal variation in PEFR between the period examined and in nonallergic disease controls. On the other hand, ipratropium bromide was effective for the improvement of PEFR at 7pm in six of eight study subjects. Moreover, there was significant relation between the levels of PEFR in the evening and the occurence of NA in two subjects with frequent NA even after admission.
It was, therefore, suggested that the cholinergic system might be one of the factors for the exacerbation of PEFR at evening, and anticholinergic drugs might be useful for the patients whose NA frequently developed early in the evening.
