Circadian rhythms in lung resistance and dynamic lung compliance of healthy children. Effects of two bronchodilators.

In two groups of healthy children synchronized with a diurnal activity (light-on at 07.00) and a nocturnal rest(light-off at 21.00), lug resistance (R1) and dynamic lung compliance (C1 dyn) were measured at fixed clock hours (07.30, 11.30, 16.30, 22.30). The measurements were performed before and 10 minutes after the inhalation of bronchodilators (a beta-sympathetic stimulating agent (orciprenaline, dose 2 mg) and a vagolytic agent (SCH 1000, doses 80 mug and 200 mug). A circadian rhythm is detected for R1 and C1 dyn and quantified by the cosinor method. R1 and C1 dyn acrophase (peak time in the 24-h scale) are not significantly different for both groups: they are located for R1 at 05.39 and 03.31, for C1 dyn at 09.31 and 12.51. R1 and C1 dyn circadian rhythms are not detectable both after 2 mg orciprenaline and 200 mug SCH 1000 inhalation. This chronopharmacologic effect of the bronchodilators might be considered indirect evidence of a circadian rhythm in the bronchial tone. This latter may be related to circadian changes in neurovegetative activity. A dose-effect difference of the vagolytic agent on R1 at night seems to indicate a relative nocturnal prominence of the vagal tone.