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In six subjects with intrinsic asthma in clinical remission, time-structure of ventilatory parameters has been evaluated in order to evaluate: 1) which indexes present statistically significant circadian fluctuations; 2) if phase-shifts occur in comparison with normal subjects. After a period of synchronization of 7 days (L/D: 07.30-23.00; meal timing at 08.00, 13.00 and 20.30) all subjects have been studied by spirometry, flow-volume loop and Raw determination 6 times in a 24-hr period at constant intervals of 4 hrs. The results have been evaluated by macroscopic and microscopic analysis statistical significant fluctuations have been shown in these functional indexes: MEF50, Raw, SRaw, SGaw, FRC and RV; no phase-shifts occurred in comparison with normal subjects. On the contrary a circadian rhythm has not been shown in FVC, FEV1, and PEF. Therefore only the effort-independent test should be used to study correctly the bronchial tone.

Seventeen asthmatic, non-atopic patients (aged 15-48 years) were studied at different hours of the day. On 3 different days, they were submitted to a fog-test at 03:00 p.m. and at 03:00 a.m. On 2 different days, they were given fenoterol (200 micrograms) or Duovent (fenoterol 200 micrograms plus ipratropium bromide 80 micrograms). We were able to demonstrate significant inter-hour differences of the basal values of all parameters, except FVC, in all patients at 03:00 p.m. and at 03:00 a.m. We did not observe any inter-hour difference after the fog-test. Both fenoterol and Duovent improved challenge-induced bronchoconstriction. After the fog-test, both drugs showed an inter-hour variability of ventilatory parameters, which was not significant without drugs because it was masked by the magnitude of the obstructive response to challenge.