Breathing during sleep in stable asthmatic subjects. Influence of inhaled bronchodilators.

The bronchoconstriction of asthma displays a circadian rhythm with exacerbations often occurring in the early morning hours. Gas exchange abnormalities during sleep in patients with severe asthma have been documented; however, the influence of sleep on gas exchange in the asthmatic with few or no daytime or nocturnal symptoms is poorly understood. To determine if abnormalities in oxygenation might occur during sleep, we studied 12 stable adult asthmatic patients with reversible airflow obstruction during sleep on three consecutive nights, with night 1 being for acclimatization. On test nights 2 and 3, the subjects received, in random double-blind fashion, either inhaled fenoterol or its placebo. Spirometry was performed before and after bronchodilator treatment and on the next morning. The mean FEV1 was 63 percent predicted before treatment. There was significant (p less than 0.05) improvement in FEV1 on fenoterol night after treatment which was also present the next morning. Mean prefenoterol FEV1 was 2.04 +/- .15 (SEM) and increased to 2.61 +/- .17 after the bronchodilator. The mean morning FEV1 was 2.27 +/- .20. Mean preplacebo FEV1 was 2.07 +/- .12 and did not change significantly with placebo bronchodilator. Sleep analysis demonstrated no significant differences in total sleep time or duration of oxyhemoglobin desaturation between nights. The incidence of sleep disordered breathing was very low (0.14 apneas/hour). The frequency of apneas and hypopneas did not change significantly with treatment. Two of the 12 subjects experienced an asthma attack on placebo night which did not recur following active bronchodilator administration. We conclude that stable asthmatic patients with few nocturnal complaints have a low frequency of disordered breathing and desaturation events during sleep.