Timing of lowest and highest peak expiratory flow in patients with asthma: influence of anti-inflammatory treatment.

Respiratory medicine

PubMedID: 10845439

Iwasaki Y, Kubota Y, Yokomura I, Ueda M, Hashimoto S, Hara H, Nakagawa M. Timing of lowest and highest peak expiratory flow in patients with asthma: influence of anti-inflammatory treatment. Respir Med. 2000;94(4):385-90.
We sought to determine the optimal time for measuring peak expiratory flow rate (PEF) in patients with mild to moderate asthma, before and after treatment with inhaled beclomethasone dipropionate (BDP). After 2 weeks of observation, BDP (400 microg/d) was given to 22 patients with mild to moderate asthma. The dose of BDP (800-1200 microg/d) was increased every 2 weeks until PEF varied by no more than 20% each day. PEF was measured four times daily: on awakening, around noon, in the evening and at bedtime. Significant (P < 0.05) rhythms were detected by single cosinor analysis in all patients, both during observation and during treatment. Analysis by the population mean-cosinor method showed that the mean mesor was 378.8+/-59.1 lmin(-1), the mean amplitude was 53.9+/-13.4 lmin(-1), and the mean acrophase was at 16:26+/-0:32 before treatment. After treatment, the mean mesor was 528.0+/-61.9 l min(-1), the mean amplitude was 37.6+/-12.2 lmin(-1), and the mean acrophase was at 16:35+/-0:32. The mesor increased significantly (P<0.05), and the amplitude decreased significantly (P<0.05) after treatment. The acrophase did not change. These data indicate that PEF is lowest at 04:30 and highest at 16:30 in patients with mild to moderate asthma, both during observation and during treatment. We conclude that if one needs to assess PEF twice a day, this should ideally be done at 04:30 and 16:30, not only before but also after treatment with BDP.