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

Abstract

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 μ g/d) was given to 22 patients with mild to moderate asthma. The dose of BDP (800–1200μ g/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 l min−1, the mean amplitude was 53·9±13·4 l min−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 l min−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.