Peak Expiratory Flow Variability and Bronchial Responsiveness to Methacholine: An Epidemiologic Study in 117 Workers

Abstract

We studied the relationships between peak expiratory flow (PEF) variability and bronchial responsiveness to methacholine in 117 workers attending the annual compulsory examination (mean age, 38.7 yr +/- 9.5; men, 86.3%). Subjects recorded their highest PEF out of three, every 3 waking hours (i.e., five times a day) for 7 days, each using a newly purchased Vitalograph peak flow meter, and underwent methacholine challenge tests with a maximal cumulative dose of 1,200 micrograms. Those with a FEV1 fall of 15% or more were considered as reactors. The variability of PEF was expressed as the amplitude percent mean, calculated from daily amplitude (highest-lowest reading/mean reading of the day x 100), averaged over 6 days, from the second to the seventh. This index had a continuous distribution, skewed towards the greatest amplitudes, and correlated negatively with FEV1 (r = -0.25, p = 0.01). Subjects with asthma (n = 8) had greater variations. In the 109 nonasthmatics, greater variability was observed in subjects with wheeze apart from colds, breathlessness, or hay fever; the average amplitude was greater in reactors than in nonreactors to methacholine (16.9% versus 9.3%, p less than 0.001). The subjects with excessive PEF variability were all methacholine reactors, but they were only a subgroup of the reactors. These results provide evidence that excessive PEF variability is an indicator of bronchial hyperresponsiveness to methacholine in a population sample.

Distribution of peak expiratory flow variability by age, gender and smoking habits in a random population sample aged 20-70 yrs

“…Mean morning PEFs are lower than mean afternoon PEFs. These results confirm the findings reported by other investigators (8,(13)(14)(15)17). PEF variability, expressed as amplitude % mean, has a normal distribution after logtransformation, whereas day-to-day variation of morning PEF is not normally distributed and this remains so after log-transformation.…”

“…3), testing was performed on log 10 -transformed data. The mean values of the amplitude % mean in the current population were lower than those described in previous studies [14,17,18]. Females had a significantly higher amplitude % mean than males (ANCOVA; p=0.022; adjusted for age, height and pack-years).…”

“…1). This pattern confirms the phenomenon of a training-effect [4,17]. Therefore, the data from day 1 were excluded from the analyses.…”

“…Twice daily PEF measurements are regularly used in general and clinical practice to monitor asthmatic patients, and PEF meters are considered useful devices to screen for asthma in a random population. Two epidemiological studies have shown PEF variability to be larger when hyperresponsiveness is present [3,17].…”

“…Moreover, PEF variability can be assessed in all subjects, including those who would not have been allowed to perform a challenge test because of low pulmonary function, respiratory symptoms, cardiovascular disease or drug therapy. Studies on PEF variability in patients [9] and in occupational populations [17], and in their families [8], have given information on the feasibility and reliability of measuring peak flow at home and at work in these selected groups.…”