Diurnal variation of PEF and its use in epidemiological studies

Diurnal variability in peak expiratory flow (PEF) has been an accepted clinical method in the management of asthma and the evaluation of occupational asthma. In this paper, the basis for this usage together with other clinical and epidemiological applications is discussed. The measured characteristics of PEF diurnal variability are described in asthmatics and asymptomatic subjects, showing the greater variability in asthmatics, and the "morning dip" related to circadian rhythm. PEF measured by pneumotachograph and the mini-Wright meter are shown to be in good agreement, but PEF measured by the latter and other small PEF meters is different in terms of absolute values, and both intraindividual variability within test sets and diurnally. The use of PEF meters, and the daily diaries in which the subject or patient records PEF and related factors are described.