Serial Lung Function Variability Using Four Portable Logging Meters

Abstract

Objective. Portable lung function logging meters that allow measurement of peak expiratory flow (PEF) and forced expiratory volume in 1 second (FEV1) are useful for the diagnosis and exclusion of asthma. The aim of this study was to investigate the within and between-session variability of PEF and FEV1 for four logging meters and to determine the sensitivity of meters to detect FEV1 and PEF diurnal changes. Methods. Thirteen assessors (all hospital staff members) were asked to record 1 week of 2-hour PEF and FEV1 measurements using four portable lung function meters. Within-session variability of PEF and FEV1 were compared for each meter using a coefficient of variation (COV). Between-session variability was quantified using parameter estimates from a cosinor analysis which modeled diurnal change for both lung function measures and also allowed for variation between days for individual sessions. Results. The mean within-session COV for FEV1 was consistently lower than that for PEF (p < 0.001). PEF showed a higher but not significantly different (p = 0.068) sensitivity for detecting diurnal variation than FEV1. PEF was also slightly more variable between days, but not significantly different than FEV1 (p = 0.409). PEF and FEV1 diurnal variability did not differ between the 4 meters (p = 0.154 and 0.882 respectively), but within-session FEV1 COV differed between meters (p = 0.009). Conclusion. PEF was marginally more sensitive to within-day variability than FEV1 but was less repeatable. Overall, differences between the 4 meters were small, suggesting that all meters are clinically useful.