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.

Keywords :

• forced expiratory volume in 1 second
• peak expiratory flow
• asthma
• diurnal variation
• cosinor analysis
• coefficient of variation