Serial lung function variability using four portable logging meters

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

Two variants of occupational asthma separable by exhaled breath nitric oxide level.

UNLABELLED Exhaled nitric oxide (FE(NO)) has been used as a marker of asthmatic inflammation in non-occupational asthma, but some asthmatics have a normal FE(NO). In this study we investigated whether, normal FE(NO) variants have less reactivity in methacholine challenge and smaller peak expiratory flow (PEF) responses than high FE(NO) variants in a group of occupational asthmatics. METHODS We measured FE(NO) and PD(20) in methacholine challenge in 60 workers currently exposed to occupational agents, who were referred consecutively to a specialist occupational lung disease clinic and whose serial PEF records confirmed occupational asthma. Bronchial responsiveness (PD(20) in methacholine challenge) and the degree of PEF change to occupational exposures, (measured by calculating diurnal variation and the area between curves score of the serial PEF record in Oasys), were compared between those with normal and raised FE(NO). Potential confounding factors such as smoking, atopy and inhaled corticosteroid use were adjusted for. RESULTS There was a significant correlation between FE(NO) and bronchial hyper-responsiveness in methacholine challenge (p = 0.011), after controlling for confounders. Reactivity to methacholine was significantly lower in the normal FE(NO) group compared to the raised FE(NO) group (p = 0.035). The two FE(NO) variants did not differ significantly according to the causal agent, the magnitude of the response in PEF to the asthmagen at work, or diurnal variation. CONCLUSIONS Occupational asthma patients present as two different variants based on FE(NO). The group with normal FE(NO) have less reactivity in methacholine challenge, while the PEF changes in relation to work are similar