Abstract

We aimed to assess changes in serial measurements of peak expiratory flow (PEF) in workers with occupational asthma (OA) due to metal-working fluid following control of microbiological contamination and use of respiratory protective equiptment.
Two hourly measurements of PEF were measured for 4 weeks before and after microbiological control in 24 workers with occupational asthma from one engine manufacturing factory, which resolved in 10 and persisted in 14 workers. The Oasys plotter (www.occupationalasthma.com) was used to generate the following indices; mean workday and restday PEF and diurnal variation ("days"; first reading at work to last reading before work the next day); area between mean hourly workday and restday PEF (area), Oasys score and Expert opinion. [Table 1] shows that the area between the mean restday and workday hourly readings was the most discriminating, and the mean diurnal variation the least discriminating variable between resolved and persisting OA.
At presentation those with persisting OA had larger reactions on workdays and less restday recovery than those who resolved. This together with the improvement following control in those with persisting OA suggests a single cause for the outbreak, rather than 2 causes, only one of which had been controlled.

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