Abstract

Background The aim of this study was to investigate the difference between encouraged and self-recorded peak expiratory flow (PEF) with unobserved readings and to investigate any long-term changes in PEF self-recording Method Patients were trained in the PEF technique and asked to keep 2-hourly PEF records until the next clinic visits. The patients PEF were then rechecked at the second clinic visit by a series of two unobserved, an observed and an encouraged PEF measurement. A subgroup of patients were reassessed at a third clinic visit. Results Forty-one patients produced serial PEF recordings. Significant differences between unobserved and encouraged readings were detected; there was a mean decrement of 21 litres/min and limits of agreement suggested that the decrement could be as high as 60 litres/min. Visual and statistical analysis of the serial PEF provided showed a consistent deterioration in PEF over the record in 54% and 39% of cases, respectively. No significant differences were found in the subgroup who attended a third clinic visit. Conclusion The results suggest that significant inaccuracies in unobserved PEF readings can occur between clinic visits and this can be reflected as a consistent deterioration in some. This should be kept in mind when interpreting self-recorded PEF measurements. Re-evaluation at the third visit following the retraining effect of the second visit on PEF technique appears to reduce inaccuracies. It is believed that PEF technique should be re-evaluated at each clinic visit.

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