Ambulatory monitoring of peak expiratory flow. Reproducibility and quality control

Eighty-five children and 230 adults from a population study performed ambulatory peak flow readings three times a day for 1 to 2 weeks following a home visit. Three peak expiratory flow (PEF) readings were reported for each of 5,809 test sessions. Within each test session, the third maneuver most frequently (40% of the time) gave the highest PEF reading. This did not vary throughout the day. In subgroups of children and women with a history of asthma or asthma symptoms (hereinafter referred to as "asthma"), the first maneuver during the evening test sessions more frequently gave the highest readings. However, maneuver-induced bronchospasm occurred during less than 5% of the test sessions in both subjects with asthma and in other subjects. The within test session PEF reproducibility was good: overall, the highest and second highest reading matched within one division (10 L/min) 73% of the time and within 30 L/min (9% of the reading) 95% of the time. The best reproducibility was noted after the first two days of testing, during evening and bedtime test sessions (vs morning), and in girls and men. In the group with at least 2 weeks of testing, the coefficient of repeatability (CR) for the week-to-week PEF lability index was 10% for healthy adults and 17% for healthy children. As expected, repeatability was not as good for adults with asthma (CR = 17%) and children with asthma (CR = 28%).