If they're not, try again until you get three numbers that are similar.
The mean difference between per cent predicted PEF and per cent predicted FEV 1 in the subset of subjects with pre-BD airflow obstruction (FEV 1 /FVC < 5th percentile) was only 3.3 percentage points. The numbers should all be very close together if you're doing it right each time. The mean difference between the two largest values of pre-BD PEF was 0.45 ± 0.47 l/s (6.5 ± 6.5) and the 90th percentile was 1.01 l/s (14.4). This measure is called a 'peak expiratory flow,' or 'PEF.' Keeping track of your PEF, is one way you can know if your condition is in control or worsening 1. If not, write down the number on the meter at which the marker now rests (spring system) or that shows on your the screen (digital), if not logged electronically.
If you're using a digital meter, turn it on. If you're using a meter with a spring system (not digital), make sure the marker on your meter is at 0 or the lowest number.
