A peak flow meter is an inexpensive, pocket-sized device that
measures peak expiratory flow (PEF), or how much air a person can exhale. To
measure PEF, the person takes a deep breath and then blows (huffs) into a tube
on the peak flow meter as hard and as fast as possible.
To get the most accurate PEF, the peak flow meter should be used
three times and the best results recorded. PEF is lowest in the early morning
and highest in the afternoon.
Results obtained by using a peak flow meter are not as accurate as
those obtained by using spirometry, another test used to measure lung function.
But the peak flow meter can be used at home, while spirometry has to be
done in a doctor's office.