Predictive Normal Values have been calculated for women and men of different ages and heights, and have been adapted (with agreement from the original Authors) for use with the new EU Scale / ISO23747 peak flow meters.
As a general rule, if your average reading is frequently one-third or more below your best it may mean that your asthma is not controlled.
If you ever have difficulty breathing or cannot obtain relief with a reliever inhaler, you should seek emergency help.
