A peak flow meter is a small device that you blow into. It measures the fastest rate of air (airflow) that you can blow out of your lungs. It records airflow in litres per minute(L/min) and provides you with a score, which is called peak expiratory flow rate (PEFR). Your doctor may prescribe a peak flow meter for you if you have asthma. There are different brands of peak flow meter. They all do the same job.
This is a companion discussion topic for the original article at https://patient.info/chest-lungs/asthma-leaflet/asthma-peak-flow-meter