Peak expiratory flow

= maximal flow rate generated during a forced expiration

The expected normal value can be calculated based on age and height. Normal values in adults vary from 350 to 600 L/min. However, its measurement is effort-dependent and cannot be reliably done by young children. So, comparing the value you get in ED to the one in the table / formula is not extremely useful. But it is useful if compared to the patient’s best or if done in a serial manner:

– to assess response to asthma therapy

– to assess deteriorating neuromuscular function in patients where you expect deterioration of the neuromuscular function (eg snake bites that can cause paralysis / Guillain-Barre syndrome / cervical spine injuries)