What is "peak flow" and how is it measured?

What is "peak flow" and how is it measured?

William Berger (Allergist and Immunologist) gives expert video advice on: How do I know if I have asthma?; Is asthma hereditary? and more...

Peak flow is a way to easily measure the maximal velocity of the air that goes through your lungs. A peak flow meter is a very simple device that has a little scale on the side, and when you hit your maximal velocity, or your peak flow, that number will be recorded. Peak flow usually in a scale of liters per minute. We know what normal peak flow should be at each age, and so if someone's peak flow is below that level, that sometimes will help us determine that they have airway obstruction, and then to see if they respond well to the medications. Peak flows are most often used to help patients monitor their own asthma at home. Very often doctors will give them zones at which their peak flows should be. There's a green zone, which is the normal level of peak flow, a yellow zone, which is the warning that there may be some trouble, and a red zone, where there are certain things that need to be done and a pending asthma attack may be occurring.