Peak flow diary in asthma

Diary record of peak expiratory flow (PEF) from an asthmatic patient over a one week period. The patient recorded PEF three times a day at waking (AM), noon (N) and upon retiring (PM). The red zone is set at 50 percent of the personal best, whereas the yellow is from 50 to 80 percent and the green zone is >80 percent. Notice the reproducible morning (AM) falls in PEF characteristic of the patient with nocturnal asthma. Also note the improvement in PEF as glucocorticoids are added to the treatment regimen.