To the Editor.—In two excellent reports Dr. Chai and co-workers1,2 relied on the day-to-day use of peak expiratory flow rate (PEFR) as an early warning indicator of attacks and as a means of adjusting drug doses for children institutionalized for chronic asthma. For the purposes indicated, they emphasize the frequent use of the PEFR measurement two to four times daily.
We find two problems with their recommendations. One relates to graphic representations without reference to age, sex, and height. For example, the rates in the patient used to illustrate one case1 did not exceed 200 liters/min during a two-week period of observation. This upper limit, while normal for a 6-year-old, would be abnormal for both males and females 7 years or older whose heights are in the 50th percentile.3 In their recent paper,2 Fig 2 indicates a top limit of 355 liters/min. This would be