Factors affecting the peak expiratory flow rate in children.

Standing height and peak expiratory flow rate (PEFR) were measured in 339 British schoolchildren aged 7-16 years. Enquiry was made into a past history of wheeze or atopy, a family history of asthma or atopy, or a cold within the preceding 2 weeks. A strong correlation was found between PEFR and height, expressed by the equation PEFR = 5.640 Ht - 472.5 (r = 0.89). Neither a recent cold nor a positive personal or family history of wheeze or atopy had any significant effect on the regression equation. Sex was also unimportant. Further examination of the data revealed that age had an effect on peak expiratory flow rate independent of height. The effect of age was linear in girls and curvilinear in boys. Five hundred and sixty-nine Greek schoolchildren were also studied and similar age effects were found on the regression of peak expiratory flow rate on height. The implication of these findings is that any population study of peak expiratory flow rates in children should ensure a normal age distribution at each height interval. Significant error in the prediction of the PEFR will result if the effect of age is ignored, particularly in pubertal boys.