The peak expiratory flow (PEF) is used in the evaluation of airway obstruction, particularly in patients with asthma. The equations proposed by Nunn and Gregg can be used to estimate a patient's expected PEF for age, gender and height.
Patient selection:
(1) Adult men and women from 15 to 85 years of age
(2) Lifelong non-smoking was the criterion used to determine "normality" in PEF.
predicted peak expiratory flow in L/min =
= EXP (X)
X for men =
= (0.544 * LN(age in years)) - (0.0151 * (age in years)) - (74.7 / (height in cm)) + 5.48
X for women =
= (0.376 * LN(age in years)) - (0.0120 * (age in years)) - (58.8 / (height in cm)) + 5.63
patient's observed PEF as percent of predicted =
= (observed PEF) / (predicted PEF) * 100
Limitations:
• "Normalcy" is affected by many variables.
• The effect of race was not included in the evaluation.
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