This PEF program calculates the diurnal variation in PEF values, the increase in PEF rate recorded in the bronchodilatation test (in percentages), and determines action treshold PEF levels in supervised self-care.
The patient usually performs a series of PEF measurements twice daily, in the morning and in the evening, usually three sequential blows at a time. Series of blows may also be performed at other times of the day as and when respiratory symptoms do occur. The best PEF value of each series of blows is used in the calculator. Instructions for PEF measurements: see Pulmonary Function Tests.
CalculatorDiurnal variation: If the difference between the highest and lowest values divided by their mean exceeds 20% (and is at least 60 l/min) the diagnosis of asthma is strongly supported.
Bronchodilatation test: The difference of the value obtained 10 to 15 minutes after the inhalation of a beta2-sympatomimetic drug and the value obtained before the inhalation as a percentage from the pre-inhalation value. Significant PEF increases suggesting the diagnosis of asthma are as follows:
Action treshold levels: If the morning PEF is under 85% of optimum level, double the dose of inhaled steroids. If the the morning PEF is 50-70% of optimum level start oral steroids for one week, and consult doctor or nurse by phone. If the PEF value is below 50% of optimum level, visit emergency department.
Reference value: When the patient's sex, age and height are fed, the calculator will give the reference values according to both the old Wright-McKerrow scale 1 and the current EU standard (EN 13826) 2. The different PEF meter types are distinguished by the color of the scale: PEF meters conforming to the EU standard have a scale with blue text on a yellow background.
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