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A peak flow meter is a small, hand-held device used to manage asthma by monitoring airflow through the bronchi and thus the degree of restriction in the airways. The peak flow meter measures the patient's maximum ability to expel air from the lungs, or peak expiratory flow rate (PEFR or PEF). Peak flow readings are higher when patients are well, and lower when the airways are constricted. From changes in recorded values, patients and doctors may determine lung functionality, severity of asthma symptoms, and treatment options.
The measurement of peak expiratory flow was pioneered by Dr. B.M. Wright, who produced the first meter specifically designed to measure this index of lung function. Since the original design of instrument was introduced in the late 1950s, and the subsequent development of a more portable, lower cost version (the 'Mini-Wright' peak flow meter), other designs and copies have become available across the world.
Scales
There are a number of non-equivalent scales used in the measurement of Peak Flow.
Graphs or tables are available of predcited normal values based on a person's gender, age and height. It should be noted that there is a wide natural variation in results from healthy test subjects.
- Wright scale - Predicted peak expiratory flow in normal adults using Wright-scale - Predicted peak expiratory flow in normal children using Wright-scale
- EN 13826 or EU scale - Downloadable PDF charts for adults and children using EU scale
- A.T.S. (American Thoracic Society) scale
In 2004 the UK switched from the original Wright scale to the newer, more accurate European scale. Limited information on convertiong between the scales exists.
Usage
The best of 3 readings is used as the recorded value of the Peak Expiratory Flow Rate. It may be plotted out on graph paper charts together with a record of symptoms. - for recording chart of PEFR readings
- Make sure the device reads zero or is at base level.
- Stand up if possible, otherwise sitting upright.
- Take as deep a breath as possible (but not through the meter).
- Place the meter in ones mouth. Close the lips tightly around the mouthpiece.
- Blow out as hard and as fast as possible (one to two seconds) without coughing, spitting or letting the tongue block the mouthpiece.
- The best of three recordings is used.
Users can record their peak flow before and 30 minutes after using the rescue inhaler. If their medicine is working an improvement should be seen in the peak flow reading.
See also
References
Footnotes
"Peak flow meter"