Although some have suggested that routine self-monitoring of peak flow in patients with asthma does not improve morbidity or mortality,¹ some studies have indicated that, when used in association with a self-management plan, routine measurement of peak expiratory flow can be effective in reducing symptoms of asthma and improving lung function.²

Peak expiratory flow rate may also have a role in detecting patients with chronic obstructive pulmonary disease.³

Indications for peak flow recording⁴

Peak expiratory flow measurement is recommended for:

• Diagnosis:
  • Diurnal variability of peak expiratory flow rate greater than 20% for at least three days in a week for two weeks is typical of asthma.
  • Or improvement in peak expiratory flow:
    • 10 minutes after high-dose bronchodilator through a spacer.
    • After a six-week course of inhaled steroids.
    • After 14 days of 30 mg prednisolone.
  • Assessment of the response to treatment.
• Monitoring:
  • The use of peak flow recording in monitoring asthma must be part of an individual management plan for the patient.
  • Quality of life indicators may be as good as peak flow for predicting exacerbations:
    • Have you had any asthma symptoms during the day?
    • Any difficulty sleeping because of symptoms?
    • Has the asthma interfered with usual activities, e.g. work, school?
  • The patient must have a clear understanding of the use and interpretation of peak flow results, and understand how to use the results to adjust treatment and seek medical advice when necessary.
• Adults should have their peak flow reassessed every 5 years, to monitor the decrease in lung function with age.

Method⁴

• The patient can be standing or sitting down.
• Ensure that the marker on the scale is set to zero.
• After a full breath in, the patient should then breathe out with a rapid forced maximal expiratory puff through the mouth and in to the meter.
• Repeat to give a total of three readings (maximum pause of 2 seconds in-between) and take the best reading as the result.

Self-management plans⁴

• Written personalised action plans as part of self-management education have been shown to improve health outcomes for people with asthma.
• They are very important for all patients with asthma, but especially those with moderate to severe disease.
• Self-management plans improve outcomes such as self-efficacy, knowledge and confidence.
• The National Asthma Campaign provides resource materials useful for providing patients with a self-management plan.⁵ These resource materials can be downloaded.

Peak flow measurement scale

The European Commission adopted a standard (EN 13826) for peak flow meters in 2004. This replaced the older Wright scale - which had been previously noted to over-represent changes in airflow in the mid-range, and under-represent changes in the low and high ranges.⁶