PEAK FLOW CHARTS FOR PATIENTS WITH ASTHMA
Peak flow monitoring is recommended for some patients with asthma, in addition to monitoring of asthma symptoms and reliever use [1] .
Short-term monitoring (2-8 weeks) may be useful in some patients:
- To assist in the diagnosis or exclusion of asthma
- To help to identify asthma triggers
- To monitor response to a new treatment or after a change in dose (up or down)
- To calculate the “trigger point” for a written asthma action plan
Long-term monitoring may be needed in some patients:
- By patients with moderate to severe asthma who have frequent exacerbations, or have little warning of exacerbations
- By patients who are found to be “poor perceivers” of airway obstruction. These patients may be recognised by their inability to detect a large (>20%) rise in lung function after bronchodilator, or who do not develop symptoms in response to a large fall in lung function, e.g. during bronchial provocation test
- By patients who are anxious and tend to over-treat minor events
Peak flow data are most useful if they are displayed on a chart rather than just written down as a list [2] . Many different charts are available in Australia for recording peak flows. Research has shown that it is very important to use the same type of chart every time, so that both patient and doctor can recognise the patient’s patterns of variation [3] . On a stretched-out chart, even a severe exacerbation may appear mild, and the beginning of the exacerbation may be hard to recognise. On a chart which is compressed horizontally, it is easy to see when the peak flow falls below that patient’s usual range, and to see gradual rises or falls in peak flow [3] .
A new peak flow chart has been developed by Dr Helen Reddel and colleagues at the Woolcock Institute of Medical Research and the Asthma Centre at Royal Prince Alfred Hospital. The chart was designed to be user-friendly for patients when they are entering their peak flows on the chart, and also to assist both patients and doctors in identifying changes in lung function. There are two versions of the chart, one for 2 months, and one for 12 months. Both charts include patient-friendly instructions. The chart and instructions have been extensively pilot tested, and are in use around Australia and in the United Kingdom. The scientific basis for the design of the chart, and a comparison of some of the currently-available peak flow charts, are included in a research paper that was published in Thorax in 2005, which may be accessed free of charge here or through the Thorax website.
This research was funded by the Asthma Foundation NSW and the Woolcock Institute of Medical Research.
1. National Asthma Council Australia, Asthma Management Handbook. 2006, Melbourne: National Asthma Council Australia Ltd.
2. Turner-Warwick, M., On observing patterns of airflow obstruction in chronic asthma. British Journal of Diseases of the Chest, 1977. 71: p. 73-86.
3. Reddel, H.K., S.D. Vincent, and J. Civitico, The need for standardisation of peak flow charts. Thorax, 2005. 60(2): p. 164-167.
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