Peak Flow Chart
A small proportion of people with asthma may benefit from peak flow monitoring.
This standardised peak flow chart allows the doctor and the person with asthma to recognise the pattern of that person's asthma over time and to identify exacerbations (flare-ups) early.
Measurement of peak expiratory flow gives an idea of how narrow or obstructed a person's airways are by measuring the maximum (or peak) rate at which they can blow air into a peak flow meter after a deep breath.
Peak flow monitoring helps measure how much, and when, the airways are changing.
Due to the wide range of ‘normal' values and high degree of variability, peak flow is not the recommended test to identify asthma. However, it can be useful in some circumstances.
A small proportion of people with asthma may benefit from regular peak flow monitoring. When monitoring is recommended, it is usually done in addition to reviewing asthma symptoms and frequency of reliever medication use.
When peak flow is being monitored regularly, the results may be recorded on a peak flow chart.
It is important to use the same peak flow meter every time.
Peak flow monitoring is not recommended for children under 12 years.
Reasons to monitor peak flow
Short-term monitoring (2-8 weeks) may be useful in some people:
- To assist in the diagnosis or exclusion of asthma, including occupational asthma
- To help to identify asthma triggers
- To monitor response to a new treatment or a change in dose (up or down)
- To calculate the "trigger point" for a written asthma action plan.
Long-term monitoring may be useful in some situations:
- For people with asthma who have frequent exacerbations (flare-ups)
- For people with moderate to severe asthma who have little warning of exacerbations
- For people with asthma who are anxious or tend to over-treat minor events
- For people with asthma who are ‘poor perceivers' of airway narrowing.
People with asthma who are ‘poor perceivers' have few symptoms when their airways narrow. They may be identified as:
- People who are unable to detect a large (>20%) rise in lung function after use of a bronchodilator
- People who do not develop symptoms in response to a large fall in lung function
People with under-treated asthma who have become used to chronically poor lung function.
Recording peak flow
Peak flow measurements are most useful if they are displayed on a chart or graph rather than just written down as a list.
A peak flow chart allows the doctor and the person with asthma to recognise the pattern of that person's asthma and see how it changes over time.
Many different charts are available in Australia for recording peak flow. Research has shown that the shape of the chart has an effect on how the pattern appears.
On a wide, stretched-out chart, even a severe exacerbation may appear mild, and the beginning of the exacerbation may be hard to recognise. On a compressed chart, it is easy to see when the peak flow falls below that person's usual range, and to recognise gradual rises or falls in peak flow.
It is very important to use the same type of chart every time so that measurements can be compared and patterns can be recognised.
Development of a new peak flow chart
Standardisation of peak flow charts is important to avoid confusion for those entering the measurements, and to allow development of pattern recognition skills by clinicians and patients. To this end, Associate Professor Helen Reddel and colleagues at the Woolcock Institute of Medical Research and the Asthma Centre at Royal Prince Alfred Hospital have developed this peak flow chart.
The chart has been designed to:
- Be user-friendly for entering peak flow measurements
- Allow easy identification of changes in lung function
The chart and instructions have been extensively pilot-tested, and are in use around Australia and in the UK. The scientific basis for the design of the chart and a comparison with some of the currently available peak flow charts was published in 2005 in the journal Thorax.
The Asthma Foundation NSW and the Woolcock Institute of Medical Research funded this research.
Peak flow chart download
The peak flow chart is available as a two-page document in PDF format that you can download here.
The first page includes easy-to-follow instructions for entering the peak flow measurements. The second page is a chart that holds 8 weeks of measurements. The pages should be printed single-sided for easy reference.
Print multiple copies of the second page if long-term monitoring is needed.
National Asthma Council Australia
- Lung function tests: information for consumers
- Lung function tests: information for health professionals
Asthma Management Handbook 2006. Melbourne: National Asthma Council Australia, 2006. See: Role of PEF monitoring
Pierce R, Johns DP. Spirometry: The Measurement and Interpretation of Ventilatory Function in Clinical Practice. Melbourne: National Asthma Council Australia, 2004. See: Mean predicted normal values.
Reddel HK, Marks GB, Jenkins CR. When can personal best peak flow be determined for asthma action plans? Thorax 2004; 59: 922-4. Available from: http://thorax.bmj.com/cgi/content/abstract/59/11/922
Reddel HK, Vincent SD, Civitico J. The need for standardisation of peak flow charts. Thorax 2005; 60: 164-7. Available from: http://thorax.bmj.com/cgi/content/abstract/60/2/164
Turner-Warwick M. On observing patterns of airflow obstruction in chronic asthma. Br J Dis Chest 1977; 71: 73-86.