Peak Flow - EN 23747

EN 23747 Standard has now been harmonised by ISO 23747 Standard. Website to be updated shortly.

New Peak   Expiratory Flow Standard


Background & Summary

How will the change affect me as a:

Background & Summary

Peak Flow Meter
"The Original Wright Peak Flow Meter" - Standard and Low Range versions

Peak flow meters play an important role in the management of asthma  for a large number of patients, by indicating the how narrow or open the airways are.  Peak flow readings are higher when patients are well, and lower when the airways are constricted.

The measurement of peak expiratory flow (PEF) 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 1950's, 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 Europe and the World.

How accurate are peak flow meters?
As a medical instrument, one would expect that all meters would be accurate; however scientists and medical researchers have noted that certain brands of peak flow meters give incorrect readings, when compared to reference testing standards, and suggested that there were two reasons for this:

  1. The meter's design produced inaccurate readings.
  2. The meter's scale was not as accurate as it could be

Many professionals use  peak expiratory flow  (P.E.F.) readings to aid decisions about treatment, and many patients rely on their peak flow meter to act as a marker for their disease - scientists became concerned that inaccurate readings may result in patients being treated less than optimally.

Since 1993, a group of European scientists have researched the problems and possible solutions, and in 2003, a new European Standard (EN 23747 ) for such instruments was published.  The new standard sets minimum acceptable levels for accuracy, repeatability and general performance, and defines a new 'scale' for P.E.F. readings - thereby addressing the two major faults with the meters previously available.  The new standard also has the advantage that readings are similar to those obtained from conventional spirometers, due to the new scale being based on 'absolute' airflows.

Peak flow meters that use the new  'E.U.' P.E.F. scale will become available in 2004, and only designs that can confirm to the strict standards within the EN 23747  definition can claim to be compliant.

It is known already that certain brands of peak flow meter, previously thought to have acceptable accuracy, have not been able to meet the more stringent accuracy requirements of the new tests.



Peak Flow Meters...Scientists introduce a new EU standard to overcome errors in asthma monitoring.

'With many of the types of meters examined it is the scale that is not accurate and this can quite easily be rectified. However the latest research has shown that some meters have more fundamental inaccuracies that are not detected by current standards. The new EU standard will prevent these meters from being available'

(Web link to summary of research that tested different peak flow meters for accuracy)


Patients and Healthcare Professionals using the 'Mini-Wright' brand of peak flow meter can be reassured that this meter has already been shown to comply with the accuracy requirements, and EU-scale Mini-Wrights that conform to the EN 23747  standard will be available from Clement Clarke International Ltd., and distributors of our products in countries across Europe.

EU EN 23747 Peak Flow Meter
'The new EU-Scale Mini-Wright Peak Flow Meter' 
compliant with EN 23747 Standard

When will the new peak flow meters be available?
The new EU-Scale meters will be introduced in the U.K. from 1st September 2004, as a replacement for the peak flow meters that presently are reimbursed through the Drug Tariff's Specification 51.  Wright-scaled meters will be phased out of use from this date onwards.

Within the rest of Europe, each country will decide when to change from the old scale to the new EU-Scale; new meters will be available throughout Europe from 2004 onwards.

N.B. The introduction of a new P.E.F. scale in Europe does not affect the United States or other countries, unless they have been using Wright-scale instruments.  The A.T.S. (American Thoracic Society) scale meter will remain unchanged. Click here to see which Mini-Wright you are using

Low range meters - an omission from the EN 23747 standard?
The EN 23747 Standard has been welcomed by many, and will improve the value of P.E.F. readings in the diagnosis and management of asthma.  Unfortunately, the new Standard has failed to recognise the value of  'low range' peak flow meters - those meters that have been requested by asthma  professionals specifically for those with peak flow readings that never go above 400 l/min.  Children, the elderly, and those with severe asthma have received low range Mini-Wrights for many years, but the new standard requires all P.E.F. meters to read between 60 and 800 l/min.

Mini-Wright Peak Flow MeterEN 23747 Peak Flow
The original Wright low range meter, and the new EU scale Mini-Wright AFS low range

Clement Clarke have researched the value of Low Range peak flow meters, and as of 1st June 2004, will make a Low Range Mini-Wright meter available, that complies with all aspects of the new EN 23747 Standard  - with the exception that the upper limit of its readings will be 400 l/min.

Patients and professionals who have previously used a low range meter can be reassured that even though a change to the new EU-scale will occur, they will still be able to request a meter designed more specifically for their individual needs.

Multiple patient use - how do we protect against cross-infection?
The original use of the Mini-Wright meter was in chest clinics, measuring the lung function of multiple patients in Hospitals and Surgeries across the country.  For over 20 years the Mini-Wright has been the only peak flow meter to feature an integral one-way valve that prevents patients from inhaling through the meter during use.

More recently, Clement Clarke have become the first company to validate multiple-patient cleaning instructions (available at, which provide recommendations for the use of the instrument by more than one patient.

The Mini-Wright is suitable for both single-patient use, and multiple-patient use, provided the respective cleaning instructions are followed.  In addition, disposable cardboard one-way mouthpieces are available for other brands of peak flow meter (which do not have the inbuilt protection of the Mini-Wright design).


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