DEVELOPMENT OF AN ACCURATE PORTABLE RECORDING PEAK-FLOW METER FOR THEDIAGNOSIS OF ASTHMA

This article describes the systematic design of an electronic recordin g peak expiratory flow (PEF) meter to provide accurate data for the di agnosis of occupational asthma. Traditional diagnosis of asthma relies on accurate data of PEF tests performed by the patients in their own homes and places of work. Unfortunately there are high error rates in data produced and recorded by the patient, most of these are transcrip tion errors and some patients falsify their records. The PEF measureme nt itself is not effort independent, the data produced depending on th e way in which the patient performs the test. Patients are taught how to perform the test giving maximal effort to the expiration being meas ured. If the measurement is performed incorrectly then errors will occ ur. Accurate data can be produced if an electronically recording PEF i nstrument is developed, thus freeing the patient from the task of reco rding the test data. It should also be capable of determining whether the PEF measurement has been correctly performed. A requirement specif ication for a recording PEF meter was produced. A commercially availab le electronic PEF meter was modified to provide the functions required for accurate serial recording of the measurements produced by the pat ients. This is now being used in three hospitals in the West Midlands for investigations into the diagnosis of occupational asthma. In inves tigating current methods of measuring PEF and other pulmonary quantiti es a greater understanding was obtained of the limitations Of current methods of measurement, and quantities being measured. It is now possi ble to define the quantities that need to be measured for accurate pul monary diagnosis and the requirements of future instrumentation to mak e these necessary measurements. We are now in the process of developin g this new instrumentation.