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Incoming links: Peak flow meter
Peak expiratory flow 2026-11-05
Peak expiratory flow is the greatest outward volumetric flow rate reached during a specified forced expiration. In an ideal continuous record,It has units of volume per time, commonly litres per second or litres per minute, whereas FEV1 and FVC are integrated volumes. The 2019 technical statement defines the peak from a maximal forced expiratory maneuver and specifies its reporting units.[ref]
Standardization of Spirometry 2019 Update by Brian L. Graham and others. Reported Values and Table 9
An original pair of triangular volumetric flow rate histories separates the quantities. Let numerical time be in seconds. One curve is L/s over ; the other is L/s over , followed by zero. Both expel 1 L in total and in the first second. Their peaks are nevertheless 2 and 4 L/s, or 120 and 240 L/min. Equal expired volume does not identify the highest volumetric flow rate.
The instrument history reflects the value of measuring that maximum directly. In 1959, Basil Martin Wright and C. B. McKerrow published a description of a portable instrument for maximum forced expiratory volumetric flow rate.[ref]
Maximum Forced Expiratory Flow Rate as a Measure of Ventilatory Capacity by Basil Martin Wright and C. B. McKerrow. BMJ 2, 1041–1046; PMID 13846051, published bylines B. M. Wright and C. B. McKerrow
The Wood Library-Museum's original-object catalogue identifies its Wright peak flow meter, records the author as B. M. Wright (Basil Martin), and describes the instrument's portability.[ref]Wright Peak Flowmeter at the Wood Library-Museum of Anesthesiology. Catalogue record, accession 1998-02-25-1, author identification and object description
A peak flow meter and a full spirometer record different amounts of information. A retained peak does not reconstruct the preceding waveform or total volume. Conversely, numerical differentiation and finite sensor response can affect a peak inferred from a recorded volume trace. Adequate temporal response, effort and the starting lung volume belong to the measurement definition. The primary standard connects early volumetric flow rate and the peak with maneuver effort and requires complementary waveform displays.[ref]
Standardization of Spirometry 2019 Update by Brian L. Graham and others. Equipment, Display; start of forced expiration
The triangular examples are mathematical constructions, not reference values or a diagnostic rule. Comparing peak measurements requires comparable units, maneuvers and instrument response rather than treating a maximum as a complete description of lung function.