APPLICATION OF PEAK EXPIRATORY FLOW IN EPIDEMIOLOGIC STUDIES OF OCCUPATION

The oldest tests of pulmonary mechanics are those based on spirometry. These tests measure either expired volume as a function of time or fl ow rate as a function of lung volume. These indirect measures of mecha nics, however, are difficult to interpret in individuals because resul ts are influenced by airway caliber, elastic recoil, air volume, muscl e power, and cooperation. Yet, the fact that they are technically simp le to perform, reasonably reproducible, and provide summary informatio n about pulmonary function has led to their widespread application in both the clinical setting and in the epidemiologic study of pulmonary disease. The most polyvalent of the tests, based on the maximum forced expiratory effort from volume-time curves, are the forced expiratory volume in the first second (FEV1) and the forced vital capacity (FVC). These tests have been used successfully to describe normal lung funct ion, to explore the process of aging in the lung, and to measure compr omised function both in individuals and in populations. The American T horacic Society (ATS) has published detailed guidelines for their coll ection and use.1 The use of these tests in field studies, however, has been somewhat limited by the need for rather cumbersome equipment wit h complex requirements for calibration. Over the years, efforts have b een directed at developing measures and measurement tools which are si mple, easy to use, and highly portable. One of these, the peak expirat ory flow (PEF), has been used for more than a century in clinical sett ings to assess pulmonary function. Practical use of the PEF has increa sed in both clinical and epidemiologic settings since the development of the Wright Peak Flow Meter in 1959(48) and its more portable and le ss expensive form, the mini-Wright meter. Wright noted that although t he PEF had initially been regarded as a more convenient. but substanda rd, method of measuring FEV1, his evidence suggested it was more stabl e and reproducible than had been thought. Wright also raised the possi bility that PEF might become a useful lung function parameter in its o wn right. The PEF rate is defined as the maximum flow which can be sus tained for a period of 10 ms during a forced expiration starting from total lung capacity. As such, it is a measure of the initial flows in a forced expiration and is a reflection of at least lung recoil and re sistance of the larger airways. In this review, the current uses of pe ak flow measurements are described as well as recent evidence suggesti ng that the measurement may have the potential for expanded applicatio n, particularly in epidemiologic studies of environmental hazards. Sin ce the recent attention to PEF has focused on the physiologic signific ance of patterns of short-term change over the day or week, this revie w will concentrate on variation in PEF.