Reference Equations Used to Predict Pulmonary Function
The linear and nonlinear regression techniques have been used to generate equations to predict “normal values” since Hutchinson first provided a quantitative index of pulmonary function based on measurements of vital capacity in more than 2,000 healthy men in 1846. The increasing importance of pulmonary function testing in diagnosing and managing lung disease and assessing impairment has required more accurate definitions of normal. Innovations in technology and equipment, standardization of procedures, and changing concepts of normality have stimulated further studies of healthy subjects and there is now a large number of different regression equations from which to choose. In response to a frequently asked question about which equations are actually being used, we surveyed institutions in the United States and Canada with training programs in adult respiratory disease to determine which equations are used and what attention is paid to ethnic differences.
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