Reference equations used to predict pulmonary function. Survey at institutions with respiratory disease training programs in the United States and Canada.

Adult respiratory disease training programs in the United States and Canada were surveyed to determine which reference equations were used to predict normal pulmonary function and how ethnic differences were approached. Replies from 139 of the 180 (77.2 percent) institutions surveyed were received and evaluated. Surprisingly few studies account for most of the equations in use: three studies account for 85 percent of the spirometric equations, two for 83 percent of the lung volume equations and five for 84 percent of the diffusing capacity equations. Although there are no definite data, the form of many of the replies suggests that equipment default settings may influence the selection process. Of those responding to the ethnic difference question, 53 percent of institutions applied no correction for ethnic differences. There was no consistent pattern to the method of correction among those who did.