Normal values are used in this text to construct predicted normal flow-volume curves.

The flow-volume curves are predicted on the basis of four predicted flow points and the predicted forced expiratory vital capacity (FVC). The value for peak expiratory flow (PEF) is plotted after 12.5% of the predicted FVC has been exhaled and connected to the zero flow-zero exhaled volume point by a straight line. Next, predicted flows after 25, 50, and 75% of the predicted FVC have been exhaled are plotted at their appropriate volumes. The PEF, forced expiratory flow after 25% of the FVC has been exhaled (FEF_{25}), FEF_{50}, and FEF_{75} are connected by straight lines. The FEF_{75} is also connected to the volume point at 100% of the predicted FVC at which flow is zero.

The equations listed in Table A-1 are used to predict the mean values of the various flows and of the FVC. Age (A) is in years, and standing height (H) is in centimeters or meters (H/100).

The sources of the equations that we use for predicting lung volumes, spirometry, and diffusing capacity are listed in Table A-2.

TABLE A-1. Equations for predicting FVC and various flows

**Appendix**

TABLE A-2. Sources of prediction equations

Total lung capacity

Miller A, Thornton JC, Warshaw R, et al. Single breath diffusing capacity in a representative sample of the population of Michigan, a large industrial state: Predicted values, lower limits of normal, and frequencies of abnormality by smoking history. Am Rev Respir Dis 127:270-277,1983.

**Spirometry**

Miller A, Thornton JC, Warshaw R, et al. Mean and instantaneous expiratory flows, FVC and FEV_{1}: prediction equations from a probability sample of Michigan, a large industrial state. Bull Eur Physiopathol Respir 22:589-597, 1986. ^{* 1 2 3 4 5 6}

**REFERENCES**

1. Polgar G, Promadhat V [eds]: Pulmonary Function Testing in Children: Techniques and Standards. Philadelphia: Saunders, 1971.

2. Knudson RJ, Lebowitz MD, Holberg CJ, Burrows B. Changes in the normal maximal expiratory flow-volume curve with growth and aging. Am Rev Respir Dis 127: 725-734,1983.

3. Miller A, Thornton JC, Warshaw R, et al. Mean and instantaneous expiratory flows, FVC and FEV1: prediction equations from a probability sample of Michigan, a large industrial state. Bull Eur Physiopathol Respir 22: 589-597, 1986.

4. Hsu KH, Jenkins DE, Hsi BP, et al. Ventilatory functions of normal children and young adults: Mexican-American, white, and black. I. Spirometry. J Pediatr 95:14-23, 1979.

5. Knudson RJ, Slatin RC, Lebowitz MD, Burrows B. The maximal expiratory flow-volume curve: Normal standards, variability, and effects of age. Am Rev Respir Dis 113: 587-600,1976.

6. Zapletal A, Motoyama EK, Van De Woestijne KP, et al. Maximum expiratory flow-volume curves and airway conductance in children and adolescents. J Appl Physiol 26: 308-316, 1969.