 ### Description

The forced expiratory flow rate (FEF) at different percentages of the vital capacity in adults can be predicted based on physical characteristics.

NOTE: Some of these equations (Knudson at FEF25% and Cherniack at FEF75%) give discrepant results. I have checked the equations versus the sources and do not see an obvious transcription error. It is interesting to note that FEF25% for Knudson is close to the value for Cherniack at FEF75% and vice versa. The coefficients for both sets of equations move in opposite ways (increase from 25-75% for Cherniack, decrease for Knudson). The authors may be using different definitions, so that FEF75% Cherniack is equivalent to FEF25% Knudson.

FEF25% in liters per second for White males 15-79 years (Cherniack, 1972) =

= (0.036 * (height in inches)) - (0.041 * (age in years)) + 1.984

FEF25% in liters per second for White females 15-79 years (Cherniack, 1972) =

= (0.023 * (height in inches)) - (0.034 * (age in years)) + 2.216

FEF25% in liters per second for White males 25-85 years (Knudson, 1976) =

= (0.088 * (height in cm)) - (0.035 * (age in years)) - 5.618

FEF25% in liters per second for White females 20-88 years (Knudson, 1976) =

= (0.043 * (height in cm)) - (0.025 * (age in years)) - 0.132

FEF50% in liters per second for White males 15-79 years (Cherniack, 1972) =

= (0.065 * (height in inches)) - (0.031 * (age in years)) + 2.403

FEF50% in liters per second for White females 15-79 years (Cherniack, 1972) =

= (0.062 * (height in inches)) - (0.023 * (age in years)) + 1.426

FEF50% in liters per second for White males 25-85 years (Knudson, 1976) =

= (0.069 * (height in cm)) - (0.015 * (age in years)) - 5.40

FEF50% in liters per second for White females 20-88 years (Knudson, 1976) =

= (0.035 * (height in cm)) - (0.013 * (age in years)) - 0.444

FEF50% in liters per second for White males 18-86 years (Roberts, 1991) =

= (-0.044 * (age in years)) + 6.456

FEF50% in liters per second for White females 18-86 years (Roberts, 1991) =

= (-0.038 * (age in years)) + 5.556

FEF75% in liters per second for White males 15-79 years (Cherniack, 1972) =

= (0.090 * (height in inches)) - (0.199 * (age in years)) + 2.726

FEF75% in liters per second for White females 15-79 years (Cherniack, 1972) =

= (0.069 * (height in inches)) - (0.019 * (age in years)) + 2.147

where:

• The factor for age is given as 0.1987 in the original table, but this gives negative results at higher ages. The 0.019 is from Wanger et al.

FEF75% in liters per second for Hispanic males 25-80 years (Coultas, 1976) =

= (0.0145 * (height in cm)) - (0.0346 * (age in years)) + 3.1578

FEF75% in liters per second for Hispanic females 25-80 years (Coultas, 1976) =

= (0.00786 * (height in cm)) - (0.0240 * (age in years)) + 1.2749

where:

• The factor for height in cm for Hispanic females is given as 0.7086, but this gives absurd results. Even the equation used gives results different from the other authors.

FEF75% in liters per second for White males 25-85 years (Knudson, 1976) =

= (0.044 * (height in cm)) - (0.012 * (age in years)) - 4.143

FEF75% in liters per second for White females 20-88 years (Knudson, 1976) =

= (-0.014 * (age in years)) + 3.042