The pulmonary diffusing capacity refers to the gas exchange between the alveoli and the pulmonary capillary blood.
Crapo and Morris (1981)
ages: 15-91 years
diffusing capacity in males =
= (0.416 * (height in cm)) - (0.219 * (age in years)) - 26.34
diffusing capacity in nonsmoking males =
= (0.410 * (height in cm)) - (0.210 * (age in years)) - 26.31
diffusing capacity in females =
= (0.256 * (height in cm)) - (0.144 * (age in years)) - 8.36
diffusing capacity in nonsmoking females =
= (0.282 * (height in cm)) - (0.157 * (age in years)) - 10.89
• The diffusing capacity is reported in mL of CO (at STPD) per minute per mm Hg.
• The first equation in the pair for each gender is from Table 2 (page 186), the second is from Table 4 (page 187).
• Although the authors list equations corrected for hemoglobin in Table 2 (page 186), patient hemoglobin is not a factor. I would use the general equation to estimate the diffusing capacity, then use the equations in 08.03.03 to adjust.
• The study was done in Utah at an altitude of 1400 meters, while the other below were done close to sea level.
Teculescu (1970) for Nonsmokers
ages: 19-67 years
= (0.333 * (height in cm)) - (0.298 * (age in years)) - 12.26
Salorinne (1976) for Nonsmokers
ages: 20-69 years
= (0.142 * (height in cm)) - (0.232 * (age in years)) + 16.3
= (0.219 * (height in cm)) - (0.115 * (age in years)) - 5.97
Frans (1975) for Nonsmokers
ages: mean 38.5, standard deviation 11.7 years
= (0.285 * (height in cm)) - (0.14 * (age in years)) - 10.3
• The table in Crapo and Morris have the intercept as +10.3, but this gives values much higher than the other estimates.
Hall (1979) for Nonsmokers
ages: 27-74 years
= (0.283 * (height in cm)) - (0.185 * (age in years)) - 8.28
Observed as Percentage of Predicted
diffusing capacity as percent of predicted =
= (measured diffusing capacity) / (predicted diffusing capacity) * 100
Percent of Predicted
61 - 80%
40 - 60%
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Purpose: To predict a patient's diffusing capacity for age and gender, then compare it to the actual measured value.
Objective: other testing