What conclusions can you draw from the following data, obtained from a 41-year-old man who admits to "occasional smoking" but otherwise reveals no past history of pulmonary problems?

ACTUAL PRED % PRED ACTUAL PRED % PRED
TLC 4.75 4.90 97% FVC 2.96 3.63 82%
FRC 2.31 2.21 105% %FEV1 82% 78%
RV 1.28 1.20 106% FEF200-1200 4.33 5.45 79%
VC 3.48 3.63 96% FEF25%-75% 1.95 3.37 58%

a. Results indicate small airway obstruction.
b. Results indicate generalized airway ob-struction.
c. Results indicate a restrictive lung disorder.
d. Results indicate a combined disease pro-cess.

ANS: A
Interpretation of the pulmonary function report: Interpretive strategies for pulmonary function testing abound. Most computer-based pulmonary function testing systems have algorithms in their software programs for computer-assisted interpretations of the pulmonary function report. A consensus for interpreting test results is growing. Table 20-8 summarizes pulmonary function changes that may occur in advanced obstructive and restrictive patterns of lung diseases, and Figure 20-16 presents a simple algorithm to assess pulmonary function test results in clinical prac-tice. When considering a pulmonary function report, the %FEV1/VC ratio is a good place to start, because it provides an initial focus as normal, restrictive, or obstructive impairment. When the %FEV1/FVC is less than the limit of normal (LLN), there is airway obstruction. When the %FEV1/FVC is greater than the LLN, there is no airway obstruction. The LLN %FEV1/FVC can be determined directly for various population using regression equations in Table 20-9 or simply estimated at 70%. If the %FEV1/FVC ratio is greater than the LLN or 70% and if the TLC is less than the LLN, often defined as less than 80% predicted normal, the patient has a restrictive im-pairment, according to this algorithm. The severity of the restriction is based on the percent pre-dicted or on the number of standard deviations below the LLN TLC according to Table 20-2. If the %FEV1/FVC ratio is less than 70%, the patient likely has an obstructive impairment; the se-verity of the obstruction is based on the percent predicted normal FEV1 according to Table 20-2. If the percent predicted normal DLCO is less than 80%, the patient has a diffusion impairment. Some laboratories also report the DLCO/VA ratio, which indexes the DLCO for lung volume measured during the single breath test. If the DLCO/VA ratio is also less than 80% of the in-dexed value, the cause of the diffusion impairment is considered within the lung, and if the DLCO/VA ratio is greater than 80% of the indexed value, the cause of the diffusion impairment is considered due to small lung volume.