Under which of the following conditions would you postpone a diffusing capacity test?

1. Just before the test, the patient smoked two cigarettes.
2. Just before the test, the patient had an episode of severe coughing.
3. Just before the test, the patient had a long wait at a busy bus stop.
a. 1 only
b. 1 and 3 only
c. 2 and 3 only
d. 1, 2, and 3

ANS: B
Performing the diffusing capacity on patients who have recently smoked a cigarette or who have been exposed to environmental carbon monoxide may hinder test validity.