You are examining the expiratory flow tracing during the patient's forced vital capacity (FVC) maneuver. At what point during the exhalation can you generally begin to see flow from the bronchioles?

a. Beyond 30%
b. Beyond 50%
c. Beyond 70%
d. Beyond 90%

ANS: B
Any flow measured in the first half of the FVC reflects on the bronchi; any flow measured be-yond 50% of the vital capacity reflects on the bronchioles.