In normal individuals, approximately what fraction of the VT is wasted ventilation (does not par-ticipate in gas exchange)?

a. One-third of the tidal volume
b. Two-thirds of the tidal volume
c. One-half the of tidal volume
d. One-quarter of the tidal volume

ANS: A
In the healthy adult, physiologic dead space is approximately one-third of the tidal volume.