Lung Volume Definitions

Question 1

tidal volume (VT)

Answer 1

air in/out of lungs in single respiratory cycle at rest

Question 2

what is minute ventilation (MV) and the normal amount?

Answer 2

total air inhaled and exhaled every minute
MV = breathing rate x tidal volume
6L/min healthy adult at rest

Question 3

alveolar ventilation rate (AV)

Answer 3

amount of air/min reaching alveoli
AV = 70% VT (350mL) x breathing rate

Question 4

what are the three volumes associated with forceful breathing?

Answer 4

inspiratory reserve volume (IRV)
expiratory reserve volume (ERV)
residual volume

Question 5

inspiratory reserve volume (IRV)

Answer 5

amount of air inhaled above the tidal volume

Question 6

expiratory reserve volume (ERV)

Answer 6

amount of air exhaled voluntarily after normal tidal volume

Question 7

residual volume

Answer 7

amount of air still in lungs even after ERV/maximal exhalation

Question 8

how do you calculate inspiratory capacity?

Answer 8

VT + IRV

Question 9

what is FRC and how do you calculate it?

Answer 9

the amount of air remaining in the lungs after a quiet respiratory cycle
FRC = residual volume + ERV

Question 10

what is vital capacity and how do you calculate it?

Answer 10

the amount of air which can be moved in/out of the lungs in one cycle
IRV + VT + ERV

Question 11

how do you calculate total lung capacity?

Answer 11

TLC = vital capacity + residual volume

Question 12

what is the definition of closing capacity?

Answer 12

the point at which dependent (bottom) small airways close during inspiration and expiration
the alveoli distal to the closed airways are not ventilated

Question 13

what should CC be higher/lower than normally?

Answer 13

higher than RV
lower than FRC
so small airways remain open during tidal breathing and gas exchange continues