Ganong's Review of Medical Physiology, 23rd Edition

CHAPTER 35

Pulmonary Function 593

LUNG VOLUMES

The amount of air that moves into the lungs with each inspira-
tion (or the amount that moves out with each expiration) is
called the
tidal volume.
The air inspired with a maximal inspira-
tory effort in excess of the tidal volume is the
inspiratory reserve
volume.
The volume expelled by an active expiratory effort after
passive expiration is the
expiratory reserve volume,
and the air
left in the lungs after a maximal expiratory effort is the
residual
volume.
Normal values for these lung volumes, and names ap-
plied to combinations of them, are shown in Figure 35–7. The
space in the conducting zone of the airways occupied by gas that
does not exchange with blood in the pulmonary vessels is the
respiratory dead space.
The
forced vital capacity (FVC),
the

largest amount of air that can be expired after a maximal inspira-

tory effort, is frequently measured clinically as an index of pul-

monary function. It gives useful information about the strength

of the respiratory muscles and other aspects of pulmonary func-

tion. The fraction of the vital capacity expired during the first

second of a forced expiration is referred to as

FEV

1

(

formerly the

timed vital capacity) (Figure 35–8). The FEV

1

to FVC ratio

(FEV

1

/FVC) is a useful tool in the diagnosis of airway disease

(Clinical Box 35–1). The amount of air inspired per minute

(pulmonary ventilation, respiratory minute volume)

is nor-

mally about 6 L (500 mL/ breath

×

12 breaths/min). The

maxi-

mal voluntary ventilation (MVV)

is the largest volume of gas

that can be moved into and out of the lungs in 1 min by volun-

tary effort. The normal MVV is 125 to 170 L/min.

FIGURE 35–7
Lung volumes and capacity measurements. Top left:
A cartoon figure representing lung space divided into lung volumes.
Dead space refers to areas where gas exchange does not occur; all other spaces are defined in the accompanying table.
Top right:
Spirometer
recordings are shown with marked lung volumes and capacities. Table at bottom defines individual measurements and values from the top
graphs. Note that residual volume, total lung capacity, and function residual capacity cannot be measure with a spirometer.
(Right figure reproduced
with permission from Widmaier EP, Raff H, Strang KT:
Vander’s Human Physiology: The Mechanisms of Body Function
, 11th ed. McGraw-Hill, 2008.)

Inspiratory reserve

volume

Maximum possible inspiration

Tidal volume

Maximum

voluntary

expiration

Expiratory reserve volume

Residual volume

Functional residual capacity

Total lung capacity

Inspiratory

capacity

Vital

capacity

Expiration Lung volume

(ml) Inspiration

1000

2000

3000

4000

5000

6000

0

(^13)
4
8
2
5
7
6
Tidal volume (TV)
Inspiratory reserve volume (IRV)
Expiratory reserve volume (ERV)
Residual volume (RV)
Respiratory Volumes and Capacities for an Average Young Adult Male
Respiratory Volumes
Respiratory Capacities
Measurement
500 ml
3000 ml
1200 ml
1200 ml
Typical Value
Amount of air inhaled or exhaled in one breath during relaxed, quiet breathing
Amount of air in excess of tidal inspiration that can be inhaled with maximum effort
Amount of air in excess of tidal expiration that can be exhaled with maximum effort
Amount of air remaining in the lungs after maximum expiration; keeps alveoli inflated
between breaths and mixes with fresh air on next inspiration
Vital capacity (VC) 4700 ml Amount of air that can be exhaled with maximum effort after maximum inspiration
(ERV + TV + IRV); used to assess strength of thoracic muscles as well as
pulmonary function
Maximum amount of air that can be inhaled after a normal tidal expiration (TV + IRV)
Amount of air remaining in the lungs after a normal tidal expiration (RV + ERV)
Maximum amount of air the lungs can contain (RV + VC)
Definition
3500 ml
2400 ml
5900 ml
Inspiratory capacity (IC)
Functional residual capacity (FRC)
8 Total lung capacity (TLC)
3
2
4
5
7
6
1
IRV
TV
ERV
RV
Dead space