Biomedical Engineering Reference
In-Depth Information
TABLE 3.3
Typical Lung Volumes for a Normal, Healthy Male
Lung Volume
Normal Values
10
3
m
3
(6,000 cm
3
)
Total lung capacity (TLC)
6.0
10
3
m
3
(1,200 cm
3
)
Residual volume (RV)
1.2
10
3
m
3
(4,800 cm
3
)
Vital capacity (VC)
4.8
10
3
m
3
(3,600 cm
3
)
Inspiratory reserve volume (IRV)
3.6
10
3
m
3
(1,200 cm
3
)
Expiratory reserve volume (ERV)
1.2
10
3
m
3
(2,400 cm
3
)
Functional residual capacity (FRC)
2.4
10
4
m
3
(150 cm
3
)
Anatomic dead volume (V
D
)
1.5
10
5
m
3
(80 cm
3
)
Upper airways volume
8.0
10
5
m
3
(70 cm
3
)
Lower airways volume
7.0
10
4
m
3
(180 cm
3
)
Physiologic dead volume (V
D
)
1.8
10
4
m
3
/s
(6,000 cm
3
/m)
Minute volume (V
e
) at rest
1.0
Respiratory period (T) at rest
4s
10
4
m
3
(400 cm
3
)
Tidal volume (V
T
) at rest
4.0
10
4
m
3
(250 cm
3
)
Alveolar ventilation volume (V
A
) at rest
2.5
10
3
m
3
/s
(10,000 m
3
/m)
Minute volume during heavy exercise
1.7
Respiratory period during heavy exercise
1.2s
10
3
m
3
(2,000 cm
3
)
Tidal volume during heavy exercise
2.0
10
3
m
3
(1,820 cm
3
)
Alveolar ventilation during heavy exercise
1.8
Since spirograms record changes in volume over time, flow rates can be determined for
different maneuvers. For example, if a patient exhales as forcefully as possible to residual
volume following inspiration to TLC, then the forced expiratory volume (FEV
1.0
) is the total
volume exhaled at the end of 1 s. The FEV
1.0
is normally about 80 percent of the vital capac-
ity. Restrictive diseases, in which inspiration is limited by reduced compliance of the lung
or chest wall or by weakness of the inspiratory muscles, result in reduced values for FEV
1.0
and vital capacity, but their ratio remains about the same. In obstructive diseases, such as
asthma, the FEV
1.0
is reduced much more than the vital capacity. In these diseases, the
TLC is abnormally large, but expiration ends prematurely. Another useful measurement
is the forced expiratory flow rate (FEF
25-75
percent), which is the average flow rate
measured over the middle half of the expiration—that is, from 25 to 75 percent of the vital
capacity. Flow-volume loops provide another method for analyzing lung function by relat-
ing the rate of inspiration and expiration to the volume of air that is moved during
each process.
