Lung Volumes and Capacities
 The
total volume contained in
the lung at the end of a
maximal inspiration is
subdivided into volumes and
subdivided into capacities.
There are 4 volume subdivisions
They do not overlap
 They can not be further divided
 When added together equal total
lung capacity

Lung Capacities
 Are
subdivisions of the total
volume that include two or
more of the 4 basic lung
volumes
Basic Lung Volumes

Tidal Volume: TV
 The amount of gas inspired or
expired with each normal breath.
 About 500 ml
Basic Lung Volumes
 Inspiratory
Reserve Volume: IRV
 Maximum amount of additional
air that can be inspired from the
end of a normal inspiration.
Basic Lung Volumes
 Expiratory
Reserve Volume: ERV
 The maximum volume of
additional air that can be expired
from the end of a normal
expiration.
Basic Lung Volumes

Residual Volume: RV
 The volume of air remaining in the lung
after a maximal expiration. This is the only
lung volume which cannot be measured
with a spirometer.
 Gas dilution tech
 nitrogen
 helium

Body Plethysmograph
Lung Capacities

Total Lung Capacity: TLC
 The volume of air contained in the
lungs at the end of a maximal
inspiration.
 Called a capacity because it is the
sum of the 4 basic lung volumes
 TLC= RV+IRV+TV+ERV
Lung Capacities

Vital Capacity: VC
 The maximum volume of air that can be
forcefully expelled from the lungs
following a maximal inspiration.
 Called a capacity because it is the sum
of inspiratory reserve volume, tidal
volume and expiratory reserve volume.
 VC= IRV+TV+ERV = TLC - RV
Lung Capacities

Functional Residual Capacity: FRC
 The volume of air remaining in the
lung at the end of a normal
expiration.
 Called a capacity because it equal
residual volume plus expiratory
reserve volume.
 FRC= RV+ERV
Lung Capacities

Inspiratory Capacity: IC
 Maximum volume of air that can be inspired
from end expiratory position.
 Called a capacity because it is the sum of
tidal volume and inspiratory reserve
volume.
 This capacity is of less clinical significance
than the other three.
 IC= TV+IRV
Respiratory Diseases

Restrictive Disease:
 Makes it more difficult to get air in to the lungs.
 They “restrict” inspiration.
 Decreased VC; Decreased TLC, RV, FRC
 Includes:
 Fibrosis
 Sarcoidosis
 Muscular diseases
 Chest wall deformities
Respiratory Diseases

Obstructive Disease
 Make it more difficult to get air out of the
lungs.
 Decrease VC; Increased TLC, RV, and
FRC
 Includes:
 Emphysema
 Chronic bronchitis
 Asthma