lecture 3: lung volumes and capacities
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Transcript lecture 3: lung volumes and capacities
Lung Volumes and Capacities
Dr ibraheem Bashayreh
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