Lung Volumes and Capacities

1
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.

2
There are 4 volume subdivisions

• They do not overlap
• They can not be further divided
• When added together equal total lung capacity

3
Lung Capacities

• Are subdivisions of the total volume that include
  two or more of the 4 basic lung volumes

4
Basic Lung Volumes

• Tidal Volume TV
• The amount of gas inspired or expired with each
  normal breath.
• About 500 ml

5
Basic Lung Volumes

• Inspiratory Reserve Volume IRV
• Maximum amount of additional air that can be
  inspired from the end of a normal inspiration.

6
Basic Lung Volumes

• Expiratory Reserve Volume ERV
• The maximum volume of additional air that can be
  expired from the end of a normal expiration.

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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

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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 RVIRVTVERV

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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 IRVTVERV TLC - RV

10
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 RVERV

11
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 TVIRV

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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

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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