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 – 600 ml

Basic Lung Volumes Inspiratory Reserve Volume: IRV  Maximum amount of additional air that can be inspired from the end of a normal inspiration.  About 3100 ml (male)  About 2000 ml (female)

Basic Lung Volumes Expiratory Reserve Volume: ERV  The maximum volume of additional air that can be expired from the end of a normal expiration.  About 1200 ml (male)  About 800 ml (female)

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.  About 1200 ml (male) 1100 (female) 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  About 6 liters (male) 4.5 liters (female)

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  About 4.6 liters (male) 3.1 liters (female)

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  About 2.3 liters (male) 1.8 liters (female)

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  About 3.5 liters (male) 2.4 liters (female)

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