Lung Volume and Lung Capacities
Lung Volumes
Tidal Volume:
Symbol: VT or TV
Description: The volume of air inhaled and exhaled with each breath
Normal Value: 500 mL or 5-10 mL/kg
Significance: The tidal volume may not vary, even with severe disease.
Inspiratory reserve volume
Symbol: IRV
Description: The maximum volume of air that can be inhaled after a normal inhalation.
Normal Value: 3000 mL
Significance: A sigh takes advantages of the IRV potential.
Expiratory reserve volume
Symbol: ERV
Description: The maximum volume of air that can be exhaled forcibly after a normal exhalation.
Normal Value: 1100 mL
Significance: Expiratory reserve volume is decreased in restrictive disorders, such as obesity, ascites, and pregnancy.
Residual Volume
Symbol: RV
Description: The volume of air remaining in the lungs after a maximum exhalation.
Normal Value: 1200 mL
Significance: Residual volume may be increased in obstructive disease.
Lung Capacities
Vital Capacity
Symbol: VC
Description: The maximum volume of air exhaled from the point of maximum inspiration.
VC = TV + IRV + ERV
Normal Values: 4600 mL
Significance: A decrease in vital capacity may be found in neuromuscular disease, generalized fatigue, atelectasis, pulmonary edema and COPD.
Inspiratory Capacity
Description: The maximum volume of air inhaled after normal expiration.
IC = TV +IRV
Normal Value: 3500 mL
Significance: A decrease in inspiratory capacity may indicate restrictive disease.
Function residual capacity
Symbol: FRC
Description: The volume of air remaining in the lungs after a normal expiration.
FRC = ERV + RV
Normal Value : 2300 mL
Significance: Functional residual capacity may be increased in COPD and decreased in ARDS.
Total Lung Capacity
Symbol:TLC
Description: The volume of air in the lungs after a maximum inspiration
TLC = TV + IRV + ERV + RV
Normal Value: 5800 mL
Significance: Total lung capacity may decreased in restrictive disease ( atelectasis, pneumonia ) and increased in COPD.
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