Lung Function

Remember, the residual volume (RV) and any capacity containing RV (TLC, FRC) cannot be measured directly with a spirometer.

Vital capacity (VC), inspiratory capacity (IC), ERV, and tidal volume (VT) can all be measured directly through spirometry.

Tidal volume (TV)

• volume inspired or expired with each breath at rest
• 500ml in males, 350ml in females

Inspiratory reserve volume (IRV) = 2-3 L

• maximum volume of air that can be inspired at the end of a normal tidal inspiration
• inspiratory capacity = TV + IRV

Expiratory reserve volume (ERV) = 750ml

• maximum volume of air that can be expired at the end of a normal tidal expiration

Residual volume (RV) = 1.2L

• volume of air remaining after maximal expiration
• increases with age
• RV = FRC - ERV

Vital capacity (VC) = 5L

• maximum volume of air that can be expired after a maximal inspiration
• 4,500ml in males, 3,500 mls in females
• decreases with age