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Total lung capacity (TLC)

TLC = IRV + Vt + ERV + RV
The volume of air contained in the lung at the end of maximal inspiration. The total volume of the lung. Values of between 80% and 120% of average value are considered normal.

Vital capacity (VC)

VC = IRV + Vt + ERV
The amount of air that can be forced out of the lungs after a maximal inspiration. Emphasis on completeness of expiration. The maximum volume of air that can be voluntarily moved in and out of the respiratory system.

Forced vital capacity (FVC)

The amount of air that can be maximally forced out of the lungs after a maximal inspiration. Emphasis on speed.

Tidal volume (Vt)

The amount of air breathed in or out during normal respiration. The volume of air an individual is normally breathing in and out. 500mL

Residual volume (RV)

The amount of air left in the lungs after a maximal exhalation. The amount of air that is always in the lungs and can never be expired (i.e.: the amount of air that stays in the lungs after maximum expiration). Values between 75% and 125% of average value are considered normal.

Expiratory reserve volume (ERV)

The amount of additional air that can be pushed out after the end expiratory level of normal breathing. (At the end of a normal breath, the lungs contain the residual volume plus the expiratory reserve volume, or around 2.4 litres. If one then goes on and exhales as much as possible, only the residual volume of 1.2 litres remains).

Inspiratory reserve volume (IRV)

IRV=VC-(Vt+ERV)
The additional air that can be inhaled after a normal tidal breath in. The maximum volume of air that can be inspired in addition to the tidal volume.

Functional residual capacity (FRC)

FRC = ERV + RV
The amount of air left in the lungs after a tidal breath out. The amount of air that stays in the lungs during normal breathing. Values of between 80% and 120% of average value are considered normal.

Inspiratory capacity (IC)

IC = Vt + IRV
The maximal volume that can be inspired following a normal expiration.

Anatomical dead space

The volume of the conducting airways. Measured with Fowler method.

Physiologic dead volume

The anatomic dead space plus the alveolar dead space.

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