Respiratory volumes, capacities, and levels

Question 1

Amount of air inhaled or exhaled with each breath under resting conditions.

Answer 1

Tidal Volume (TV)

Question 2

Amount of air that can be forcefully inhaled after a normal tidal volume inhalation.

Relies on muscle strength, lung compliance (elastic recoil) and a normal starting point (which is the end of Tidal volume).

Answer 2

Inspiratory reserve volume (IRV)

Question 3

Amount of air that can be forcefully exhaled after a normal tidal volume exhalation.

Relies on muscle strength and low airway resistance. (It is reduced in pregnancy, obesity, severe or proximal obstruction of the trachea/bronchi).

Answer 3

Expiratory reserve volume (ERV)

Question 4

Amount of air remaining in the lungs after a forced exhalation. Cannot be measured by spirometry.

Answer 4

Residual volume (RV)

Question 5

Maximum amount of air contained in lungs after a maximum inspiratory effort.

Answer 5

Total lung capacity (TLC)

Question 6

Maximum amount of air that can be expired after a maximum Inspiratory effort.

Answer 6

Vital capacity (VC)

Question 7

Maximum amount of air that can be inspired after a normal expiration.

Answer 7

Inspiratory Capacity (IC)

Question 8

Volume of air remaining in the lungs after a normal tidal volume expiration.

Answer 8

Functional residual capacity (FRC)

Question 9

The maximum level of thoracic pressure that can be reached through maximal effort of the inspiratory musculature.

Answer 9

Maximal inspiratory level

Question 10

A state of equilibrium (the atmospheric and lung pressures are the same). There is no effort upon exhaling to this level, and the body will naturally seek to find it.

Answer 10

Resting expiratory level

REL

Question 11

The maximum level of exhalation that can be reached through maximal effort of the expiratory musculature.

Answer 11

Maximal expiratory level