Total lung capacity: the volume in the lungs at maximal inflation, the sum of VC and RV.

TV

Tidal volume: that volume of air moved into or out of the lungs during quiet breathing (VT indicates a subdivision of the lung; when tidal volume is precisely measured, as in gas exchange calculation, the symbol VT or VT is used.)

RV

Residual volume: the volume of air remaining in the lungs after a maximal exhalation

ERV

Expiratory reserve volume: the maximal volume of air that can be exhaled from the end-expiratory position

IRV

Inspiratory reserve volume: the maximal volume that can be inhaled from the end-inspiratory level

IC

Inspiratory capacity: the sum of IRV and TV

IVC

Inspiratory vital capacity: the maximum volume of air inhaled from the point of maximum expiration

VC

Vital capacity: the volume of air breathed out after the deepest inhalation.

VT

Tidal volume: that volume of air moved into or out of the lungs during quiet breathing (VT indicates a subdivision of the lung; when tidal volume is precisely measured, as in gas exchange calculation, the symbol VT or VT is used.)

FRC

Functional residual capacity: the volume in the lungs at the end-expiratory position

RV/TLC%

Residual volume expressed as percent of TLC

VA

Alveolar gas volume

VL

Actual volume of the lung including the volume of the conducting airway.

FVC

Forced vital capacity: the determination of the vital capacity from a maximally forced expiratory effort

FEVt

Forced expiratory volume (time): a generic term indicating the volume of air exhaled under forced conditions in the first t seconds

FEV1

Volume that has been exhaled at the end of the first second of forced expiration

FEFx

Forced expiratory flow related to some portion of the FVC curve; modifiers refer to amount of FVC already exhaled

FEFmax

The maximum instantaneous flow achieved during a FVC maneuver

FIF

Forced inspiratory flow: (Specific measurement of the forced inspiratory curve is denoted by nomenclature analogous to that for the forced expiratory curve. For example, maximum inspiratory flow is denoted FIFmax. Unless otherwise specified, volume qualifiers indicate the volume inspired from RV at the point of measurement.)

Lung volumes and lung capacities refer to the volume of air associated with different phases of the respiratory cycle. Lung volumes are directly measured; Lung capacities are inferred from lung volumes.

The average total lung capacity of an adult human male is about 6 litres of air,[1] but only a small amount of this capacity is used during normal breathing. The lung capacity of freediver and world record holder Herbert Nitsch is measured to be 10 Liters, which he can expand to 15 Liters with a special technique called “packing” or “buccal pumping”.

Tidal breathing is normal, resting breathing; the tidal volume is the volume of air that is inhaled or exhaled in only a single such breath.

The average human respiratory rate is 30-60 breaths per minute at birth,[2] decreasing to 12-20 breaths per minute in adults.[3]

A person who is born and lives at sea level will develop a slightly smaller lung capacity than a person who spends their life at a high altitude. This is because the partial pressure of oxygen is lower at higher altitude which, as a result means that oxygen less readily diffuses into the bloodstream. In response to higher altitude, the body's diffusing capacity increases in order to process more air.

When someone living at or near sea level travels to locations at high altitudes (e.g., the Andes; Denver, Colorado; Tibet; the Himalayas) that person can develop a condition called altitude sickness because their lungs remove adequate amounts of carbon dioxide but they do not take in enough oxygen. (In normal individuals, carbon dioxide is the primary determinant of respiratory drive.)

The tidal volume, vital capacity, inspiratory capacity and expiratory reserve volume can be measured directly with a spirometer. These are the basic elements of a ventilatory pulmonary function test.

Determination of the residual volume is more difficult as it is impossible to "completely" breathe out. Therefore measurement of the residual volume has to be done via indirect methods such as radiographic planimetry, body plethysmography, closed circuit dilution (including the helium dilution technique) and nitrogen washout.

In absence of such, estimates of residual volume have been prepared as a proportion of body mass for infants (18.1 mL/kg),[8] or as a proportion of vital capacity (0.24 for men and 0.28 for women)[9] or in relation to height and age ((0.0275* Age [Years]+0.0189*Height [cm]-2.6139) litres for normal-mass individuals and (0.0277*Age [Years]+0.0138*Height [cm]-2.3967) litres for overweight individuals).[10] Standard errors in prediction equations for residual volume have been measured at 579 mL for men and 355 mL for women, while the use of 0.24*FVC gave a standard error of 318 mL.[11]

Online calculators are available that can compute predicted lung volumes, and other spirometric parameters based on a patient's age, height, weight, and ethnic origin for many reference sources.