The volume of air exchanged during normal breathing is called the

• Total lung capacity – Volume of air in the lungs after a maximal inhalation (~ 6 litres in a normal adult male)
• Vital capacity – Volume of air that can be exchanged by the lungs via a maximal inhalation and exhalation
• Residual volume – Volume of air that is always present in the lungs (~ 20% of total lung capacity)
• Tidal volume – Volume of air that is exchanged via normal breathing (~ 500 ml per breath)

Ventilation rate (breathing frequency) at rest for a typical adult is roughly 12 – 16 breaths per minute

• Ventilation rate can be substantially increased with physical activity (maximal increase is roughly 5 – 6 fold over normal)

A number of factors contribute to an individual’s total lung capacity and ventilation rate, including:

• Height (taller people tend to have larger chests and hence larger total lung capacities)
• Location (people living at high altitudes tend to have larger capacities to compensate for the lower atmospheric pressure)

  Lung volumes and lung capacities refer to the volume of air in the lungs at different phases of the respiratory cycle.

  The average total lung capacity of an adult human male is about 6 litres of air.

  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,[1] decreasing to 12–20 breaths per minute in adults.[2]

  Factors affecting volumes[edit]

  Several factors affect lung volumes; some can be controlled, and some cannot be controlled. Lung volumes vary with different people as follows:

  Larger volumeSmaller volumestaller peopleshorter peoplepeople who live at higher altitudespeople who live at lower altitudesfitobese[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. Also, due to the lower environmental air pressure at higher altitudes, the air pressure within the breathing system must be lower in order to inhale; in order to meet this requirement, the thoracic diaphragm has a tendency to lower to a greater extent during inhalation, which in turn causes an increase in lung volume.

  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.)

  Lung function development is reduced in children who grow up near motorways[4][5] although this seems at least in part reversible.[6] Air pollution exposure affects FEV1 in asthmatics, but also affects FVC and FEV1 in healthy adults even at low concentrations.[7]

  Specific changes in lung volumes also occur during pregnancy. Functional residual capacity drops 18–20%,[8] typically falling from 1.7 to 1.35 litres,[citation needed] due to the compression of the diaphragm by the uterus.[citation needed] The compression also causes a decreased total lung capacity (TLC) by 5%[8] and decreased expiratory reserve volume by 20%.[8] Tidal volume increases by 30–40%, from 0.5 to 0.7 litres,[8] and minute ventilation by 30–40%[8][9] giving an increase in pulmonary ventilation. This is necessary to meet the increased oxygen requirement of the body, which reaches 50 ml/min, 20 ml of which goes to reproductive tissues. Overall, the net change in maximum breathing capacity is zero.[8]

  Average lung volumes in healthy adults[10]VolumeValue (litres)In menIn womenInspiratory reserve volume (IRV)3.31.9Tidal volume (TV)0.50.5Expiratory reserve volume (ERV)1.10.7Residual volume (RV)1.21.1Lung capacities in healthy adults[10]VolumeAverage value (litres)DerivationIn menIn womenVital capacity4.83.1IRV + TV + ERVInspiratory capacity3.82.4IRV + TVFunctional residual capacity2.41.8ERV + RVTotal lung capacity6.04.2IRV + TV + ERV + RV

  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),[11] or as a proportion of vital capacity (0.24 for men and 0.28 for women)[12] 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).[13] 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.[14]

  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.

  British rower and three-time Olympic gold medalist, Pete Reed, is reported to hold the largest recorded lung capacity of 11.68 litres;[15][16][17] US swimmer, Michael Phelps is also said to have a lung capacity of around 12 litres.[16][18]

  Weight of breath[edit]

  The mass of one breath is approximately a gram (0.5-5 g). A litre of air weighs about 1.2 g (1.2 kg/m3).[19] A half litre ordinary tidal breath[10] weighs 0.6 g; a maximal 4.8 litre breath (average vital capacity for males)[10] weighs approximately 5.8 g.

  Restrictive and obstructive[edit]

  Scheme of changes in lung volumes in restricted and obstructed lung in comparison with healthy lung.

  The results (in particular FEV1/FVC and FRC) can be used to distinguish between restrictive and obstructive pulmonary diseases:

  What is the volume of air exchanged during normal breathing?

  Tidal volume (TV) measures the amount of air that is inspired and expired during a normal breath. On average, this volume is around one-half liter, which is a little less than the capacity of a 20-ounce drink bottle.

  What is normal air capacity called?

  Lung capacity or total lung capacity (TLC) is the volume of air in the lungs upon the maximum effort of inspiration. Among healthy adults, the average lung capacity is about 6 liters. Age, gender, body composition, and ethnicity are factors affecting the different ranges of lung capacity among individuals.

  What is inspiratory and expiratory capacity?

  After normal expiration, the amount of air inhaled by a person is called inspiratory capacity (IC). After normal inspiration, the amount of air is exhaled by a person is called expiratory capacity (EC).