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Lung volumes and lung capacities are measures of the
volume Volume is a measure of regions in three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch) ...
of
air An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
in the
lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...
s 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 Tidal is the adjectival form of tide. Tidal may also refer to: * ''Tidal'' (album), a 1996 album by Fiona Apple * Tidal (king), a king involved in the Battle of the Vale of Siddim * TidalCycles TidalCycles (also known as Tidal) is a live coding ...
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, decreasing to 12–20 breaths per minute in adults.


Factors affecting volumes

Several factors affect lung volumes; some can be controlled, and some cannot be controlled. Lung volumes vary with different people as follows: A person who is born and lives at
sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...
will develop a slightly smaller lung capacity than a person who spends their life at a high
altitude Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum (geodesy), datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometr ...
. 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 The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...
;
Denver, Colorado Denver ( ) is a List of municipalities in Colorado#Consolidated city and county, consolidated city and county, the List of capitals in the United States, capital and List of municipalities in Colorado, most populous city of the U.S. state of ...
;
Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the Tibetan people. Also resident on the plateau are other ethnic groups s ...
; the
Himalayas The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than list of h ...
) that person can develop a condition called
altitude sickness Altitude sickness, the mildest form being acute mountain sickness (AMS), is a harmful effect of high altitude, caused by rapid exposure to low amounts of oxygen at high elevation. People's bodies can respond to high altitude in different wa ...
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 although this seems at least in part reversible. Air pollution exposure affects FEV1 in asthmatics, but also affects FVC and FEV1 in healthy adults even at low concentrations. Specific changes in lung volumes also occur during pregnancy.
Functional residual capacity Functional residual capacity (FRC) is the lung volume, volume of air present in the lungs at the end of passive Exhalation, expiration.Hopkins E, Sharma S. Physiology, Functional Residual Capacity. pdated 2022 Jan 4 In: StatPearls nternet...
drops 18–20%, typically falling from 1.7 to 1.35 litres, due to the compression of the diaphragm by the uterus. The compression also causes a decreased total lung capacity (TLC) by 5% and decreased expiratory reserve volume by 20%.
Tidal volume Tidal is the adjectival form of tide. Tidal may also refer to: * ''Tidal'' (album), a 1996 album by Fiona Apple * Tidal (king), a king involved in the Battle of the Vale of Siddim * TidalCycles TidalCycles (also known as Tidal) is a live coding ...
increases by 30–40%, from 0.5 to 0.7 litres, and minute ventilation by 30–40% 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.


Values

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 The helium dilution technique is the way of measuring the functional residual capacity of the lungs (the volume left in the lungs after normal Exhalation, expiration). This technique is a closed-circuit system where a spirometer is filled with a ...
) 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), or as a proportion of ''vital capacity'' (0.24 for men and 0.28 for women) or in relation to height and age ((0.0275* Age ears0.0189*Height m��2.6139) litres for normal-mass individuals and (0.0277*Age ears0.0138*Height m��2.3967) litres for overweight individuals). 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.
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; US swimmer
Michael Phelps Michael Fred Phelps II (born June 30, 1985) is an American former competitive swimmer. He is the most successful and most decorated Olympian of all time with a total of 28 medals. Phelps also holds the all-time records for Olympic gold me ...
is also said to have a lung capacity of around 12 litres.


Weight of breath

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). Atmosphere of Earth#Density and mass A half litre ordinary tidal breath weighs 0.6 g; a maximal 4.8 litre breath (average vital capacity for males) weighs approximately 5.8 g.


Restrictive and obstructive

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


See also

*
Pulmonary function testing Pulmonary function testing (PFT) is a complete evaluation of the respiratory system including patient history, physical examinations, and tests of pulmonary function. The primary purpose of pulmonary function testing is to identify the severity ...
(PFT) * Spirometry


References


External links


Lung function fundamentals (anaesthetist.com)Volume of human lungs
{{Respiratory physiology Respiratory physiology Pulmonary function testing