Lung volumes: Difference between revisions
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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. |
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. |
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When someone living at or near sea level travels to locations at high altitudes (e.g., the [[Andes]] |
When someone living at or near sea level travels to locations at high altitudes (e.g., the [[Andes]]; [[Denver, Colorado]]; [[Tibet]]; the [[Himalayas]]; etc.) 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.) |
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[[Maternal physiological changes in pregnancy#Respiratory|Specific changes]] in lung volumes also occur during pregnancy. Decreased [[functional residual capacity]] is seen, typically falling from 1.7 to 1.35 litres,{{citation needed|date=January 2010}} due to the compression of the [[Thoracic diaphragm|diaphragm]] by the uterus. The compression also causes a decreased [[total lung capacity]] (TLC) by 5% and decreased [[expiratory reserve volume]]. [[Tidal volume]] increases with 30-40%, from 0.45 to 0.65 litres,{{citation needed|date=January 2010}} and [[minute ventilation]] by 30-40%<ref name="isbn81-8147-920-3">{{cite book |author= Guyton and hall |authorlink= |editor= |others= |title=Textbook of Medical Physiology |edition=11 |publisher=Saunders |location=Philadelphia |year=2005 |origyear= |pages= 103g |quote= |isbn=81-8147-920-3 |oclc= |doi= |url= |accessdate=}}</ref> 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.<ref name="simpson breathing">{{cite book |last= Simpson |first= Kathleen Rice |coauthors= Patricia A Creehan |title= Perinatal Nursing |url= http://books.google.com/books?id=oz_4cTmVFD4C&pg=PA66 |edition= 3rd |year= 2007 |publisher= Lippincott Williams & Wilkins |isbn= 978-0-7817-6759-0 |pages= 65–66}}</ref> |
[[Maternal physiological changes in pregnancy#Respiratory|Specific changes]] in lung volumes also occur during pregnancy. Decreased [[functional residual capacity]] is seen, typically falling from 1.7 to 1.35 litres,{{citation needed|date=January 2010}} due to the compression of the [[Thoracic diaphragm|diaphragm]] by the uterus. The compression also causes a decreased [[total lung capacity]] (TLC) by 5% and decreased [[expiratory reserve volume]]. [[Tidal volume]] increases with 30-40%, from 0.45 to 0.65 litres,{{citation needed|date=January 2010}} and [[minute ventilation]] by 30-40%<ref name="isbn81-8147-920-3">{{cite book |author= Guyton and hall |authorlink= |editor= |others= |title=Textbook of Medical Physiology |edition=11 |publisher=Saunders |location=Philadelphia |year=2005 |origyear= |pages= 103g |quote= |isbn=81-8147-920-3 |oclc= |doi= |url= |accessdate=}}</ref> 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.<ref name="simpson breathing">{{cite book |last= Simpson |first= Kathleen Rice |coauthors= Patricia A Creehan |title= Perinatal Nursing |url= http://books.google.com/books?id=oz_4cTmVFD4C&pg=PA66 |edition= 3rd |year= 2007 |publisher= Lippincott Williams & Wilkins |isbn= 978-0-7817-6759-0 |pages= 65–66}}</ref> |
Revision as of 23:59, 16 July 2012
This article needs more reliable medical references for verification or relies too heavily on primary sources. (March 2012) |
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.
Tidal breathing is normal, resting breathing; the tidal volume is the volume of air that is inhaled or exhaled in a single such breath.
An average human breathes some 12-20 times per minute.[citation needed]
Factors affecting volumes
This section needs additional citations for verification. (December 2010) |
Several factors affect lung volumes; some can be controlled and some cannot. Lung volumes vary with different people as follows:
Larger volumes | Smaller volumes |
---|---|
taller people | shorter people |
non-smokers | smokers |
people who live at higher altitudes | people who live at lower altitudes |
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; etc.) 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.)
Specific changes in lung volumes also occur during pregnancy. Decreased functional residual capacity is seen, typically falling from 1.7 to 1.35 litres,[citation needed] 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. Tidal volume increases with 30-40%, from 0.45 to 0.65 litres,[citation needed] and minute ventilation by 30-40%[2] 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.[3]
Values
Volume | Value (litres) | |
---|---|---|
In men | In women | |
Inspiratory reserve volume | 3.3 | 1.9 |
Tidal volume | 0.5 | 0.5 |
Expiratory reserve volume | 1.0 | 0.7 |
Residual volume | 1.2 | 1.1 |
Volume | Average value (litres) | Derivation | |
---|---|---|---|
In men | In women | ||
Vital capacity | 4.6 | 3.1 | IRV plus TV plus ERV |
Inspiratory capacity | 3.8 | 2.4 | IRV plus TV |
Functional residual capacity | 2.2 | 1.8 | ERV plus RV |
Total lung capacity | 6.0 | 4.2 | IRV plus TV plus ERV plus 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 (18.1ml/kg),[5] or as a proportion of vital capacity (0.24 for men and 0.28 for women)[6] or in relation to height and age ((0.0275*AgeInYears+0.0189*HeightInCentimetres-2.6139) litres for normal-weight individuals and (0.0277*AgeInYears+0.0138*HeightInCentimeters-2.3967) litres for overweight individuals).[7] Standard errors in prediction equations for residual volume have been measured at 579ml for men and 355ml for women, while the use of 0.24*FVC gave a standard error of 318ml.[8]
Restrictive and obstructive
The results (in particular FEV1/FVC and FRC) can be used to distinguish between restrictive and obstructive pulmonary diseases:
Type | Examples | Description | FEV1/FVC |
restrictive diseases | pulmonary fibrosis, Infant Respiratory Distress Syndrome, weak respiratory muscles, pneumothorax | volumes are decreased | often in a normal range (0.8 - 1.0) |
obstructive diseases | asthma or COPD | volumes are essentially normal but flow rates are impeded | often low (Asthma can reduce the ratio to 0.6, Emphysema can reduce the ratio to 0.78 - 0.45) |
See also
References
- ^ Marieb, Elaine (2010). Human Anatomy and Physiology (8th Ed.). Prentice Hall PTR. p. 824. ISBN 978-0-321-69415-7.
{{cite book}}
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suggested) (help) - ^ Guyton and hall (2005). Textbook of Medical Physiology (11 ed.). Philadelphia: Saunders. pp. 103g. ISBN 81-8147-920-3.
- ^ Simpson, Kathleen Rice (2007). Perinatal Nursing (3rd ed.). Lippincott Williams & Wilkins. pp. 65–66. ISBN 978-0-7817-6759-0.
{{cite book}}
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suggested) (help) - ^ a b Ganong, William. "Fig. 34-7". Review of Medical Physiology (21st ed.).
- ^ Morris, Mohy G. (2010). "Comprehensive integrated spirometry using raised volume passive and forced expirations and multiple-breath nitrogen washout in infants". Respiratory Physiology & Neurobiology. 170 (2): 123–140. doi:10.1016/j.resp.2009.10.010. ISSN 1569-9048. PMC 2858579. PMID 19897058.
- ^ Wilmore, J. H. (1969). "The use of actual predicted and constant residual volumes in the assessment of body composition by underwater weighing". Med Sci Sports. 1: 87–90.
- ^ MILLER, WAYNE C.; SWENSEN, THOMAS; WALLACE, JANET P. (1998). "Derivation of prediction equations for RV in overweight men and women". Medicine & Science in Sports & Exercise. 30 (2): 322–327. PMID 9502364.
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ Morrow JR Jr, Jackson AS, Bradley PW, Hartung GH. (1986). "Accuracy of measured and predicted residual lung volume on body density measurement". Med Sci Sports Exerc. 18 (6): 647–52. PMID 3784877.
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