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pCO₂, pCO₂, or $P_{{\ce {CO2}}}$ is the partial pressure of carbon dioxide (CO₂), often used in reference to blood but also used in meteorology, climate science, oceanography, and limnology to describe the fractional pressure of CO₂ as a function of its concentration in gas or dissolved phases. The units of pCO₂ are mmHg, atm, torr, Pa, or any other standard unit of atmospheric pressure. The pCO₂ of Earth's atmosphere has risen from approximately 280 ppm (parts-per-million) to a mean 2019 value of 409.8 ppm as a result of anthropogenic release of carbon dioxide from fossil fuel burning.^{[citation needed]} This is the highest atmospheric concentration to have existed on Earth for at least the last 800,000 years.^[1]

Medicine

In medicine, the partial pressure of carbon dioxide in arterial blood is called $P_{a_{{\ce {CO2}}}}$ or PaCO₂. Measurement of $P_{a_{{\ce {CO2}}}}$ in the systemic circulation indicates the effectiveness of ventilation at the lungs' alveoli, given the diffusing capacity of the gas. It is a good indicator of respiratory function and the closely related factor of acid–base homeostasis, reflecting the amount of acid in the blood (without lactic acid). Normal values for humans are in the range 35–45 mmHg. Values less than this may indicate hyperventilation and (if blood pH is greater than 7.45) respiratory alkalosis. Values greater than 45 mmHg may indicate hypoventilation, and (if blood pH is less than 7.35) respiratory acidosis.^[2]^[3]

Aquatic sciences

Oceanographers and limnologists use pCO₂ to measure the amount of carbon dioxide dissolved in water, as well as to parameterize its flux into (influx) and out of (efflux) the atmosphere. Carbon dioxide reacts with water to form bicarbonate and carbonate ions, such that the relative solubility of carbon dioxide in water is greater than that of other unreactive gasses (e.g. Helium). As more carbon dioxide dissolves in water, its pCO₂ rises until it equals the pCO₂ of the overlying atmosphere. Conversely, a body of water with a pCO₂ greater than that of the atmosphere effluxes carbon dioxide.^[4]^[5]

pCO₂ is additionally affected by water temperature and salinity. Carbon dioxide is less soluble in warmer water than cooler water, so hot water will exhibit a larger pCO₂ than cold water with the same concentration of carbon dioxide. pCO₂ can be used to describe the inorganic carbon system of a body of water, together with other parameters such as pH, dissolved inorganic carbon, and alkalinity. Together, these parameters describe the concentration and speciation of inorganic carbon species (CO_{2 (aq)}, HCO₃⁻, CO₃^2-) in water.^[5]

Biological processes such as respiration and photosynthesis affect and can be affected by aquatic pCO₂. Respiration degrades organic matter, releasing CO₂ into the water column and increasing pCO₂. Photosynthesis assimilates inorganic carbon, thereby decreasing aquatic pCO₂.^[4]

References

^ Lindsey, Rebecca (2020). "Climate Change: Atmospheric Carbon Dioxide". www.climate.gov. Retrieved 2021-02-25.
^ Dugdale DC, Zieve D. Gasometría arterial. Medline Plus. 09/01/2012.
^ Leticia Godoy Dias Sanderson. Gasometria arterial - Artigo de revisão. Fevereiro 2012. Archived 2014-10-17 at the Wayback Machine
^ ^a ^b Millero, Frank J. (2013). Chemical oceanography (4 ed.). Boca Raton: Taylor & Francis. ISBN 978-1-4665-1255-9. OCLC 958798815.
^ ^a ^b Zeebe, Richard E. (2001). CO2 in seawater : equilibrium, kinetics, isotopes. Dieter A. Wolf-Gladrow. Amsterdam. ISBN 978-0-08-052922-6. OCLC 246683387.{{cite book}}: CS1 maint: location missing publisher (link)

This article incorporates text by Glynda Rees Doyle and Jodie Anita McCutcheon available under the CC BY 4.0 license.

[1] Lindsey, Rebecca (2020). "Climate Change: Atmospheric Carbon Dioxide". www.climate.gov. Retrieved 2021-02-25.

[2] Dugdale DC, Zieve D. Gasometría arterial. Medline Plus. 09/01/2012.

[3] Leticia Godoy Dias Sanderson. Gasometria arterial - Artigo de revisão. Fevereiro 2012. Archived 2014-10-17 at the Wayback Machine

[:0-4] Millero, Frank J. (2013). Chemical oceanography (4 ed.). Boca Raton: Taylor & Francis. ISBN 978-1-4665-1255-9. OCLC 958798815.

[:1-5] Zeebe, Richard E. (2001). CO2 in seawater : equilibrium, kinetics, isotopes. Dieter A. Wolf-Gladrow. Amsterdam. ISBN 978-0-08-052922-6. OCLC 246683387.{{cite book}}: CS1 maint: location missing publisher (link)

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@@ Line 1: / Line 1: @@
+{{short description|Partial pressure of carbon dioxide, often used in reference to blood}}
+{{DISPLAYTITLE:pCO<sub>2</sub>}}
 [[File:Carbon-dioxide-3D-vdW.svg|thumb|[[Carbon dioxide]] molecule.]]
+'''''p''CO<sub>2</sub>, pCO<sub>2</sub>''', or <math chem="">P_\ce{CO2}</math> is the [[partial pressure]] of [[carbon dioxide]] (CO<sub>2</sub>), often used in reference to [[blood]] but also used in [[meteorology]], [[Climatology|climate science]], [[oceanography]], and [[limnology]] to describe the fractional pressure of CO<sub>2</sub> as a function of its concentration in gas or dissolved phases.   The units of ''p''CO<sub>2</sub> are [[Millimetre of mercury|mmHg]], [[Standard atmosphere (unit)|atm]], [[torr]], [[Pascal (unit)|Pa]], or any other standard unit of [[atmospheric pressure]].  The ''p''CO<sub>2</sub> of [[Earth|Earth's]] atmosphere has risen from approximately 280 ppm ([[Parts-per notation|parts-per-million]]) to a mean 2019 value of 409.8 ppm as a result of [[Climate change|anthropogenic]] release of carbon dioxide from [[fossil fuel]] burning.{{Citation needed|date=November 2024}} This is the highest atmospheric concentration to have existed on Earth for at least the last 800,000 years.<ref>{{Cite web|last=Lindsey|first=Rebecca|date=2020|title=Climate Change: Atmospheric Carbon Dioxide|url=https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide|access-date=2021-02-25|website=www.climate.gov|language=en}}</ref>
-The '''pCO<sub>2</sub>''' is the partial pressure of [[carbon dioxide]] (CO<sub>2</sub>) in [[arterial blood]]. It is also represented as PaCO<sub>2</sub>. Expresses the effectiveness of alveolar ventilation, given the diffusing capacity of the gas. It is a good indicator of respiratory function and reflects the amount of acid in the blood (without lactic acid).
-== Values ==
+== Medicine ==
+{{Main|Hypercapnia|Hypocapnia}}
-* Its normal values are in the range 35-45 [[mmHg]].
+In medicine, the partial pressure of carbon dioxide in [[arterial blood]] is called '''<math chem="">P_{a_\ce{CO2}}</math>''' or '''PaCO<sub>2</sub>'''. Measurement of <math chem="">P_{a_\ce{CO2}}</math> in the [[systemic circulation]] indicates the effectiveness of [[ventilation (physiology)|ventilation]] at the lungs' [[pulmonary alveolus|alveoli]], given the [[diffusing capacity]] of the gas. It is a good indicator of respiratory function and the closely related factor of [[acid–base homeostasis]], reflecting the amount of acid in the blood (without lactic acid).  Normal values for humans are in the range 35–45 [[Millimetre of mercury|mmHg]].  Values less than this may indicate [[hyperventilation]] and (if blood [[pH]] is greater than 7.45) [[respiratory alkalosis]].  Values greater than 45 mmHg may indicate [[hypoventilation]], and (if blood pH is less than 7.35) respiratory [[acidosis]].<ref>[https://www.nlm.nih.gov/medlineplus/spanish/ency/article/003855.htm Dugdale DC, Zieve D. Gasometría arterial. Medline Plus. 09/01/2012.]</ref><ref>[http://www.redentor.inf.br/arquivos/pos/publicacoes/21082012Microsoft%20Word%20-%20trabalho%20conclusao%20de%20curso.pdf Leticia Godoy Dias Sanderson. Gasometria arterial - Artigo de revisão. Fevereiro 2012.] {{webarchive|url=https://web.archive.org/web/20141017103958/http://www.redentor.inf.br/arquivos/pos/publicacoes/21082012Microsoft%20Word%20-%20trabalho%20conclusao%20de%20curso.pdf|date=2014-10-17}}</ref>
-* If the pCO<sub>2</sub> is less than 35 mmHg, the patient is [[hyperventilation|hyperventilating]], and if the [[pH]] (potential hydrogen) is greater than 7.45, corresponding to a [[respiratory alkalosis]].
-* If the pCO<sub>2</sub> is higher than 45 mmHg, the patient is [[hypoventilation|hypoventilating]], and if the pH is less than 7.35, is in [[respiratory acidosis]].<ref>[http://www.nlm.nih.gov/medlineplus/spanish/ency/article/003855.htm Dugdale DC, Zieve D. Gasometría arterial. Medline Plus. 09/01/2012.]</ref><ref>[http://www.redentor.inf.br/arquivos/pos/publicacoes/21082012Microsoft%20Word%20-%20trabalho%20conclusao%20de%20curso.pdf Leticia Godoy Dias Sanderson. Gasometria arterial - Artigo de revisão. Fevereiro 2012.]</ref>
+== Aquatic sciences ==
+{{see also|Ocean acidification|Freshwater acidification}}
+Oceanographers and limnologists use ''p''CO<sub>2</sub> to measure the amount of carbon dioxide dissolved in water, as well as to parameterize its [[flux]] into (influx) and out of (efflux) the atmosphere.  Carbon dioxide reacts with water to form [[bicarbonate]] and [[carbonate]] ions, such that the relative solubility of carbon dioxide in water is greater than that of other unreactive gasses (e.g. [[Helium]]).  As more carbon dioxide dissolves in water, its ''p''CO<sub>2</sub> rises until it equals the ''p''CO<sub>2</sub> of the overlying atmosphere.  Conversely, a body of water with a ''p''CO<sub>2</sub> greater than that of the atmosphere effluxes carbon dioxide.<ref name=":0">{{Cite book|last=Millero|first=Frank J.|url=https://www.worldcat.org/oclc/958798815|title=Chemical oceanography|date=2013|publisher=Taylor & Francis|isbn=978-1-4665-1255-9|edition=4|location=Boca Raton|oclc=958798815}}</ref><ref name=":1">{{Cite book|last=Zeebe|first=Richard E.|url=https://www.worldcat.org/oclc/246683387|title=CO2 in seawater : equilibrium, kinetics, isotopes|date=2001|others=Dieter A. Wolf-Gladrow|isbn=978-0-08-052922-6|location=Amsterdam|oclc=246683387}}</ref>
+''p''CO<sub>2</sub> is additionally affected by water [[temperature]] and [[salinity]].  Carbon dioxide is less soluble in warmer water than cooler water, so hot water will exhibit a larger ''p''CO<sub>2</sub> than cold water with the same concentration of carbon dioxide.  ''p''CO<sub>2</sub> can be used to describe the inorganic carbon system of a body of water, together with other parameters such as pH, [[dissolved inorganic carbon]], and [[alkalinity]].   Together, these parameters describe the concentration and speciation of inorganic carbon species (CO<sub>2 (aq)</sub>, HCO<sub>3</sub><sup>−</sup>, CO<sub>3</sub><sup>2-</sup>) in water.<ref name=":1" />
+Biological processes such as [[Cellular respiration|respiration]] and [[photosynthesis]] affect and can be affected by aquatic ''p''CO<sub>2</sub>.  Respiration degrades [[organic matter]], releasing CO<sub>2</sub> into the water column and increasing ''p''CO<sub>2</sub>.  Photosynthesis assimilates inorganic carbon, thereby decreasing aquatic ''p''CO<sub>2</sub>.<ref name=":0" />
 == See also ==
@@ Line 13: / Line 22: @@
 * [[Blood gas tension]]
 * [[Chemical equilibrium]]
+* [[Hypercapnia]]
 * [[pH]]
+*[[Carbon cycle|Carbon Cycle]]
-* [[pKa]]
+* [[xCO2|xCO<sub>2</sub>]]
 == References ==
 {{reflist}}
-[[Category:Acid–base chemistry| ]]
+[[Category:Acid–base chemistry]]
 [[Category:Analytical chemistry]]
 [[Category:Equilibrium chemistry]]
 [[Category:Units of measurement]]
+[[Category:Chemical oceanography]]
+[[Category:Limnology]]
+{{CC-notice|cc=by4|url=https://opentextbc.ca/clinicalskills|author(s)=Glynda Rees Doyle and Jodie Anita McCutcheon}}