Oxygen saturation
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220971047
2008-06-22T13:29:10Z
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'''Oxygen saturation''' is a relative measure of the amount of [[oxygen]] that is [[dissolve]]d or carried in a given medium. It can be measured with a dissolved oxygen probe such as an [[oxygen sensor]] or an [[optode]] in liquid media, usually water.
==Medical science==
In [[medicine]], '''oxygen saturation''' (S<sub>O<sub>2</sub></sub>), commonly abbreviated as "sats", measures the percentage of [[hemoglobin]] binding sites in the bloodstream occupied by oxygen. At low partial pressures of oxygen, most hemoglobin is deoxygenated. At around 90% (the value varies according to the clinical context) oxygen saturation increases according to an [[oxygen-hemoglobin dissociation curve]] and approaches 100% at partial oxygen pressures of >10 kPa. A [[pulse oximeter]] relies on the light absorption characteristics of saturated hemoglobin to give an indication of oxygen saturation. An Sa<sub>O<sub>2</sub></sub> (arterial oxygen saturation) value below 90% is termed [[hypoxemia]]. This may be due to various medical conditions.
The Sv<sub>O<sub>2</sub></sub> (venous oxygen saturation) is measured to see how much oxygen the body consumes. Under clinical treatment, a Sv<sub>O<sub>2</sub></sub> below 60%, indicates that the body is in lack of oxygen, and ischemic diseases occur. This measurement is often used under treatment with a heart-lung machine (Extra Corporal Circulation), and can give the perfusionist an idea of how much flow the patient needs to stay healthy.
Tissue [[oxygen]] saturation (St<sub>O<sub>2</sub></sub>) can be measured by [[near infrared spectroscopy]]. Although the measurements are still widely discussed, they give an idea of tissue oxygenation in various conditions.
Saturation of Peripheral Oxygen (Sp<sub>O<sub>2</sub></sub>) is an estimation of the oxygen saturation level usually measured with a [[pulse oximeter]] device.
== Environmental sciences ==
[[Image:AYool WOA surf O2.png|thumb|right|Annual mean sea surface dissolved '''oxygen''' for the [[World Ocean]]. Data from the [[World Ocean Atlas]] [http://www.nodc.noaa.gov/OC5/WOA01/ 2001].]]
[[Image:AYool WOA AOU 180E.png|thumb|right|[[Pacific Ocean]] sections of dissolved oxygen and [[apparent oxygen utilisation]]. Data from the [[World Ocean Atlas]] [http://www.nodc.noaa.gov/OC5/WOA05/pr_woa05.html 2005].]]
In [[water|aquatic]] environments, '''oxygen saturation''' is a relative measure of the amount of [[oxygen]] (O<sub><small>2</small></sub>) dissolved in the water. Supersaturation can sometimes be harmful for organisms and cause decompression sickness. '''Dissolved oxygen''' ('''DO''') is measured in standard solution units such as millilitres O<sub>2</sub> per litre (ml/L), millimoles O<sub><small>2</small></sub> per litre (mmol/L), milligrams O<sub><small>2</small></sub> per litre (mg/L) and moles O<sub>2</sub> m<small>3</small>. For example, in freshwater under atmospheric pressure at 20°C, O<sub>2</sub> saturation is 9.1 mg/L.
Solubility tables (based upon temperature) and corrections for different salinities and pressures can be found at the [http://water.usgs.gov/owq/FieldManual/Chapter6/6.2.4.pdf USGS web site]. Tables such as these of ''DO'' in milliliters per liter (ml/L) are based upon empirical equations that have been worked out and tested (e.g. Weiss, 1970):
<center>
<math>ln(DO) = A1 + A2*100/T + A3*ln(T/100) + A4*T/100 + S*[B1 + B2*T/100 + B3*(T/100)^2]</math>
</center>
Where ''ln'' is the [[natural log]] and the other variables take the following values:
<center>
{|
|-
| ''A1''
| =
| -173.4292
|
| ''B1''
| =
| -0.033096
|-
| ''A2''
| =
| 249.6339
|
| ''B2''
| =
| 0.014259
|-
| ''A3''
| =
| 143.3483
|
| ''B3''
| =
| -0.001700
|-
| ''A4''
| =
| -21.8492
|-
| ''T''
| =
| temperature ([[kelvin]]s)
|
| ''S''
| =
| salinity (g/kg)
|}
</center>
To convert the calculated ''DO'' above from ml/L to mg/L, multiply the answer by 1.4276.
==See also==
* [[Pulse oximetry]]
* [[Apparent oxygen utilisation]]
* [[Arterial blood gas]]
* [[Wastewater quality indicators]] discusses both [[Biochemical oxygen demand|BOD]] and [[Chemical oxygen demand|COD]] as indicators of wastewater quality.
==References==
* {{cite journal |author=Weiss, R. |title=The solubility of nitrogen, oxygen, and argon in water and seawater |journal=Deep-Sea Res. |date=1970 |volume=17 |issue= |pages=721–35}}
* [http://www.altitude.org/calculators/saturationgraph/saturationgraph.htm Interactive haemoglobin saturation graph]
==External links==
[[Category:Aquatic ecology]]
[[Category:Blood]]
[[Category:Water quality indicators]]
[[Category:Oxygen]]
[[da:Iltmætning]]
[[de:Sauerstoffsättigung]]
[[ko:포화 산소량]]
[[ja:溶存酸素量]]
[[pl:Saturacja (medycyna)]]
[[fi:Happisaturaatio]]