Oxygen saturation



Oxygen saturation is a relative measure of the amount of optode in liquid media, usually water.

Medical science

In medicine, oxygen saturation (SO2) measures the percentage of pulse oximeter relies on the light absorption characteristics of saturated hemoglobin to give an indication of oxygen saturation. An SaO2 (arterial oxygen saturation) value below 90% is termed hypoxemia. This may be due to various medical conditions.

The SvO2 (venous oxygen saturation) is measured to see how much oxygen the body consumes. Under clinical treatment, a SvO2 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 near infrared spectroscopy. Although the measurements are still widely discussed, they give an idea of tissue oxygenation in various conditions.

Saturation of Peripheral Oxygen (SpO2) is an estimation of the oxygen saturation level usually measured with a pulse oximeter device.

Environmental sciences

  In aquatic environments, oxygen saturation is a relative measure of the amount of oxygen (O2) 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 millimoles O2 per liter (mmol/L), milligrams O2

  • 20 °C, normal pressure, freshwater: 9.1 mg/L = 100% saturation

Solubility tables (based upon temperature) and corrections for different salinities and pressures can be found at the 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): 

  ln(DO) = A1 + A2 * 100 / T + A3 * ln(T / 100) + A4 * T / 100 + S * [B1 + B2 * T / 100 + B3 * (T / 100)2]
   
  Where:
  A1 =  − 173.4292
  A2 = 249.6339
  A3 = 143.3483
  A4 =  − 21.8492
  B1 =  − 0.033096
  B2 = 0.014259
  B3 =  − 0.001700
  T = temperature in kelvins
  S = salinity in g/kg.
  DO = dissolved oxygen in ml/L.  
       ln is the natural log.  Multiply DO by 1.4276 to obtain mg/L.

See also

  • Apparent oxygen utilisation
  • COD as indicators of wastewater quality.

References

  • Weiss, R. (1970). "The solubility of nitrogen, oxygen, and argon in water and seawater". Deep-Sea Res. 17: 721-35.
  • Interactive haemoglobin saturation graph

External links
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Oxygen_saturation". A list of authors is available in Wikipedia.