Oxygen saturation (symbolSO2) is a relative measure of the concentration ofoxygen that isdissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It can be measured with a dissolved oxygen probe such as anoxygen sensor or anoptode in liquid media, usually water.[1] The standard unit of oxygen saturation is percent (%).
Oxygen saturation can be measured regionally and noninvasively.Arterial oxygen saturation (SaO2) is commonly measured usingpulse oximetry. Tissue saturation at peripheral scale can be measured usingNIRSTooltip near-infrared spectroscopy. This technique can be applied on both muscle and brain.
Inmedicine, oxygen saturation refers tooxygenation, or when oxygen molecules (O
2) enter thetissues of the body. In this caseblood is oxygenated in thelungs, where oxygen molecules travel from the air into the blood. Oxygen saturation ((O
2) sats) measures the percentage ofhemoglobin binding sites in the bloodstream occupied by oxygen. Fish, invertebrates, plants, and aerobic bacteria all require oxygen.
Inaquatic environments, oxygen saturation is a ratio of the concentration of "dissolvedoxygen" (DO, O2), to the maximum amount of oxygen that will dissolve in that water body, at the temperature and pressure which constitute stable equilibrium conditions. Well-aerated water (such as a fast-moving stream) without oxygen producers or consumers is 100% saturated.[2]
Stagnant water can become somewhatsupersaturated with oxygen (i.e., reach more than 100% saturation) either because of the presence of photosynthetic aquatic oxygen producers or because of a slow equilibration after a change of atmospheric conditions.[2] Stagnant water in the presence of decaying matter will typically have an oxygen concentration much less than 100%, which is due to anaerobic bacteria being much less efficient at breaking down organic material.[citation needed][3] Similarly as in water, oxygen concentration also plays a key role in the breakdown of organic matter in soils. Higher oxygen saturation allows aerobic bacteria to persist, which breaks down decaying organic material in soils much more efficiently than anaerobic bacteria.[4] Thus, soils with high oxygen saturation will have less organic matter per volume than those with low oxygen saturation.[4]
Environmental oxygenation can be important to thesustainability of a particularecosystem. TheUS Environmental Protection Agency has published a table of maximum equilibrium dissolved oxygen concentration versus temperature at atmospheric pressure.[5] The optimal levels in an estuary for dissolved oxygen is higher than six ppm.[6] Insufficient oxygen (environmental hypoxia), often caused by the decomposition of organic matter andnutrient pollution, may occur in bodies of water such asponds andrivers, tending to suppress the presence ofaerobic organisms such asfish. Deoxygenation increases the relative population ofanaerobic organisms such as plants and somebacteria, resulting infish kills and other adverse events. The net effect is to alter thebalance of nature by increasing the concentration of anaerobic over aerobicspecies.
