Examine individual changes

'{{Short description|Medical measurement}} {{For|oxygen saturation in general|Oxygen saturation|}} [[File:Blutkreislauf.png|thumbnail|right|Blood circulation: Red = oxygenated (arteries), Blue = deoxygenated (veins)]] '''Oxygen saturation''' is the fraction of [[oxygen]]-saturated [[haemoglobin]] relative to total haemoglobin (unsaturated + saturated) in the [[blood]]. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal arterial '''blood oxygen saturation levels''' in humans are 97–100 percent.<ref name="Kobayashi et al., 2018">{{cite journal |last1=Kobayashi |first1=M |last2=Fukuda |first2=S |last3=Takano |first3=KI |last4=Kamizono |first4=J |last5=Ichikawa |first5=K |title=Can a pulse oxygen saturation of 95% to 96% help predict further vital sign destabilization in school-aged children?: A retrospective observational study. |journal=Medicine |date=June 2018 |volume=97 |issue=25 |pages=e11135 |doi=10.1097/MD.0000000000011135 |pmid=29924014|pmc=6023980 |s2cid=49312513 }}</ref> If the level is below 90 percent, it is considered low and called [[hypoxemia]].<ref>{{cite web|title=Hypoxemia (low blood oxygen)|url=http://www.mayoclinic.com/health/hypoxemia/MY00219|work=[[Mayo Clinic]]|publisher=mayoclinic.com|access-date=6 June 2013}}</ref> Arterial blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed. Continued low oxygen levels may lead to respiratory or cardiac arrest. [[Oxygen therapy]] may be used to assist in raising blood oxygen levels. Oxygenation occurs when [[Allotropes of oxygen#Dioxygen|oxygen]] molecules ({{chem|O|2}}) enter the [[Tissue (biology)|tissues]] of the body. For example, [[blood]] is oxygenated in the [[lung]]s, where oxygen molecules travel from the air and into the blood. Oxygenation is commonly used to refer to medical oxygen saturation. ==Definition== [[File:Oxyhaemoglobin dissociation curve.png|thumb|Hemoglobin saturation curve]] In [[medicine]], '''oxygen saturation''', commonly referred to as "sats", measures the percentage of [[hemoglobin]] binding sites in the bloodstream occupied by oxygen.<ref>{{cite book|url=https://books.google.com/books?id=3PJVLH1NmQAC&q=definition+of+oxygen+saturation+so2&pg=PA370|title=Clinical Laboratory Medicine| first1 = Kenneth D. | last1 = McClatchey|publisher=[[Lippincott Williams & Wilkins]]|location=[[Philadelphia]]|year=2002|page=370 | via = [[Google Books]] |isbn=9780683307511}}</ref>{{rp|page=[https://books.google.com/books?id=3PJVLH1NmQAC&q=definition+of+oxygen+saturation+so2&pg=PA370 370]}} 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 >11 kPa. A [[pulse oximeter]] relies on the light absorption characteristics of saturated hemoglobin to give an indication of oxygen saturation.<ref>{{Cite web |title=Pulse Oximetry Basic Principles and Interpretation {{!}} Iowa Head and Neck Protocols |url=https://medicine.uiowa.edu/iowaprotocols/pulse-oximetry-basic-principles-and-interpretation |access-date=2023-03-29 |website=medicine.uiowa.edu |language=en}}</ref> ==Physiology== The body maintains a stable level of oxygen saturation for the most part by chemical processes of [[aerobic metabolism]] associated with [[breathing]]. Using the [[respiratory system]], red blood cells, specifically the [[hemoglobin]], gather oxygen in the lungs and distribute it to the rest of the body. The needs of the body's blood oxygen may fluctuate such as during exercise when more oxygen is required <ref>{{cite web|title=Understanding Blood Oxygen Levels at Rest|url=http://www.fitday.com/fitness-articles/fitness/cardio/understanding-blood-oxygen-levels-at-rest.html#b|website=fitday.com|access-date=6 June 2013}}</ref> or when living at higher altitudes. A blood cell is said to be "saturated" when carrying a normal amount of oxygen.<ref>{{cite web|last=Ellison|first=Bronwyn|title=Normal Range of Blood Oxygen Leven|url=http://www.livestrong.com/article/124374-normal-range-blood-oxygen-level/|website=Livestrong.com|access-date=6 June 2013}}</ref> Both [[hyperoxia|too high]] and [[hypoxia (medical)|too low]] levels can have adverse effects on the body.<ref>{{Cite web|url=https://www.webmd.com/asthma/guide/hypoxia-hypoxemia|title=Hypoxia and Hypoxemia: Symptoms, Treatment, Causes|website=WebMD|language=en|access-date=2019-03-11}}</ref> ==Measurement== An SaO₂ (arterial oxygen saturation, as determined by an [[arterial blood gas test]]<ref name=":0">{{Cite web|url=http://incenter.medical.philips.com/doclib/enc/fetch/586262/586457/Understanding_Pulse_Oximetry.pdf%3Fnodeid%3D586458%26vernum%3D2|title=Understanding Pulse Oximetry: SpO2 Concepts|publisher=Philips Medical Systems|access-date=19 August 2016}}</ref>) value below 90% indicates [[hypoxemia]] (which can also be caused by [[anemia]]). Hypoxemia due to low SaO₂ is indicated by [[cyanosis]]. Oxygen saturation can be measured in different tissues:<ref name=":0" /> {{unordered list | Venous oxygen saturation (SvO₂) is the percentage of oxygenated hemoglobin returning to the right side of the heart. It can be measured to see if oxygen delivery meets the tissues' demands. SvO₂ typically varies between 60% and 80%.<ref>{{Cite web|url=https://www.lhsc.on.ca/critical-care-trauma-centre/central-venous/mixed-venous-oxygen-saturation|title=Central Venous/Mixed Venous Oxygen Saturation &#124; LHSC}}</ref> A lower value 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]] ([[Extracorporeal membrane oxygenation|extracorporeal circulation]]), and can give the perfusionist an idea of how much flow the patient needs to stay healthy. | Tissue oxygen saturation (StO₂) can be measured by [[near infrared spectroscopy]]. Although the measurements are still widely discussed, they give an idea of tissue oxygenation in various conditions. | Peripheral oxygen saturation (SpO₂) is typically measured at a fingertip using a pulse oximeter. }} ==Pulse oximetry== {{Main article|Pulse oximetry}} [[File:Wrist-oximeter.jpg|thumbnail|right|Example pulse oximeter]] Pulse oximetry is a method used to estimate the percentage of oxygen bound to [[hemoglobin]] in the blood.<ref name="Aguilar">{{cite book | vauthors = Peláez EA, Villegas ER | title = 2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society | chapter = LED power reduction trade-offs for ambulatory pulse oximetry | volume = 2007 | pages = 2296–99 | date = 2007 | pmid = 18002450 | doi = 10.1109/IEMBS.2007.4352784 | isbn = 978-1-4244-0787-3 | s2cid = 34626885 }}</ref> This approximation to SaO₂ is designated SpO₂ (peripheral oxygen saturation). The pulse oximeter is a small device that clips to the body (typically a finger, an earlobe or an infant's foot) and displays its reading, or transfers it to another device. Oxygenated and deoxygenated hemoglobin differ in absorption of light of different wavelengths. The oximeter uses [[light-emitting diode]]s of different wavelengths in conjunction with a light-sensitive sensor to measure the absorption of red and infrared wavelengths in the extremity, and estimates the SpO₂ from the absorption spectrum.<ref name=":0" /> ==Medical significance== Healthy individuals at sea level usually exhibit oxygen saturation values between 96% and 99%, and should be above 94%. At 1,600 meters' altitude (about one [[mile]] high) oxygen saturation should be above 92%.<ref>{{cite web | title = Normal oxygen level | work = National Jewish Health | publisher = [[MedHelp]] | date = February 23, 2009 | url = http://www.medhelp.org/posts/Respiratory-Disorders/Normal-oxygen-level/show/760829 | access-date = 2014-01-28 }}</ref> An SaO₂ (arterial oxygen saturation) value below 90% causes [[Hypoxia (medical)|hypoxia]] (which can also be caused by [[anemia]]). Hypoxia due to low SaO₂ is indicated by [[cyanosis]], but oxygen saturation does not directly reflect tissue oxygenation. The affinity of hemoglobin to oxygen may impair or enhance oxygen release at the tissue level. Oxygen is more readily released to the tissues (i.e., [[hemoglobin]] has a lower affinity for oxygen) when pH is decreased, body temperature is increased, arterial partial pressure of carbon dioxide (PaCO₂) is increased, and 2,3-DPG levels (a byproduct of glucose metabolism also found in stored blood products) are increased. When the hemoglobin has greater affinity for oxygen, less is available to the tissues. Conditions such as increased pH, decreased temperature, decreased PaCO₂, and decreased 2,3-DPG will increase oxygen binding to the hemoglobin and limit its release to the tissue.<ref>{{Cite web|url=http://www.aacn.org/WD/Practice/Docs/ch_14_PO.pdf|title=Oxygen Saturation Monitoring by Pulse Oximetry|last=Schutz|date=2001|website=American Association of Critical Care Nurses|url-status=dead|access-date=September 10, 2011|archive-url=https://web.archive.org/web/20120131222646/http://www.aacn.org/WD/Practice/Docs/ch_14_PO.pdf|archive-date=January 31, 2012}}</ref> ==See also== * [[Arteriovenous oxygen difference]] ==References== {{Reflist|30em}} ==External links== * [https://web.archive.org/web/20100831024941/http://www.altitude.org/hemoglobin_saturation.php Interactive hemoglobin saturation graph] {{Respiratory physiology}} {{Authority control}} [[Category:Blood]] [[Category:Diagnostic intensive care medicine]] [[Category:Diagnostic emergency medicine]] [[Category:Diagnostic pulmonology]] [[Category:Oxygen]] [[Category:Medical terminology]]'