Editing Oxygen (section)

===Toxicity===
{{Main|Oxygen toxicity}}
[[File:Symptoms of oxygen toxicity.png|thumb|left|upright=1.35|Main symptoms of oxygen toxicity<ref>{{cite journal |author=Dharmeshkumar N Patel |display-authors=4 |author2=Ashish Goel |author3=SB Agarwal |author4=Praveenkumar Garg |author5=Krishna K Lakhani |title=Oxygen Toxicity |journal=Indian Academy of Clinical Medicine |volume=4 |issue=3 |page=234 |date=2003 |url=http://medind.nic.in/jac/t03/i3/jact03i3p234.pdf |access-date=April 26, 2009 |archive-date=September 22, 2015 |archive-url=https://web.archive.org/web/20150922093352/http://medind.nic.in/jac/t03/i3/jact03i3p234.pdf |url-status=dead }}</ref>|alt=A diagram showing a male torso and listing symptoms of oxygen toxicity: Eyes&nbsp;– visual field loss, nearsightedness, cataract formation, bleeding, fibrosis; Head&nbsp;– seizures; Muscles&nbsp;– twitching; Respiratory system&nbsp;– jerky breathing, irritation, coughing, pain, shortness of breath, tracheobronchitis, acute respiratory distress syndrome.]]

Oxygen gas ({{chem|O|2}}) can be [[Oxygen toxicity|toxic]] at elevated [[partial pressure]]s, leading to [[convulsion]]s and other health problems.<ref name="Acott" /><ref group=lower-alpha>Since {{chem|O|2}}'s partial pressure is the fraction of {{chem|O|2}} times the total pressure, elevated partial pressures can occur either from high {{chem|O|2}} fraction in breathing gas or from high breathing gas pressure, or a combination of both.</ref><ref name="ECE511">[[#Reference-idCook1968|Cook & Lauer 1968]], p. 511</ref> Oxygen toxicity usually begins to occur at partial pressures more than 50 kilo[[Pascal (unit)|pascals]]&nbsp;(kPa), equal to about 50% oxygen composition at standard pressure or 2.5 times the normal sea-level {{chem|O|2}} partial pressure of about 21&nbsp;kPa. This is not a problem except for patients on [[mechanical ventilator]]s, since gas supplied through [[oxygen mask]]s in medical applications is typically composed of only 30–50% {{chem|O|2}} by volume (about 30&nbsp;kPa at standard pressure).<ref name="NBB299" />

At one time, [[Premature birth|premature babies]] were placed in incubators containing {{chem|O|2}}-rich air, but this practice was discontinued after some babies were blinded by the oxygen content being too high.<ref name="NBB299" />

Breathing pure {{chem|O|2}} in space applications, such as in some modern space suits, or in early spacecraft such as [[Apollo spacecraft|Apollo]], causes no damage due to the low total pressures used.<ref name="pmid11541018" /><ref>{{cite web|last = Wade|first = Mark|date = 2007|url = http://www.astronautix.com/craftfam/spasuits.htm|title = Space Suits|publisher = Encyclopedia Astronautica |access-date=December 16, 2007 |url-status = dead|archive-url = https://web.archive.org/web/20071213122134/http://www.astronautix.com/craftfam/spasuits.htm |archive-date = December 13, 2007}}</ref> In the case of spacesuits, the {{chem|O|2}} partial pressure in the breathing gas is, in general, about 30&nbsp;kPa (1.4 times normal), and the resulting {{chem|O|2}} partial pressure in the astronaut's arterial blood is only marginally more than normal sea-level {{chem|O|2}} partial pressure.<ref>{{cite web |url=http://www.globalrph.com/martin_4_most2.htm |title=The Four Most Important Equations In Clinical Practice |last=Martin |first=Lawrence |website=GlobalRPh |publisher=David McAuley |access-date=June 19, 2013 |archive-date=September 5, 2018 |archive-url=https://web.archive.org/web/20180905215615/http://www.globalrph.com/martin_4_most2.htm |url-status=live }}</ref>

Oxygen toxicity to the lungs and [[central nervous system]] can also occur in deep [[scuba diving]] and [[surface-supplied diving]].<ref name="NBB299" /><ref name="Acott" /> Prolonged breathing of an air mixture with an {{chem|O|2}} partial pressure more than 60&nbsp;kPa can eventually lead to permanent [[pulmonary fibrosis]].<ref name="BMJ">{{cite journal |author=Wilmshurst P |title=Diving and oxygen |journal=BMJ |volume=317 |issue=7164 |pages=996–99 |date=1998 |pmid=9765173 |pmc=1114047 |doi=10.1136/bmj.317.7164.996}}</ref> Exposure to an {{chem|O|2}} partial pressure greater than 160&nbsp;kPa (about 1.6 atm) may lead to convulsions (normally fatal for divers). Acute oxygen toxicity (causing seizures, its most feared effect for divers) can occur by breathing an air mixture with 21% {{chem|O|2}} at {{convert|66|m|abbr=on}} or more of depth; the same thing can occur by breathing 100% {{chem|O|2}} at only {{convert|6|m|abbr=on}}.<ref name="BMJ" /><ref name="Donald">{{cite book |last=Donald |first=Kenneth |title=Oxygen and the Diver |isbn = 978-1-85421-176-7|date=1992 |publisher=SPA in conjunction with K. Donald |location=England}}</ref><ref name="Donald1">{{cite journal |author=Donald K. W. |title=Oxygen Poisoning in Man: Part I |journal=Br Med J |volume=1 |issue=4506 |pages=667–72 |date=1947 |pmc=2053251 |doi=10.1136/bmj.1.4506.667 |pmid=20248086}}</ref><ref name="Donald2">{{cite journal |author=Donald K. W. |title=Oxygen Poisoning in Man: Part II |journal=Br Med J |volume=1 |pages=712–17 |date=1947 |pmc=2053400|issue=4507 |doi=10.1136/bmj.1.4507.712 |pmid=20248096}}</ref>