View source for Oxygen therapy

{{Short description|Use of oxygen as a medical treatment}}
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| image             = Simple face mask.jpg
| width             = 250px
| alt               =
| caption           = A person wearing a simple face mask
<!-- Clinical data -->
| synonyms          = supplemental oxygen, enriched air
| pronounce         =
| tradename         =
| Drugs.com         = {{Drugs.com|pro|oxygen}}
| MedlinePlus       =
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| routes_of_administration = inhaled
| legal_AU = <!-- S2, S3, S4, S5, S6, S7, S8, S9 or Unscheduled-->
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| legal_CA = <!-- OTC, Rx-only, Schedule I, II, III, IV, V, VI, VII, VIII -->
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<!-- Identifiers -->
| CAS_number        = 7782-44-7
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = S88TT14065
| class             = medical gas
| ATCvet            =
| ATC_prefix        = V03
| ATC_suffix        = AN01
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<!-- Chemical and physical data -->
| chemical_formula  = O<sub>2</sub>
| molecular_weight  =
}}
<!-- Definition and medical uses -->
'''Oxygen therapy''', also referred to as '''supplemental oxygen''', is the use of [[oxygen]] as [[medical therapy|medical treatment]].<ref name=BNF69>{{cite book|title=British national formulary: BNF 69|date=2015|publisher=British Medical Association|isbn=978-0-85711-156-2|pages=217–218, 302|edition=69}}</ref> [[Supplemental oxygen]] can also refer to the use of oxygen enriched air at altitude. Acute indications for [[therapy]] include [[hypoxemia]] (low blood oxygen levels), [[carbon monoxide toxicity]] and [[cluster headache]]. It may also be prophylactically given to maintain blood oxygen levels during the induction of [[anesthesia]].<ref name="WHO2008">{{cite book | title = WHO Model Formulary 2008 | year = 2009 | isbn = 978-92-4-154765-9 | vauthors = ((World Health Organization)) | veditors = Stuart MC, Kouimtzi M, Hill SR | hdl = 10665/44053 | author-link = World Health Organization | publisher = World Health Organization | hdl-access=free | page=20 }}</ref> Oxygen therapy is often useful in chronic hypoxemia caused by conditions such as severe [[COPD]] or [[cystic fibrosis]].<ref name="Jami2006">{{cite book| veditors = Jamison DT, Breman JG, Measham AR, Alleyne G, Claeson M, Evans DB, Jha P, Mills A, Musgrove P |url=https://books.google.com/books?id=Ds93H98Z6D0C&pg=PA689|title=Disease Control Priorities in Developing Countries |date=2006|publisher=World Bank Publications|isbn=978-0-8213-6180-1|page=689|language=en|archive-url=https://web.archive.org/web/20170510193648/https://books.google.ca/books?id=Ds93H98Z6D0C&pg=PA689|archive-date=2017-05-10|url-status=live}}</ref><ref name=BNF69/> Oxygen can be delivered via [[nasal cannula]], [[Oxygen mask|face mask]], or [[endotracheal intubation]]  at normal atmospheric pressure, or in a [[hyperbaric oxygen|hyperbaric chamber]].<ref>{{cite book| vauthors = Macintosh M, Moore T |title=Caring for the Seriously Ill Patient 2E|date=1999|publisher=CRC Press|isbn=978-0-340-70582-7|page=57|edition=2|url=https://books.google.com/books?id=T8-owObnIgUC&pg=PA57|language=en|url-status=live|archive-url=https://web.archive.org/web/20170118051021/https://books.google.ca/books?id=T8-owObnIgUC&pg=PA57|archive-date=2017-01-18}}</ref><ref>{{cite book| vauthors = Dart RC |title=Medical Toxicology|date=2004|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-2845-4|pages=217–219|url=https://books.google.com/books?id=BfdighlyGiwC&pg=PA217|language=en|url-status=live|archive-url=https://web.archive.org/web/20170118050646/https://books.google.ca/books?id=BfdighlyGiwC&pg=PA217|archive-date=2017-01-18}}</ref> It can also be given through bypassing the airway, such as in [[Extracorporeal membrane oxygenation|ECMO]] therapy.

<!-- Side effects and mechanism -->
Oxygen is required for normal [[cell metabolism|cellular metabolism]].<ref>{{cite book| vauthors = Peate I, Wild K, Nair M |title=Nursing Practice: Knowledge and Care|date=2014|publisher=John Wiley & Sons|isbn=978-1-118-48136-3|page=572|url=https://books.google.com/books?id=xqXCBwAAQBAJ&pg=PA572|language=en|url-status=live|archive-url=https://web.archive.org/web/20170118031908/https://books.google.ca/books?id=xqXCBwAAQBAJ&pg=PA572|archive-date=2017-01-18}}</ref> However, excessively high concentrations can result in [[oxygen toxicity]], leading to lung damage and [[respiratory failure]].<ref name=WHO2008 /><ref name=Mar1997/> Higher oxygen concentrations can also increase the risk of airway fires, particularly while smoking.<ref name="BNF69" /> Oxygen therapy can also dry out the nasal mucosa without humidification.<ref name=BNF69/> In most conditions, an oxygen saturation of 94–96% is adequate, while in those at risk of [[carbon dioxide retention]], saturations of 88–92% are preferred.<ref name="BNF69" /><ref name="Chu2018" /> In cases of carbon monoxide toxicity or [[cardiac arrest]], saturations should be as high as possible.<ref name=BNF69/><ref name=Chu2018>{{cite journal | vauthors = Chu DK, Kim LH, Young PJ, Zamiri N, Almenawer SA, Jaeschke R, Szczeklik W, Schünemann HJ, Neary JD, Alhazzani W | display-authors = 6 | title = Mortality and morbidity in acutely ill adults treated with liberal versus conservative oxygen therapy (IOTA): a systematic review and meta-analysis | journal = Lancet | volume = 391 | issue = 10131 | pages = 1693–1705 | date = April 2018 | pmid = 29726345 | doi = 10.1016/S0140-6736(18)30479-3 | s2cid = 19162595 | url = https://ruj.uj.edu.pl/xmlui/handle/item/117071 }}</ref> While [[Atmosphere of Earth|air]] is typically 21% oxygen by volume, oxygen therapy can increase O<sub>2</sub> content of air up to 100%.<ref name=Mar1997>{{cite book| vauthors = Martin L |title=Scuba Diving Explained: Questions and Answers on Physiology and Medical Aspects of Scuba Diving|date=1997|publisher=Lawrence Martin|isbn=978-0-941332-56-9|page=H-1|url=https://books.google.com/books?id=tcg2WR4uJr0C&pg=SL8-PA1|language=en|url-status=live|archive-url=https://web.archive.org/web/20170118050525/https://books.google.ca/books?id=tcg2WR4uJr0C&pg=SL8-PA1|archive-date=2017-01-18}}</ref>

<!-- History and culture -->
The medical use of oxygen first became common around 1917, and is the most common hospital treatment in the developed world.<ref name="BNF69" /><ref>{{cite book|url=https://books.google.com/books?id=f2YOpCMNFD4C&pg=PA398|title=Textbook of Anesthesia for Postgraduates|vauthors=Agasti TK|date=2010|publisher=JP Medical Ltd|isbn=978-93-80704-94-4|page=398|language=en|archive-url=https://web.archive.org/web/20170510193501/https://books.google.ca/books?id=f2YOpCMNFD4C&pg=PA398|archive-date=2017-05-10|url-status=live}}</ref><ref>{{cite book|url=https://books.google.com/books?id=KZceAQAAIAAJ|title=A Short History of Anaesthesia: The First 150 Years|vauthors=Rushman GB, Davies NJ, Atkinson RS|date=1996|publisher=Butterworth-Heinemann|isbn=978-0-7506-3066-5|page=39|language=en|archive-url=https://web.archive.org/web/20170510193656/https://books.google.ca/books?id=KZceAQAAIAAJ&q|archive-date=2017-05-10|url-status=live}}</ref><ref name=":Wyatt et al 2012">{{cite book|url=https://books.google.com/books?id=VFpIAgAAQBAJ&pg=PA95|title=Oxford Handbook of Emergency Medicine|vauthors=Wyatt JP, Illingworth RN, Graham CA, Hogg K, Robertson C, Clancy M|date=2012|publisher=OUP Oxford|isbn=978-0-19-101605-9|page=95|language=en|archive-url=https://web.archive.org/web/20170118030945/https://books.google.ca/books?id=VFpIAgAAQBAJ&pg=PA95|archive-date=2017-01-18|url-status=live}}</ref> It is currently on the [[WHO Model List of Essential Medicines|World Health Organization's List of Essential Medicines]].<ref name=":Wyatt et al 2012" /> Home oxygen can be provided either by [[oxygen tanks]] or [[oxygen concentrator]].<ref name=BNF69/>

==Medical uses==
[[File:Oxygen piping.png|thumb|right|Oxygen piping and regulator with flow meter, for oxygen therapy, mounted in an [[ambulance]]]]
Oxygen is widely used by hospitals, [[Emergency medical services|EMS]], and [[First aid|first-aid]] providers in a variety of conditions and settings. A few indications frequently requiring high-flow oxygen include [[resuscitation]], [[major trauma]], [[anaphylaxis]], major [[bleeding]], [[Shock (circulatory)|shock]], active [[convulsions]], and [[hypothermia]].<ref name="jrcalc">{{cite web|date=April 2009|title=Clinical Guidelines Update – Oxygen|url=http://www2.warwick.ac.uk/fac/med/research/hsri/emergencycare/prehospitalcare/jrcalcstakeholderwebsite/clinicalpracticeupdates/oxygen_guideline_combined_final_published_version_22apr09sb.pdf|url-status=live|archive-url=https://web.archive.org/web/20090711020246/http://www2.warwick.ac.uk/fac/med/research/hsri/emergencycare/prehospitalcare/jrcalcstakeholderwebsite/clinicalpracticeupdates/oxygen_guideline_combined_final_published_version_22apr09sb.pdf|archive-date=2009-07-11|access-date=2009-06-29|publisher=Joint Royal Colleges Ambulance Liaison Committee/Warwick University}}</ref><ref name="thorax">{{cite journal | vauthors = O'Driscoll BR, Howard LS, Davison AG | title = BTS guideline for emergency oxygen use in adult patients | journal = Thorax | volume = 63 | issue = Suppl 6:vi | pages = vi1-68 | date = October 2008 | pmid = 18838559 | doi = 10.1136/thx.2008.102947 | publisher = British Thoracic Society | doi-access = free }}</ref>

=== Acute conditions ===
In context of acute hypoxemia, oxygen therapy should be titrated to a target level based on [[pulse oximetry]] (94–96% in most patients, or 88–92% in people with COPD).<ref name="jrcalc" /><ref name="Chu2018" />  This can be performed by increasing oxygen delivery, described as F<sub>I</sub>O<sub>2</sub>(fraction of inspired oxygen). In 2018, the [[British Medical Journal]] recommended that oxygen therapy be stopped for saturations greater than 96% and not started for saturations above 90 to 93%.<ref name="BMJ2018Oct">{{cite journal | vauthors = Siemieniuk RA, Chu DK, Kim LH, Güell-Rous MR, Alhazzani W, Soccal PM, Karanicolas PJ, Farhoumand PD, Siemieniuk JL, Satia I, Irusen EM, Refaat MM, Mikita JS, Smith M, Cohen DN, Vandvik PO, Agoritsas T, Lytvyn L, Guyatt GH | display-authors = 6 | title = Oxygen therapy for acutely ill medical patients: a clinical practice guideline | journal = BMJ | volume = 363 | article-number = k4169 | date = October 2018 | pmid = 30355567 | doi = 10.1136/bmj.k4169 | s2cid = 53032977 }}</ref> This may be due to an association between excessive oxygenation in the acutely ill and increased mortality.<ref name="Chu2018" /> Exceptions to these recommendations include [[carbon monoxide poisoning]], [[cluster headache]]s, [[sickle cell crisis]], and [[pneumothorax]].<ref name="BMJ2018Oct" />

Oxygen therapy has also been used as emergency treatment for [[decompression sickness]] for years.<ref name="Brubakk">{{cite book| vauthors = Brubakk AO, Neuman TS |title=Bennett and Elliott's physiology and medicine of diving|publisher=Saunders Ltd.|year=2003|isbn=0-7020-2571-2|edition=5th Rev|location=United States|page=800}}</ref> Recompression in a [[hyperbaric chamber]] with 100% oxygen is the standard treatment for [[decompression illness]].<ref name="Brubakk" /><ref>{{cite web|author=Undersea and Hyperbaric Medical Society|title=Decompression Sickness or Illness and Arterial Gas Embolism|url=http://www.uhms.org/ResourceLibrary/Indications/DecompressionSickness/tabid/275/Default.aspx|archive-url=https://web.archive.org/web/20080705210353/http://www.uhms.org/ResourceLibrary/Indications/DecompressionSickness/tabid/275/Default.aspx|archive-date=2008-07-05|access-date=2008-05-30}}</ref><ref>{{cite journal| vauthors = Acott C |year=1999|title=A brief history of diving and decompression illness|url=http://archive.rubicon-foundation.org/6004|url-status=usurped|journal=South Pacific Underwater Medicine Society Journal|volume=29|issue=2|issn=0813-1988|oclc=16986801|archive-url=https://web.archive.org/web/20090201173320/http://archive.rubicon-foundation.org/6004|archive-date=2009-02-01|access-date=2008-05-30}}</ref> The success of recompression therapy is greatest if given within four hours after resurfacing, with earlier treatment associated with a decreased number of recompression treatments required for resolution.<ref name="Longphre">{{cite journal | vauthors = Longphre JM, Denoble PJ, Moon RE, Vann RD, Freiberger JJ | title = First aid normobaric oxygen for the treatment of recreational diving injuries | journal = Undersea & Hyperbaric Medicine | volume = 34 | issue = 1 | pages = 43–9 | year = 2007 | pmid = 17393938 | url = http://archive.rubicon-foundation.org/5514 | url-status = usurped | access-date = 2008-05-30 | oclc = 26915585 | archive-date = 2008-06-13 | archive-url = https://web.archive.org/web/20080613163501/http://archive.rubicon-foundation.org/5514 }}</ref> It has been suggested in literature that [[heliox]] may be a better alternative to oxygen therapy.<ref>{{cite journal | vauthors = Kol S, Adir Y, Gordon CR, Melamed Y | title = Oxy-helium treatment of severe spinal decompression sickness after air diving | journal = Undersea & Hyperbaric Medicine | volume = 20 | issue = 2 | pages = 147–54 | date = June 1993 | pmid = 8329941 | url = http://archive.rubicon-foundation.org/2133 | url-status = usurped | access-date = 2008-05-30 | archive-url = https://web.archive.org/web/20090201172647/http://archive.rubicon-foundation.org/2133 | archive-date = 2009-02-01 }}</ref>

In the context of stroke, oxygen therapy may be beneficial as long as hyperoxic environments are avoided.<ref name="Vincent 2017">{{cite journal | vauthors = Vincent JL, Taccone FS, He X | title = Harmful Effects of Hyperoxia in Postcardiac Arrest, Sepsis, Traumatic Brain Injury, or Stroke: The Importance of Individualized Oxygen Therapy in Critically Ill Patients | journal = Canadian Respiratory Journal | volume = 2017 | article-number = 2834956 | date = 2017 | pmid = 28246487 | pmc = 5299175 | doi = 10.1155/2017/2834956 | doi-access = free }}</ref>

People receiving outpatient oxygen therapy for hypoxemia following acute illness or hospitalization should be re-assessed by a physician prior to prescription renewal to gauge the necessity of ongoing oxygen therapy.<ref name="ACCPandATSfive">{{Citation|author1=American College of Chest Physicians|title=Five Things Physicians and Patients Should Question|date=September 2013|url=http://www.choosingwisely.org/doctor-patient-lists/american-college-of-chest-physicians-and-american-thoracic-society/|work=[[Choosing Wisely]]: an initiative of the [[ABIM Foundation]]|archive-url=https://web.archive.org/web/20131103063427/http://www.choosingwisely.org/doctor-patient-lists/american-college-of-chest-physicians-and-american-thoracic-society/|publisher=American College of Chest Physicians and American Thoracic Society|access-date=2013-01-06|archive-date=2013-11-03|author2=American Thoracic Society|author1-link=American College of Chest Physicians|author2-link=American Thoracic Society|url-status=live}}, which cites
* {{cite journal | vauthors = Croxton TL, Bailey WC | title = Long-term oxygen treatment in chronic obstructive pulmonary disease: recommendations for future research: an NHLBI workshop report | journal = American Journal of Respiratory and Critical Care Medicine | volume = 174 | issue = 4 | pages = 373–8 | date = August 2006 | pmid = 16614349 | pmc = 2648117 | doi = 10.1164/rccm.200507-1161WS | author3 = for the NHLBI Working Group on Long-term Oxygen Treatment in COPD }}
* {{cite journal | vauthors = O'Driscoll BR, Howard LS, Davison AG | title = BTS guideline for emergency oxygen use in adult patients | journal = Thorax | volume = 63 | issue = Suppl 6 | pages = vi1-68 | date = October 2008 | pmid = 18838559 | doi = 10.1136/thx.2008.102947 | doi-access = free }}
* {{cite journal | vauthors = Macnee W | title = Prescription of oxygen: still problems after all these years | journal = American Journal of Respiratory and Critical Care Medicine | volume = 172 | issue = 5 | pages = 517–8 | date = September 2005 | pmid = 16120712 | doi = 10.1164/rccm.2506007 }}</ref> If the initial hypoxemia has resolved, additional treatment may be an unnecessary use of resources.<ref name="ACCPandATSfive" />

=== Chronic conditions ===
Common conditions which may require a baseline of supplementary oxygen include [[chronic obstructive pulmonary disease]] (COPD), [[chronic bronchitis]], and [[emphysema]]. Patients may also require additional oxygen during acute exacerbations. Oxygen may also be prescribed for [[breathlessness]], end-stage cardiac failure, respiratory failure, advanced cancer, or neurodegenerative disease in spite of relatively normal blood oxygen levels. Physiologically, it may be indicated in people with arterial oxygen partial pressure Pa{{chem|O|2}} ≤ 55mmHg (7.3kPa) or arterial oxygen saturation Sa{{chem|O|2}} ≤ 88%.<ref name="McDonald et al 2005">{{cite journal | vauthors = McDonald CF, Crockett AJ, Young IH | title = Adult domiciliary oxygen therapy. Position statement of the Thoracic Society of Australia and New Zealand | journal = The Medical Journal of Australia | volume = 182 | issue = 12 | pages = 621–6 | date = June 2005 | pmid = 15963018 | doi = 10.5694/j.1326-5377.2005.tb06848.x | hdl-access = free | hdl = 2440/17207 | s2cid = 1056683 }}</ref><ref name="Stoller-2010">{{cite journal | vauthors = Stoller JK, Panos RJ, Krachman S, Doherty DE, Make B | title = Oxygen therapy for patients with COPD: current evidence and the long-term oxygen treatment trial | journal = Chest | volume = 138 | issue = 1 | pages = 179–87 | date = July 2010 | pmid = 20605816 | pmc = 2897694 | doi = 10.1378/chest.09-2555 }}</ref><ref name="Cranston et al 2005">{{cite journal | vauthors = Cranston JM, Crockett AJ, Moss JR, Alpers JH | title = Domiciliary oxygen for chronic obstructive pulmonary disease | journal = The Cochrane Database of Systematic Reviews | issue = 4 | article-number = CD001744 | date = October 2005 | volume = 2008 | pmid = 16235285 | pmc = 6464709 | doi = 10.1002/14651858.cd001744.pub2 | publisher = John Wiley & Sons, Ltd }}</ref>

Careful titration of oxygen therapy should be considered in patients with chronic conditions predisposing them to carbon dioxide retention (e.g., COPD, emphysema). In these instances, oxygen therapy may decrease respiratory drive, leading to accumulation of carbon dioxide (hypercapnia), [[Acidosis|acidemia]], and increased mortality secondary to respiratory failure.<ref name="tasmanian" /> Improved outcomes have been observed with titrated oxygen treatment largely due to gradual improvement of the [[ventilation/perfusion ratio]].<ref>{{cite journal | vauthors = Kim V, Benditt JO, Wise RA, Sharafkhaneh A | title = Oxygen therapy in chronic obstructive pulmonary disease | journal = Proceedings of the American Thoracic Society | volume = 5 | issue = 4 | pages = 513–8 | date = May 2008 | pmid = 18453364 | pmc = 2645328 | doi = 10.1513/pats.200708-124ET }}</ref> The risks associated with loss of respiratory drive are far outweighed by the risks of withholding emergency oxygen, so emergency administration of oxygen is never contraindicated. Transfer from the field to definitive care with titrated oxygen typically occurs long before significant reductions to the respiratory drive are observed.{{cn|date=June 2024}}

=== Contraindications ===
There are certain situations in which oxygen therapy has been shown to negatively impact a person's condition.<ref name="Patarinski1976">{{cite journal | vauthors = Patarinski D | title = [Indications and contraindications for oxygen therapy of respiratory insufficiency] | language = bg, en | journal = Vutreshni Bolesti | volume = 15 | issue = 4 | pages = 44–50 | year = 1976 | pmid = 1007238 }}</ref>
* Oxygen therapy can exacerbate the effects of [[paraquat#Toxicity|paraquat poisoning]] and should be withheld unless severe respiratory distress or respiratory arrest is present. Paraquat poisoning is rare, with about 200 deaths globally from 1958 to 1978.<ref>{{cite journal | vauthors = Agarwal R, Srinivas R, Aggarwal AN, Gupta D | title = Experience with paraquat poisoning in a respiratory intensive care unit in North India | journal = Singapore Medical Journal | volume = 47 | issue = 12 | pages = 1033–1037 | date = December 2006 | pmid = 17139398 | url = http://www.sma.org.sg/smj/4712/4712a2.pdf }}</ref>
* Oxygen therapy is not recommended for people with [[pulmonary fibrosis]] or [[bleomycin]]-associated lung damage.<ref name="phecc2009">{{cite web|date=15 July 2009|title=EMT Medication Formulary|url=http://www.phecit.ie/Documents/Clinical%20Practice%20Guidelines/EMT%203rd%20Edition%20CPGs/EMT%20Appendix%201%20Medication%20Formulary.pdf|archive-url=https://web.archive.org/web/20110514030405/http://www.phecit.ie/Documents/Clinical%20Practice%20Guidelines/EMT%203rd%20Edition%20CPGs/EMT%20Appendix%201%20Medication%20Formulary.pdf|archive-date=14 May 2011|access-date=2010-04-14|work=PHECC Clinical Practice Guidelines|publisher=[[Pre-Hospital Emergency Care Council]]|page=84}}</ref>
* [[Acute respiratory distress syndrome|ARDS]] caused by acid aspiration may be exacerbated with oxygen therapy according to some animal studies.<ref>{{cite journal | vauthors = Knight PR, Kurek C, Davidson BA, Nader ND, Patel A, Sokolowski J, Notter RH, Holm BA | display-authors = 6 | title = Acid aspiration increases sensitivity to increased ambient oxygen concentrations | journal = American Journal of Physiology. Lung Cellular and Molecular Physiology | volume = 278 | issue = 6 | pages = L1240-7 | date = June 2000 | pmid = 10835330 | doi = 10.1152/ajplung.2000.278.6.L1240 | s2cid = 12450589 }}</ref><ref>{{cite journal | vauthors = Nader-Djalal N, Knight PR, Thusu K, Davidson BA, Holm BA, Johnson KJ, Dandona P | title = Reactive oxygen species contribute to oxygen-related lung injury after acid aspiration | journal = Anesthesia and Analgesia | volume = 87 | issue = 1 | pages = 127–33 | date = July 1998 | pmid = 9661561 | doi = 10.1097/00000539-199807000-00028 | s2cid = 19132661 | doi-access = free }}</ref>
* Hyperoxic environments should be avoided in cases of sepsis.<ref name="Vincent 2017" />[[File:o2regulator.JPG|thumb|right|[[Pin Index Safety System|Pin-indexed]] Oxygen Regulator for portable D-Cylinder, usually carried in an ambulance's resuscitation kit]]
=== Adverse effects ===
In some instances, oxygen delivery can lead to particular complications in population subsets.
* In infants with respiratory failure, administration of high levels of oxygen can sometimes promote overgrowth of new blood vessels in the eye leading to blindness. This phenomenon is known as [[retinopathy of prematurity]] (ROP).{{cn|date=June 2024}}
* In rare instances, people receiving hyperbaric oxygen therapy have had seizures, which has been previously attributed to [[oxygen toxicity]].<ref name="smerz">{{cite journal | vauthors = Smerz RW | title = Incidence of oxygen toxicity during the treatment of dysbarism | journal = Undersea & Hyperbaric Medicine | volume = 31 | issue = 2 | pages = 199–202 | year = 2004 | pmid = 15485081 }}</ref><ref>{{cite journal | vauthors = Hampson NB, Simonson SG, Kramer CC, Piantadosi CA | title = Central nervous system oxygen toxicity during hyperbaric treatment of patients with carbon monoxide poisoning | journal = Undersea & Hyperbaric Medicine | volume = 23 | issue = 4 | pages = 215–219 | date = December 1996 | pmid = 8989851 }}</ref>
* There is some evidence that extended HBOT can accelerate development of [[cataracts]].{{cn|date=June 2024}}

===Alternative medicine===

Some practitioners of [[alternative medicine]] have promoted "oxygen therapy" as a cure for many human ailments including [[AIDS]], [[Alzheimer's disease]] and [[cancer]]. According to the [[American Cancer Society]], "available scientific evidence does not support claims that putting oxygen-releasing chemicals into a person's body is effective in treating cancer", and some of these treatments can be dangerous.<ref>{{cite web|date=26 December 2012|title=Oxygen Therapy|url=http://www.cancer.org/treatment/treatmentsandsideeffects/complementaryandalternativemedicine/pharmacologicalandbiologicaltreatment/oxygen-therapy|url-status=live|archive-url=https://web.archive.org/web/20120321213742/http://www.cancer.org/Treatment/TreatmentsandSideEffects/ComplementaryandAlternativeMedicine/PharmacologicalandBiologicalTreatment/oxygen-therapy|archive-date=21 March 2012|access-date=2013-09-20|publisher=[[American Cancer Society]]}}</ref>

== Physiologic effects ==
Oxygen supplementation has a variety of physiologic effects on the human body. Whether or not these effects are adverse to a patient is dependent upon clinical context. Cases in which an excess amount of oxygen is available to organs is known as [[hyperoxia]].<ref name="Consequences of hyperoxia and the t">{{cite journal | vauthors = Mach WJ, Thimmesch AR, Pierce JT, Pierce JD | title = Consequences of hyperoxia and the toxicity of oxygen in the lung | journal = Nursing Research and Practice | volume = 2011 | article-number = 260482 | date = 2011-06-05 | pmid = 21994818 | doi = 10.1155/2011/260482 | pmc = 3169834 | doi-access = free }}</ref> While the following effects may observed with noninvasive high-dose oxygen therapy (i.e., not [[Extracorporeal membrane oxygenation|ECMO]]), delivery of oxygen at higher pressures is associated with exacerbation of the following associated effects.{{cn|date=June 2024}}

=== Absorption atelectasis ===
It has been hypothesized that oxygen therapy may promote accelerated development of [[atelectasis]] (partial or complete lung collapse), as well as denitrogenation of gas cavities (e.g., [[pneumothorax]], [[pneumocephalus]]).<ref name="Mechanisms of atelectasis in the pe">{{cite journal | vauthors = Hedenstierna G, Edmark L | title = Mechanisms of atelectasis in the perioperative period | journal = Best Practice & Research. Clinical Anaesthesiology | volume = 24 | issue = 2 | pages = 157–69 | date = June 2010 | pmid = 20608554 | doi = 10.1016/j.bpa.2009.12.002 }}</ref><ref name="Domino 2010">{{cite journal | vauthors = Domino KB | title = Pre-emergence Oxygenation and Postoperative Atelectasis | journal = Anesthesiology | volume = 131 | issue = 4 | pages = 771–773 | date = October 2019 | pmid = 31283741 | doi = 10.1097/ALN.0000000000002875 | s2cid = 195842599 | doi-access = free }}</ref> This concept is based on the idea that oxygen is more quickly absorbed compared to nitrogen within the body, leading oxygen-rich areas that are poorly ventilated to be rapidly absorbed, leading to atelectasis.<ref name="Mechanisms of atelectasis in the pe"/> It is thought that higher [[Fraction of inspired oxygen|fractions of inhaled oxygen]] (''F<sub>I</sub>''O<sub>2</sub>) are associated with increasing rates of atelectasis in the clinical scenario.<ref>{{cite journal | vauthors = Dale WA, Rahn H | title = Rate of gas absorption during atelectasis | journal = The American Journal of Physiology | volume = 170 | issue = 3 | pages = 606–13 | date = September 1952 | pmid = 12985936 | doi = 10.1152/ajplegacy.1952.170.3.606 }}</ref> In clinically healthy adults, it is believed that absorption atelectasis typically does not have any significant implications when managed properly.<ref>{{cite journal | vauthors = O'Brien J | title = Absorption atelectasis: incidence and clinical implications | journal = AANA Journal | volume = 81 | issue = 3 | pages = 205–208 | date = June 2013 | pmid = 23923671 }}</ref>

=== Airway inflammation ===
In regard to the airway, both [[tracheobronchitis]] and [[mucositis]] have been observed with high levels of oxygen delivery (typically >40% O2).<ref>{{cite journal | vauthors = Kallet RH, Matthay MA | title = Hyperoxic acute lung injury | journal = Respiratory Care | volume = 58 | issue = 1 | pages = 123–41 | date = January 2013 | pmid = 23271823 | pmc = 3915523 | doi = 10.4187/respcare.01963 }}</ref> Within the lungs, these elevated concentrations of oxygen have been associated with increased alveolar toxicity (coined the [[Oxygen toxicity|Lorrain-Smith effect]]).<ref name="Consequences of hyperoxia and the t"/> Mucosal damage is observed to increase with elevated atmospheric pressure and oxygen concentrations, which may result in the development of [[Acute respiratory distress syndrome|ARDS]] and possibly death.<ref>{{cite journal | vauthors = Mach WJ, Thimmesch AR, Pierce JT, Pierce JD | title = Consequences of hyperoxia and the toxicity of oxygen in the lung | journal = Nursing Research and Practice | volume = 2011 | article-number = 260482 | date = 2011 | pmid = 21994818 | pmc = 3169834 | doi = 10.1155/2011/260482 | doi-access = free }}</ref><ref>{{cite book | vauthors = Cooper JS, Phuyal P, Shah N | chapter = Oxygen Toxicity |date=2021 | chapter-url= https://www.ncbi.nlm.nih.gov/books/NBK430743/| title=StatPearls|place=Treasure Island (FL)|publisher=StatPearls Publishing|pmid=28613494|access-date=2021-11-12}}</ref>

=== Central nervous system effects ===
Decreased cerebral blood flow and [[intracranial pressure]] (ICP) have been reported in hyperoxic conditions, with mixed results regarding impact on cognition.<ref>{{Cite book| vauthors = Cipolla MJ |url=https://www.ncbi.nlm.nih.gov/books/NBK53082/|title=Control of Cerebral Blood Flow|date=2009|publisher=Morgan & Claypool Life Sciences|language=en}}</ref><ref>{{cite journal | vauthors = Sheng M, Liu P, Mao D, Ge Y, Lu H | title = The impact of hyperoxia on brain activity: A resting-state and task-evoked electroencephalography (EEG) study | journal = PLOS ONE | volume = 12 | issue = 5 | article-number = e0176610 | date = 2017-05-02 | pmid = 28464001 | pmc = 5412995 | doi = 10.1371/journal.pone.0176610 | bibcode = 2017PLoSO..1276610S | doi-access = free }}</ref><ref>{{Cite journal| vauthors = Seo HJ, Bahk WM, Jun TY, Chae JH |date=2007-02-01|title=The Effect of Oxygen Inhalation on Cognitive Function and EEG in Healthy Adults|journal=Clinical Psychopharmacology and Neuroscience|url=https://www.cpn.or.kr/journal/view.html?spage=25&volume=5&number=1|language=en|volume=5|issue=1|pages=25–30|issn=1738-1088}}</ref><ref name="Brugniaux et al 2018">{{cite journal | vauthors = Brugniaux JV, Coombs GB, Barak OF, Dujic Z, Sekhon MS, Ainslie PN | title = Highs and lows of hyperoxia: physiological, performance, and clinical aspects | journal = American Journal of Physiology. Regulatory, Integrative and Comparative Physiology | volume = 315 | issue = 1 | pages = R1–R27 | date = July 2018 | pmid = 29488785 | doi = 10.1152/ajpregu.00165.2017 | s2cid = 3634189 | doi-access = free }}</ref> Hyperoxia as also been associated with [[seizure]]s, [[cataract]] formation, and reversible [[myopia]].<ref>{{cite journal | vauthors = Tibbles PM, Edelsberg JS | title = Hyperbaric-oxygen therapy | journal = The New England Journal of Medicine | volume = 334 | issue = 25 | pages = 1642–8 | date = June 1996 | pmid = 8628361 | doi = 10.1056/NEJM199606203342506 }}</ref>

=== Hypercapnea ===
Among {{CO2}} retainers, excess exposure to oxygen in context of the [[Haldane effect]] causes decreased binding of [[deoxyhemoglobin]] to {{CO2}} in the blood.<ref>{{cite journal | vauthors = Christiansen J, Douglas CG, Haldane JS | title = The absorption and dissociation of carbon dioxide by human blood | journal = The Journal of Physiology | volume = 48 | issue = 4 | pages = 244–71 | date = July 1914 | pmid = 16993252 | pmc = 1420520 | doi = 10.1113/jphysiol.1914.sp001659 }}</ref> This unloading of {{CO2}} may contribute to the development of [[Acid–base disorder|acid-base disorders]] due to the associated increase in [[PaCO2]] ([[Hypercapnia|hypercapnea]]).  Patients with underlying lung disease such as [[Effect of oxygen on chronic obstructive pulmonary disease|COPD may not be able to adequately clear the additional {{CO2}}]] produced by this effect, worsening their condition.<ref>{{cite journal | vauthors = Hanson CW, Marshall BE, Frasch HF, Marshall C | title = Causes of hypercarbia with oxygen therapy in patients with chronic obstructive pulmonary disease | journal = Critical Care Medicine | volume = 24 | issue = 1 | pages = 23–8 | date = January 1996 | pmid = 8565533 | doi = 10.1097/00003246-199601000-00007 | doi-access = free }}</ref> In addition, oxygen therapy has also been shown to decrease respiratory drive, further contributing to possible hypercapnea.<ref name="Domino 2010" />

=== Immunological effects ===
Hyperoxic environments have been observed to decrease [[granulocyte]] rolling and [[Leukocyte extravasation|diapedesis]] in specific circumstances in humans.<ref>{{cite journal | vauthors = Waisman D, Brod V, Wolff R, Sabo E, Chernin M, Weintraub Z, Rotschild A, Bitterman H | display-authors = 6 | title = Effects of hyperoxia on local and remote microcirculatory inflammatory response after splanchnic ischemia and reperfusion | journal = American Journal of Physiology. Heart and Circulatory Physiology | volume = 285 | issue = 2 | pages = H643-52 | date = August 2003 | pmid = 12714329 | doi = 10.1152/ajpheart.00900.2002 }}</ref> In regard to anaerobic infections, cases of [[necrotizing fasciitis]] have been observed to require fewer debridement operations and have improvement in regard to mortality in patients treated with hyperbaric oxygen therapy.<ref>{{cite journal | vauthors = Riseman JA, Zamboni WA, Curtis A, Graham DR, Konrad HR, Ross DS | title = Hyperbaric oxygen therapy for necrotizing fasciitis reduces mortality and the need for debridements | language = English | journal = Surgery | volume = 108 | issue = 5 | pages = 847–50 | date = November 1990 | pmid = 2237764 }}</ref> This may stem from oxygen intolerance of otherwise anaerobic microorganisms.{{cn|date=June 2024}}

=== Oxidative stress ===
Sustained exposure to oxygen may overwhelm the body's capacity to deal with [[oxidative stress]].<ref>{{cite journal | vauthors = Heffner JE, Repine JE | title = Pulmonary strategies of antioxidant defense | journal = The American Review of Respiratory Disease | volume = 140 | issue = 2 | pages = 531–54 | date = August 1989 | pmid = 2669581 | doi = 10.1164/ajrccm/140.2.531 }}</ref>  Rates of oxidative stress appears to be influenced by both oxygen concentration and length of exposure, with general toxicity observed to occur within hours in certain hyperoxic conditions.<ref>{{cite journal | vauthors = Clark JM, Lambertsen CJ | title = Rate of development of pulmonary O2 toxicity in man during O2 breathing at 2.0 Ata | journal = Journal of Applied Physiology | volume = 30 | issue = 5 | pages = 739–52 | date = May 1971 | pmid = 4929472 | doi = 10.1152/jappl.1971.30.5.739 }}</ref>

=== Reduction in erythropoiesis ===
Hyperoxia is observed to result in a serum reduction in [[erythropoietin]], resulting in reduced stimulus for [[erythropoiesis]].<ref name="Kokot et al 1994">{{cite journal | vauthors = Kokot M, Kokot F, Franek E, Wiecek A, Nowicki M, Duława J | title = Effect of isobaric hyperoxemia on erythropoietin secretion in hypertensive patients | journal = Hypertension | volume = 24 | issue = 4 | pages = 486–90 | date = October 1994 | pmid = 8088916 | doi = 10.1161/01.HYP.24.4.486 | doi-access = free }}</ref> Hyperoxia at normobaric environments does not appear to be able to halt erythropoiesis completely.<ref name="Kokot et al 1994" />

=== Pulmonary vasodilation ===
Within the lungs, hypoxia is observed to be a potent pulmonary [[Vasoconstriction|vasoconstrictor]], due to inhibition of an outward potassium current and activation of inward sodium current leading to pulmonary vascular muscular contraction.<ref>{{cite journal | vauthors = Sylvester JT, Shimoda LA, Aaronson PI, Ward JP | title = Hypoxic pulmonary vasoconstriction | journal = Physiological Reviews | volume = 92 | issue = 1 | pages = 367–520 | date = January 2012 | pmid = 22298659 | doi = 10.1152/physrev.00041.2010 | pmc = 9469196 }}</ref> However, the effects of hyperoxia do not seem to have a particularly strong vasodilatory effect from the few studies that have been performed on patients with [[pulmonary hypertension]].<ref name="Groves et al 1987">{{cite journal | vauthors = Groves BM, Reeves JT, Sutton JR, Wagner PD, Cymerman A, Malconian MK, Rock PB, Young PM, Houston CS | display-authors = 6 | title = Operation Everest II: elevated high-altitude pulmonary resistance unresponsive to oxygen | journal = Journal of Applied Physiology | volume = 63 | issue = 2 | pages = 521–30 | date = August 1987 | pmid = 3654410 | doi = 10.1152/jappl.1987.63.2.521 }}</ref><ref name="Day 2015">{{cite journal | vauthors = Day RW | title = Comparison between the Acute Pulmonary Vascular Effects of Oxygen with Nitric Oxide and Sildenafil | journal = Frontiers in Pediatrics | volume = 3 | page = 16 | date = 2015 | pmid = 25785258 | doi = 10.3389/fped.2015.00016 | pmc = 4347295 | doi-access = free }}</ref> As a result, an effect appears to be present but minor.<ref name="Groves et al 1987" /><ref name="Day 2015" />

=== Systemic vasoconstriction ===
In the systemic vasculature, oxygen serves as a vasoconstrictor, leading to mildly increased blood pressure and decreased cardiac output and heart rate. Hyperbaric conditions do not seem to have a significant impact on these overall physiologic effects.<ref>{{cite book |doi=10.1007/1-4020-4448-8_6 |chapter=Physiologic Effects of Hyperbaric Oxygen on Hemodynamics and Microcirculation |title=Handbook on Hyperbaric Medicine |year=2006 | vauthors = Mathieu D, Favory R, Collet F, Linke JC, Wattel F |pages=75–101 |isbn=1-4020-4376-7 }}</ref><ref name="Brugniaux et al 2018" /> Clinically, this may lead to increased [[Cardiac shunt|left-to-right shunting]] in certain patient populations, such as those with [[atrial septal defect]]. While the mechanism of the vasoconstriction is unknown, one proposed theory is that increased [[reactive oxygen species]] from oxygen therapy accelerates the degradation of endothelial [[nitric oxide]], a vasodilator.<ref>{{cite journal | vauthors = McNulty PH, King N, Scott S, Hartman G, McCann J, Kozak M, Chambers CE, Demers LM, Sinoway LI | display-authors = 6 | title = Effects of supplemental oxygen administration on coronary blood flow in patients undergoing cardiac catheterization | journal = American Journal of Physiology. Heart and Circulatory Physiology | volume = 288 | issue = 3 | pages = H1057-62 | date = March 2005 | pmid = 15706043 | doi = 10.1152/ajpheart.00625.2004 }}</ref><ref name="Brugniaux et al 2018"/> These vasoconstrictive effects are thought to be the underlying mechanism helping to abort cluster headaches.<ref>{{cite web| vauthors = Sands G |title=Oxygen Therapy for Headaches|url=http://www.headaches.org/consumer/topicsheets/oxygen.html|archive-url=https://web.archive.org/web/20071201004515/http://www.headaches.org/consumer/topicsheets/oxygen.html|archive-date=2007-12-01|access-date=2007-11-26}}</ref>

Dissolved oxygen in hyperoxic conditions may make also a significant contribution to total gas transport.<ref>{{cite book| vauthors = Jain KK |title=Textbook of Hyperbaric Medicine|year=2017|isbn=978-3-319-47138-9|pages=11–22|chapter=Physical, Physiological, and Biochemical Aspects of Hyperbaric Oxygenation|doi=10.1007/978-3-319-47140-2_2}}</ref>

==Storage and sources==
[[File:Home oxygen canisters.jpg|thumb|High pressure gas cylinders containing oxygen to be used at home. When in use, a regulator is connected to the cylinder valve and delivers gas at a constant low pressure through a hose to a mask that fits over a person's nose and mouth.]]
[[File:Home oxygen concentrator.jpg|thumb|A home oxygen concentrator for a person with [[emphysema]]]] [[File:Nasalprongs.JPG|thumb|Nasal cannula]]
[[File:NRBer.JPG|thumb|Non-rebreather mask]]

Oxygen can be separated by a number of methods (e.g., [[chemical reaction]], [[fractional distillation]]) to enable immediate or future use. The main methods utilized for oxygen therapy include:

# Liquid storage – [[Liquid oxygen]] is stored in insulated tanks at low temperature and allowed to [[boiling|boil]] (at a temperature of 90.188 K (−182.96&nbsp;°C)) during use, releasing gaseous oxygen. This method is widely utilized at hospitals due to high oxygen requirements. See [[Vacuum Insulated Evaporator]] for more information on this method of storage.
# Compressed gas storage – Oxygen gas is compressed in a [[gas cylinder]], which provides a convenient storage method (refrigeration not required). Large oxygen cylinders hold a volume of {{convert|6500|L|cuft}} and can last about two days at a flow rate of 2 litres per minute (LPM). A small portable M6 (B) cylinder holds {{convert|164|or|170|L|cuft}} and weighs about {{convert|1.3|to|1.6|kg|lb}}.<ref name="cprsavers">{{cite web |url=http://www.cpr-savers.com/Industrials/oxygen%20supply/luxfer-oxygen-cylinder-tanks.html |title=Luxfer Aluminum Oxygen Cylinders |publisher=CPR Savers & First Aid Supply |access-date=2010-04-18 |url-status=live |archive-url=https://web.archive.org/web/20100418170156/http://www.cpr-savers.com/Industrials/oxygen%20supply/luxfer-oxygen-cylinder-tanks.html |archive-date=2010-04-18 }}</ref> These tanks can last 4–6 hours with a [[Oxygen therapy#Oxygen conserving devices|conserving regulator]],{{clarify|what is a conserving regulator?|date=December 2022}} which adjust flow based on a person's breathing rate. Conserving regulators may not be effective for patients who breathe through their mouth.{{clarify|Why not?|date=December 2022}}
# Instant usage – The use of an electrically powered [[oxygen concentrator]]<ref>{{cite web |url= http://www.inspiredrc.com/POC%20AARC%20Dec%202006.pdf |title= Portable Oxygen Concentrators (POC) Performance Variables that Affect Therapy |access-date= 2007-07-03 | vauthors = McCoy R |archive-url= https://web.archive.org/web/20070709231633/http://www.inspiredrc.com/POC%20AARC%20Dec%202006.pdf |archive-date= 2007-07-09 }}</ref>  or a chemical reaction based unit<ref>{{Cite web|url=http://www.wemjournal.org/wmsonline/?request=get-document&issn=1080-6032&volume=013&issue=04&page=0253|title=Wilderness & Environmental Medicine: Sage Journals}}</ref> can create sufficient oxygen for immediate personal use. These units (especially the electrically powered versions) are widely used for home oxygen therapy as portable personal oxygen. One particular advantage includes continuous supply without need for bulky oxygen cylinders.

===Hazards and risk===
Highly concentrated sources of oxygen also increase risk for rapid combustion. Oxygen itself is not flammable, but the addition of concentrated oxygen to a fire greatly increases its intensity, and can aid the combustion of materials that are relatively inert under normal conditions. Fire and [[explosion]] hazards exist when concentrated oxidants and [[fuel]]s are brought together in close proximity, although an ignition event (e.g., heat or spark) is needed to trigger combustion.<ref name="astm-tpt">{{cite conference| veditors = Werley BL |year=1991|title=Fire Hazards in Oxygen Systems|location=Philadelphia|publisher=[[ASTM International]] Subcommittee G-4.05|book-title=ASTM Technical Professional training}}</ref>

Concentrated oxygen will allow combustion to proceed rapidly and energetically.<ref name="astm-tpt" /> Steel pipes and storage vessels used to store and transmit both gaseous and [[liquid oxygen]] will act as a fuel; and therefore the design and manufacture of oxygen systems requires special training to ensure that ignition sources are minimized.<ref name="astm-tpt" /> Highly concentrated oxygen in a high-pressure environment can spontaneously ignite hydrocarbons such as oil and grease, resulting in a fire or explosion. The heat caused by rapid pressurization serves as the ignition source. For this reason, storage vessels, regulators, piping and any other equipment used with highly concentrated oxygen must be "oxygen-clean" prior to use to ensure the absence of potential fuels. This does not only apply to pure oxygen; any concentration significantly higher than atmospheric (approximately 21%) carries a potential ignition risk.{{cn|date=June 2024}}

Some hospitals have instituted "no-smoking" policies which can help keep ignition sources away from medically piped oxygen. These policies do not eliminate the risk of injury among patients with portable oxygen systems, especially among smokers.<ref>{{cite journal | vauthors = Lindford AJ, Tehrani H, Sassoon EM, O'Neill TJ | title = Home oxygen therapy and cigarette smoking: a dangerous practice | journal = Annals of Burns and Fire Disasters | volume = 19 | issue = 2 | pages = 99–100 | date = June 2006 | pmid = 21991033 | pmc = 3188038 }}</ref> Other potential sources of ignition include candles, aromatherapy, medical equipment, cooking, and deliberate vandalism.{{cn|date=June 2024}}

==Delivery==
Various devices are used for oxygen administration. In most cases, the oxygen will first pass through a [[pressure regulator]], used to control the high pressure of oxygen delivered from a cylinder (or other source) to a lower pressure. This lower pressure is then controlled by a [[flowmeter]] (which may be preset or selectable) which controls the flow at a measured rate (e.g., litres per minute [LPM]). The typical flowmeter range for medical oxygen is between 0 and 15 LPM with some units capable of obtaining up to 25 LPM. Many wall flowmeters using a [[Thorpe tube flowmeter|Thorpe tube]] design are able to be dialed to "flush" oxygen which is beneficial in emergency situations.{{cn|date=June 2024}}

===Low-dose oxygen===
Many people only require slight increases in inhaled oxygen, rather than pure or near-pure oxygen.<ref>{{harvnb|Kallstrom|2002}}</ref> These requirements can be met through a number of devices dependent on situation, flow requirements, and personal preference.

A [[nasal cannula]] (NC) is a thin tube with two small nozzles inserted into a person's nostrils. It can provide oxygen at low flow rates, 1–6 litres per minute (LPM), delivering an oxygen concentration of 24–40%.<ref name="Hardavella et al 2019">{{cite journal | vauthors = Hardavella G, Karampinis I, Frille A, Sreter K, Rousalova I | title = Oxygen devices and delivery systems | journal = Breathe | volume = 15 | issue = 3 | pages = e108–e116 | date = September 2019 | pmid = 31777573 | pmc = 6876135 | doi = 10.1183/20734735.0204-2019 }}</ref>

There are also a number of face mask options, such as the [[simple face mask]], often used at between 5 and 10 LPM, capable of delivering oxygen concentrations between 35% and 55%.<ref name="Hardavella et al 2019" /> This is closely related to the more controlled [[air-entrainment masks]], also known as Venturi masks, which can accurately deliver a predetermined oxygen concentration from 24 to 50%.<ref name="Hardavella et al 2019" />

In some instances, a partial rebreathing mask can be used, which is based on a simple mask, but features a reservoir bag, which can provide oxygen concentrations of 40–70% at 5–15 LPM.{{cn|date=June 2024}}

Demand oxygen delivery systems (DODS) or oxygen resuscitators deliver oxygen only when the person inhales or the caregiver presses a button on the mask (e.g., nonbreathing patient).<ref name="Gloeckl 2019">{{cite journal | vauthors = Gloeckl R, Osadnik C, Bies L, Leitl D, Koczulla AR, Kenn K | title = Comparison of continuous flow versus demand oxygen delivery systems in patients with COPD: A systematic review and meta-analysis | journal = Respirology | volume = 24 | issue = 4 | pages = 329–337 | date = April 2019 | pmid = 30556614 | doi = 10.1111/resp.13457 | s2cid = 58768054 | doi-access = free }}</ref> These systems greatly conserve oxygen compared to steady-flow masks, and are useful in emergency situations when a limited supply of oxygen is available and there is a delay in transporting the person to higher care.<ref name="Gloeckl 2019" /> Due to utilization of a variety of methods for oxygenation requirements performance differences arise.<ref>{{cite journal | vauthors = Bliss PL, McCoy RW, Adams AB | title = Characteristics of demand oxygen delivery systems: maximum output and setting recommendations | journal = Respiratory Care | volume = 49 | issue = 2 | pages = 160–165 | date = February 2004 | pmid = 14744265 }}</ref> They are very useful in [[CPR]], as the caregiver can deliver rescue breaths composed of 100% oxygen with the press of a button. Care must be taken not to over-inflate the person's lungs, for which some systems employ safety valves. These systems may not be appropriate for people who are unconscious or in respiratory distress because of the required respiratory effort.{{cn|date=June 2024}}

===High flow oxygen delivery===
For patients requiring high concentrations of oxygen, a number of devices are available. The most commonly utilized device is the [[non-rebreather mask]] (or reservoir mask). Non-rebreather masks draw oxygen from attached reservoir bags with one-way valves that direct exhaled air out of the mask. If flow rate is not sufficient (~10L/min), the bag may collapse on inspiration.<ref name="Hardavella et al 2019" /> This type of mask is indicated for acute medical emergencies. The delivered F<sub>I</sub>O<sub>2</sub> (Inhalation volumetric fraction of molecular oxygen) of this system is 60–80%, depending on oxygen flow and breathing pattern.<ref>{{cite journal |vauthors=Garcia JA, Gardner D, Vines D, Shelledy D, Wettstein R, Peters J |title=The Oxygen Concentrations Delivered by Different Oxygen Therapy Systems |journal=Chest |volume=128 |issue=4 |pages=389S–390S |date=October 2005 |doi=10.1378/chest.128.4_meetingabstracts.389s-b }}</ref><ref>{{Cite web|url=http://www.cardinal.com/mps/focus/respiratory/abstracts/abstracts/ab2003/OF-03-257.asp|title=Earl, John. Delivery of High Fi{{chem|O|2}}. Cardinal Health Respiratory Abstracts.|access-date=2020-08-25|archive-date=2007-10-20|archive-url=https://archive.today/20071020045146/http://www.cardinal.com/mps/focus/respiratory/abstracts/abstracts/ab2003/OF-03-257.asp|url-status=bot: unknown}}</ref>

Another type of device is a humidified high flow [[nasal cannula]] which enables flows exceeding a person's peak inspiratory flow demand to be delivered via nasal cannula, thus providing F<sub>I</sub>O<sub>2</sub> of up to 100%  because there is no entrainment of room air.<ref>{{cite web | url = http://www.myoptiflow.com/therapy/ | title = What Is Optiflow? Accurate Oxygen Delivery | publisher = Fisher & Paykel Healthcare Limited | archive-url = https://web.archive.org/web/20130403074007/http://www.myoptiflow.com/therapy/ | archive-date=2013-04-03 }}</ref>  This also allows the person to continue to talk, eat, and drink while still receiving therapy.<ref name="sim2008">{{cite journal | vauthors = Sim MA, Dean P, Kinsella J, Black R, Carter R, Hughes M | title = Performance of oxygen delivery devices when the breathing pattern of respiratory failure is simulated | journal = Anaesthesia | volume = 63 | issue = 9 | pages = 938–40 | date = September 2008 | pmid = 18540928 | doi = 10.1111/j.1365-2044.2008.05536.x | s2cid = 205248111 | doi-access = free }}</ref> This type of delivery method is associated with greater overall comfort, improved oxygenation, respiratory rates and reduced sputumstatis compared with face mask oxygen.<ref>{{cite journal | vauthors = Roca O, Riera J, Torres F, Masclans JR | title = High-flow oxygen therapy in acute respiratory failure | journal = Respiratory Care | volume = 55 | issue = 4 | pages = 408–13 | date = April 2010 | pmid = 20406507 | url = http://www.myoptiflow.com/benefits/outcomes/roca-2010/ | url-status = live | archive-url = https://web.archive.org/web/20130511015517/http://www.myoptiflow.com/benefits/outcomes/roca-2010/ | archive-date = 2013-05-11 }}</ref><ref>{{cite journal | vauthors = Veenstra P, Veeger NJ, Koppers RJ, Duiverman ML, van Geffen WH | title = High-flow nasal cannula oxygen therapy for admitted COPD-patients. A retrospective cohort study | journal = PLOS ONE | volume = 17 | issue = 10 | article-number = e0272372 | date = 2022-10-05 | pmid = 36197917 | pmc = 9534431 | doi = 10.1371/journal.pone.0272372 | doi-access = free | bibcode = 2022PLoSO..1772372V }}</ref>

In specialist applications such as aviation, tight-fitting masks can be used. These masks also have applications in [[anaesthesia]], [[carbon monoxide poisoning]] treatment and in [[hyperbaric oxygen therapy]].{{cn|date=June 2024}}

===Positive pressure delivery===
Patients who are unable to breathe on their own will require positive pressure to move oxygen into their lungs for gaseous exchange to take place. Systems for delivery vary in complexity and cost, starting with a basic [[pocket mask]] adjunct which can be used to manually deliver [[artificial respiration]] with supplemental oxygen delivered through a mask port.

Many [[emergency medical service]] members, [[first aid]] personnel, and hospital staff may use a [[bag-valve-mask]] (BVM), which is a malleable bag attached to a face mask (or invasive airway such as an [[endotracheal tube]] or [[laryngeal mask airway]]), usually with a reservoir bag attached, which is manually manipulated by the healthcare professional to push oxygen (or air) into the lungs. This is the only procedure allowed for initial treatment of [[cyanide poisoning]] in the [[UK]] workplace.<ref>{{cite web | url = http://www.hse.gov.uk/pubns/misc076.htm | title = Cyanide poisoning – New recommendations on first aid treatment | work = Home Health and Safety Executive (HSE) | publisher = UK Government | archive-url = https://web.archive.org/web/20091020204249/http://www.hse.gov.uk/pubns/misc076.htm | archive-date=2009-10-20 }}</ref>[[File:o2regulator.JPG|thumb|right|[[Pin Index Safety System|Pin-indexed]] Oxygen Regulator for portable D-Cylinder, usually carried in an ambulance's resuscitation kit]]Automated versions of the BVM system, known as a [[resuscitator]] or pneupac can also deliver measured and timed doses of oxygen directly to people through a facemask or airway. These systems are related to the [[anaesthetic machine]]s used in operations under [[general anaesthesia]] that allow a variable amount of oxygen to be delivered, along with other gases including air, [[nitrous oxide]] and [[inhalational anaesthetic]]s.

===Drug delivery===
Oxygen and other compressed gases are used in conjunction with a [[nebulizer]] to allow delivery of medications to the upper and/or lower airways. Nebulizers use compressed gas to propel liquid medication into therapeutically sized aerosol droplets for deposition to the appropriate portion of the airway. A typical compressed gas flow rate of 8–10 L/min is used to [[nebulize]] medications, saline, sterile water, or a combination these treatments into a therapeutic aerosol for inhalation. In the clinical setting, room air (ambient mix of several gasses), [[molecular oxygen]], and [[Heliox]]{{citation needed|date=May 2016}} are the most common gases used to nebulize a [[Bolus (medicine)|bolus]] treatment or a continuous volume of therapeutic aerosols.

===Exhalation filters for oxygen masks===
Filtered oxygen masks have the ability to prevent exhaled particles from being released into the surrounding environment. These masks are normally of a closed design such that leaks are minimized and breathing of room air is controlled through a series of one-way valves. Filtration of exhaled breaths is accomplished either by placing a filter on the exhalation port or through an integral filter that is part of the mask itself. These masks first became popular in the Toronto (Canada) healthcare community during the 2003 SARS Crisis. SARS was identified as being respiratory based, and it was determined that conventional oxygen therapy devices were not designed for the containment of exhaled particles.<ref>{{cite journal | vauthors = Hui DS, Hall SD, Chan MT, Chow BK, Ng SS, Gin T, Sung JJ | title = Exhaled air dispersion during oxygen delivery via a simple oxygen mask | journal = Chest | volume = 132 | issue = 2 | pages = 540–6 | date = August 2007 | pmid = 17573505 | pmc = 7094533 | doi = 10.1378/chest.07-0636 }}</ref><ref>{{cite journal | vauthors = Mardimae A, Slessarev M, Han J, Sasano H, Sasano N, Azami T, Fedorko L, Savage T, Fowler R, Fisher JA | display-authors = 6 | title = Modified N95 mask delivers high inspired oxygen concentrations while effectively filtering aerosolized microparticles | journal = Annals of Emergency Medicine | volume = 48 | issue = 4 | pages = 391–9, 399.e1-2 | date = October 2006 | pmid = 16997675 | pmc = 7118976 | doi = 10.1016/j.annemergmed.2006.06.039 }}</ref><ref>{{cite journal | vauthors = Somogyi R, Vesely AE, Azami T, Preiss D, Fisher J, Correia J, Fowler RA | title = Dispersal of respiratory droplets with open vs closed oxygen delivery masks: implications for the transmission of severe acute respiratory syndrome | journal = Chest | volume = 125 | issue = 3 | pages = 1155–7 | date = March 2004 | pmid = 15006983 | pmc = 7094599 | doi = 10.1378/chest.125.3.1155 }}</ref>  In 2003, the HiOx<sup>80</sup> oxygen mask was released for sale. The HiOx<sup>80</sup> mask is a closed design mask that allows a filter to be placed on the exhalation port. Several new designs have emerged in the global healthcare community for the containment and filtration of potentially infectious particles. Other designs include the ISO-{{chem|O|2}} oxygen mask, the Flo<sub>2</sub>Max oxygen mask, and the O-Mask.

Typical oxygen masks allow a person to breathe in a mixture of room air and therapeutic oxygen. However, as filtered oxygen masks use a closed design that minimizes or eliminates the person's contact with and ability to inhale room air, delivered oxygen concentrations in such devices have been found to be elevated, approaching 99% using adequate oxygen flows.{{citation needed|date=May 2016}} Because all exhaled particles are contained within the mask, [[Nebulizer|nebulized]] medications are also prevented from releasing into the surrounding atmosphere, decreasing the occupational exposure to healthcare staff and other people.{{citation needed|date=May 2016}}

=== Aircraft ===
In the United States, most airlines restrict the devices allowed on board an aircraft. As a result, passengers are restricted in what devices they can use. Some airlines will provide cylinders for passengers with an associated fee. Other airlines allow passengers to carry on approved portable concentrators. However, the lists of approved devices varies by airline so passengers may need to check with any airline they are planning to fly on. Passengers are generally not allowed to carry on personal cylinders. In all cases, passengers need to notify the airline in advance of their equipment.

Effective May 13, 2009, the Department of Transportation and FAA ruled that a select number of portable oxygen concentrators are approved for use on all commercial flights.<ref name="faa">{{cite web|title=FAA Approved Portable Oxygen Concentrators – Positive Testing Results|publisher=faa.gov|access-date=2014-06-22|quote= (As of November 2014) Positive Testing Results: AirSep FreeStyle, AirSep LifeStyle, AirSep Focus, AirSep Freestyle 5, (Caire) SeQual eQuinox / Oxywell (model 4000), Delphi RS-00400 / Oxus RS-00400, DeVilbiss Healthcare iGo,  Inogen One,  Inogen One G2,  lnogen One G3,  lnova Labs LifeChoice Activox,  International Biophysics LifeChoice / lnova Labs LifeChoice, Invacare XPO2,  Invacare Solo 2,  Oxylife Independence Oxygen Concentrator, Precision Medical EasyPulse,  Respironics EverGo,  Respironics SimplyGo,  Sequal Eclipse,  SeQual SAROS,  VBox Trooper|url-status=live |url=http://www.faa.gov/about/initiatives/cabin_safety/portable_oxygen/ |archive-url=https://web.archive.org/web/20140702171156/http://www.faa.gov/about/initiatives/cabin_safety/portable_oxygen/|archive-date=2014-07-02}}</ref> FAA regulations require larger airplanes to carry D-cylinders of oxygen for use in case of an emergency.

===Oxygen conserving devices===
Since the 1980s, devices have been available which conserve stored oxygen by delivering it during the portion of the breathing cycle when it is more effectively used. This has the effect of stored oxygen lasting longer, or a smaller, and therefore lighter, portable oxygen delivery system being practicable. This class of device can also be used with portable oxygen concentrators, making them more efficient.<ref name="Tiep and Carter 2008" >{{cite journal | vauthors = Tiep B, Carter R | title = Oxygen conserving devices and methodologies | journal = Chronic Respiratory Disease | volume = 5 | issue = 2 | pages = 109–114 | date = 2008 | pmid = 18539725 | doi = 10.1177/1479972308090691 | publisher = crd.sagepub.com | s2cid = 6141420 | doi-access = free }}</ref>

The delivery of supplemental oxygen is most effective if it is made at a point in the breathing cycle when it will be inhaled to the alveoli, where gas transfer occurs. oxygen delivered later in the cycle will be inhaled into [[physiological dead space]], wher it serves no useful purpose as it cannot diffuse into the blood. Oxygen delivered during stages of the breathing cycle in which it is not inhaled is also wasted.<ref name="Tiep and Carter 2008" />

A continuous constant flow rate uses a simple regulator, but is inefficient as a high percentage of the delivered gas does not reach the alveoli, and over half is not inhaled at all. A system which accumulates free-flow oxygen during resting and exhalation stages, (reservoir cannulas) makes a larger part of the oxygen available for inhalation, and it will be selectively inhaled during the initial part of inhalation, which reaches furthest into the lungs. A similar function is provided by a mechanical demand regulator which provides gas only during inhalation, but requires some physical effort by the user, and also ventilates dead space with oxygen. A third class of system (pulse dose oxygen conserving device, or demand pulse devices) senses the start of inhalation and provides a metered bolus, which if correctly matched to requirements, will be sufficient and effectively inhaled into the alveoli.Such systems can be pneumatically or electrically controlled.<ref name="Tiep and Carter 2008" />

Adaptive demand systems<ref name="Tiep and Carter 2008" />
A development in pulse demand delivery are devices that automatically adjust the volume of the pulsed bolus to suit the activity level of the user. This adaptive response in intended to reduce desaturation responses caused by exercise rate variation.

Pulsed delivery devices are available as stand alone modules or integrated into a system specifically designed to use compressed gas, liquid oxygen or oxygen concentrator sources. Integrated design usually allows optimisation of the system for the source type at the cost of versatility.<ref name="Tiep and Carter 2008" />

Transtracheal oxygen catheters are inserted directly into the trachea through a small opening in the front of the neck for that purpose. The opening is directed downward, towards the bifurcation of the bronchi. Oxygen introduced through the catheter bypasses the dead spaces of the nose, pharynx and upper trachea during inhalation, and during continuous flow, will accumulate in the anatomic dead space at the end of exhalation and be available for immediate inhalation to the alveoli on the following inhalation. This reduces wastage and provides efficiency roughly three times greater than with external continuous flow. This is roughly equivalent to a [[reservoir cannula]]. Transtracheal catheters have been found to be effective during rest, exercise and sleep.<ref name="Tiep and Carter 2008" />

== See also ==
{{Portal|Medicine}}
* {{annotated link|Bottled oxygen (climbing)}}
* {{annotated link|Breathing gas}}
* {{annotated link|Emergency medical services}}
* {{annotated link|Hyperbaric oxygen therapy}}
* {{annotated link|Mechanical ventilation}}
* {{annotated link|Nebulizer}}
* {{annotated link|Oxygen bar}}
* {{annotated link|Oxygen firebreak}}
* {{annotated link|Oxygen tent}}
* {{annotated link|Respiratory therapist}}
* [[Redento D. Ferranti]] - Early use of oxygen therapy in the U.S. as an effective approach to rehabilitation for [[Chronic obstructive pulmonary disease|COPD]] patients.

== References ==
{{reflist |colwidth=32em |refs=
<ref name=tasmanian>{{cite journal | vauthors = Austin MA, Wills KE, Blizzard L, Walters EH, Wood-Baker R | title = Effect of high flow oxygen on mortality in chronic obstructive pulmonary disease patients in prehospital setting: randomised controlled trial | journal = BMJ | volume = 341 | issue = oct18 2 | article-number = c5462 | date = October 2010 | pmid = 20959284 | pmc = 2957540 | doi = 10.1136/bmj.c5462 }}</ref>
}}

== Further reading ==
* {{Cite journal |vauthors=Cahill Lambert AE |title=Adult domiciliary oxygen therapy: a patient's perspective |journal=The Medical Journal of Australia |volume=183 |issue=9 |pages=472–3 |date=November 2005 |pmid=16274348 |doi=10.5694/j.1326-5377.2005.tb07125.x |s2cid=77689244 }}
* {{Cite journal |vauthors=Kallstrom TJ |title=AARC Clinical Practice Guideline: oxygen therapy for adults in the acute care facility--2002 revision & update |journal=Respiratory Care |volume=47 |issue=6 |pages=717–20 |date=June 2002 |pmid=12078655 |url=http://www.rcjournal.com/cpgs/otachcpg-update.html }}
* {{cite web |title=Study: Change in how medics use oxygen could reduce deaths |url=https://www.ems1.com/medical-clinical/articles/study-change-in-how-medics-use-oxygen-could-reduce-deaths-BSazaVXAhkTrUwWw/ |publisher=Lexipol |date=November 5, 2010 |access-date=2025-03-17}} (see comments for study meta-analysis)

{{Breathing apparatus|medical}}
{{Respiratory system procedures}}
{{Underwater diving|divmed}}

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