Editing Cardiopulmonary resuscitation (section)

== Pathophysiology ==
CPR is used on people in cardiac arrest to [[Oxygenation (medical)|oxygenate]] the blood and maintain a [[cardiac output]] to keep vital organs alive. Blood circulation and oxygenation are required to transport [[oxygen]] to the tissues. The physiology of CPR involves generating a pressure gradient between the arterial and venous vascular beds; CPR achieves this via multiple mechanisms.<ref>{{cite web|date=February 2015|title=ICU Physiology in 1,000 Words: Cardiopulmonary Resuscitation|url=http://pulmccm.org/main/2015/review-articles/icu-physiology-1000-words-cardiopulmonary-resuscitation/|url-status=live|archive-url=https://web.archive.org/web/20150326232456/http://pulmccm.org/main/2015/review-articles/icu-physiology-1000-words-cardiopulmonary-resuscitation/|archive-date=2015-03-26|access-date=2015-03-20}}</ref> 

The [[Human brain|brain]] may sustain [[brain damage|damage]] after blood flow has been stopped for about four minutes and irreversible damage after about seven minutes.<ref>{{cite web| vauthors = Smith N |title=Anoxic Brain Damage|url=http://www.thirdage.com/encyclopedia/anoxic-brain-damage-anoxic-brain-injury-hypoxic-brain-injury|url-status=dead|archive-url=https://web.archive.org/web/20090129175857/http://www.thirdage.com/encyclopedia/anoxic-brain-damage-anoxic-brain-injury-hypoxic-brain-injury|archive-date=2009-01-29|access-date=2018-12-07|publisher=Third Age}}</ref><ref>{{cite web| vauthors = Tuhrim S |title=Anoxic Brain Injury|url=http://www.mountsinai.org/patient-care/health-library/diseases-and-conditions/anoxic-brain-damage|url-status=live|archive-url=https://web.archive.org/web/20120515030759/http://www.mountsinai.org/patient-care/health-library/diseases-and-conditions/anoxic-brain-damage|archive-date=2012-05-15|publisher=Mount Sinai Medical Centre}}</ref><ref>{{cite book| vauthors = Brass L |url=http://www.med.yale.edu/library/heartbk/18.pdf|title=Heart Book. Chapter 18:Stroke|publisher=Yale University|archive-url=https://web.archive.org/web/20090131022504/http://www.med.yale.edu/library/heartbk/18.pdf|archive-date=2009-01-31|url-status=live }}</ref><ref>{{cite web| vauthors = Turkowski K |title=A pleas for VBAC education|url=http://www.worldserver.com/turk/birthing/VBAC-Ed.html|url-status=live|archive-url=https://web.archive.org/web/20090429043723/http://www.worldserver.com/turk/birthing/VBAC-Ed.html|archive-date=2009-04-29}}</ref><ref>{{cite web|title=Hyperbaric Oxygen Therapy|url=http://www.familyhealthnews.com/articles-hyperbaric-oxygen-therapy.html|url-status=dead|archive-url=https://web.archive.org/web/20090429052150/http://www.familyhealthnews.com/articles-hyperbaric-oxygen-therapy.html|archive-date=2009-04-29|access-date=2018-12-07|publisher=Family Health News}}</ref> Typically if blood flow ceases for one to two hours, then body cells [[necrosis|die]]. Therefore, in general, CPR is effective only if performed within seven minutes of the stoppage of blood flow.<ref>{{Cite web |title=Cardiopulmonary resuscitation (CPR): First aid |url=https://www.mayoclinic.org/first-aid/first-aid-cpr/basics/art-20056600 |access-date=2023-09-12 |website=Mayo Clinic |language=en}}</ref> The heart also rapidly loses the ability to maintain a normal rhythm. Low body temperatures, as sometimes seen in near-drownings, prolong the time the brain survives.

Following cardiac arrest, effective CPR enables enough oxygen to reach the brain to delay [[brain stem death]] and allows the heart to remain responsive to [[defibrillation]] attempts.<ref>{{Cite book |vauthors=((Institute of Medicine))|veditors=Graham R, McCoy MA, Schultz AM |url=https://www.ncbi.nlm.nih.gov/books/NBK321505/ |title=Emergency Medical Services Response to Cardiac Arrest |location=Washington, DC |date=2015-09-29 |publisher=National Academies Press (US) |language=en}}</ref> If an incorrect compression rate is used during CPR, going against standing [[American Heart Association]] (AHA) guidelines of 100–120 compressions per minute, this can cause a net decrease in venous return of blood, for what is required, to fill the heart.<ref name="The Physiology">{{cite journal | vauthors = Lurie KG, Nemergut EC, Yannopoulos D, Sweeney M | title = The Physiology of Cardiopulmonary Resuscitation | journal = Anesthesia and Analgesia | volume = 122 | issue = 3 | pages = 767–783 | date = March 2016 | pmid = 26562060 | doi = 10.1213/ANE.0000000000000926 | s2cid = 30360787 }}</ref> For example, if a compression rate of above 120 compressions per minute is used consistently throughout the entire CPR process, this error could adversely affect survival rates and outcomes for the victim.<ref name="The Physiology" />