EBM Consult

Oxygen (O2) Supplementation Use During Acute Coronary Syndrome (ACS)


  • P = Adults with suspected acute coronary syndrome (ACS) with a normal pulse ox ≥ 90%
  • I  = Supplemental oxygen by nasal cannula or facemask
  • C = No supplemental oxygen
  • O = Reduction in mortality, progression of myocardial infarction, angina, and/or CV related complications
  • T = Acute setting (within 12 to 24 hours up to 30 days)
  • S = Pre-hospital care or emergency department

Note: PICOTS stands for (P) for patient, (I) for intervention of interest, (C) for comparison, (O) for outcome(s) of interest or relevance, (T) for timing, and (S) for setting.


Patients with acute coronary syndrome (ACS; unstable angina, NSTEMI, STEMI) should initially receive 2-4 L/min supplemental oxygen (O2) per nasal cannula if they have an oxygen saturation by a pulse oximetry < 90%, are experiencing dyspnea, or have heart failure, as there is conflicting evidence about possible harm in normoxic patients. 

  • Current guidelines by the American Heart Association (AHA) do not recommend supplemental oxygen use in normoxic patients with suspected ACS.
  • A Cochrane review of 4 trials in patients with acute MI is concerning for a possible greater risk of death in patients getting supplemental O2. However, there is conflicting evidence, and thus the use of supplemental oxygen should be studied in a clinical trial to verify its effect on morbidity and mortality.  The current AHA guidelines both recommend its use in the above situations. 
  • There is some evidence in patients with stable CAD undergoing elective cardiac cath that supplemental O2 (breathing 100% FiO2 at 15 L/min via face mask) may increase coronary vascular resistance, reduce coronary blood flow, and increase mortality risk.
  • Could also reduce respiratory drive in patients with known COPD or chronic hypercapnia, thereby worsening carbon dioxide retention and risk for respiratory acidosis.

Author: Anthony J. Busti, MD, PharmD, FNLA, FAHA
Editors:  Dylan Kellogg, MD
Last Reviewed:  December 2016

Guideline Statements

  • 2015 AHA ACLS Guidelines:
    "The provision of supplementary oxygen to patients with suspected ACS who are normoxic has notbeen shown to reduce mortality or hasten the resolution of chest pain.Withholding supplementary oxygen in these patients has been shown to minimallyreduce infarct size. The usefulness of supplementary oxygen therapy has notbeen established in normoxic patients. In the prehospital, ED, and hospitalsettings, the withholding of supplementary oxygen therapy in normoxic patientswith suspected or confirmed acute coronary syndrome may be considered (Class IIb,LOE C-LD)." 

  • 2014 AHA/ACC NSTEMI Guidelines: 
    "Supplemental oxygen should be administered to patients with NSTE-ACS with arterial oxygen saturation less than 90%, respiratory distress, or other high-risk features of hypoxemia. (Class I, Level of Evidence: C)"

  • 2013 AHA/ACC STEMI Guidelines: 
    "Indications:clinically significant hypoxemia (oxygen saturation <90%), HF, Dyspnea.  2 to 4 L/min via nasal cannula. Increase rateor change to face mask as needed. Caution with chronic obstructive pulmonarydisease and CO2 retention." (Note: no ranking or level of evidence provided.)

Cochrane Review

  • Cabello JB et al. Oxygen therapy for acute myocardial infarction. Cochrane Database Syst Rev 2013;8:CD007160. PubMed

Clinical Trials

  • McNulty PH et al. Effects of supplemental oxygen administration on coronary blood flow in patients undergoing cardiac catheterization. Am J Physiol Hear Circ Physiol 2005;288(3):H1057-62. PubMed
  • Maroko PR et al. Reduction of infarct size by oxygen inhalation following acute coronary occlusion. Circulation 1975;52(3):360-8. PubMed

Review Articles

  • Moradkhan R et al.  Revisiting the role of oxygen therapy in cardiac patients. J Am Coll Cardiol 2010;56(13):1013-6. 

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