Is routine oxygen therapy harmful in Occlusion Myocardial Infarction (OMI) patients with normal oxygen saturation (SpO2) levels?

Routine Oxygen Therapy in OMI with Normal SpO2 is Harmful and Not Recommended

Routine oxygen therapy is not recommended for patients with Occlusion Myocardial Infarction (OMI) who have normal oxygen saturation levels (SpO2 ≥90%) as it may potentially increase myocardial injury and infarct size without providing clinical benefit. 1

Evidence Against Routine Oxygen Use in Normoxemic OMI Patients

• Multiple randomized trials have demonstrated a lack of cardiovascular benefit with routine supplemental oxygen in patients with normal oxygen saturation levels (≥90%) presenting with suspected or confirmed myocardial infarction 1

• The 2025 ACC/AHA/ACEP/NAEMSP/SCAI guidelines specifically note that studies have suggested worse short- and long-term mortality with liberal compared to conservative administration of supplemental oxygen in patients without hypoxia 1

• The European Society of Cardiology (ESC) 2018 guidelines explicitly state that "routine oxygen is not recommended in patients with SaO2 ≥90%" with a Class III, Level B recommendation (meaning evidence indicates it should not be done) 1

• The AVOID trial (Air Versus Oxygen in ST-Segment-Elevation Myocardial Infarction) demonstrated that supplemental oxygen (8 L/min) in STEMI patients with oxygen saturations ≥94% not only lacked benefit but also showed a possible increase in myocardial injury and infarct size 1

Optimal Oxygen Saturation Range

• The relationship between oxygenation and outcomes appears to be U-shaped, with the lowest mortality rate observed in patients with an SpO2 of 94% to 96% at presentation 1

• The DETO2X-AMI trial (6,629 patients with suspected MI and oxygen saturation ≥90%) found that supplemental oxygen (6 L/min) did not reduce:

  • All-cause mortality at 1 year
  • Rehospitalization with MI
  • This lack of benefit was consistent even in patients with lower baseline oxygen saturations (90%-94%) 1, 2

When Oxygen Therapy IS Indicated

• Oxygen therapy is clearly indicated for OMI patients with:
  • Hypoxemia (SpO2 <90% or PaO2 <60 mmHg) 1
  • Overt pulmonary congestion 1
  • Respiratory distress 1

Potential Mechanisms of Harm

• Hyperoxia may be harmful in patients with uncomplicated MI due to:
  • Increased production of reactive oxygen species and related oxidative stress 3
  • Reductions in coronary blood flow from hyperoxia-induced vasoconstriction 3
  • Decreased myocardial oxygen consumption 3

Clinical Approach to Oxygen Management in OMI

1. Measure oxygen saturation in all patients with suspected OMI using pulse oximetry 4
2. For patients with SpO2 <90%: Administer supplemental oxygen to maintain SpO2 ≥90% 1
3. For patients with SpO2 ≥90%: Do not administer routine supplemental oxygen 1
4. Monitor oxygen saturation continuously, as hypoxemia can develop during the course of treatment (occurred in 7.7% of patients in the ambient-air group in the DETO2X-AMI trial) 2
5. If hypoxemia develops during treatment (SpO2 <90%), promptly initiate oxygen therapy 1

Special Considerations

• Patients with certain conditions were typically excluded from oxygen studies and may require individualized assessment:

  • Home oxygen requirement
  • Active bronchospasm requiring supplemental oxygen
  • Cardiac arrest at presentation 1

• Low-normal baseline oxygen saturation (90-94%) or development of hypoxemia during treatment has been identified as an independent marker of poor prognosis, requiring close monitoring 5

• A meta-analysis of 7 studies (7,702 total patients) confirmed the lack of benefit of routine oxygen therapy in patients with acute myocardial infarction with normal oxygen saturation levels for:

  • All-cause mortality
  • Recurrent ischemia or myocardial infarction
  • Heart failure
  • Occurrence of arrhythmia events 6