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Oxygen -- Yes, it can be toxic !!

2018 British Medical Journal review of the data and clinical practice guideline
·        Give O2 if SpO2 <90%
·        Goal SpO2 no higher than 94%
·        Goal SpO2 is then 90-94%.  Higher O2 saturations can lead to WORSE outcomes in many cases.

Hyperoxia can cause:
·        systemic vasoconstriction (hypertension) and increase cardiac output (1).
o   But…it dilates pulmonary vessels.  Opposing effects.
·        May actually INCREASE infarct size in acute MI. Hyperoxia causes coronary vasoconstriction.  (The O in MONA is dead!) (2,3)
o   No benefit to supplemental oxygen in AMI….if you are not hypoxic to start with.
·        Titrated oxygen treatment in COPD exacerbations had better outcomes than high flow oxygen. ( titrated oxygen = Nasal canula, SpO2 88-92%.  High flow = O2 8-10 L/min) (3)
o   Less acidosis with titrated O2 vs high flow.  High flow in COPD can lead to acidosis that is correctable with reduced oxygen concentration.
o   Titrated oxygen reduced death from respiratory failure 58% for all patients and 78% for COPD patients.
·        Hyperoxia can depress respiratory drive.  This can be dangerous in asthma, COPD, and obesity hypoventilation syndrome (5).

 

1.      Circulatory and metabolic effects of oxygen in myocardial infarction - PubMed (nih.gov)

2.      Air Versus Oxygen in ST-Segment-Elevation Myocardial Infarction - PubMed (nih.gov)

3.      Oxygen Therapy in Suspected Acute Myocardial Infarction - PubMed (nih.gov)

4.      Effect of high flow oxygen on mortality in chronic obstructive pulmonary disease patients in prehospital setting: randomised controlled trial (nih.gov)

5.      Episode 29: Why is hyperoxia harmful? – The Curious Clinicians

6.      Physiology, Respiratory Drive - StatPearls - NCBI Bookshelf (nih.gov)