Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

One hundred percent oxygen in the treatment of acute myocardial infarction and severe angina pectoris


In the absence of hypoxia, is supplemental oxygen good for a patient with cardiac chest pain, but no hypoxia or shortness of breath?

We take it for granted that giving oxygen is good, and more oxygen is better, even if the patient is not hypoxic or short of breath, but what does the research show for cardiac patients?

This double-blinded study, released only 62 years ago – in 1950, strongly suggests that supplemental oxygen is not good for patients with chest pain and/or ECG changes.

In previous studies4 we investigated the modifying influence of various drugs on the electrocardiographic response to standard exercise in patients with coronary insufficiency. It was pointed out that certain cases of angina pectoris show transient electrocardiographic changes (RS-T segment depression and T wave inversion) of constant pattern in response to the Master two-step test. In such patients it is possible to determine the specific effect of various drugs in preventing these previously recorded electrocardiographic patterns of myocardial anoxia. Consequently this method of study appeared favorable for assessing objectively both the prophylactic and therapeutic effect of oxygen (in high concentrations) on experimentally induced coronary insufficiency in human subjects.[1]

Out of over one hundred patients screened for this, they found five patients who consistently responded as described above. They repeatedly tested these patients to see the effect with 100% oxygen[2] or with room air – delivered with staff and patients blinded to which was which.

In five patients with angina pectoris the administration of 100 per cent oxygen did not favorably influence the onset or duration of pain or the electrocardiographic alterations induced by standard exercise. On the contrary, oxygen therapy actually appeared responsible for more pronounced and persistent electrocardiographic changes in several patients.[1]

Oxygen is good.

More is better.

Where is the evidence?

Did somebody just make it up?

Ethical standards should have required us to question the routine use of any treatment lacking evidence of benefit and lacking evidence of safety.

Too often, our treatments are based on wishful thinking, rather than evidence.

Any standard of care that does not have evidence of benefit needs to have an expiration date.

These observations appear to indicate that oxygen therapy is without value in cases of acute myocardial infarction and angina pectoris in which the oxygen saturation of arterial blood is normal.[1]

Click on image to make it larger. From Magic Circle (1886) by William B. Waterhouse with the witches’ potion from Macbeth.

We have been recklessly exposing our patients to this treatment with no demonstrable value (or safety) for over six decades, because of blind optimism. We appear to be more interested in looking like we are doing something than we are in truly helping our patients.

We wish to strongly emphasize that oxygen should be freely administered when an indication for its use is recognized or even suspected. Its indiscriminate employment, however, may result in more harm than good in the individual case.[1]

It is OK to harm those thousands, maybe even hundreds of thousands of patients, based on “What if it worked?”

Bleeding to remove evil humors, rotating tourniquets for acute pulmonary edema, trendelenburg position for shock, or any of the other wishful thinking-based treatments, . . . . Our patients deserve better.


[1] One hundred percent oxygen in the treatment of acute myocardial infarction and severe angina pectoris.
J Am Med Assoc. 1950 Sep 30;144(5):373-5. No abstract available.
PMID: 14774103 [PubMed – indexed for MEDLINE]

[2] 100% oxygen?

A patient does not receive 100% oxygen because the patient is receiving high-flow oxygen through a face mask. The nasal cannula is just as capable of delivering 100% oxygen as the mask is. What is coming out of the cannula is 100% oxygen (unless there is air mixed in at the source). What is coming out of the mask is 100% oxygen (unless there is air mixed in at the source).

What the patient is breathing in is mixed with the surrounding air, unless there is a perfect seal on the mask. An endotracheal tube does a better job of delivering 100% oxygen (unless there is air mixed in at the source).

Even with CPAP Continuous Positive Airway Pressure), high-flow oxygen probably does not deliver 100% oxygen to real patients, but we like to believe that we have more control over treatments.

We deceive ourselves, as well as our patients.

RUSSEK HI, REGAN FD, & NAEGELE CF (1950). One hundred percent oxygen in the treatment of acute myocardial infarction and severe angina pectoris. Journal of the American Medical Association, 144 (5), 373-5 PMID: 14774103



  1. Dextrose is also necessary for life, but thanks to a disease called diabetes we accept that too much of it is bad. No one gets in trouble if they put every patient on a NRB mask, though.

  2. The recent recognition of evidence that high-flow O2 may do more harm than good in chest pain patients (even if some of said evidence is 50+ years old) makes me also wonder how many patients with conditions other than cardiac chest pain are also being harmed by unnecessary administration of of high-flow O2. Ischemic strokes, for example, share some similarities in pathophysiology with acute MI … I see it as being quite possible that these patients, as well, could potentially be harmed by the indiscriminate administration of high-flow O2 in the absence of hypoxemia.

    My state protocols still say, regarding oxygen, that any patient with a “priority condition” (which refers to just about any illness or injury more serious than a hangnail) should receive high-flow O2, although the actual chest pain/ACS protocol was updated with a recommendation to titrate O2 administration for SpO2 of 94% or higher. Fortunately, the vast majority of us take a lot more factors into consideration when treating a patient, but I think it’s about time to reconsider this recommendation.

  3. I love your inadvertent humor.

    This is probably where you can find the ignorant and/or closed minded people in EMS. If you try to explain to them the dangers of hyperoxygenation and you get shut out.

    I’ve been seeing more protocols being written broadly to have something along the lines of

    “O2 PRN – SpO2 >95%”

  4. “Have you or someone you know suffered a disabling injury or death after receiving the drug oxygen? If you suffered a heart attack and received high doses of oxygen and then had a worsening of your condition or suffered disabling cardiac injury, it may have been due to oxygen. Call Rogue & Medic LLP today to see what our expert attorneys can do for you. You could be entitled to thousands of dollars in personal injury claims. You didn’t choose to suffer a heart attack, but you can choose to regain the money owed to you if you suffered additional pain and suffering at the hands of caregivers. Call Rogue & Medic LLP today!”

    What if we in EMS were held liable for the damages caused by incorrect pharmacological treatment? What if we were held responsible for the injuries caused by our faulty, non-evidence-based practices? If we could be sued for the damages they cause, would we still give high doses of epinephrine? High-flow oxygen? Perform spinal immobilization? Withhold pain management? Transport to the hospital lights and sirens?

  5. Great article! We are linking to this particularly great post on our site.
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