Supplemental Oxygen: Too Much Of A Good Thing?
Just because it’s in the air, it doesn’t mean we should give unlimited amounts of oxygen to patients
I was not feeling well all week: having fever and chills despite taking antibiotics. Finally, the fever broke after four days, and I thought the worst was over. Then the chest pain started….while at work in the ICU. I kept ignoring it, thinking it was “muscle” or “heartburn.” But, it wouldn’t go away. I took some famotidine, and it improved. When it came back the next day, again at work, I thought I should check it out. I texted my Cardiologist friend, and I wanted him to quickly look at my EKG. He sent me to the ED.
It all happened so fast. The EKG said I was having a heart attack, and I knew something was up when three nurses came into the room at once. One of them started me on oxygen, even though my oxygen level was totally normal. Before I knew it, I was being wheeled away to the cardiac cath lab, as the troponin level came back very elevated.
This very same situation happens in millions of EDs across our country, and I have lost count of the number of times I have seen supplemental oxygen be started on patients who have normal oxygen levels on room air. First of all, it is important to note that room air only has 21% oxygen. This is the same at sea level as it is at the summit of Mount Everest. So, how bad could extra oxygen be?
Turns out…quite possibly very bad.
In May 2018, a systematic review and meta-analysis of oxygen therapy for acutely ill patients was published in the Lancet medical journal. Over 16,000 patients were studied, and they found that a liberal oxygen strategy increased the risk of in-hospital mortality by 21% and 30-day mortality by 14%. These findings were statistically significant. Based on this study, a clinical practice guideline was published by the British Medical Journal. The recommendations are summarized as follows:
Now, there were some caveats to this, as noted below:
Still, this represents a significant paradigm shift. As a Pulmonologist, I can’t help but chuckle when I read medical records that document the initiation of supplemental oxygen on a patient that had a normal oxygen level. And I have already written about the problem I have with providers documenting “hypoxia” when there is no evidence to back it up.
Yet, it seems that the widespread practice of adding oxygen to acutely ill patients may be harming them. In fact, the Lancet article indicated that treating 71 patients with oxygen will lead to one death. Applied on a large scale, this may be a staggering number, and it should give clinicians and hospital leadership pause.
Back to my episode of chest pain, the cardiac cath was negative, thankfully, and my chest pain was due to a viral inflammation of my heart. Yet, did I need the oxygen they gave me? Nope. I was already oxygenating quite well.
When it comes to the patients we treat on a daily basis, based on the Lancet study, it is reasonable to do the following (of course, clinical judgment should always apply):
- Withhold oxygen if the patient already has an oxygen saturation of 93% or better.
- If the patient’s oxygen saturation is between 90–92%, supplemental oxygen also should not be given, although the evidence for this is not as strong.
- If we place patients on oxygen, we should aim for no more than an oxygen saturation of 96%
Even though oxygen has been used as a medical therapy since the 1880s, it seems that more oxygen is NOT better. Changing this practice — nay, cultural norm — will not be easy; it will take a lot of education and re-education. But if unnecessary supplemental oxygen is hurting our patients, don’t we owe it to them to rethink what we have been doing?
The opinions expressed in this post are my own and do not reflect those of my employer or the organizations with which I am affiliated.