Hospitalization and oxygen therapy thresholds

Tl;dr: Not knowing much about this and not a doctor, my current policy is to go to a hospital if SpO2 drops below ~92% and my hospital isn’t completely overrun, unless my SpO2 is naturally low or some other extenuating circumstance. If I was forced to use an oxygen concentrator outside of a hospital, I would target a ~~94-96% SpO2 range, trying very hard to make sure I didn’t hit 99%

If you do have COVID and shortness of breath, when do you go to a hospital?

Hopefully you already have a pulse oximeter as Julia Wise recommends . But sources say anywhere between 90 and 95% SpO2 is the threshold for hospitalization ( WHO says <= 93% is classified as severe, ctrl+f “O2”), while other sources say you should threshold on trouble breathing and shortness of breath, not the actual SpO2 number.

It seems to me that using “trouble breathing” as the indicator would track the lung blockages and thus immune response relatively well, while O2 as an indicator would track the danger metric directly (if in fact the primary source of death is insufficient oxygen; if anyone knows this, would be useful).

The benefit of looking at trouble breathing is that it’s an advance indicator. Usually people progress from oxygen therapy to ventilators relatively quickly. If you have naturally low SpO2, your O2 might drop under threshold (say, 93%) in the early stages with mild trouble breathing, but you wouldn’t have much of a dangerous immune response until later. In this case, you’d have wanted to use difficulty breathing as your indicator instead of SpO2.

That being said, having low oxygen seems pretty bad for you, both by common sense and science. For example, 92% or lower is associated with increased morbidity in pneumonia patients ; <90% is increased with 36% increased morbidity . Since it’s hard to measure even moderate effects due to the treatment-correlated-with-severity issue, my guess is that there’s some general bodily harm from reduced oxygen even at levels like 95%, though I don’t know how much. So at some SpO2 threshold, I think you want to be supplementing oxygen even if your breathing doesn’t feel that difficult.

Unfortunately, it seems like you can’t supplement oxygen at 95%, because over-oxygenating causes neuronal damage . Standard targets appear to be 94-98% or 92-96%. This study says it seems bad to set your target range during oxygen therapy to greater than 92-96%, because one inevitably exceeds the upper target occasionally. This review/musing muses that it’s a difficult problem, evidence for hyperoxaemia being pretty bad is “comparatively strong”, but not strong enough to warrant especially conservative oxygen titration. Because of these numbers, I think 92-93% is a reasonable threshold to self-hospitalize, since anything above this means they probably shouldn’t be oxygenating you anyways.

If hospitals are overloaded and you have to do oxygen therapy yourself (really try not to do this), I think the targets above are still reasonable, subject to your ability to titrate well with the machine. If you have lots of trouble, of course be conservative. However, you may be able to do better than hospitals: the first study above says that “even in a research setting in the intensive care unit, in which patients receiving mechanical ventilation are closely monitored, most patients who were randomized to an SpO2 target of 90–92% and were receiving supplementary oxygen did not have their inspired oxygen reduced if the SpO2 was 99% or 100%.” So—seems like you could easily do better monitoring than this if you were oxygenating at home. This is why I would probably shoot for 94-96% myself.