One Long COVID case points at something most people at altitude never notice
I have been working through a case with a patient that may explain something a lot of people in the Long COVID world have been feeling and cannot quite name.
The setup: Long COVID, plus obstructive sleep apnea, on CPAP. Daytime oxygen readings at 93 percent, which looks basically fine on paper. In real life, grinding fatigue that never fully lifts. And one detail that kept nagging at both of us – he consistently feels noticeably better at sea level than he does here in Colorado.
That last piece is the thread worth pulling on, because once you follow it, several things that did not fit together suddenly do.
Here is what I keep coming back to. The percentage of oxygen in the air is essentially the same in Denver as it is in Miami, close to 21 percent either way. What changes at altitude is the pressure behind it. And a standard pulse oximeter reading hides that difference almost completely – the number can look nearly identical in both places even when the actual force driving oxygen into tissue is meaningfully lower up here.
For someone with plenty of physiologic reserve, that is a rounding error. For someone whose reserve has already been spent, by a virus or a lung or a heart or low iron, it may be exactly the difference between functioning and not.
Which raises the real question: if that is what is happening, what do you actually do about it? And who else does this apply to besides the Long COVID crowd?
I wrote the full case up for our members – the physiology in detail, the experiment we are running with supplemental oxygen layered on top of CPAP, the boundaries of what I am and am not claiming, and the much longer list of people this reaches. It is in our Medical Mysteries section, which is part of the It’s My Health membership.
Authored by Gerard Guillory, MD
Gerard Guillory, MD, is a board-certified internist who practiced for nearly four decades with a focus on functional, root-cause medicine. He is the author of three books on irritable bowel syndrome and the founder of It’s My Health, where he and his team put current health news in context and help members understand the underlying causes of chronic symptoms.
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