This article (below) talks about HBOT and is not full of horrifying photos, and I don't recommend you google "Gangrene" if you aren't prepared to look at some really horrifying photos. I am not going to link to any resources on gangrene because I can't readily find any that don't make me cringe and I live with a serious medical condition (and processed accident claims for five plus years), so I am pretty callous about stuff like that. (Someone not taking my warning about medical photos seriously previously: https://news.ycombinator.com/item?id=20680819)
https://www.hopkinsmedicine.org/health/treatment-tests-and-t...
One of the potential causes of gangrene is anaerobic bacteria. And, so, my layman's understanding is that what happens is HBOT forces oxygen into tissues because it's under pressure. It's like some multiple of earth's atmospheric pressure and it can help kill anaerobic infection by exposing them to oxygen in parts of the body that otherwise wouldn't be getting good oxygen for some reason.
I have a form of cystic fibrosis. It is best known as a respiratory condition, but that's not really accurate. It's a genetic disorder and it impairs cell function throughout the body and this impacts some tissues more obviously than others, such as the lungs.
So cystic fibrosis causes a compromised immune system but, like, I spent a lot of years wondering "What does that even mean? Where is the immune system in my body? Which organs are they? How does CF make me so vulnerable to infection?"
And the answer is that "the immune system" doesn't really mean a specific set of organs like "the circulatory system" or "the digestive system" means a specific set of organs. It's just kind of a catch phrase for "how the body protects itself" and it's not really that well understood or explained exactly that happens.
People tend to die really young with CF (like in their 30s or younger) and they very often die of lung infection and treatment of lung issues is a really big part of managing CF.
So one of the things I have concluded is that most likely one of the ways CF impairs my immune function is low oxygen in the body. Oxygen gets used to kill stuff. I think oxygen is an underrecognized part of your arsenal of tools to protect yourself from infection and it's useful against some things that are really nasty, like anaerobic infections, which tend to be ugly, from what I gather.
So I have only skimmed this study. The science is probably over my head and, as if often the case, I am only futzing around on HN because I'm too tired to work at the moment (see the aforementioned deadly genetic disorder). So I am not going to thoroughly read this piece. If I were that mentally focused, I would be working.
But I've skimmed it and I've skimmed the comments here and someone has pointed out this is not about red blood cells, it's about immune cells.
And I will suggest it is plausible that immune cells in the blood would be revitalized by HBOT and "made younger" (that's basically what telomere length gets used as a proxy for) because of what I know about how HBOT gets used to treat certain infections and what I think -- the word think indicates personal opinion, so "don't @ me" as they say on twitter -- what I think about the importance of oxygen to immune function based on trying to understand "So, what on earth does it mean that my immune system is impaired? And how does that work with CF?"