The oxygen boost from spleen contraction during the dive reflex is temporary and lasts only during the breath-hold period.

“So this is if anyone um and again I hesitate to to tell people to do this but if you hold your breath and put your face in a bowl full of cold water your body responds as if you're diving um and and what that means is that um your your heart rate slows down um your blood vessels and the extremities constrict uh because you know your fingers will be okay with a little bit less oxygen but your brain really needs that oxygen. So, it's keeping the blood central where you need it the most. Um, and then your spleen contracts.”

“And we dive deep into fascinating mechanisms such as the mamalian dive reflex, a physiological reaction to breath holding in cold water that, as Dr. Ardo explains can dramatically alter the physiology of your spleen to allow significant increases in red blood cell count and oxygen availability to your brain and body.”

“Um but one thing that's that's slightly different from what you're talking about is that after you stop holding your breath your spleen takes that oxygen back um essentially. So that's it refills with red blood cells and that oxygen is no that extra boost is no longer in circulation. Ah so it's only during the breath hold. That's right. Only when you need it the most.”

“Um, but the spleen is a reservoir. I mean, it spleen does many things, but one of the things that it does is it's a reservoir for red blood cells that are carrying oxygen. And so, through that contraction, those oxygen rich red blood cells are now pushed into circulation, and you get an oxygen boost. How significant is that oxygen boost? It's about 10% in in most of us.”

“You're talking about a 10% increase in available oxygen through a contraction of the spleen. I didn't even know this the spleen could contract. Yeah, that's right. Um just when you put your face into colder than ambient temperature water. Uh yeah, usually in um like lab protocols, we do it at about 10° C or 50° Fahrenheit. So quite a bit colder. For how long? Um well, depends on how long you can hold your breath. Oh, right. Um yeah. So the but you know the extent to which like how long the contraction actually takes. I think we have room to to learn more about that. Um but one thing that's that's slightly different from what you're talking about is that after you stop holding your breath your spleen takes that oxygen back um essentially. So that's it refills with red blood cells and that oxygen is no that extra boost is no longer in circulation. Ah so it's only during the breath hold. That's right. Only when you need it the most. Interesting. What an incredible adaptation of the human body. Yeah.”

“And then your spleen contracts. And so, the spleen certainly wasn't the first organ that I thought about when thinking about diving, but the spleen is a reservoir, I mean, the spleen does many things, but one of the things that it does is it's a reservoir for red blood cells that are carrying oxygen. And so through that contraction, those oxygen-rich red blood cells are now pushed into circulation and you get an oxygen boost. How significant is that oxygen boost? It's about 10% in most of us.”