In the 80s I had a non-biologist friend who told me about something in development which could act as a blood replacement. They wanted to fill a swimming pool with it, sit on the bottom of the pool, and meditate. I suggested the viscosity of a pool filled with anything like blood would be a whole lot more viscous than air, and so would require a lot more muscular effort to move in and out of their lungs. And so the experience wouldn’t be as relaxing as they thought. All these decades later, and researchers are still working on it.
Liquid breathing is definitely possible, you’ve even done it before (in the womb), but it’s probably not possible with something like blood. I think your friend was probably mixing up two different concepts
https://en.wikipedia.org/wiki/Blood_substitute
In the 80s I had a non-biologist friend who told me about something in development which could act as a blood replacement. They wanted to fill a swimming pool with it, sit on the bottom of the pool, and meditate. I suggested the viscosity of a pool filled with anything like blood would be a whole lot more viscous than air, and so would require a lot more muscular effort to move in and out of their lungs. And so the experience wouldn’t be as relaxing as they thought. All these decades later, and researchers are still working on it.
Liquid breathing is definitely possible, you’ve even done it before (in the womb), but it’s probably not possible with something like blood. I think your friend was probably mixing up two different concepts