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Comment by modeless | Hacker News Reader

Cool, could these be modified to let people hold their breath underwater for hours like seals or sea turtles?

The usual problem for breath-holding is not lack of oxygen, but surplus of CO2. It is the latter that creates the panicked urge to breathe.

Free divers and stunt magicians therefore hyperventilate prior to diving, or getting sealed inside an ice block, or whatever. The disadvantage to this is that they then have no natural physiological gauge to determine when they are actually running low on oxygen, as the CO2 signal is delayed past the point where unconsciousness due to hypoxia occurs.

With artificial RBCs, you could perhaps load them up with an oxygen-storage protein like myoglobin instead of just oxygen-transporting hemoglobin, and use bicarbonate concentration as a trigger to release O2 and bind CO2--borrowing from both whales and crocodilians.

It might also be useful to develop an artificial lung or gill that employs perfluorodecalin flowing through narrow tubes of gas-permeable membrane to transport gases.

IANAS, but I like to think that Yes, you can hold your breath longer with synthetic blood. Popular Mechanics covered this in 2006[1], an article I will never forget. But it's a speculative piece. More research has been done recently, a cursory google search for "synthetic blood" indicates many possibilities.

[1] https://www.popularmechanics.com/science/health/a646/2713146...

I am also not a seal, but this sounds really fascinating and so tantalizingly plausible.

Isn't a big problem the CO2 piling up ?

Seems solvable too. As well as the bends.

I believe pressure also plays a factor there (and the ability for our bodies to get oxygen to said cells).

In other words, I doubt it.

I think you could potentially (not in any way feasible with the current state of technology) design a different oxygen carrying protein than hemoglobin that only releases the oxygen in high pressure environments. But as you can't replenish them underwater, that will probably only buy you a few minutes at best rather than hours.

At any pressure a human underwater is likely to experience (besides perhaps being immediately transported to the bottom of the Mariana Trench) it is not practically the fluid/blood that is being compressed but tissues and gases, so barring a barometer it would be difficult to tell this new haemogolobin to hit release.

I’m sure you’re already are of the oxygen Haemoglobin dissociation Curve so O2-Hb release is already influenced by a number of forces that occur whilst holding your breath for ages (like increased CO2 causing decreased pH, increased DPG in oxygen poor tissues). What we would need is something that can carry a shit-ton more O2. So either a more efficient Hb molecule (could we get to 8 O2s?) or a way not to thicken a persons blood so much that they have a heart attack (the problem with just infusing more of the same stuff in)

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