View Full Version : Fluid Breathing

Mike Byrne
2001-Oct-26, 10:38 PM
On the old board, someone asked about the possibility of fluid breathing in space and in the movie "The Abyss". I found a link that explains the concept, as well as some recent research. /phpBB/images/smiles/icon_cool.gif


Richard of Chelmsford
2004-Jun-03, 11:57 AM
I would just panic, then drown! :o

kenneth rodman
2004-Jun-03, 06:18 PM
i think most people do panic at first. they settle down once they know they can still breath

2006-Apr-08, 12:28 PM
Thats what my science teacher said and i event saw i movie where they put a rat in this liquide and it panics for a while then just starts beathed a lot slower. i gess because liquids are thick and non-conpressable. it looked quite fun is see a rat breath a liquid

grant hutchison
2006-Apr-08, 02:02 PM
i think most people do panic at first. they settle down once they know they can still breathThe link seems to be non-functional, but AFAIK people don't liquid-breathe in the way shown on The Abyss: it's very hard work to move enough liquid in and out. So at present it's used primarily in Intensive Care Units, in which people are sedated and attached to ventilators that do the work for them.

Grant Hutchison

2006-Apr-08, 03:41 PM
Air is a fluid, so think liquid-breathing.

Those initial mice, in the '60s, shown breathing liquid, were under a death sentence. They died from pulmonary damage weeks later. Later techniques got better survival rates, but required pumping of oxygenated fluid, not normal breathing.

Wikipeida: Liquid-breathing (http://en.wikipedia.org/wiki/Liquid_breathing) -- some or all of which is acknowledged as coming from the scienceweb.org site (still not working), so maybe there's nothing new there.

2006-Apr-09, 01:33 AM
IIRC the technique was developed to allow divers to withstand pressures not survivable with just oxygen alone. Perhaps it would be useful for a trip into the atmosphere of gas giants.

2006-Apr-12, 12:06 PM
that what happen to my pet rat :(


but do you think it will ever work? (fluid breathing)

Kaptain K
2006-Apr-12, 03:48 PM
As I recall, the biggest problem with liquid breathing is that liquids are so much denser and more viscous than gases that the muscles have to work so much harder that they quickly give out. Sort of like a world class runner can run 100 meters in 10 seconds, but nobody can run a kilometer in 100 seconds (1 min. 40 sec.).

grant hutchison
2006-Apr-12, 05:36 PM
As I recall, the biggest problem with liquid breathing is that liquids are so much denser and more viscous than gases that the muscles have to work so much harder that they quickly give out.That's right. And carbon dioxide is quite insoluble in the current fluorocarbons, so it's difficult to get rid of it, even if you do manage to breathe enough liquid to keep yourself oxygenated.
So the only application I'm aware of at present is in people on breathing machines in Intensive Care Units, who are suffering from catastrophically bad lung inflammation. Something called "partial liquid breathing" is used. A small quantity of liquid is run into the lungs, and its weight tends to push open airways that would otherwise be too clogged and inflamed to open on their own. Then oxygen is ventilated in and out of the lungs, and it transfers to the blood through the liquid in those airways, which wouldn't otherwise have received any oxygen at all.
It's a great thing and it probably saves lives, but it's a far cry from The Abyss.

Grant Hutchison

2006-Apr-12, 08:03 PM
Isn't this liquid breathing for divers under pressure a complete red herring?

Usually, pressure isn't a problem by itself, as long as gas spaces within the body are allowed to equalise the pressure. The problem is the "partial pressure" of gases in the mixture being breathed. For instance, nitrogen is present in air as 80% of the mixture (okay 79%, but 80 to keep it simple) so its partial presure is 760x80%mmHg = 608mmHg. Breath air at a greater pressure, say twice normal pressure, and the nitrogen partial pressure (P) will be 1216mmHg, even though it is still present as 80% of the mixture.
At five times normal air pressure, which is that 100feet below the sea, the PN will be 3040mmHg, and at that pressure, nitrogen begins to be an anesthetic. Divers feel drunk and can die from doing things they would never do while underwater, or just fall asleep - nitrogen narcosis.

This is not the same as the bends, which only occurs on rising after a deep dive, when gas in the body and in solution in body fluids, is not allowed to equalise slowly.

Oxygen at high pressure and high partial pressure is also a problem, as are helium and hydrogen. The point is that it is the partuial pressure than governs the ability of a gas to dissolve in a liquid (ignoring the differing solubility of different gases), either a body liquid or a breathable liquid. The problem lies in the gas mixture and pressure and using a gas as a neutral intermediary gains nothing.


PS Grant - I'm no expert on partial liquid breathing, but isn't it the lower surface tension of the liquid that helps open airways, not the weight? J

grant hutchison
2006-Apr-12, 09:04 PM
Isn't this liquid breathing for divers under pressure a complete red herring?I don't think so. As you increase the pressure of a breathing gas mixture in order to match the ambient pressure at greater depths, you struggle to find a "carrier" mix for the oxygen, as you say: all the usual gases have side effects when high partial pressures dissolve in the tissues, and oxygen itself is toxic if you allow its partial pressure to get too high.
But liquid breathing makes the whole problem disappear, because it requires no carrier gases: the pressure in the lung is maintained by the incompressibility of the liquid itself, and you simply dissolve enough oxygen in that to maintain the necessary partial pressure to deliver oxygen to the blood in normal quantities. No toxic effects, and no dissolved gases coming out of solution when you surface, either.

PS Grant - I'm no expert on partial liquid breathing, but isn't it the lower surface tension of the liquid that helps open airways, not the weight?Yes, if you've lost surfactant from the alveoli, the reduced surface tension of the tissue-liquid interface will certainly help the alveoli re-expand when they're collapsed: I should have mentioned that, so thanks for pointing it out.
But having a puddle of liquid in the dependent part of your lungs also helps hold the airways open by a direct pressure effect because of the hydrostatic head of fluid. You can imagine that a ventilator will open "tight" airways for a moment as it cycles to high pressure, and then they'll close again as soon as the ventilator cycles to let the patient breathe out. But the hydrostatic pressure of the instilled liquid maintains a constant pressure that holds these airways open against tissue recoil throughout the breathing cycle. It's called "liquid PEEP" (positive end-expired pressure).

Grant Hutchison

2006-Apr-12, 10:35 PM
Do a search of the words perflubron. Liqui-Vent, fluisol...

grant hutchison
2006-Apr-13, 08:49 AM
Another useful feature of partial liquid breathing for people with sick inflamed lungs: because the liquid used is denser than water, inflammatory fluid and tissue debris tends to float out of the alveoli and small airways and rise to the liquid surface, where it can be accessed and removed. Then, when the liquid evaporates, it leaves a cleaner lung behind.

Grant Hutchison

2006-Apr-13, 11:33 AM
Thank you, Grant, always ready for a bit of CME!

But I'm still puzzled by this carrier gas/liquid thing. May I run this past you to see if I have it right?
The PP of oxygen, as an example, cannot rise above about 500mmHg without being toxic to the brain. So deep divers breath a very low oxygen gas mix, often with helium as the carrier, and as you say, helium has its own probs at high pressure.

If a deep diver is to breath liquid with oxygen dissolved in it, Dalton's Law applies. The PP of a gas dissolved in the liquid is the same as the gas mixture in contact with the liquid. To exclude other gases, the fluid must be prepared by exposing it to pure oxygen at a very LOW pressure, so that the O2 is at a partial pressure of the equivalent of 21% in air at sea level (Say O2 at 760/5=150mmHg?). As an aside: But these fluids are volatile? They'll have to be cooled to prevent boiling at that low pressure.

Seal the liquid and dissolved O2 and warm it to room temp and pressure. A gas bubble above the liquid can only contain liquid vapour and oxygen, so atmospheric pressure on incompressible liquid will prevent any bubbles forming. As will the ambient pressure at depth.
The deep diver will breath the liquid under pressure, I presume after washing out all their other gases. The partial pressures in their tissues will now be those of oxygen and dissolved liquid, the liquid taking the place of all other gases in the partial pressure equation. Wow, never thought of it that way, and it's difficult to take in. It's all a matter of preserving the physical state in solution terms of the original low pressure set up. Definitely, no bubbles in the system!

In practical terms, the cooled solution vessel seems clumsy. A better way would be to use a side stream method, saturating a small amount of liquid with O2 and adding that to the liquid mainstream in measured quantity, like an anaesthesia vapouriser? That allows for varying the PO2 for different depths. A very low flow side stream, as this liquid must work in a circle system.


2006-Apr-13, 03:09 PM
Actually, whenever I think of "liquid breathing", I think of the acceleration tanks used in Joe Haldeman's The Forever War, which allow ships to pull high-gee maneuvers without squashing the crew. If we ever get into really advanced propulsion regimes (fission, fusion, antimatter), I think such a feature could be useful--all the more so because it would only be for short intervals.

grant hutchison
2006-Apr-13, 03:50 PM
But I'm still puzzled by this carrier gas/liquid thing.From the gas/liquid physics point of view, I've always thought of it as follows.
The liquid filling the diver's lungs (and middle ear and sinuses) would be at ambient hydrostatic pressure for the depth dived, as would the diver's tissues and body fluids. Dissolved in the breathing liquid would be a quantity of oxygen with a partial pressure of 20kPa or so (equivalent to 21% of an atmosphere), which would be in dynamic equilibrium with the oxygen dissolved in the diver's tissues: there would be a net influx through the diver's lungs to compensate for metabolic consumption of oxygen. Also dissolved in the liquid would be a quantity of carbon dioxide with a sufficiently low partial pressure to encourage outward diffusion of carbon dioxide from the diver's blood through the lungs: somewhere in the breathing system CO2 would need to be extracted from the liquid, so again we have a dynamic equilibrium. Dissolved in the diver's tissues would be a quantity of fluorocarbon, in equilibrium with the vapour pressure of the fluorocarbon liquid in use. Dissolved in the fluorocarbon would be a quantity of water, in equilibrium with the vapour pressure of body water. (Since water and fluorocarbon are poorly intersoluble, the actual molar concentrations necessary to maintain these vapour pressure equilibria would probably be quite small.)
Everything is in equilibrium, with the partial pressures of dissolved gases in all cases very low compared to the ambient hydrostatic pressure. (I guess there would also be a slow diffusion of gas and vapour through the diver's suit, along partial pressure gradients between the ambient water and the diver's suit environment.)

As to the practicalities of oxygenating the breathing liquid, I've never read any sort of engineering treatment of that. But I've imagined a simple system involving a high-pressure oxygen source and a sensor for oxygen partial pressure (something like a Clark electrode or a fuel cell). When the measured oxygen partial pressure is lower than required, the high pressure source bubbles oxygen through the breathing liquid until the partial pressure is restored. Liquid would circulate through an enclosed unit in which this reoxygenation took place.

Having said all that, I honestly don't imagine we'll ever see divers breathing this stuff: the sheer work of breathing liquid seems like a show-stopper, to me.

Grant Hutchison