Liquid Breathing
What, How, and Why on Liquid Breathing.
Breathe in.
Fresh air?
Breathe out.
You’re taking in a gas that is going to diffuse into your body.
Okay, now breathe in again.
This time, imagine that you’re breathing in a liquid.
Ouch? But the liquid is actually also transporting gasses into your body, much like normal breathing.
This is known as liquid breathing (in a nutshell).
Gasses can dissolve in liquid solutions, and these solutions can help transport those gases inside the body or where they need to be. There are a lot of situations in which gases need to get somewhere where it is hard to take them, for example, during deep-sea diving or inside a premature baby who cannot breathe well. The gases can be delivered by being dissolved in a solution, but there are limits to how much gas can be contained in the solution as well. Being able to intake necessary gasses through a liquid is called liquid breathing.
Gases in Solution
But first, how do gases dissolve into liquids?
When the gas comes into contact with the liquid, the molecules can slip between and around the molecules of the liquid. This is similar to how in a fizzy drink, there are bubbles of gas submerged in and around the liquid. There is a necessary equilibrium though, as when gas may rise to the surface, it could just escape. This is seen when fizzy drinks are left out for a while, the gas rises and leaves and so the drinks get stale.
One cannot just put gases into a liquid and have them merge perfectly; some parameters and variables affect the chemistry of being able to dissolve gas in a solution. One big factor in the ability of a gas to dissolve in a solution can be explained by gaining an understanding of Henry’s Law of Solubility. This law states that the concentration of dissolved gas in a liquid is directly proportional to the partial pressure of that solution (LibreTexts, 2020). This means that the amount of gas that can be in a solution has to be proportional to the force exerted by the solution of gas and liquid. So according to Henry's Law, the higher the pressure of the gas, the higher the solubility. The more pressure that gas has the more soluble it is in terms of when it can be dissolved into a liquid or solution. This can be explained by looking at a soda can, a lot of gas is put into this small can but this can is quite pressurized meaning that more gas can “fit”, or more gas can dissolve into, the liquid inside the can. The inverse also helps to understand because when you open the can and release a lot of the pressure, the gas loses solubility and the drink goes stale as there is less gas. This is one factor that can influence the ability of gases to dissolve in solutions.
Another factor that influences the ability of gases to dissolve in solutions is the temperature (Pauller, 2015). Essentially, the warmer the solution, the less gas it will hold since there is more kinetic energy so the gas does not stay between the molecules of the solvent. Alternatively, the colder a solution, the more likely the molecules are to stay in between the molecules of a liquid because there is less kinetic energy so fewer atoms and bouncing and move around. This can be seen when opening a fizzy drink that is cold and does not fizz over the rim, versus when a fizzy drink at a warmer temperature usually goes over the rim (Pauller, 2015).
There are other factors such as the size of the molecules. The bigger the molecules are, the more likely they are to be more soluble because they experience more van der Waals forces (AK LECTURES, 2015). This means that the atoms are more likely to stick to each other because of the polarity, and this means less gas slipping out from in between the molecules of the liquid. The chemical reactivity also influences solubility (AK LECTURES, 2015). Chemicals that react to each other, or are somehow more molecularly attracted to each other also increase solubility for the same reasons as the size of the molecule.
Nitrogen at a Depth
One situation in which maintaining the solubility of a gas in a liquid is for scuba divers who go deep-sea diving. They have to intake nitrogen at deep levels through liquids, and because of the depth, nitrogen can tend to behave in different ways in their bodies.
As explained by Henry’s Law, the deeper the diver is and the higher the pressure gets, the more soluble the nitrogen inside them is. This means that more nitrogen ends up in their bloodstream and throughout their tissues. This can be quite problematic because nitrogen usually leaves the diver’s body naturally through an exhale or through the skin, but when it does so into the bloodstream and tissues, it poses risk when the pressure suddenly decreases and the temperature in their bodies increases and causes the solubility to decrease and “fizz” up in the body. This is called narcosis (Kirkland, 2022). Decompression sickness often referred to as the bends, can also occur when the scuba diver rises too fast (Harvard, 2019).
Solutions to the Issues of Using Nitrogen at a Depth
Efforts have been taken to avoid or solve these issues, but they still vary and do not all work perfectly well. Some divers breathe a mixture of gases including oxygen, helium, and nitrogen to lessen the negative effects (LibreTexts, 2021). Some other divers focus on preventing the bend from the decompression sickness by decompressing slowly, they get to higher levels, stay there for a while until their bodies slowly adjust to the pressure changes, and then repeat until they get higher. But sometimes divers need to repeatedly go very deep and undergoing these processes just harms the body even more. There is a solution in place for this though, saturation diving. This is when the diver stays under pressure in the water long enough for their tissues and bloodstream to come to equilibrium with the partial pressure of the gas they are breathing(Furguson, 2017), this basically means that the gas would be absorbed as if normally because the bodies pressure also adjusts accordingly to the environment.
A New Solution: Liquid Breathing
Breathing in these gases directly means that as they move with your bloodstream and tissues there are likely to dissolve into them with the pressure and temperature. But with a new solution, liquid breathing, these issues are less critical and a lot of other side effects of deep diving with nitrogen can be reduced.
Liquid breathing is when a gas is dissolved into a liquid that can hold high amounts of that gas and they create a solution that can go into a human’s lungs without very bad side effects and more pros than cons (Messier, 2021). When this solution goes to the lungs, it delivers the gases directly to the lungs and greatly increases gas exchange. The liquid, in turn, can also hold large amounts of carbon dioxide, so this also aids in gas exchange. What this means is that the gases that would have been absorbed by the bloodstream and tissue are instead being carried in by this liquid, being used where they are needed, and the stuff that needs to get out of the body would go into the liquid and greatly decrease the amount of gas that gets absorbed by the bloodstream and tissues.
Liquid breathing still needs some work until it can safely be used in scuba diving. It is a reality but needs time and research. The strongest recent advancement is when in 1966 the liquid chosen was perfluorocarbon (Messier, 2021). This liquid can hold a lot of gas and is good for the human body because it reduces inflammation and does not cause harm to the body.
However, liquid breathing has other use cases that are quite helpful. One of the most prominent use cases in medicine is using liquid breathing to help premature babies. Our bodies produce a protective substance called pulmonary surfactant and this allows our half a billion alveoli, sacs of tissue in our bodies that let us absorb oxygen into the bloodstream, to stay protected and open. Premature babies are not able to create this substance sufficiently because of their developmental issues but liquid ventilation allows their delicate lungs to be filled with the solutions that deliver the gases they need directly to their lungs and bloodstream, allowing their alveoli to open up as well (Messier, 2021). Traditionally, hospitals used ventilators but this put their lungs at risk because they were so delicate. Alternatively, this solution using liquid breathing mimics the conditions inside a womb, so it is safe for the baby (Messier, 2021).
Conclusion
Deep-sea divers face many issues because of the immense pressure and temperature changes their bodies go through in their profession. Premature babies' alveolitis cannot stay open often because they do not produce enough pulmonary surfactant to keep them safe. However, there is a solution that is still being heavily researched and advanced. Liquid breathing is intaking solutions that contain dissolved gasses, and these gas-rich liquids can be used in various critical situations such as deep-sea diving or premature babies.
References
AK Lectures. (2012, November 12). Factors That Affect Solubility. [Video] YouTube. https://www.youtube.com/watch?v=k-TZFogQa1E
Decompression Sickness. (2019, January 2). Harvard. https://www.health.harvard.edu/a_to_z/decompression-sickness-a-toz#:~:text=Decompression%20sickness%2C%20also%20called%20generalized,altitude%20or%20unpressuriz ed%20air%20travel.
Ferguson, S. Saturation Diving. (2017, August 1). DAN. https://dan.org/alert-diver/article/saturation-diving/
Henry’s Law. (2020, August 13). LibreTexts. https://med.libretexts.org/@go/page/7996
The Bends. (2021, January 22). LibreTexts. https://chem.libretexts.org/@go/page/1343
Kirkland PJ, Mathew D, Modi P, et al. Nitrogen Narcosis In Diving. [Updated 2022 Feb 7]. https://www.ncbi.nlm.nih.gov/books/NBK470304/
Messier, G. CAN HUMANS BREATHE LIQUID LIKE IN THE ABYSS?. (2021, August 13). Today I Found Out. https://www.todayifoundout.com/index.php/2021/08/can-humans-breathe-liquid-like-in-the-abyss/
Noel Pauller. (2015, April 17). How Temperature Affects Gas Solubility — A Science Experiment with Mr Pauller. [Video] YouTube. https://www.youtube.com/watch?v=wK4reyh86w0
