Can you breathe in liquid?

© Looper

Leviathan Press:

Although it was only one hour (and the specific liquid PFC was breathed), such an achievement is obviously exciting. However, it seems that there is still a long way to go before we can breathe directly in the water in the future. If the thorny problem of carbon dioxide emissions can be solved, and some reliable way to obtain oxygen directly from seawater or fresh water is proposed, it is really hard to imagine how drastic the impact will be on the entire civilization when people move into the deep blue.

At the end of James Cameron’s 1989 underwater thriller The Abyss, rig worker Bud Brigman, played by Ed Harris, dons a diving suit.

He breathes a special oxygenated liquid instead of air, so he can avoid the deadly side effects of the extreme pressure underwater and sink to the bottom of the deep sea trench to dismantle the nuclear warhead. You must be thinking that this is just a memorable movie plot and that this technology must only exist in science fiction. Is it really so?

© Douban Movies

The facts may be different from what you think.

The breathable liquid in the movie, oxygenated perfluorocarbon liquid, is real. Although Harris held his breath while filming the scenes in the diving suit, the scenes earlier in the movie where the mice breathe freely in the liquid are real. The Abyss is undoubtedly the most famous movie to depict liquid breathing technology, which has been studied for more than a century. Although it is not yet used in deep-sea diving, it may still be able to save lives in the medical field.

Experimentation with liquid breathing began shortly after World War I, when doctors began investigating oxygenated salt solutions to treat soldiers whose lungs had been damaged by poison gas. But real research didn’t begin until the late 1950s, at the height of the Cold War, when the U.S. Navy tried to find a way for crews to escape sinking submarines without contracting decompression sickness.

Decompression sickness, also known as scuba diving, is a disease caused by breathing underwater at a certain depth (high air pressure). As divers descend, as the water pressure increases, more and more nitrogen dissolves in body tissues. If they quickly ascend to the surface, the sudden change in pressure causes the nitrogen to escape from its dissolved state, forming tiny bubbles that can cause severe joint pain, air embolism, stroke, and death.

© New England Journal of Medicine

Therefore, divers must ascend slowly, stopping several times to decompress and allow the nitrogen to gradually escape from the body. However, if the diver or someone escaping the submarine can breathe oxygenated liquid instead of air, decompression is not necessary.

Liquid breathing can also reduce or even eliminate other hazards of deep diving, such as nitrogen intoxication (also known as "the ecstasy of the deep," a drunken intoxication reaction caused by inhaling nitrogen at high pressures). At certain depths, oxygen itself can also cause hazards, such as oxygen toxicity.

To avoid these situations, divers use various gas combinations for deep-sea breathing, such as helium-oxygen mixtures or oxygen-nitrogen-helium mixtures. Even so, this only works to a certain extent. For example, at 160 meters underwater, breathing helium can cause severe tremors, as well as neurological diseases such as high-pressure neurological syndrome. The deepest depth that divers can dive with compressed gas is 2,300 feet - and that's in a land-based diving chamber.

In 1962, Dr. Johannes Klystra of Duke University led a team that allowed mice and other small animals to breathe in oxygenated salt solutions compressed to 160 atmospheres of pressure (only at such high pressures can enough oxygen be dissolved in the liquid). The experiment lasted about an hour, but the animals soon died of respiratory acidosis (i.e., carbon dioxide poisoning).

This illustrates a major shortcoming of liquid breathing that has long troubled researchers: while breathing liquid can easily supply oxygen to the body, it is far less efficient at removing carbon dioxide. To prevent acidosis, people need to move an average of 5 liters of breathing liquid through their lungs every minute when they are at rest, and 10 liters of breathing liquid every minute when they are active—flow rates that human lungs cannot achieve on their own. Therefore, any practical liquid breathing system must efficiently pump liquid in and out of the lungs, just like the mechanical ventilators used in hospitals.

In 1966, American researchers Leland Clark and Frank Gollan made a major breakthrough in liquid respiration research when they replaced Klestra's oxygenated salt solution with a new liquid, perfluorocarbons (PFCs).

(www.annalsthoracicsurgery.org/article/S0003-4975(02)03733-5/fulltext)

PFCs are a colorless liquid made of carbon and fluorine, originally developed as part of the Manhattan Project during World War II. The combination of these two elements is extremely strong, making PFCs very stable and difficult to break down. It is twice as dense as water but only half as viscous, so it can store almost 20 times more oxygen and carbon dioxide than water can.

(link.springer.com/article/10.1007/s00424-020-02482-2)

© SpringerLink

It is precisely because of this characteristic that PFC has become an ideal liquid breathing material. In Clark and Golan's early experiments, they simply immersed mice and rats in oxygenated PFC and allowed them to breathe freely. Although the animals had difficulty breathing smoothly in this high-density liquid, they all survived, and none of them showed any adverse reactions after 20 hours of immersion. For larger animals, forced exhaust equipment is required to prevent carbon dioxide accumulation. Breathing experiments on dogs under anesthesia further demonstrated the effectiveness of PFC as a breathing liquid.

© Science Direct

Clark and Golan's findings on PFCs were soon surpassed by Klestra, who between 1969 and 1975 completed what is considered the most comprehensive study of liquid breathing ever conducted. His subjects included both animals and humans. During his studies, U.S. Navy diver Francis J. Falejcyk became the first person to breathe oxygenated saline solutions and PFCs.

Aside from receiving local anesthesia to facilitate intubation, he received no medical assistance and had no severe discomfort. However, a problem later occurred while draining fluid from his lungs, and he developed pneumonia. In 1971, Falk gave a lecture about these experiences, with Cameron, then 17, in the audience, which inspired the latter to write a short story, which eventually became the screenplay for The Abyss.

Klestra's research showed that under normal circumstances, humans can breathe PFC for up to one hour without carbon dioxide poisoning, so liquid breathing technology is feasible for people escaping from a sinking submarine. In order to apply this technology more widely, Klestra also experimented with an emulsion of PFC and sodium hydroxide, which can better absorb carbon dioxide from the blood.

(www.scientificamerican.com/index.cfm/_api/render/file/?method=inline&fileID=C71A44ED-B140-4670-8AD72D6F46692A6E)

However, in the end, none of these technologies have been put to practical use. According to reports, the US Navy SEALs conducted experiments on liquid breathing in the 1980s, but found that people were very strenuous when breathing PFC, and several divers sprained and fractured ribs due to excessive force during test exercises.

One proposed solution to acidosis is to equip divers with a venous shunt device to remove carbon dioxide directly from the blood. Unfortunately, this approach comes with considerable medical and logistical problems, and liquid breathing technology still has a long way to go before it can be used in deep-sea diving.

However, it may also play an important role in medicine, particularly in the care of premature babies.

© Wattpad

Human lungs have about 500 million alveoli, tiny sacs through which oxygen is absorbed into the blood. To prevent the alveoli from collapsing like a wet paper bag, the body produces a surfactant, a mixture of lipids that reduces the surface tension of water and keeps the alveoli open.

However, premature babies cannot produce enough pulmonary surfactant, and most of their alveoli will collapse after birth, causing difficulty breathing. For decades, traditional mechanical ventilators have helped premature babies breathe smoothly, but the high pressure generated by these machines can seriously damage the delicate lungs. If breathing fluid is injected into the lungs, the liquid can reproduce the amniotic fluid environment in the womb, open the alveoli, and greatly increase the efficiency of gas exchange. In addition, doctors can also use this technology to administer drugs directly into the lungs.

JS Greenspan of Temple University Hospital in Philadelphia, a pioneer in neonatal liquid ventilation, placed 13 premature infants on liquid ventilators in 1989 for between 24 and 96 hours. All of the children were able to breathe air, and 11 of them had significant improvements in lung function, though six died from causes unrelated to the experiment.

In 1995, RB Hirschl conducted similar experiments on 19 people, including both adult patients, infants and newborns. In the end, 11 patients' lung function improved and they survived, which further confirmed the effectiveness of liquid breathing technology.

© The Safety Zone

However, the supporting equipment for liquid breathing technology is very complex and expensive, so BP Fulman invented a simplified version of "partial liquid breathing" technology, namely PLV (partial liquid ventilation) in 1991. The lungs only need to be partially loaded with breathing liquid, and the rest can be input with air through a conventional mechanical ventilator. In this way, about 40% of the alveoli can be opened, and the discharge of carbon dioxide is also more efficient.

Another proposed approach is to convert the breathing liquid into an aerosol containing air or oxygen, which has a similar effect and is much more comfortable for the patient to breathe. In 1995, Mike Darwin and Steven Harris demonstrated how liquid breathing techniques can be used to induce therapeutic hypothermia.

This refers to reducing the body's temperature after cardiac arrest to reduce damage to the brain and other tissues. The two achieved an unprecedented 0.5 degrees Celsius per minute by filling the lungs with liquid PFC, which is much more efficient than our current technology. After breakthroughs big and small, the US Food and Drug Administration has approved liquid perfusion technology to enter the "fast track review" channel to make this potentially life-saving technology available in the clinic as soon as possible.

So if Cameron wants to explore the Mariana Trench in the near future, he will still have to rely on a complex submarine. But the breakthroughs mentioned above may bring comfort - the technology that inspired him as a child may save countless lives in the future.

By Gilles Messier

Translated by Yord

Proofreader/Pharmacist

Original article/www.todayifoundout.com/index.php/2021/08/can-humans-breathe-liquid-like-in-the-abyss/

This article is based on the Creative Commons License (BY-NC) and is published by Yord on Leviathan

The article only reflects the author's views and does not necessarily represent the position of Leviathan