Oxygenated perfluorocarbon liquids are real
The breathable liquid in the movie, the oxygenated perfluorocarbon liquid, is real. Although Harris held his breath while filming the scene in the diving suit, the scene where the mouse is breathing freely in the liquid earlier in the film is real. The Abyss is undoubtedly the most famous film depicting liquid breathing technology, which has been studied for over a century. Although people can’t use it for deep-sea diving, it still has the potential to play a role in medicine and save lives.
Experiments related to liquid breathing began shortly after World War I, when doctors began studying oxygenated salt solutions to treat soldiers whose lungs had been damaged by poison gas. But it wasn’t until the late 1950s, at the height of the Cold War, that real research took place, as the U.S. Navy tried to find a way to help sailors escape sinking submarines and avoid decompression sickness.
Diving decompression sickness, also known as diver’s disease, is a disease caused by breathing at a certain depth underwater (high pressure). As the diver descends, as the water pressure increases, more and more nitrogen gas dissolves into the body tissues. If they rise to the surface quickly, the sudden change in pressure can cause nitrogen gas to escape from the dissolved state, forming tiny air bubbles that can lead to severe joint pain, air embolism, and death.
As a result, the diver must ascend slowly and make multiple stops to decompress, allowing the nitrogen to gradually drain from the body. However, if the diver or the person escaping the submarine can breathe oxygenated liquid instead of air, there is no need for decompression.
Brigman breathes a special kind of oxygenated liquid in “The Abyss”
Liquid breathing techniques can also reduce or even eliminate other hazards of deep diving, such as nitrogen intoxication (also known as “deep ecstasy”, the intoxication-like poisoning effect of inhaling nitrogen at high pressure). 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 or oxy-nitrogen-helium. Still, it only works to a certain extent. For example, at 160 meters underwater, breathing helium can trigger severe tremors, as well as neurological conditions such as hypertensive neurological syndrome. The deepest dive that a diver can dive with compressed gas is 701 meters — and that’s still in a land-based diving chamber.
In 1962, a team led by Dr. Johannes Kleinstra of Duke University allowed mice and other small animals to compress at 160 atmospheres (only at such a high pressure can enough oxygen be dissolved in a liquid). Breathe in an oxygenated salt solution. The experiment lasted about an hour, but the animals died quickly from respiratory acidosis (i.e. carbon dioxide poisoning).
This shows one of the major drawbacks of liquid breathing techniques that vex researchers: While breathing liquid can easily supply oxygen to the body, it is far less efficient at expelling carbon dioxide. In order to prevent acidosis, people need an average of 5 liters of breathing fluid per minute to flow through the lungs when they are at rest, and 10 liters of breathing fluid per minute when they are active – the human lungs themselves This flow rate cannot be achieved. Therefore, any practical liquid breathing system must pump fluid in/out of the lungs as efficiently as a mechanical ventilator in a hospital.
In Clark and Golan’s early experiments, they simply immersed mice and rats in oxygenated PFCs and let them breathe freely.
PFC is a colorless liquid composed of carbon and fluorine. It is twice as dense as water but half as viscous, so it can store almost 20 times more oxygen and carbon dioxide than water can.
In 1966, American researchers Leland Clark and Frank Golan made a major breakthrough in the study of liquid respiration, they replaced the oxygenated salt solution of Crestra to a new liquid, namely perfluorocarbon. (PFC).
PFC is a colorless liquid made up of carbon and fluorine that started out as part of the Manhattan Project during World War II. The combination of these two elements is extremely strong, so PFC is very stable and does not easily decompose. It is twice as dense but half as viscous, so it can store almost 20 times more oxygen and carbon dioxide than water can.
It is because of this characteristic that PFC becomes an ideal liquid breathing material. In Clark and Golan’s early experiments, they simply immersed mice and rats in oxygenated PFCs and let them breathe freely. Although the animals did not breathe well in the dense fluid, all survived, and after 20 hours of immersion, none of the animals had an adverse effect. For larger animals, mandatory exhaust equipment is required to prevent carbon dioxide build-up. Breathing experiments on dogs under anesthesia further demonstrate the effectiveness of PFC as a breathing fluid.
Clark and Golan’s findings on PFC were quickly surpassed by Kleinstra. The latter completed what is arguably the most comprehensive study of liquid breathing ever conducted between 1969 and 1975. His experimental subjects include animals and humans. During the research, U.S. Navy diver Francis Falk became the first person to breathe an oxygenated salt solution and PFC.
Apart from receiving local anesthesia to facilitate intubation, he received no other medical assistance throughout the procedure, and he did not experience intense discomfort. He later developed pneumonia, however, when he had problems pumping fluid from his lungs. In 1971, Falk gave a lecture on these experiences with Cameron, then 17, in the audience, which inspired the latter to write the short story that eventually led to the script for The Abyss. .
Kleinstra’s research shows that under normal circumstances, humans can breathe PFC for up to an hour without carbon dioxide poisoning, so liquid breathing technology is feasible for people escaping a sinking submarine. To apply the technique more widely, Kleinstra also experimented with an emulsion of PFC and sodium hydroxide, a substance that better absorbs carbon dioxide from the blood.
Application of liquid breathing technology in medical field
However, in the end, none of these technologies have been put into practical use. According to reports, the U.S. Navy SEALs experimented with liquid breathing in the 1980s, but found that it was very difficult for people to breathe PFC, and several divers caused rib sprains and fractures due to excessive force during the test.
One solution to acidosis is to equip divers with a venous shunt that removes carbon dioxide directly from the blood. Unfortunately, there are considerable medical and logistical problems with this approach, and liquid breathing technology has a long way to go before it can be officially used in deep-sea diving.
However, it may also play an important role in medicine, particularly in the care of premature babies.
The human lung has about 500 million alveoli, through which oxygen is absorbed into the bloodstream. To keep the alveoli from collapsing like wet paper bags, the body produces a pulmonary surfactant. This is a lipid mixture that lowers the surface tension of water, keeping the alveoli open.
However, premature babies do not produce enough lung surfactant, and after birth, most of their alveoli collapse, making it difficult to breathe. For decades, conventional mechanical ventilators have helped premature babies breathe, but the high pressures these machines generate can severely damage delicate lungs. If breathing fluid is injected into the lungs, the fluid can reproduce the amniotic fluid environment in the womb, opening the alveoli and greatly increasing the efficiency of gas exchange. In addition, doctors can use the technology to deliver drugs directly to the lungs.
JS Greenspan of Temple University Hospital in Philadelphia is a pioneer in neonatal liquid breathing techniques. In 1989, he put 13 premature babies on liquid ventilators for 24 to 96 hours. All of the children were able to breathe later, and 11 of them had significant improvements in lung function, although six died from factors unrelated to the experiment.
In 1995, RB Herhir performed a similar experiment on 19 people, including adult patients, as well as infants and neonates. In the end, 11 patients had improved lung function and survived, further confirming the effectiveness of the liquid breathing technique.
Helping young children breathe with liquid breathing techniques
However, the supporting equipment to achieve liquid breathing technology is very complex and expensive, so in 1991 BP Foreman invented a simplified version of the “partial liquid breathing” technology, or PLV. The lungs only need to be partially loaded with breathing fluid, and the rest can be fed with air through a conventional mechanical ventilator. In this way, about 40% of the alveoli can be opened, and the expulsion of carbon dioxide is also more efficient.
Another suggested option is to convert the breathing fluid into a spray containing air or oxygen, which has similar effects and is much more comfortable for the patient to breathe. In 1995, Mike Darwin and Steven Harris demonstrated how liquid breathing techniques could be used to induce therapeutic hypothermia.
This refers to reducing damage to the brain and other tissues by lowering the body temperature after cardiac arrest. By filling the lungs with liquid PFC, the pair achieved an unprecedented reduction of 0.5 degrees Celsius per minute, which is far more efficient than our current technology. After breakthroughs big and small, the FDA has approved the fluid infusion technology into “fast-track review” to make this potentially life-saving technology work in the clinic as soon as possible.
So, if Cameron wants to explore the Mariana Trench for some time to come, he will still have to resort to a submarine. But the aforementioned breakthroughs may offer solace—the technology that inspired him as a child has the potential to save countless lives in the future.