Researchers at Duke University in the 1960s under the leadership of Dr. Johanner Kylstra began studying the possibility of mammals breathing oxygen enriched liquids. They hoped to find improvements in treating pulmonary diseases as well as allowing deep sea divers to work at deeper depths for longer duration and reduce the likelihood of developing the bends (GHB chapter 24 “Drainage Ditches”). They started with oxygenated pressurized saline–salt water–and immersed lab rats into the solution. These rodents actually managed to live for an hour breathing the liquid. Oxygenation was maintained fairly well, but carbon-dioxide (CO2) did not diffuse well from the lungs into the solution. The level of carbon-dioxide, known as partial pressure, increased in the blood stream resulting in rising carbonic acid levels (GHB chapter31 “Baking Soda and Acid Burns”).
Clearly a better liquid medium was needed, and additional experimentation lead to the development of perfluorocarbons (PFC). Not only could lab rats breathing this solution maintain adequate oxygen levels in the blood, but carbon-dioxide was better able to be exchanged in the lungs with sufficiently low blood partial pressures resulting.
The studies got a huge publicity boost when the 1989 movie “The Abyss” was shown in theatres nationwide. The lab rat scene portrayed 1 of these rodents being immersed in the PFC solution and respiring the substance. To perform the segment 6 different rats were sequentially used and the Duke researchers assisted in setting up the episode. All rats survived. At this point in the film, the actor Ed Harris was shown donning his diving suit and helmet and then breathing the mixture. Reportedly, he actually considered inhaling the liquid, but eventually was talked out of it by other cast members. There was concern it might damage his vocal cords. In the end, the scene showed him surrounded by pink fluid in the helmet, but he did not actually inhale.
Subsequent human volunteers were recruited to experimentally breathe oxygenated PFC but found that both the physical and psychologic stress made the effort impractical. The viscosity of the fluid-especially compared to gas-required significant respiratory effort, and there was concern for subsequent development of pulmonary infection. In addition, even though oxygen levels were well maintained, carbon-dioxide still was not sufficiently scrubbed from the lungs and eventually built up. There is really no good substitute for a gaseous respiratory mixture.
Currently we are all breathing an atmosphere that contains 21% oxygen, 79% nitrogen, and the remaining 1% includes carbon-dioxide, water vapor, argon and additional trace gases. This is not accidental-it is the perfect combination of elements . Slightly higher oxygen levels would lead to conflagration when reacting with fire or sparks. A little less and we are too lethargic to function. Nitrogen is the perfect filler-it is inert in living creatures, but bacteria associated with plants can convert it into fertilizing material. This seemingly tiny amount of carbon-dioxide is required for plant life. Furthermore, the barometric pressure at which most of us reside is ideal for oxygenation of our blood. The equivalent of breathing 21% oxygen at sea level would require 30% at 10,000 ft and 48% at 20,000 ft. The earth’s size and gravity are also exactly required for maintaining this balance. Mars at 38% of the earth’s gravity has no atmosphere. On the other hand, a larger planet would possess a denser atmosphere requiring more effort to inhale and exhale. Besides that, we would be heavier, requiring more energy to move. We would need more caloric intake and oxygen utilization at the exact same time we could provide ourselves with less.
Astronauts spending extended times in 0 gravity experience reduced skeletal muscle mass, and shrinkage of the heart size. The heart does not have to work as hard in space. On earth both skeletal and heart muscles work against gravity. Space travelers returning to earth are significantly weaker and require assistance until they can regain pre flight stability.
The laws of physics and chemistry are fairly rigid. However, we have a tendency to think of biologic systems as perfectly adaptable. Genetic mutations and evolution presumably permit us to work around any physical/chemical obstacles. If human engineers discover a problem in design, significant planning and effort must be made to work around this. Blind mutations and evolutionary adaptation does not have this luxury. Every aspect of human biology requires precise maintenance of performance. As in so many other examples, our respiratory system is in perfect harmony with the physical and chemical environment in which it resides. Accidental? Pure materialistic blind wandering-just happening to stumble on the perfect blend? I think not. This was planned.