Wednesday, 13 July 2011

Aquaman's not so Sucky Superhero Surfactants

As I mentioned before I am a total nerd.  Growing up I bought comic books.  I never bought an Aquaman comic book though.  He was always deemed the lamest superhero.  After writing this blog and reading 20,000 Leagues I think that Aquaman has some merits as a superhero.  I stumbled onto a couple of years ago the Physics of Superheroes by Prof. James Kakalios and I would like to contribute something extra to his writing.

James Kakalios mentions that we all breath water.  We start by breathing air through our nose or mouth down our bronchial tube warming and moistening the air before it goes into our lungs.  The lungs are unbelievable.  It has a huge membrane surface area.  I still cannot imagine why people smoke.  If they knew how great the lungs are.  The air needs to be premoistoned before it goes into the lungs.  Why? 'In fact he air has to be at 100 percent relative humidity as it moves down the ever more finely branched tubes on its way to the alveoli' Kokolios states. 

The alveoli are small little spherical buds where exchange of oxygen and carbon dioxide occurs. These pockets are roughly 0.1 to 0.3 mm in diameter and have a large membrane surface area, they are smaller than the period at the end of this sentence. Capillaries located on the other side of the alveolar bud are narrow blood vessels that drop off a payload of carbon dioxide and pick up some oxygen before going to the heart.  The membrane surface area has to be large so the alveolar spheres have to be small and the capillaries have to be narrow.  This maximizes the ratio of surface area to volume so more regions for gas exchange to occur.

A transition between the gas molecules between the interior of the alveoli from the brochial tubes to the capillaries needs to take place.  The transition of these gas molecules needs a thin coating of water on the interior of the alveolar surface.  The water layer facilitates the transfer of gases.  Without it the inner cell walls of the alveoli would become dried out by contacting the air directly.  When it is dissolved from the gas phase an oxygen molecule can be transferred into the liquid phase allowing the oxygen to get picked up by the hemoglobin chromophores in red blood cells.  Thus the alveoli are considered to be air bubbles in water and we could not breath without a little water interacting on the surface of these air bubbles.  Aquaman, as well as that of Marvel Comics Prince Namor, the Sub-Mariner, and all the other denizens of comic books’ have the interesting ability to extract oxygen directly underwater.  Aquaman, and the others lack fish gills so he must have some sort of super power adaptation to allow him to continue breathing even when completely underwater and potentially with a significant amount of pressure exerted on his body.
However, unlike Aquaman when normal humans fill the lungs with water it can cause asphyxiation.  The surface tension of the outside water is sufficient to cause the alveolar buds to close up preventing oxygen into the blood stream.

As James Kakalios' suggests that pulmonary surfactants in Aquaman's lungs and also have very strong lungs to withstand the increased force to breath the denser water could help him to breath.  Pulmonary surfactants is a surface-active lipoprotein complex (with lipids and proteins) that has dipalmitoylphosphotidylcholine that has its tails facing the air.  The pulmonary surfactants' lipids face the air reducing the surface tension.  Aquaman then must have some adaptation to allow him to reduce the surface tension of water easier allowing him to extract air bubbles.  He might also have some adaptation with his hemoglobin (or myoglobin) that allows him to pick up the transferred oxygen better.

When writing this I was wondering if there was something out there that could make us into Aquaman.  My colleague told me about a rat that could be under water that he saw on television.  I looked up how this is possible.  It was from the James Cameron movie The Abyss.  (a clip is below).  This diving suit for liquid breathing uses highly oxygenated perfluorocarbons to dissolve into the blood through the alveoli.  These perfluorocarbons are very good surfactants (like teflon) that can go through lung tissue into the blood.   Perfluorochemical (perfluorocarbon) molecules and depending on their structures may impart different physical properties such as respiratory gas solubility, density, viscosity, vapor pressure and lipid solubility.  So this technology could be used for medical uses, deep sea diving, and space travel by modifying the structure and the delivery.  However, obstacles still need to be overcome.  Firstly some sort of gas exchanger has to be used to replenish the oxygenated perfluorocarbons.  So this is slightly different as Aquaman directly uses the water to get oxygen.   Secondly since the liquid is more dense and we would require more CO2 to be removed from the blood we would need some sort of attached ventilator as well as lungs as strong as Aquaman's.  So in the end Aquaman is not so crappy after all since we still do not have the technology to effectively breath under water to fight crime.