ND Chief

Maybe we can put this topic to rest and let the fiction authors and hollywood types keep dreaming. There are a few problems with Dan Brown's fictional accounts and "The Abyss" solution to deep diving saturation of tissues in a diver. The liquid which touches the alveolar sacs inside the lungs must be at the perfect pH and salinity levels so that the body will not "reject" it, filling the lungs with fluid after the liquid has been removed or expelled from the lungs (secondary drowning followed by pneumonia) Air or gas breathing is performed when the vacuum created by contraction of the diaphragm during inspiration pulls air from outside the body into the lungs and down the bronchial tubes, past the bronchi and into the alveolar sacs. If the diver could suppress the involuntary action of coughing upon inspiration of liquid, he would then begin an extremely laborious task of pulling something hydraulic through a pneumatic designed system. In my opinion, no serious work could be performed due to the need for increased respiration. Even if you increased the percentage of oxygen in the mixture, liquid does not flow with the same efficiency air or a lighter gas would. Increasing the O2 any higher than 3.1 ATA PPO2 (or 310% surface equivalent value) could cause CNS O2 toxicity (as demonstrated in air and mixed gas diving). If the diver were even able to "breathe" liquid media on the surface, due to the incompressable nature of liquid, any voids within the alveolar sacs could rupture, causing a POIS (Pulmonary Over Inflation Syndrome), which could lead to arterial gas embolism and possible death. If all the above points were worked out and the diver were able to inspire the liquid, supress involuntary coughing and lung spasms, achieve complete lung saturation, breathe normally, and avoid hypoxia all on the surface... If the pumping mechanism were sound enough to supply the correct volume of breathing media, accurate enough to supply the correct pressure without over inflation of the lungs, and anyone were stupid enough to attempt an actual dive, then you would need to consider how to perform the valsalva maneuver with no air to push up your eustachian tubes. Remember the middle ear is air-filled, its the inner ear that is fluid-filled. So, anyone ever try pushing liquid up your eustachian tubes? A maximum depth of around 12ft or 4m will cause damage to the tympanic membrane, at 33ft or 11m the middle ear volume would be reduced to 50%. The ear drum is flexible, but not to that extent. It will burst without valsalva. The physical properties of gasses circulating into and out of the lungs differ greatly from the properties of a liquid circulating into and back out of the lungs. Fish have gills which allow gas transfer to occur through fluid flow across the capillary beds, not into and back out of spaces not designed for liquid. Great stuff for the books and movies though! All material above can be found for reference in the US Navy Diving Manual Rev. 6.