Nucleation

Understanding nucleation as a process and what divers can do to mitigate it.

Divers have a generalized concept that decompression bubbles form with ascent and reduced its sizes with a decrease in ambient pressure but this isn’t completely accurate, tiny microbubbles are already present prior depressurization. Which means that two factors should be present for the occurrence of DCS, micronuclei and supersaturation.

Although our internal body have no contact with air underwater except for the lungs and skin, gas seeds must be present in the blood, capillaries and other tissues prior depressurization.
We know that physical processes can also enlarge micronuclei. Expansion of a fluid can do this and is called Reynolds cavitation. We can tell bubbles forms in a squeezed garden hose when water flows; It is sometimes called boiling at room temperature.

There’s a significant evidence to suggest that micronuclei exist in living tissue, but with short longevity. This idea came from the studies of E.N. Harvey. He believes that changes in barometric pressure on the body were too small to form new bubbles, so he reasoned that these new bubbles formations should came from a musculoskeletal activity (mechanical activity) and postulate that mechanical forces were responsible for the relative ease by which a gas phase formed in living tissue.

What we know

Today’s evidence came from animal experimentation and it’s well known that physical activities produced bubbles (kinetic activity). Also isobaric counter diffusion proof that in vivo micronucleus exist. So Within the topic of decompression nucleation control is done by evaluating the efficiency of decompression tables which dealt with supersaturations controls only by the Haldane Method.

In diving, Henry’s law states that gases dissolve in liquids in proportion to partial pressure of the gas itself. It the total pressure is reduced, more dissolved Nitrogen molecules exist surrounded by liquid than in balanced. This balance exists whereby dissolved nitrogen molecules are surrounded by liquid and then free in a pattern that changes back and forth many thousands of times per second. The pressure reduction upsets this balance and the overall tendency is to have more free nitrogen molecules (non- solvated) groupe together and, consecutively form macroscopic gaseous nitrogen bubbles.

This process starts with very small entities (submicron in radius) that could be formed by thermal activities, now physical (musculoskeletal) activities can transform this tiny entities into micron-size bubbles, the lifetimes of theses will be short (tens of minutes) in the absence of stabilization. So oxygen linked to hydrogen on a different molecule must be ruptured to create a cavity and for a fraction of a second this cavity will be filled with water vapor ( it’s a tiny hole of vaporous cavity in liquid water filled with gaseous) an all this process is stochastic.:

So the process could be view as:

Random fluctuations of water molecules→cavities of varying dimensions→cavities enlarge to microbubbles→quasi-stable microbubbles→Deco bubble growth

In conclusion, kinetic activities of our musculoskeletal system assisted in cavity formation. So a diver after decompress with a moderate rest will help to reduce micronuclei formation and bubble growth, contrary to a full rest or excessive activity. This moderate rest will help to blood flow that carries off dissolved inert gas.


Base on the article named Liquids as a hole: nucleation in diving. Published by Michel Powell in Tech Diving Magazine, issue 5.  Pag. 22- 37.

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