Just like a lot of things in nature, things fall on a bell shaped curve. Same as with divers developing bubbles. There are some that demonstrate bubbles more and less than what falls in the middle of the curve! Mind you, there are inter- and intra-individual variation of this phenomena. What this means is that on any given day, Diver A may develop less bubbles but on another day develops more bubbles for the same dive with the same profile, same temperature...etc.
That has been documented for a while and when you read the studies, you will see this.
Factors that may vary the amount of bubble development on any given day may be related to last exercise prior to diving, and the phenomena of adaptation, as well as processes yet to be discovered. Regarding adaptation: Here it has shown that as you continue to dive the same depth, the amount of bubbles formed become less and less.
If you are interested reading the studies yourself, I have compiled a list of over 200 articles on diving related research and posted it on the AddHelium website under "Resource Library:
Add Helium Resource Library | Add Helium
Another very important thing to keep in mind is: JUST BECAUSE YOU HAVE BUBBLES, DOES NOT MEAN THAT YOU ARE GOING TO BEND!
The relationship of developing DCS and bubbles is still not understood. Most of us have bubbles but very few of us develop DCS.
For those with further interests on studies regarding PFO's, the above recently updated list has few more additions in that section, as well.
Happy Reading and Safe Diving!
Claudia