[jss]

After three months of trying I was finally allowed to speak with someone within Spinal Kinetics that was about to help with the question of SCUBA diving with the M6.

The short answer is that they have not tested it under those conditions, but think that it should be Ok provided that you don't do any nitrox diving where you're at depths greater than 135 feet, or at 135 foot depth for extended periods.

The polymer sheath around the core and weave of the M6 is NOT an air tight seal. There are two vent ports that allow fluids to travel in and out of the core of the M6 (which is exactly how an automotive shock absorber works). When the sheath is installed, whatever fraction of the atmosphere that is present is what is inside the M6 when it is implanted in the host (me). Over time, the hosts extracellular fluid (ECF) displaces the air within the M6 sheath as the M6 fills with ECF.

There are two obvious problems here for SCUBA. As we descend, pressure increases, more and more gases become soluble in our blood and other tissues. As we ascend, the gases become less soluble and come out of the solution of our blood or other tissues. When we ascend too fast, bubbles form in our tissues (this is called "The Bends"). This leaves many questions...

How long does it take for all of the gas in the M6 to be replaced with ECF? At what rate is gas saturated ECF ported into the M6? Is enough ported in that there is still enough to form a bubble during a normal ascent? If a bubble does form, is it possible that it can be large enough to deform the M6 in a way that was not intended? Since the sheath was intended to contain wear debris from the internal components, what happens when one or both ports become clogged?

These are all questions on which we can speculate and hypothesize, but Spinal Kinetics currently has no plans do the testing that would allow them to be answered. It sounds like the M6 should not contra-indicate SCUBA. I may do a shallow dive of not more than 33 feet.