Reverse Dive Profiles follow-up

[rcohn]

Dr Deco,

I asked a followup question regarding your comment in the Reverse Dive Profiles thread which was lost in the noise, so I'm reposting it here.

Why does it not appear that shallow-to-deep is bad? It is my feeling that the answer lies in regeneration of tissue micronuclei during the activity in the surface interval. Thus, any nuclei that you might loose in the first compress/depress cycle will be reformed during you normal surface activities and walking about. Much is probably regained simply by climbing the ladder during reboarding the dive boat. If this hypothesis is correct, then obviously the order of the dive is irrelevant, and the interdive activity is more relevant. This activity, as I have stated on several occasions in this FORUM, should involve limb movement but not straining or heavy lifting with arms, legs, or spine.

I was wondering about the distribution of the reformed micronuclei. It would seem that an activity such as walking would create micronuclei in the joints from tribonucleation and prehaps in the muscles. I've heard speculation that the damaging nuclei are more likely to come from the lipid tissues or in/around nerves such as the spinal column. Do you have any thoughts on how micronuclei distribution would affect the risk of DCS? Do the micronuclei travel from one generation site to spread throughout the body?

Thanks.

Ralph

 

[Dr Deco]

Ralph:

Thanks for the question. (Sorry, I did not see it on the other posting.)

First, nuclei do not travel from place to place in the body. This is because the lungs filter out any bubbles in the vascular system (in general), and extravascular bubbles cannot move because they are not connected in any way to the vascular system. When I spoke earlier about regeneration, I was considering the formation of new micronuclei from kinetic activity (= movement) of the body.

We definitely detect (with Doppler flow meter bubble detectors) more gas bubbles coming from movable tissues than from non-moving ones. Thus, bubbles come (I believe) in the following order of concentration: MUSCLE >> ADIPOSE (= fat) >> KIDNEY, BRAIN > INNER EAR. Most likely connective tissue (= tendons and ligaments) is in the same category as “muscle” when it comes to producing nuclei. Therefore, we generally see pain-only DCS (“the bends”) before we encounter neurological problems. This is very fortunate for diving, in general. [There is encountered a higher incidence in the field of neurological-to-“bends” problems in recreational diving than one expects from laboratory data. Why this is true is speculative.]

The regeneration in joints (= joint spaces, synovial fluid) does not seem to be a problem, since the injection of gas (by a syringe and needle) does not provoke discomfort, and gas seen on x-ray appears to be benign.

If a free gas phase (= gas bubbles) should form in areas of the spinal cord, severe problems could result. Here we have a tissue that is both movable (= flexing of the spine) and has a high solubility for nitrogen gas. If nuclei form and grow during the decompression (or interdive interval), then nerves can become compressed, or blood flow is compromised (or blocked completely) and anoxia (= oxygen lack) results.

Concerning nuclei in the spinal coard, I have even heard from people who can “pop” their back just as some can “crack” their knuckles. One person reported that after a dive and immediately after the “cracking” he became paralyzed. Prompt recompression (in water in this case in Hawaii) halted any further deterioration. Very lucky fellow, indeed.