interesting...

[ffelix]

Dr Deco once bubbled...

Oxygen at Depth

It probably would be of value but I am not really sure if it would be worth the effort. There are various ways to maximize the efficiency and, if you were to add all of them together, you would probably be constantly worrying and not enjoy the dive.

Ha! I'm sure you're right. It was just a theoretical additional (or higher) use for those spare-airs...

Thanks again for the great info Dr. Deco! Very interesting about bending and flexing of the spinal column increasing DCI risk (presumably due to the critical location of the bubbles formed?). On first thought, I would have attributed more overall effect to the larger structures of the legs, since these muscles use so much oxygen (lots of on & off-gassing). I'll take a look at the old threads.

Also a great point about technical diving skills spilling over, Saturation.

 

[Dr Deco]

Dear ffelix:

Bubble Formation

I suspect that bubble formation occurs by hydrodynamic cavitation in all movable structures of the body to a more or less degree. It certainly occurs in muscles and one can easily find gas bubbles in them upon dissection. They are also a large source of the Doppler bubbles (I believe).

Because the spine is constantly flexing, I believe that it is a possible source for small nuclei to form. This is my hypothesis only. Large gas phases between the disks do occur for certain and are referred to as the “vacuum phenomena.” Our "trouble makers" are probably within the blood capillaries or extravascular and compressing nerve axons. :lifter:

As mentioned before, this will probably need some degree of investigation by filed reports. A prospective laboratory test of spinal cord DCS will not be performed in the laboratory with current capabilities.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :grad:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[Saturation]

Dr Deco once bubbled...
Hello ffelix:
Neurological DCS
I suppose I would have to take issue with the statement that a “majority of DCS 2 that happen with bends within table limits are likely from divers with PFOs, rapid ascents, or barotrauma rather than true bends.” I am definitely of the persuasion that bending and flexing of the spinal cord during reboarding with gear, etc, can be a nucleating activity. This is not an "arterialization mechanism."

Hi Dr. Deco:

Its certainly possible and worth testing, as Shakespeare said "... all things are possible if our mind be so."

Motion in the spinal cord is exceedingly limited by its supporting structures and with a scuba tank aligned with the spine, extensive flexion is not possible, since it, and say a backplate, serve as a backboard to limit motion.The spinal cord floats in fluid, surrounded by the vertebral canal and further supported by very powerful groups of thick muscles and ligaments, all forming a shield for the spinal cord.

Many patients who suffer from back pains and arthritis find instant relief once in the water, suggesting at least, in-water, the spine is under least amounts of stress.

However, on surfacing, the vertebrae would have to take the brunt of the body weight plus tank, but again, this would not cause undue movement of the cord itself, but that of the vertebrae and its supporting muscles. Divers could, go into a tirade of calisthenics during the SIT that could be a nidus for trouble!

Autochthonic mechanisms could occur by ascent rate mechanisms.

Many studies have already associated PFO and shunts with both AGE, spinal DCI, and cutaneous DCI.

 

[Dr Deco]

Hi Saturation:

I was thinking of the flexion of the spine when bending over and straightening up again.

It certainly is open to speculation.

Dr D.