Deco stops

[The Iceni]

O-ring once bubbled...
However, this is not how it is done over here on the East Coast. Boat hooks wreck, divers ascend anchor line.

Make a list of the plusses and minuses including safety and I think you may consider drift deco is better all round.

Last time I checked the Capt's up here don't give a rat's arse whether I want to drift deco or not.

If you have the equivalent of our health and safety executive I think your skippers might be "encouraged" to change their attitude.

 

[O-ring]

Dr Paul Thomas once bubbled...


Make a list of the pluses and minuses including safety and I think you may consider drift deco is better all round.

...I am just saying that the captains and boats up here do it this way and don't seem to care what anyone else has to say about it. GI3 has been hammering them for years now to no avail...

 

[WreckWriter]

O-ring once bubbled...

...I am just saying that the captains and boats up here do it this way and don't seem to care what anyone else has to say about it. GI3 has been hammering them for years now to no avail...

yea, I understand the problem. It'll change in time.

 

[Doppler]

Dr Paul Thomas once bubbled...


1) Exercise is good because it reduces effective tissue half-times and therefore speeds up decompression adding a considerable margin of safety for DCI. (I refer to Dr Deco's earlier post and his attachment.)

2) Exercise is bad because it increases the risks of CNS oxygen toxicity.

Paul, can you cite teh study from which yu took the jpeg attached to your posting. Thanks

DD

 

[Saturation]

Many good folks, I'm officially away on a diving trip. Will read threads and answer when dry docked. See you all in 2 weeks.

 

[The Iceni]

Doppler once bubbled...
Paul, can you cite the study from which you took the jpeg attached to your posting.

'fraid not, but this thread is the one on which I believe Dr Deco first quoted the study.

I presume it was done by NASA scientists.

I will ask Dr Deco to confirm.

 

[Saturation]

Yes, but you are seeing exercise here homogenously, as the curve shows the halftime eventually plateaus at a level. In addition, exercise increases the risk for cavitation.

So while beneficial for circulatory issues, its detremental for CNS oxtox risk [ at greater depths though] andcavitation.

The solution is as Dr. Deco suggest, flexing once arms and legs rather than staying immobile, similar to swimming with METS < 4.

Dr Paul Thomas once bubbled...


1) Exercise is good because it reduces effective tissue half-times and therefore speeds up decompression adding a considerable margin of safety for DCI. (I refer to Dr Deco's earlier post and his attachment.)

2) Exercise is bad because it increases the risks of CNS oxygen toxicity.

 

[Saturation]

Dr Paul Thomas once bubbled...
CNS oxtox is a random event above a ppO2 of 1 bar but can be lessened by relative hyperventilation. It is assumed a diver is largely at rest during deco although Dr Deco recommends cyclical finning at stops to maintain effective tissue perfusion and maximum off-gassing. I am not sure this makes sense. If it takes a certain time for equalisation at the start of any gas change it takes the same time for equalisation at the end of that change. Surely this is just swings and roundabouts since what is taken away at the start must be added at the end?

Yes, rest is better at deco although some activity at a low worklevel is inevitably involved such as in swimming between buddies, checking gear, or stabilizing oneself in a drift.

Yes, all things being equal, the time for equalization should be identical in and out, however, the large pp02 1.6 to begin with drifts down towards the backgas pp02, the 02 window slowly contracts, and provides more benefit than the backgas pp02 alone. Again, its only in reference to a possible hypothesis to explain Mr. Irvine's recommendation of not adding the backgas break times to the total 02 deco time.

 

[Saturation]

O-ring once bubbled...
What would you say to the argument that a jon line is a safety device against oxtox at the 20' stop because it tethers you to the anchor line where your buddies can get to you and help you to the surface?

Assuming we cannot do drift deco and we must deco on a single anchor or downline, divers tend to crowd at the same stop depth during deco. The jon line was principally meant to allow more divers to hold depth in a current while being attached to the downline.

I can think of better safety devices than a jon line, such as a fixed deco line at 20' as a variant of a tag line. Diver's needn't carry a jon line and have easier navigation to the boat's ladder.