O2 during SI?

[xoomboy]

Hi there,

I've read a lot of reports about people breathing oxygen at the 20ft stop and such to off-gas more efficiently, but no one ever mentions continuing that at the surface between dives.

Do people breathe O2 during their surface intervals, or does it not help much?

Matt

 

[FredT]

Total surface interval, %of total dissolved gas in slow tissue loading, and how much O2 you have on board can all make a difference.

When pushed on "time to fly" with minimal slow tissue loading a couple hours on O2 can flush most of the N2 out of your system. A few hours playing on several of the better deco computer models will show fairly quickly when the pactice makes sense.

The practice is/was fairly common for working divers in cold water who cut the shallow stops down and finish up with an hour or so on O2 at ambient. Some rig hunters off LA will do deck deco during the SI to lower the gas loading in fast to fast-medium tissue. The dives there are very deep and very short so lowering faster tissue loading helps provide a bit of DCS cushion there. To do the "deck deco" in front of a longer dive may not hurt anything but your pocketbook, but it won't gain you much either.

FT

 

[BRW]

Surface O2 is great if you can do it.

Our Dive Team Ops here (5 four man deco teams) require back to back to back repetitive deco diving. We use O2 on the surface for 30 minutes and 15 minutes off until back in the water. This enhances safety, and cuts subsequent deco time down by as much as 20% on next dive(s). No real surprise to many tech divers doing similar things

Of course, this requires dive planning, surface support, redundant equipment. And nitty oxtox accounting and management.

 

[Dr Deco]

Dear xoomboy:

Surface oxygen

There is no question that oxygen would be of value as the other responders have indicated. Oxygen breathing provides the biggest nitrogen gradient that you can achieve . Tech divers, commercial and military divers will utilize oxygen when possible in shallow water.

Oxygen would also be of help in the water (the “hidden stop”) before you climb up the boat ladder . That is probably getting a bit complicated. It sure would help if you were to inadvertently perform a Valsalva-like maneuver while climbing aboard.

On the surface

To promote off gassing on the surface, I recommend some activity with the arms and legs. However, not strenuous activity, and do not sleep. If one were to breathe oxygen while doing these activities during the SI, then washout would be enhanced.

Dr Deco :doctor:

 

[xoomboy]

Thanks for the info, everyone. Your answers definitely matched with my gut feeling. But as I said previously, I don't hear much about people breathing O2 during the surface interval.

I'm assuming that FredT's comments of the quantity of O2 available during the SI, as well as cost are probably the main reason why people do not continue to breathe the gas when they get out of the water. I have to confess, though, I have no idea how much a tank of oxygen costs (or helium, for that matter).

Dr Deco once bubbled...
It sure would help if you were to inadvertently perform a Valsalva-like maneuver while climbing aboard.

I did some research on the Valsalva maneuver. Here is
one page that I found.

Not sure if I missed some subtle humor, or just the concept entirely (most likely the case), but would you mind elaborating a little? I'm interested to find out what you mean. I can imagine doing something like that when flipping over the rail to get back in, but would this be bad?

Thanks!

Matt

 

[roakey]

xoomboy once bubbled...
I have to confess, though, I have no idea how much a tank of oxygen costs (or helium, for that matter).

300 cf of ABO O2 in a "T" bottle, $250 to buy the bottle and $30 a fill.

291 cf of UHP He in a "T" bottle, same cost for the bottle, $70 a fill.

YMMV

Roak

 

[FredT]

The O2 quantity on board is a referral to the fact that you'll need to reserve enough to get two bent divers to help or additional O2 in case the world turns brown. On the deeper rigs that can be a 4 to 6 hour trip if the USCG choppers are busy elsewhere. Even if readily available it may be a couple hours run to where they are in operating range of their base, so LOTS of O2 is necessary as reserve.

Weight limits on the boat may prohibit hauling enough O2 for everyone to do deck deco.

FT

 

[pescador775]

Sounds like an Italian commie conspirator. Actually, refers to a theory concerning heavy lifting or severe potty training which can cause bubbles flowing in the heart of susceptible individuals to be shunted to the arterial side. Not good. Avoid heavy lifting during and directly after boarding.