What to do if . . .

[boulderjohn]

They say that does not work. There is a good reason it does not work but I don't 100% understand it.

I'm not sure who the "they" is. Is it possible you (and some others) are confusing the question of going back down to do a deco stop with going back down to recompress after the diver has decompression sickness?

Returning to the water as a substitute for a hyperbaric chamber is generally not recommended because the diver could not stay down long enough to go through a true recompression process, the diver would get way too cold before it would do any good, and the diver would not have access to the fluids that are normally part of recompression therapy.

In the scenario suggested in the thread, the diver does not have DCS; the diver is trying to prevent it.

 

[Thalassamania]

They say that does not work..

Who are they?

There is a good reason it does not work but I don't 100% understand it. The short answer is to think about "tisue compartments" and "nitrogen gradients". Or maybe the real-short answer is that humans are not sodaa botles. If you go up then go down again you will have gas moving in two directions

I think it would work if humans were just a bag of liquid with no other tissue types but we arn't soda bottles. Once the gas has come out of solution in some slow tissue I think it has harder to re-disolve it and going back to 15 feet is ineffective. Some other effects like the nitrogen in a bone has to first get into the blood and then be exchanged through the lungs. If you go back down the fast tissues will be taking in even more nitrogen because to went from a .78 PP nitrogen environment (the boat) to a higher PP nitrogen environment (air at 15 feet) Breathing O2 at the surface is the way to go.

So once yo have a gas micro-buble in some tissue that has poor blood flow going back to 15 feet for a few minutes will only load the blod back up with more nitrogen reducing the nitrogen gradient that the bubbkle sees.

15 feet for 15 min will not make you start in taking up nitrogen, your fast tissues are already way above 1.5 and 15 min will just start to hit your 30 min tissue. With all due respect, I don't mind being told I'm wrong, hell ... I love to learn things, but your dealing with people’s health here, they need to be able to make informed decisions. I rarely say anything like this in a post, but right now it is imperative. Please, before providing advice, learn a little bit about the subject.

The standard advice is to breath O2 on the surface.

No the standard is set by the U.S. Navy and the standard advice is to follow the U.S. Navy's omitted decompression procedure. If you'd rather trust your health and well being to someone whom you thing knows more about decompression than the U.S. Navy does, knock yourself out.

 

[serambin]

This thread confirms my believe in this site. My partners and I are planning to buy an off-shore boat for diving this summer. At one time, I dove oil rigs off the Louisiana coast and spearfished. My partners are interested in this type of diving. The 'planned dive' goes out the window when you shoot a 45 lb snapper who is determined to go down just as you are determined to go up.

Planning dives and diving your plan strikes me as a great idea, but please remember, some of the most experienced divers in most areas of 'instructions' have, on occasion, failed to dive their plan. Some have died.

What I believe is that very few people ( as you might see in responses to this thread, including me) can make a reasoned choice on what to do if something goes wrong.

Diving safety can not be about the necessity of achieving perfection in the execution of dives, but rather about making our sport as safe as possible because of an unforseen event (including stupidity), things sometimes go wrong. If you don't believe this, then just dive enough and you will.

Thanks to everyone,

Stan

 

[dumpsterDiver]

My answer is as follows:

You should have a scuba tank of 100% oxygen and a dedicated scuba regulator on the boat. This should be tied to a 18 ft rope and a float.
If you mis the deco, toss the deco rig, go down on the oxygen (with a buddy) and hang for a good 10 minutes. then continue for a while on oxygen on the boat.

If you mis a short stop and have oxygen in a medical bottle only, then I would stay on the boat and breath that for a good while.

If I had no oxygen on the boat, and extra air in a tank, I would go down to at least 30 feet and then come up slow (like 25 minutes).

This all assumes that you have not experienced any symptoms. Telling the diver that this situation should never arise does not address the question.

 

[dumpsterDiver]

If you are spearing big fish offshore in deep water, then you need to talk to spearfisherman not "recreational" divers. Spearing large fish where there is no bottom (400-600 ft) on air is so far from most recreational diving, that most of the posts are not applicable.

You NEED to get a minimum of two scuba bottles of oxygen for that type of diving. One to do emergency deco, and one to use on the way in while the helo heads out.

You NEED to have this bottle pre-rigged with a Float that can not be dragged under by a diver and thus exceed the max depth. You also NEED to understand that this carries the risk of someone toxing, but this risk is quite reasonable compared to the dangers of spearing big fish in deep water.

 

[TheRedHead]

Why would you do your omitted deco stop at 30 feet, dumpster? Why O2 at 18 feet instead of 15 feet? How long would you breathe O2, i.e, what's a while? There has to be a method to the madness.

 

[lowwall]

The 'planned dive' goes out the window when you shoot a 45 lb snapper who is determined to go down just as you are determined to go up.

The plan doesn't go anywhere. You make a decision to either follow it and lose a fish and some gear or ignore it. If you know you will choose the latter, then you need to get the training and have the gas and gear necessary to carry off the ensuing profile. Otherwise, you're going to be putting yourself in situations that have no good alternatives.

What I believe is that very few people ( as you might see in responses to this thread, including me) can make a reasoned choice on what to do if something goes wrong.

I've seen lots of reasoned choices. That there is no general agreement is because either alternative comes with its own set of risks.

 

[dumpsterDiver]

I would go to 30 on air to shrink the bubbles and pray as I ascended.

The max depth on oxygen (1.6 atm) is 20 feet, so an 18 ft line keeps you above 20 ft.

How long to breath oxygen? Depends on how I feel and how much is left on the boat. Immediate Deco on oxygen can be very effective. 10 minutes on oxygen is reasonable, 40 minutes with no symptoms is too long and dangerous without breaks. Somewhere in the middle is reasonable.

I witnessed a dive accident last year, where the solo spearfisherman lost his mouth piece, inhaled some water, couldn't deploy his pony reg (for some reason). He ditched the gun, breathed from his standard BC inflator and swam to the surface from 110 feet as fast as he possibly could go. He shot to the surface and his Bc was full when he got there. He was using 32% nitrox and said he almost passed out on ascent. upon surfacing, he was panicked.

We took his fish off him, asked if he could go down on oxygen and we had him on oxygen at 20 feet within 90 seconds of surfacing. We had a safety diver watch him for 12-15 minutes and he came up and was fine, although diving was done.

 

[Cacia]

what about shooting a bag with your slate attached that says "need gas at 15 feet"

I like this.
note to self: sharpee

if I opted to not get back down...I would head to the chamber even if asymptomatic.(on O2)
A spinal hit is ugly. better to be in transit already. If I was in a very remote place, it would be hard to convince me to not go back down with another diver.


I know, I know, some say it is voo-doo but I would pop aspirin.

 

[H2Andy]

10 minutes on oxygen is reasonable, 40 minutes with no symptoms is too long and dangerous without breaks.

NOAA's single-exposure time for O2 at 1.6 ata is 45 minutes

if i was in that position, i'd use O2 for as close to those 45 minutes as i could

generally, acceptable deco practice is to get back in the water quickly and
follow the deco protocol as planned, but mutliply times by 1.5 or 2.0