[cedricverdier]

Hi all

After having post the following article:

http://www.rebreatherworld.com/close...selection.html

there was an interesting discussion about oxygen toxicity at depth:

http://www.rebreatherworld.com/techn...eep-dives.html


Unfortunately it looks like no technical diving training agency ever published a comprehensive list of actions for a 1st aid treatment of a convulsing rebreather diver underwater (or at least I didn't find any reference to it).

Looking at different sources (US Navy diving Manual, different threads on this forum and others, French Navy diving manual, etc.), I found the following steps to be realistic:



What do you do if a convulsion happens?

• Flushing the loop

If a diver convulses, the rebreather should be flushed immediately, if possible with a gas of lower oxygen content

• Wait for the end of the convulsion

- If depth control is possible, the diver's depth should be kept constant until the convulsion subsides.
- If an ascent must take place, it should be done as slowly as possible.

• Check the mouthpiece

- Leave the victim's mouthpiece in his mouth.
- If it is not in his mouth, do not attempt to replace it but ensure that the mouthpiece is switched to the surface position. In this case the ascent should start immediately (but slowly)

• Protect the airways

Ensure that his airway is open after the convulsion stops by keeping the neck extended.
- If the mask is empty, leave it in place.
- If the mask is partially or completely flooded, pinch the nose to make sure no water will enter the airways. If necessary remove the mask to pinch the nose.

• Get positive buoyancy

- Grasp the victim and assume a position behind the convulsing diver.
- Release the victim's weight belt unless he is wearing a dry suit, in which case the weight belt should be left in place to prevent the diver from assuming a face-down position on the surface.
- If additional buoyancy is required, inflate the victim's BC. The rescuer should not release his own weight belt or inflate his own BC.

• Start ascending

- Make a controlled ascent to the 1st deep stop, maintaining a slight pressure on the diver's chest to assist exhalation. Evaluate the victim again here.
- If during the deep stops the victim still does not breathe, the rescuer should punch the victim to vent gas at at least 18m then at 9m.

• Perform the deep stops

Perform as many of the deep stops scheduled on ascent as possible in order to:
- avoid a serious double injury for both victim and rescuer,
- allow the victim additional time to recover,
- off-gas the victim,
- make possible to punch the gas out,
- reduce the risk for pulmonary barotraumas

• Ascent to the surface

- If necessary, blow the last stops.
- Upon reaching the surface, inflate the victim's BC if not previously done.
- Call for help.

• Protect the airways at the surface

- Remove the victim's mouthpiece
- Switch the valve to SURFACE to prevent the possibility of the rig flooding and weighing down the victim.
- Ensure the victim is breathing or initiate mouth-to-mouth resuscitation.

• Treat the victim and the rescuer

- Rescuer should breathe O2 on surface.
- If the situation stabilizes, rescuer can return to complete his last stops as a 'missed' deco protocol.
- Transport the victim to the nearest chamber and have the victim evaluated by a diving physician.


Please give me your opinion about what’s missing or what’s irrelevant (I wear a bullet-proof vest)

Cheers

[Sutty]

Why not try to insert an O/C breatheable-gas reg into the victims mouth (while purging) if they have lost their loop? Are you assuming that if not breathing the victim will stay that way? As they relax you may well be able to insert a reg, and they may well re-start breathing either after clonic phase or tonic phase, and with diminished airway reflexes will almost certainly then drown if no reg or loop in place. The lungs may well not contain high O2 concentrations (remember O2-off effect) and if not breathing and several minutes of stops are done then the victim is likely to die en-route to the surface. I think you have to give them the opportunity to breathe to have a significant chance of survival.

Neil

[Deepwreck]

This is a problematic situation, and no right answar will ever be enough. For example if you take the convulsed diver to the surface asap you risk your own life, but possibly give the convulsed diver a better chance of living. On the other hand if you perform all or the vast majority of your stops, you have most likely killed the convulsed diver if that diver is not breathing. No one can go without air for 5 or more min without brain injuries, that is if they survive at all. The only time I have heard of people drownding and being underwater for long periods of time are in cases of icewater, where the person is submerged in cold water. The cold can slow all metebalic activities, and is used in some surgeries to cool the body. Open heart surgery is one such example.

I have thought about this situation, and conventional wisdom is to get the diver to the surface asap. I just wonder if your comments on doing most of the deco is correct? What do you do? I wouldn't want anyone to die, and I don't want to get bent.

What does everyone think.

[Sutty]

Another factor in deciding your actions could be whether the victim (eg their lips) appear pink or blue - you will probably need a torch to tell though, even in blue-water conditions due to the lack of red light.

[E-man]

I tell my buddies to put an air reg in my mouth while i'm convulsing and keep it there while we ascend, not ascending until the convulsion stops.

[ScubaDadMiami]

During the toxing/spasm phase, the muscles will be rigid, and the diver will likely not inhale much. This is why the rescuer should wait before ascending. This will avoid overpressure barotrauma to the lungs.

After the spasm phase, then the muscles relax, and the diver will likely expel expanding gas during the ascent. So, it is more likely that gas will be exiting the lungs during this phase (unless the injured diver must be swum for a distance that is not vertical). Opening the mouth to put in a regulator might only achieve water introduction/drowning. That's why you leave it in if it is there but do not put it in if it is not already there.

There is no right answer. You can only balance the risk you are willing to take about yourself against what might or might not save someone else.

[Janos]

I have practiced this in the pool, both as a victim and a rescuer. You can splay the reg against the outside of the mouth and purge it. To do this, you need to bend the flanges of the reg against the outside of the mouth.

If done right, my experience was that it was very hard for me not to breathe successfully, and I didn't inhale any water. The downside is of course that a purging reg uses up a lot of gas.

Janos

[Sutty]

My surface experience of seizures is that there is little or no coordinated breathing during the tonic (stiff) phase, but that there is breathing, or an attempt at it if the airway is closed, during the clonic (jerking) phase.

So if its me having the seizure wait til I start to jerk and try to insert a purging reg, it may not work. If not able to, then hold my mouth/lips closed and try again if things look to have changed, or I stop jerking. Then if I'm breathing hold the reg in and lift me to the surface doing as many stops as you feel able to or feel appropriate. If I am not breathing then still lift me but mainly take care of your own interests - you are alive & well, I may not be. If I'm still not breathing 10 mins later and you still have stops to do just send me to the surface and look after yourself.
Importantly, if it doesn't work out don't beat yourself up about it, you did what seemed the best at the time, which is all we can ask of anyone

Just my thoughts on it - hope it doesn't happen to any of us!

Neil

[Genesis]

My view is this (whether on OC or CC doesn't change much).... this is what I'd like someone I'm diving with to do, and this is what I will do:

1. I will not ascend a diver with an active convulsion in progress. That will almost certainly kill him due to air embolism.

2. A diver that has convulsed (suspected or seen) and who has a regulator in his mouth is going to be assessed for muscle tone (e.g. are you still seizing) and when the airway can be opened (or is open) will be ascended slowly.

3. If the victim has lost his mouthpiece, I will not attempt to "replace" it, but WILL attempt to seal (externally) a mouthpiece with a breathable mix against the lips in the hope that if breathing resumes air will be inspired instead of water. If respiration begins I will THEN attempt to replace the mouthpiece during an exhale IF I judge it possible to do so without drowning the victim. In all cases I will act to the best of my ability to insure that the mouthpiece so presented has air in it and not water.

4. If the victim has significant decompression accrued and DOES NOT begin breathing by the time I reach the first mandatory stop, I will at that time decide what MY risk is of blowing off the decompression I have accrued to surface with the victim. If that risk is unreasonable, I will send the victim up an upline so as to assure that he is not "lost". If that risk is REASONABLE, I will ascend with him.

5. If the victim BEGINS or IS breathing, I will perform as much of the decompression as I am able on the gas he is breathing. So long as he is breathing, he is alive and will remain so; compounding whatever happened originally with a DCS hit is not something I am willing to do. I will blow that deco schedule only if I must due to gas limitations or the victim ceasing respiration at some point during the ascent.

I believe that's the "best shot" at both of us surviving the event.....

[hoppyinca]

I am sure this will differ from diver to diver; however, what would be a "reasonable" or "acceptable" risk when it comes to omitting Deco?

I have "blown off" a minute or two from my last stop due to getting cold/ current, what have you; however, this was in relatively warm and clear water, with no to low stress during the dive, and diving a square table profile when the Max Depth was not actually held for the Max BT of profile I was following.

I am just wondering if anyone has actually thought about this in detail and made a personal limit for what they consider a "reasonable" or "acceptable" risk... I have not...