Your reaction to this emergency situation.

[DevonDiver]

Devon, what would you say for max depth in this case?

It's only ever going to be a personal limit. The golden rule being: "Don't endanger your own life, to rescue another".

Hopefully, most divers will have some idea of their own personal limit. I'd understand if that limit was pushed in order to conduct a rescue, especially of a loved one or close friend, but the diver concerned should maintain an awareness of when that depth was starting to put them into danger. I'd be very self-aware of narcosis and my breathing rate on that descent. It comes down to maintaining the self-discipline and emotional detachment necessary to admit when you need to abort the rescue.

My max depth - deep enough to get a sinking recreational diver. Enough said. It'd depend on my self-assessment when conducting that descent though.

 

[Thanshin]

If regulator is in, keep it in. If out, forget it. Support their head, keeping their airway open/head horizontal.

I'm interested in the combinations of these two:
- If reg is out, why forget it instead of putting in mouth and purging?
- Airway open even if reg out because better risking to fill lungs with water than overexpansion?

And an additional question raised by this answer: Is there no situation where one should compress the unconscious diver thorax while ascending, to avoid lung overexpansion?

 

[DevonDiver]

Time is critical. Simplicity means time. Simplicity also prevents rescuer stress.

- If they've aspirated water (water in lungs), then there is no air to expand - and purging won't remove that water and 'un-drown' them. They need to be top-side ASAP.

- If they haven't aspirated water, but aren't breathing - then chances are their glottis is closed. Purged air will go to their stomach. With luck, water would go to their stomach. Whilst submerged, you can't diagnose if they've drowned (aspirated water) or 'just' passed unconscious (ceased respiration). Don't waste time trying.

- Compressing the thorax? Expanding air will either exit, or it won't. Compressing the thorax means compressing the lungs. That could easily do far more damage, especially if the lungs are at limit with expanded air. The force you exert on the thorax will be greater than the tensile strength of the lung tissue. The lungs could burst before you 'blow open' the glottis and release air. That's my speculation - someone with greater medical/anatomy knowledge should definitely correct me if I am wrong.. Either way, I don't think I would spare time to perform procedures like that. Speed is the critical factor.

Basically... the person is dying. Grab them and get up as quickly as safety permits. There's always going to be a lot of 'what-ifs'.. but you don't want to over-complicate a rescue by throwing in a dozen extra procedures to cover all the hypotheticals. Get 'em up. Fix them on the surface.

 

[raoulsttexas]

I'm interested in the combinations of these two:
- If reg is out, why forget it instead of putting in mouth and purging?
- Airway open even if reg out because better risking to fill lungs with water than overexpansion?

And an additional question raised by this answer: Is there no situation where one should compress the unconscious diver thorax while ascending, to avoid lung overexpansion?

If they're unconscious with reg out, they're most likely filled with water. you need to get the water out before they can breathe again...most likely not going to happen while underwater.
Holding the reg in the mouth requires the rescuer to commit 1 hand exclusively to hold the reg during the entire ascent. The other hand is holding onto the valve, or trying to maintain safe ascent rates (fiddling with bc's) or doing whatever other chaos is happening during the rescue. Having that extra hand free...well, it'd just make things SLIGHTLY easier.

If the person is unconscious, they aren't holding they're breath. The expansion during ascent will force the water (safely) out of the lungs.

EDIT: ummm... yeah....what Devon said....just WAY better than I did.

 

[beautybelow]

My wife doesn't dive, but I can fully understand that if she did I might well be tempted to take a risk, but really you have to set a limit and stick to it.

I wonder if anyone could really set a limit and stick to it if it was your wife, or your child.

If you are prepared to dive to 100' to begin with you should be prepared/experienced enough to catch them in that hypothetical scenario and do what has been described above by Andy as a rescue.

 

[Mantaman]

Devon's golden rule is paramount. Don't be accident victim Number 2.

Do all you can as long as its safe but be smart and remeber narcossis is real in depth and affects your thoughts so be cautious.

 

[beautybelow]

Devon's golden rule is paramount. Don't be accident victim Number 2.

Do all you can as long as its safe but be smart and remeber narcossis is real in depth and affects your thoughts so be cautious.

I was commenting on another layer opened up by another poster.

But...wouldn't you be subject to or willing to risk your life to save your wife or child? If you thought there was a chance? Would you even look at your depth gauge if you were chasing your wife down? Narcosis?

Now what Roatanman said about a snoring roommate...but who knows, maybe he would end up being rich and put you in his will.

My golden rule would probably be to save my family. I know that's not what the OP's original question was getting at but in the thread the "if it was my wife thing" stuck out at me a little.

 

[Thanshin]

But...wouldn't you be subject to or willing to risk your life to save your wife or child? If you thought there was a chance? Would you even look at your depth gauge if you were chasing your wife down? Narcosis?

What if thinking about it has left you with subconscious thoughts about this very situation and where you think it's your child you're following down it's really a narcosis induced hallucination?

 

[beautybelow]

Then I would want to bottle it and sell it.

 

[DevonDiver]

What if thinking about it has left you with subconscious thoughts about this very situation and where you think it's your child you're following down it's really a narcosis induced hallucination?

Narcosis doesn't really work like that.

Nonetheless, you want to monitor yourself on the descent. If in doubt, abort, surface and raise the alarm.