Rescuing an unconscious diver underwater.

[muddiver]

Well, there are several mechanisms that might result in embolism. One is laryngospasm, which is not unlikely if somebody has aspirated water. Another is blockage of the posterior pharynx by the tongue. Another is obstruction of the airways with aspirated water. Remember that all you need for embolism is that the gas in the lungs is expanding faster than it can escape, not that it has to be blocked altogether.

Unconscious or dead people don't hold their breath. Undertakers don't have to deflate their "client's" lungs.

Don't confuse an obstructed airway preventing inhalation with the ability to hold your breath.

In first aid rescue breathing you extend the airway to:

(1) Allow the casualty to breath for themselves or
(2) Allow you to apply rescue breaths.

You will never encounter a situation where, when you open a non-breathing casualty's airway, they exhale.

Extending the airway underwater simply wastes time, overrides the victim's gag-reflex, allowing water to enter the lungs, possibly worsening their condition if they are succesfully resuscitated and gives you something else to worry about during a rescue when you've already got your hands full.

These staements are contridictory. It would be interesting to see a study on this subject. Unfortunately, I think that all of the training on surfacing an underwater casulty is based on "best quess" medical theory.

I tend to side with Hickdive because I can not see how an unconscious and relaxed person is going to hold in expanding gas in their lungs.

 

[PfcAJ]

Hickdive, you're using surface logic for an underwater situation.

Even without a "full breath" underwater, as the gas expands, it will quickly fill the remaining lung volume and could cause barotrauma and AGE.

By holding under the victims chin (rescuer on top) opening the airway, you allow that expanding gas to escape. That expanding gas will also keep water from entering the airway, and if you accidentally descend a bit, the mask will prevent water from entering the nose, and the position of the hand under the chin either holds the reg in place (no water gets in) or the mouth closed (no water gets in).

 

[OceanEd]

Having taught a lot of Rescue Divers over the years, and having experimented a lot with different techniques I find that the following seems to work the best when deciding how to get the diver to the surface.

If they are unconscious on the bottom at any depth they can be heavy and it is hard to start ascending with them, even after you ditch the weight belt. You can control the diver if you are on his right side and perpendicular to the diver and slightly above him. Your right arm is on his upper front and your right hand can deal with his head. Your left arm is behind him and over the tank. In this way you have solid control of the body position Your left hand can be on his automatic inflator and you can put air into his BC to start both of you up off the bottom. On the way up you can control your ascent by using the auto inflator on his BC.

If you have to do all this and use your personal BC to help with buoyancy then you are not really going to hand enough hands available or you might have a hard time controlling the body.

Once you get the person to the surface you are gong to want to provide positive buoyancy and by using this method you are already doing that and in the right position to deal with them on the surface.

 

[Hickdive]

Hickdive, you're using surface logic for an underwater situation.

Even without a "full breath" underwater, as the gas expands, it will quickly fill the remaining lung volume and could cause barotrauma and AGE.

Umm, I'm perfectly well aware of that - would you like me to remind you to continue breathing whilst reading Scubaboard?

By holding under the victims chin (rescuer on top) opening the airway, you allow that expanding gas to escape. That expanding gas will also keep water from entering the airway, and if you accidentally descend a bit, the mask will prevent water from entering the nose, and the position of the hand under the chin either holds the reg in place (no water gets in) or the mouth closed (no water gets in).

Presupposing;

(1) The ascent concludes before the lungs are fully vented.
(2) The casualty retains their mouthpiece or the rescuer spends time re-inserting it.

Further; If the rescuer is holding the mouth closed and the casualty is wearing a mask, as you suggest in your last sentence, then extending the airway is pointless since you've occluded the airway mechanically, you could actually cause barotrauma by doing this. If I specifically wanted to murder someone underwater, forcing them to hold their breath by removing their regulator and then sealing their mouth with my hand and swimming them to the surface would be a good way of doing it. Don't forget that it takes just 80mmHg pressure differential to cause alveolar rupture* (equivalent to an ascent of 1.2m or 4ft), an overpressure easily obtained with a tight fighting mask and hand over the mouth. Please tell me you're not offering anyone this dangerous advice professionally. Or are we going to delve further into the realms of fantasy by coming up with some even more complex method?

To re-iterate; please demonstrate how an unconscious person holds their breath. Just because someone can't inhale isn't at all the same as them being unable to exhale. Spending time applying a surface rescue technique i.e. extending the airway to assist a non-breathing casualty who cannot inhale is inappropriate underwater. In doing so you're applying surface thinking to an underwater problem, wasting time and potentially making the casualty's situation worse.

As a final point, in the last 25 years there have been NO instances recorded in the BSAC Incident Report of an unconscious casualty being brought to the surface by CBL and suffering pulmonary barotrauma as a result, regardless of whether or not their neck has been extended. In ALL instances where such injuries have been sustained the casualty has been conscious.

*Forensic Medicine;Clinical and Pathological Aspects J P James (editor) et al 2003 page 294.

 

[PfcAJ]

Yeah, air will vent out from a mask. Unless the diver can't exhale through their nose during the course of a normal dive... I think that would be quite uncomfortable...

Go read some autopsy reports from diving accidents. Almost all have " Arterial Gas Embolism" in them somewhere. If the deceased has exhaled and is unconscious, how do you think those AGE's happened?

Also, holding the mouth closed (under the chin) does not prevent air from escaping. Clench your teeth now blow out. How can that be?! The lips form sort of a one way valve against the teeth. However, if the person's neck is bent down, the obstruction is in two directions. Nothing comes in, and nothing comes out. Bad news bears.

 

[PfcAJ]

Deleted. Double post

 

[boulderjohn]

As a final point, in the last 25 years there have been NO instances recorded in the BSAC Incident Report of an unconscious casualty being brought to the surface by CBL and suffering pulmonary barotrauma as a result, regardless of whether or not their neck has been extended. In ALL instances where such injuries have been sustained the casualty has been conscious.

*Forensic Medicine;Clinical and Pathological Aspects J P James (editor) et al 2003 page 294.

Go read some autopsy reports from diving accidents. Almost all have " Arterial Gas Embolism" in them somewhere. If the deceased has exhaled and is unconscious, how do you think those AGE's happened?

First of all, I am not taking a position in this issue in this post--I am just pointing out that the first post quoted pretty much answers the question of the second.

I have read every description of diving fatalities in he DAN reports of the last few years. Yes, quite a few have AGEs. However, I am having trouble remembering even a single case where an unconscious diver was brought to the surface in such a way that there was any possibility that the embolism occurred during the ascent. In fact, I don't recall a case where an unconscious diver who was possibly alive was brought to the surface. (I did not reread them all prior to this post, so I could be wrong.) The AGE cases pretty much followed a conscious ascent by the diver.

 

[muddiver]

Then might the question be: Has there ever been a case where an unconcious diver was brought to the surface alive?

Maybe we are over thinking, over training and over speculating for an event that is most likely fatal anyway based on the currently accepted configuration of recreational scuba equipment.

 

[TSandM]

Muddiver, I think you're spot on. I've seen a lot of autopsy results that listed AGE, and the discussion is always that the person was basically dead when retrieved and brought to the surface.

There are a few circumstances where a diver could be unresponsive at depth and survive -- severe narcosis is one, hypercarbia is another. But you generally won't get narced into unresponsiveness in recreational depths. A completely unresponsive diver in recreational depths has likely seized, drowned, or experienced some catastrophic interruption in circulation or brain function. Consciousness is a very basic function; to lose it, you must either shut down the reticular activating system in the brainstem, or globally depress both cerebral hemispheres. Having either occur during a dive would require something very bad. Which is not to say that one should not make the effort to retrieve an unresponsive diver, unless it is extremely clear that he is dead. In that case the retrieval may be left to more experienced people, if the finding diver does not feel confident in executing the retrieval safely -- do not create a second victim!

 

[muddiver]

Agreed, and my second point is "just get the diver to the surface" then you can start worrying about how to ventalate them and possably ressucitate them.