Rescue of an Unconscious Diver Underwater

[Kevrumbo]

Some of the situations with unconscious divers prohibit direct ascents. So what do you do until then?

Unless they are running a ffm it's almost certainly not going to be a happy ending, but it's a possibly useful course of action.

Thank you for the offer.

In this thread right now, the issue in which some are interested is raising a diver who is undergoing a seizure. As you know, some contend that the diver should not be raised during the tonic or clonic phases, but the study disagrees. I wonder if you could go into that in more detail.

Hello John,

This was one of the more difficult issues. As you correctly point out there is a long standing belief that bringing a diver to the surface during a seizure is dangerous because the glottis (the airway at the larynx) will be closed and the airway will be blocked. This would create a risk of pulmonary barotrauma because air would be prevented from escaping from the lungs during the ascent. That is the basis for the long held belief that one must wait until the seizure has finished before bringing the diver to the surface.

However, there are some other facts that are important.

First and most importantly, the assumption that the glottis is inevitably closed during a seizure is incorrect. We see sometimes see non-diving patients suffering "status epilepticus" which essentially means a seizure that does not terminate, and which may continue for a long time. If the airway were closed in this setting it would be a non-survivable event but the vast majority of patients survive prolonged seizures. Moreover, I (and many of my anesthesia or ER colleagues) have been able to manually ventilate such patients with a bag - mask during a seizure which, again, means that the airway is not completely closed. In addition, we obtained a video of the glottis in pigs during a seizure which showed that although there is certainly a partial and rapidly fluctuating obstruction of the glottis during a seizure, it is also open on a rapidly fluctuating basis.

Second, the first thing that a patient starts to do after a seizure (but while still unconscious) is to start breathing heavily. If they did that with an unprotected airway underwater, then they will inhale water and drown.

If you put these two facts together, then it is possible to draw the conclusion that the period when a diver is seizing but not breathing may actually be the correct time to bring them to the surface, because if you hold them underwater until the seizure finishes and they start to breathe, then they will almost certainly drown. This is particularly true if the airway is unprotected (regulator out) and our conclusion was that in this setting the risk of pulmonary barotrauma in bringing them to the surface was less than the risk of drowning by holding them underwater until the seizure had finished.

We gave different advice if the regulator or mouthpiece or full face mask was still in place. We could argue about how much "airway protection" is provided by a regulator held in place, but we thought that if the reg / mouthpiece remained in place and the rescuer could hold it there, then the balance of risk would shift in favour of waiting until the seizure had finished before bringing the victim to the surface. In this setting, it is anticipated that if the victim starts breathing then they are much less likely to drown because the reg / mouthpiece is still in place.

That is the logic behind the recommendations around seizures.

Simon M

Simon, as trained in a witnessed actively toxing/seizing diver scenario, the motivation to replace the regulator in the victim's mouth with support and efforting a best seal as possible, and with a slight continuous reg purge --was to expel and prevent further water intrusion into the victim's airway.

Please elaborate and clarify further on this point, and in general give your assessment on the usefulness & viability of this procedure as demonstrated in the training video below:

 

[Dr Simon Mitchell]

So Simon, you're a rebreather diver. Do you use a gag strap or Full Face Mask (FFM)? If so, which do you use and why? Is it an emotional or science based decision?

Hello Pete,

I do use a gag strap, always. I have the Drager one, and choose this because it is very readily adjustable, and has a nicely designed flange that acts to "crowd" the lips around the mouthpiece in a way clearly intended to improve the seal.

The decision is based on evidence that is as good as we are ever likely to have on this matter. In 2011 Gempp and colleagues published a paper describing loss of consciousness events in 54 military rebreather divers where only 3 resulted in fatal drownings. All 54 were using the Drager gag strap. I believe that 3 drownings out of 54 loss of consciousness events is an unexpectedly small proportion. There were other mitigating safety factors such as buddy diving, but nevertheless, it is still a small number that constitutes evidence of efficacy of the gag straps in preventing drowning. They are also nice to use on a long dive.

The reference is:

Gempp E, Louge P, Blatteau JE, Hugon M. Descriptive epidemiology of 153 diving injuries with rebreathers among French military divers from 1979 to 2009. Military Medicine 2011;176:446-450.

I would be happy to send you a copy of the paper if you pm me an email address.

Simon M

 

[Dr Simon Mitchell]

Simon, as trained in a witnessed actively toxing/seizing diver scenario, the motivation to replace the regulator in the victim's mouth with support and efforting a best seal as possible, and with a slight continuous reg purge --was to expel and prevent further water intrusion into the victim's airway.

Please elaborate and clarify further on this point, and in general give your assessment on the usefulness & viability of this procedure as demonstrated in the training video below:

Hello Kev,

Can I be clear there is little room for hard dogma from anyone (including me) in relation to most aspects of this issue. So, I don't pretend to have definitive evidence based answers. However, I would make a couple of comments about that video.

First, it is most unlikely to be as easy to replace a regulator in a seizing diver as portrayed. Most people suffering seizures clamp their mouths shut and messing around trying to get the mouth open and then accurately place a regulator is likely to waste valuable time and risks flooding the airway with water. What is most likely to keep the airway dry is to establish an ascent, and the expanding gas passing out of the airway will help prevent water passing in. It is remarkable how often we have seen unconscious divers brought to the surface quickly with little or no water contamination of the lungs.

Second, I can understand the logic behind continuous gentle purging of the regulator, but this is a potentially dangerous intervention. The difficulty is in knowing what gentle purging means and accurately maintaining it. If you overdo it there is a danger of increasing the risk of pulmonary barotrauma during the ascent. There was an Australian military case in which this occurred. With substantial regulator purge from moderate depth (I can't remember exactly - around 40m I think) there was gross introduction of air into the circulation and the diver died. Moreover, it contributes to task loading of the rescuer and if you get on with the ascent, it should not be necessary in preventing water entry to the airway for the reason I describe above.

Third, while I get that the video adheres to the UTD philosophy of trying to make everything look as relaxed as possible, the ascent is too unhurried and slow. If I was not overly concerned with my own decompression obligation I would have just grabbed the diver, put their head in a neutral position, and swum quickly to the surface. There is little doubt that this is what would be best for the unconscious diver. In the scenario depicted (a diver with reg in place, clearly breathing) the slow approach taken looks OK and maybe could work, but rescues are not usually like that. Also, the notion that an airway can be managed and well protected from water entry in a breathing but unconscious diver over the course of a nice relaxed ascent while the rescuer also adjusts multiple buoyancy controls is tenuous at best. There is a good chance that a rescuer would drown a diver in trying to do it. Nevertheless, I refer back to my comment about dogma above, and have to admit that I cannot definitively claim it can't be done.

Simon M

 

[Storker]

while I get that the video adheres to the UTD philosophy of trying to make everything look as relaxed as possible, the ascent is too unhurried and slow. If I was not overly concerned with my own decompression obligation I would have just grabbed the diver, put their head in a neutral position, and swum quickly to the surface. There is little doubt that this is what would be best for the unconscious diver

Thank you for stating this. The slow ascent that you seem skeptical to was taught in my PADI Rescue class. I wasn't particularly thrilled, since I, too, believe that the best place for an unconscious diver to be is at the surface, and reaching the surface as quickly as possible without an unacceptable risk of DCS or barotrauma should be the rescuer's main concern. I didn't, however, feel competent to argue that point with the instructor.

Another point that I like to make when discussing emergency procedures, is that in an emergency, any procedure should be as simple and uncomplicated as possible, with as few options to choose between as possible.

Stress really decreases our ability to think straight and make complex evaluations, so "get the victim to the surface as quickly as possible without compromising your own safety" is IMO a better strategy than an "if this, then that" type of procedure.

 

[Edward3c]

When teaching CBL (Controlled Buoyancy Lift) I'm looking for a controlled ascent, which in training is still faster than a normal mid-water ascent. In training I have to be watchful of the student's, the acting casualt's and my safety.

The Malta incident added a new prospective. How to initiate a CBL mid-water when the casually may still be sinking?

Another aspect I will throw into the mix. Studies of coral identification have revealed nitrogen narcosis starts to impair decision making from 15m. So attempting do this if becomes more difficult as depth increases. Simple actions are more likely to be remembered.

 

[tbeck3579]

There is an exception though, if the dive was in a cave or under ice, then it will need to be purged first and then replaced.

While I know nothing about technical diving, I thought about the inability to surface in those places -- air isn't available and you can't ascend quickly. I also wondered if it means when "there is air available". Under ice there is an air gap between the water and the ice; obviously a cave can have places where plenty of air is available. I have no idea if either of those scenarios is what the writer was referring to. I'm guessing it means use good judgement because every situation is different.

 

[The Chairman]

obviously a cave can have places where plenty of air is available.

There are precious few caves where this happens. It's an anomaly found only in very shallow caves. I have yet to experience such a cave.

 

[Kevrumbo]

Third, while I get that the video adheres to the UTD philosophy of trying to make everything look as relaxed as possible, the ascent is too unhurried and slow. If I was not overly concerned with my own decompression obligation I would have just grabbed the diver, put their head in a neutral position, and swum quickly to the surface. . . .

Perhaps if the toxing diver was at a 6m O2 stop, then just grabbing the diver's head in a neutral position & swimming quickly to the surface would be the best tactic -but what about from a deeper 21m Eanx50 deco stop?

Also if I knew that boat crew surface rescue support would be some distance away because of current and swells for instance, or especially visibility conditions that would preclude the boat crew from immediately spotting the unconscious victim on the surface (i.g. Fog or thick marine layer developing during the dive -both common weather phenomena here in offshore California diving), I would rather take a chance at performing the toxing diver rescue as depicted in the video, instead of sending the victim up alone on an uncontrolled buoyant ascent to ultimately embolize and drown on the surface. . .

 

[The Chairman]

instead of sending the victim up alone on an uncontrolled buoyant ascent to ultimately emboliize and drown on the surface.

Your reasoning is flawed here. You treat that as a given when it's not.

 

[Kevrumbo]

. . .instead of sending the victim up alone on an uncontrolled buoyant ascent to ultimately embolize and drown on the surface. . .

Your reasoning is flawed here. You treat that as a given when it's not.

Ok Pete. . . I would send you up then in an uncontrolled buoyant ascent into a surface fog bank.

I'll somehow find you later when I finally surface, and start resuscitation efforts then as needed because it's not a given that you'll be immediately unconscious, embolized or drowned. . .