Rescue of an Unconscious Diver Underwater

[The Chairman]

Really?

Ya Rly. He's kind and you're simply not taking the hint. Take the hint. We won't mind. He won't either.

 

[RayfromTX]

Prime example of what I'm talking about.

 

[tbeck3579]

I think Kev doesn't understand how statistical evidence differs??? The next sentence from the doc is spoken in a manner that shows the doc understands statistical evidence: "So, I don't pretend to have definitive evidence based answers." Very few things provide us with definitive answers; there are only statistical probabilities. Definition of dogma: "a settled or established opinion, belief, or principle". So the doc, being a man of science, is open to a well researched theoretical opinion that can be formed into a hypothesis; i.e., a question that can be statistically evaluated. Kev's opinion can't be proven because he doesn't have good research to form a theoretical opinion and therefore can not provide statistical evidence to support it; it's called 'junk" science.

 

[Kevrumbo]

My buddy will be able to make a quick, controlled ascent with me if I tox, and that's what I'll be expecting of them. Just as I'll be able to make a quick, controlled ascent with my buddy if they tox or become unresponsive for some other reason. And my buddy has every right to expect that from me. I might have to breathe down the O2 tank, or spend a few hours in a chamber just to make sure, but that'll be about it. And I'm totally prepared to live with those consequences if my buddy becomes unconscious for some reason, because I'm not comfortable with a dead buddy if I could do anything to prevent them dying.

You're playing reductio ad absurdum and false dilemma once more.

There is no argumentative fallacy nor false dilemma, but a legitimate draconian series of ad hoc decisions and actions that are entirely situational dependent: refer again to the flow chart in the Alert Diver Article Alert Diver | Rescue of an Unconscious Diver ;the most controversial process box contains the legend "Head in neutral position -Ascend according to training agency recommendations". As originally taught by GUE and per UTD's current protocol, the go to DIR method that was always promoted as being the best implementation protocol was the Toxing Diver Rescue Technique.

However:

@boulderjohn

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
---------
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

 

[RayfromTX]

That seems like an insult but I know that it's not. It is simply a common definition used in the scientific community to describe non-adherance to the scientific method.

 

[Kevrumbo]

I think Kev doesn't understand how statistical evidence differs??? The next sentence from the doc is spoken in a manner that shows the doc understands statistical evidence: "So, I don't pretend to have definitive evidence based answers." Very few things provide us with definitive answers; there are only statistical probabilities. Definition of dogma: "a settled or established opinion, belief, or principle". So the doc, being a man of science, is open to a well researched theoretical opinion that can be formed into a hypothesis; i.e., a question that can be statically evaluated. Kev's opinion can't be proven because he doesn't have good research to form a theoretical opinion and therefore can not provide statistical evidence to support it; it's called 'junk" science.

Where does Dr. Simon Mitchell mention anything objective about mathematic statistical evidence? How did you infer "reading between the lines" such a wildly disparate rebuff and rhetorical conclusion from Simon Mitchell's original post in context above?

That seems like an insult but I know that it's not. It is simply a common definition used in the scientific community to describe non-adherance to the scientific method.

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 like to make a couple comments about that video. . . There's a good chance that a rescuer would drown a diver in trying to do it [Toxing Diver Rescue]. Nevertheless, I refer back to my comment about dogma above, and have to admit that I cannot definitively claim it can't be done

@tbeck3579 , the original position paper was more of a qualitative recommendation report -a "best practice" decision tree proposal- rather than a quantitative scientific statistical study per se:

Mitchell, Simon J; Bennett, Michael H; Bird, Nick; Doolette, David J; Hobbs, Gene W; Kay, Edward; Moon, Richard E; Neuman, Tom S; Vann, Richard D; Walker, Richard; Wyatt, H Alan (2012). "Recommendations for rescue of a submerged unresponsive compressed-gas diver." Undersea and Hyperbaric Medicine 39 (6): 1099–1108. http://archive.rubicon-foundation.o

 

[tbeck3579]

@tbeck3579 , the original position paper was more of a qualitative recommendation report, rather than a quantitative scientific statistical study per se:

Mitchell, Simon J; Bennett, Michael H; Bird, Nick; Doolette, David J; Hobbs, Gene W; Kay, Edward; Moon, Richard E; Neuman, Tom S; Vann, Richard D; Walker, Richard; Wyatt, H Alan (2012). "Recommendations for rescue of a submerged unresponsive compressed-gas diver." Undersea and Hyperbaric Medicine 39 (6): 1099–1108. http://archive.rubicon-foundation.o

I won't argue with you because you don't have a well researched argument to argue. In my mind, it is your personal opinion and your entitled to your own personal opinion.

 

[flyboy08]

I wonder in reality how many unconscious divers are actually rescued compared to succumbing to their unfortunate death?I would assume small to any since most incidents I have read lead to the former.


I'm happy with my Rescue diver course I took. I feel prepared to assist if I happen to be there within moments...anything longer is questionable.

 

[Kevrumbo]

I won't argue with you because you don't have a well researched argument to argue. In my mind, it is your personal opinion and your entitled to your own personal opinion.

Again, it's just a non-statistical recommendation paper that's suppposed to be argued about and discussed. . .

From Recommendations for rescue of a submerged unresponsive compressed-gas diver.

Finally, the purpose of this paper is to address certain

medical aspects of diver rescue; and particularly those

that cause controversy. It does not address mechanical

details of practical rescue techniques (methods of

buoyancy control during ascent, for example) unless

there is particular relevance to a medical consideration.

The prescription of practical techniques is left to the

respective diver training agencies. As a basis for discussion,

this paper will refer to the methods recommended

in the Professional Association of Diving Instructors

(PADI) Rescue Diver Manual [2].

______

SUMMARY OF RECOMMENDATIONS

We have generated a diver rescue algorithm which summarizes

the important recommendations made in this

paper (Figure 1). . .


The committee also re-emphasizes several other key

contextualizing comments: First, application of this

pathway is contingent on appropriate diver rescue training.

Second, it is entirely appropriate for rescuers to avoid

causing harm to themselves in applying these rescue

strategies. Third, recent changes in protocols for community

cardiac arrest are of doubtful relevance to diver

rescue interventions. Fourth, it is acknowledged that

there may be circumstances in diver emergencies

that are not adequately accounted for in these recommendations.

It is difficult to provide a universally

applicable guideline without the risk of it being hopelessly

overcomplicated. These recommendations should not be

seen as immutable rules for all situations.

Finally, it is reiterated that rescue and resuscitation

of an unresponsive diver from depth is frequently

unsuccessful. Notwithstanding this attempt to optimize

current advice, unresponsive divers rescued from depth

have a poor prognosis.

 

[tbeck3579]

I think you have put forth your argument and there isn't much to add. If you feel comfortable with it, go for it. I do what I believe to be in my best interest. I try to consider the "big picture" and alternative views because all of my decisions have consequences, good and bad. I don't get "do-overs". I will need to live with my decision, no one else.