Accidents. Resuscitation. AED. Should AED be mandatory on diving boats?

[Dr Simon Mitchell]

I'm not sure the evidence supports your assumption.

Hi Tursiops,

I think there is truth on both sides of this sub-discussion.

In a diving scenario there are two broad causative factors for a cardiac arrest.

1. A primary cardiac event (what most people would refer to as a heart attack) typically caused by blockage of one of the coronary arteries. Such an event could obviously occur anywhere in a predisposed individual, but given the aging diving population and the stress / exercise sometimes associated with diving it is perhaps not surprising that they can occur on dive trips.

2. A secondary event where the heart stops pumping due to some other issue, with the most likely in diving being hypoxia in a drowning or out of air scenario (which is what SapphireMind is referring to).

It is also entirely possible you could be dealing with both if, for example, a primary cardiac event occurs underwater causing the victim to become unconscious and drown.

This is a generalisation, but a primary cardiac event more likely to produce a shockable arrhythmia than a secondary event. Primary events are therefore more likely to be treatable using an AED. In contrast, the "way out" of a secondary event (at least initially) typically involves correcting the problem that has caused the heart to stop pumping (such as correction of hypoxia). This is SapphireMind's correct point.

What can we take out of this as divers? There are a couple of points I would make.

1. Primary cardiac events do occur on dive boats / during diving. Indeed, a high quality DAN study suggested that the disabling injury in approximately 30% of diving fatalities was a primary cardiac event [1]. Leaving aside the debate about cost vs benefit, this is probably reason enough on its own to see AEDs on dive boats as a good idea.

2. Secondary events are inevitable in drowning / hypoxia scenarios in the absence of appropriate intervention. That is why it is important for all of us to be trained in proper CPR (not just compression-only) and (if possible) to give rescue breaths in-water after retrieval of an unresponsive diver from depth if removal onto surface support is not an immediate option [2]. If a hypoxic diver has stopped breathing but has not yet gone into cardiac arrest then you will probably save their life by restoring oxygenation.

3. Just to avoid confusion, as divers we don't need to be worried about whether we are dealing with a primary or secondary event so long as we apply the basic principles of good life support. Where a diver is unresponsive and not breathing, then we simply apply a high quality CPR sequence as soon as possible, and if an AED is available put the pads on and let the machine decide whether it wants to shock the victim. If you do these things, then you will be doing the right thing no matter whether it is a primary or secondary event.

Simon M

1. Denoble PJ, Caruso JL, Dear G de L, Pieper CF, Vann RD. Common causes of open-circuit recreational diving fatalities. Undersea Hyperb Med. 2008;35:393-406.

2. Mitchell SJ, Bennett MH, Bird N, Doolette DJ, Hobbs GW, Kay E, Moon RE, Neumann TS, Vann RD, Walker R, Wyatt HA. Recommendations for rescue of a submerged unconscious compressed gas diver. Undersea Hyperb Med 2012;39:1099-1108

 

[tursiops]

Hi Tursiops,

I think there is truth on both sides of this sub-discussion.

In a diving scenario there are two broad causative factors for a cardiac arrest.

1. A primary cardiac event (what most people would refer to as a heart attack) typically caused by blockage of one of the coronary arteries. Such an event could obviously occur anywhere in a predisposed individual, but given the aging diving population and the stress / exercise sometimes associated with diving it is perhaps not surprising that they can occur on dive trips.

2. A secondary event where the heart stops pumping due to some other issue, with the most likely in diving being hypoxia in a drowning or out of air scenario (which is what SapphireMind is referring to).

It is also entirely possible you could be dealing with both if, for example, a primary cardiac event occurs underwater causing the victim to become unconscious and drown.

This is a generalisation, but a primary cardiac event more likely to produce a shockable arrhythmia than a secondary event. Primary events are therefore more likely to be treatable using an AED. In contrast, the "way out" of a secondary event (at least initially) typically involves correcting the problem that has caused the heart to stop pumping (such as correction of hypoxia). This is SapphireMind's correct point.

What can we take out of this as divers? There are a couple of points I would make.

1. Primary cardiac events do occur on dive boats / during diving. Indeed, a high quality DAN study suggested that the disabling injury in approximately 30% of diving fatalities was a primary cardiac event [1]. Leaving aside the debate about cost vs benefit, this is probably reason enough on its own to see AEDs on dive boats as a good idea.

2. Secondary events are inevitable in drowning / hypoxia scenarios in the absence of appropriate intervention. That is why it is important for all of us to be trained in proper CPR (not just compression-only) and (if possible) to give rescue breaths in-water after retrieval of an unresponsive diver from depth if removal onto surface support is not an immediate option [2]. If a hypoxic diver has stopped breathing but has not yet gone into cardiac arrest then you will probably save their life by restoring oxygenation.

3. Just to avoid confusion, as divers we don't need to be worried about whether we are dealing with a primary or secondary event so long as we apply the basic principles of good life support. Where a diver is unresponsive and not breathing, then we simply apply a high quality CPR sequence as soon as possible, and if an AED is available put the pads on and let the machine decide whether it wants to shock the victim. If you do these things, then you will be doing the right thing no matter whether it is a primary or secondary event.

Simon M

1. Denoble PJ, Caruso JL, Dear G de L, Pieper CF, Vann RD. Common causes of open-circuit recreational diving fatalities. Undersea Hyperb Med. 2008;35:393-406.

2. Mitchell SJ, Bennett MH, Bird N, Doolette DJ, Hobbs GW, Kay E, Moon RE, Neumann TS, Vann RD, Walker R, Wyatt HA. Recommendations for rescue of a submerged unconscious compressed gas diver. Undersea Hyperb Med 2012;39:1099-1108

Thanks for the thoughtful and helpful input.
I was thinking of your scenario (1) only, since that is the most common and likely event (by far) as I read the DAN stats.

 

[Protondecay123]

Hi Tursiops,

I think there is truth on both sides of this sub-discussion.

In a diving scenario there are two broad causative factors for a cardiac arrest.

1. A primary cardiac event (what most people would refer to as a heart attack) typically caused by blockage of one of the coronary arteries. Such an event could obviously occur anywhere in a predisposed individual, but given the aging diving population and the stress / exercise sometimes associated with diving it is perhaps not surprising that they can occur on dive trips.

2. A secondary event where the heart stops pumping due to some other issue, with the most likely in diving being hypoxia in a drowning or out of air scenario (which is what SapphireMind is referring to).

It is also entirely possible you could be dealing with both if, for example, a primary cardiac event occurs underwater causing the victim to become unconscious and drown.

This is a generalisation, but a primary cardiac event more likely to produce a shockable arrhythmia than a secondary event. Primary events are therefore more likely to be treatable using an AED. In contrast, the "way out" of a secondary event (at least initially) typically involves correcting the problem that has caused the heart to stop pumping (such as correction of hypoxia). This is SapphireMind's correct point.

What can we take out of this as divers? There are a couple of points I would make.

1. Primary cardiac events do occur on dive boats / during diving. Indeed, a high quality DAN study suggested that the disabling injury in approximately 30% of diving fatalities was a primary cardiac event [1]. Leaving aside the debate about cost vs benefit, this is probably reason enough on its own to see AEDs on dive boats as a good idea.

2. Secondary events are inevitable in drowning / hypoxia scenarios in the absence of appropriate intervention. That is why it is important for all of us to be trained in proper CPR (not just compression-only) and (if possible) to give rescue breaths in-water after retrieval of an unresponsive diver from depth if removal onto surface support is not an immediate option [2]. If a hypoxic diver has stopped breathing but has not yet gone into cardiac arrest then you will probably save their life by restoring oxygenation.

3. Just to avoid confusion, as divers we don't need to be worried about whether we are dealing with a primary or secondary event so long as we apply the basic principles of good life support. Where a diver is unresponsive and not breathing, then we simply apply a high quality CPR sequence as soon as possible, and if an AED is available put the pads on and let the machine decide whether it wants to shock the victim. If you do these things, then you will be doing the right thing no matter whether it is a primary or secondary event.

Simon M

1. Denoble PJ, Caruso JL, Dear G de L, Pieper CF, Vann RD. Common causes of open-circuit recreational diving fatalities. Undersea Hyperb Med. 2008;35:393-406.

2. Mitchell SJ, Bennett MH, Bird N, Doolette DJ, Hobbs GW, Kay E, Moon RE, Neumann TS, Vann RD, Walker R, Wyatt HA. Recommendations for rescue of a submerged unconscious compressed gas diver. Undersea Hyperb Med 2012;39:1099-1108

Peer reviewed sources! Yes!

 

[Firebar]

As the BSAC report was being issued I was in the middle of doing my O2 course. One of the instructors had had an employee have a heart attack at work a few weeks before who was saved by the AED. It’s not just the shocks it’s the instructions for the Basic Life Support that it provided until the ambulance arrived.

From a cost of having units near water point of view if I were a commercial entity I wouldn’t be that concerned. The cost of replacing an AED that you got wet is a lot lower than the cost of a human life to an insurance company. Anecdotally I was talking to a commercial yacht skipper involved in a Man Overboard at night in the Irish Sea, he threw inflated life jackets over the side (12 of them, at ~£150 per) to try and leave a trail back to the person, his insurer replaced all the kit that went over the side, no questions asked, because it was a lot less than any potential claim for a death.

 

[SapphireMind]

Totally agree with everything @Dr Simon Mitchell said. I was only intending to point out that AEDs are not the cure-all the general public usually thinks they are. Almost everything people attribute to AEDs, are really the effects of epi But definitely agree in an emergency situation, you shouldn't be trying to figure out whether it's primary or secondary. Those only affect what interventions are likely to work and the likelihood of success in general

 

[Edward3c]

...
The cost of replacing an AED that you got wet is a lot lower than the cost of a human life to an insurance company.
...

An AED to be used near or on water should have an IP (Ingress Protection) rating of 55 or higher.

 

[thin_air]

Totally agree with everything @Dr Simon Mitchell said. I was only intending to point out that AEDs are not the cure-all the general public usually thinks they are. Almost everything people attribute to AEDs, are really the effects of epi But definitely agree in an emergency situation, you shouldn't be trying to figure out whether it's primary or secondary. Those only affect what interventions are likely to work and the likelihood of success in general

I don't believe the evidence bears this out.
There have been many studies looking at OHCA (out of hospital cardiac arrests) and changes in outcomes with epi, nothing points strongly one way or another. Epi may lead to higher ROSC (return of spontaneous circulation) but poorer neurologically intact outcomes and an increased 30 day mortality.
There is most likely a role for epi in OHCA for non-shockable rhythms, where early defib (by definition) is not an option (see ILCOR and ECC guidelines for full reference, beyond the scope of this conversation).

I have seen no data to support that epi does more than good CPR and defib (infact, the trend is very much opposite this, with effective CPR and early defib increasing survival, and epi not changing much if anything).

To avoid re-inventing the wheel, I will simply link to https://first10em.com/epinephrine/ which provides a good overview of the current data. (and one can follow a link to the recent PARAMEDIC2 trial)

I agree that AEDs are not a cure all, but to say that epi has more impact on outcomes than AEDs is misleading given the current literature. The Feb article in Circulation (Impact of Bystander Automated External Defibrillator Use on Survival and Functional Outcomes in Shockable Observed Public Cardiac Arrests. - PubMed - NCBI) showed that the benefits of AEDs are quite robust. There is no data that i have found which demonstrates the same for epi.

If you have resources that support your point, please point me in their direction.

Getting back on topic, the presence of AEDs on dive boats will most likely lead to increased survival of those experiencing arrests onboard (the degree of this would depend on a great many factors). Epi is not appropriate at this level of rescuer and would probably not provide a measurable change in outcomes. O2 probably has negligible effect on the outcome of non-DCI caused arrests. O2 is obviously needed for DCI events. I don't have the experience or knowledge of the literature to intelligently assess the benefits of AED and/or O2 for DCI related arrests, although my gut would say good BLS and early defib (if appropriate) is the most important, and get high-flow O2 on to the best of your ability, as long as it doesn't interfere with the good BLS/AED use.

And as for making it mandatory, there are enough rules out there already....

 

[caydiver]

I know this might mean but I feel divers need to have a level of personal responsibility. We had a chap on the boat last year that started talking about his heart surgery on the surface interval. We didn’t let him do the second dive and he was pissed. We used to ask people including those who come a few times a year to fill out the medical statement. Some folks thought it was an invasion of their privacy so now we ask that guests just read it over and tell is if there are any yes answers. Few actually read it. A gentleman three weeks ago said his last dive was two years prior. On the boat he admitted to other regular guests that it had been 7 years ago and he had a total of 5. He was terrible in the water and the DM spent ages working with him on the line. Luckily our other guests were self sufficient divers and actually felt sorry for the DM. Years ago when we asked to see log books it was easier to gage what was going on. Certified divers are supposed to stay dive fit, folks are supposed to have regular medical. If this was adhered to there would be less risk. I am not saying having the AED is a bad idea but I don’t see it as the first line of defense. Individual honesty and health awareness would go a long way to many instances not occurring. This doesn’t even touch on instances such as a DM an the op he worked for being sued because while his CPR efforts were successful the individual did suffer a hairline fracture on a rib and his wife was traumatized. Really? Sad if watching someone save your husband’s life is something to sue over rather than be incredibly grateful for. All of our people have the training to use an AED and they are only minutes away as our dives sites are so close to shore. Making it mandatory is not going to help in every locale and saying that an op doesn’t care about divers is preposterous. Losing someone could destroy an ops reputation, destroy a truly excellent DM (have seen it happen), and even lead to them going out of business.

 

[BlueTrin]

I know this might mean but I feel divers need to have a level of personal responsibility. We had a chap on the boat last year that started talking about his heart surgery on the surface interval. We didn’t let him do the second dive and he was pissed. We used to ask people including those who come a few times a year to fill out the medical statement. Some folks thought it was an invasion of their privacy so now we ask that guests just read it over and tell is if there are any yes answers. Few actually read it. A gentleman three weeks ago said his last dive was two years prior. On the boat he admitted to other regular guests that it had been 7 years ago and he had a total of 5. He was terrible in the water and the DM spent ages working with him on the line. Luckily our other guests were self sufficient divers and actually felt sorry for the DM. Years ago when we asked to see log books it was easier to gage what was going on. Certified divers are supposed to stay dive fit, folks are supposed to have regular medical. If this was adhered to there would be less risk. I am not saying having the AED is a bad idea but I don’t see it as the first line of defense. Individual honesty and health awareness would go a long way to many instances not occurring. This doesn’t even touch on instances such as a DM an the op he worked for being sued because while his CPR efforts were successful the individual did suffer a hairline fracture on a rib and his wife was traumatized. Really? Sad if watching someone save your husband’s life is something to sue over rather than be incredibly grateful for. All of our people have the training to use an AED and they are only minutes away as our dives sites are so close to shore. Making it mandatory is not going to help in every locale and saying that an op doesn’t care about divers is preposterous. Losing someone could destroy an ops reputation, destroy a truly excellent DM (have seen it happen), and even lead to them going out of business.

But did you check if maybe his doctor gave him the go ahead for diving ? (Only asking out of curiosity)

 

[caydiver]

Wouldn’t have believed him at that point. He lied at the beginning before he did the first dive. The news broke in between the first and second dive when there was no way to access the situation and he never mentioned any okay when they spoke to him about the second dive. He was too busy saying how he wasn’t paying for anything and was going to blow us out of the water with a nasty review. We charged him for 2T and gave the other 2 couples a break because it was not fair to them so it was a loss for us but thankfully not a tragic one. We also let our fellow ops know in case he tried them without the necessary clearance as we all do. So I totally disagree with statements saying ops only care about the money. I think most of our colleagues have integrity.