Diver Death Belize Blue Hole

[Mike]

1 dive at the blue hole or 3 dives at half moon caye? I'd gladly have skipped the blue hole and it's ho hum, yawn, dive and enjoyed an extra dive at half moon caye where there was actually something to see and to do and enjoy a long bottom time instead of a bounce dive to see some rocks.

 

[chillyinCanada]

A diver may be given that choice if they are on a liveaboard or staying out at the Atolls but from San Pedro, a diver's only choice is to dive it, sit it out or snorkel the BH and the next dive will be the Halfmoon Caye., which I could also dive all day. A third dive (usually at Aquarium)follows lunch on Halfmoon Caye itself. The Amigos del Mar boat is large, well kept and comfortable. The crew is awesome. It's quite a wonderful way to spend a day, with or without making the BH dive.

I feel for the family and friends of the diver who passed. I also feel for the crew and the other divers on Ramon's boat that day. However, two minutes into the dive doesn't get you over the lip of the Hole. The diver may have been at 40 feet over a sandy bottom but just as good a chance he wasn't, in that, there is often a surface swim to original descent point.

 

[boulderjohn]

There are some papers on the DAN website including a guy who toxed @ 1.3. It turns out that the Cialis and similar drugs increase susceptibility.

Could you provide a link? I searched the site and could not find it. I found this article that mentions a possible link between Cialis and increased risk of oxygen toxicity, without any specifics.

Here is a Blog by Steve Lewis of TDI talking about exposure limits. He mentions the NOAA CNS tables and summarizes it like this:

Before moving on to methodology for tracking NOAA Daily Limits – NOAA seems to be the most accepted scale or system – let’s recap.

The oxygen exposure time for a single dive is compared to the Single Dive Exposure Limits on the NOAA table (1.6 for 45 mins, 1.5 for 120 mins 1.4 for 150 mins and so on).

So, NOAA's recommended limit for a PPO2 of 1.6 is 45 minutes, and it is 120 minutes for a PPO2 of 1.5 and 150 minutes for 1.4. This quote ends there, but according to NOAA, the single dive limit for 1.3 is 180 minutes--something not accomplished by a lot of divers on AL 80s.

It was for that reason that I suspected that it would be highly unlikely for someone to have a CNS incident in two minutes on this dive.

You, on the other hand, believe there have been cases when people have toxed with even less exposure than this. You said someone toxed on 1.3--I assume at about 2 minutes, since that was the topic of this thread. I would be very interested in getting the details on this, because it would become an important part of the next Advanced Nitrox and Decompression Procedures classes I teach. So, if you can provide the link, I would appreciate it highly.

 

[flots am]

You, on the other hand, believe there have been cases when people have toxed with even less exposure than this.

I said they had toxed at less than 1.6, not in less than two minutes.

Could you provide a link? I searched the site and could not find it. I found this article that mentions a possible link between Cialis and increased risk of oxygen toxicity, without any specifics.

. . .

I assume at about 2 minutes, since that was the topic of this thread. I would be very interested in getting the details on this, because it would become an important part of the next Advanced Nitrox and Decompression Procedures classes I teach. So, if you can provide the link, I would appreciate it highly.

They seem to have reorganized their website(s) and Google hasn't quite caught up.

In any case:

https://www.google.com/#q=cns+"oxygen+toxicity"+pde5+-cheap

Alert Diver | DAN Research Updates

Alert Diver | Understanding Oxygen Toxicity

DAN | Mobile

 

[Mike]

Interesting that in those DAN articles they state that other factors increase the chance to get Ox tox, such as environmental conditions (water temp) and they make a distinction between an excising diver and a non-exercising diver.

 

[TN-Steve]

Interesting that in those DAN articles they state that other factors increase the chance to get Ox tox, such as environmental conditions (water temp) and they make a distinction between an excising diver and a non-exercising diver.

I wonder if a diver that was perhaps highly stressed, breathing hard, elevated pulse rate might physiologically be similar to one that is exercising, and subject to some of the same effects?

Steve

 

[boulderjohn]

I said they had toxed at less than 1.6, not in less than two minutes.

Oh, I am so sorry. I had emphasized the time factor ( which was about two minutes) when I wrote...

As for oxygen toxicity, if the diver were accidentally diving EANx 32 and got all the way to 130 feet, that diver would still be within the contingency limit (1.6 PPO2) for that mix. Moreover, there is a time factor in your exposure--you don't just go past the "safe" limit for a few seconds and seize. In fact, according to a standard single dive oxygen exposure table (the "CNS clock"), there is not enough gas in an AL80 for a diver with excellent air consumption to get into the danger zone on this dive. Of course, CNS is not totally predictable, but for this to be an oxygen toxicity event would be extraordinarily unlikely.

And so when you wrote...

People have toxed with less. The level for O2 Toxicity is effected by C02, exercise, drugs, and a number of other factors.

I naturally assumed you were including time in your response telling me that people have been toxed for less than the situation described.

I am not trying to be a jerk about this. There are people who going to make decisions on their diving based on what they read here. You said that people have had CNS toxicity for less than described in this incident, and these people are gong to make decisions about their diving based on this. I think it is important to be accurate for the same of those reading this thread and deciding about their diving decisions.

They seem to have reorganized their website(s) and Google hasn't quite caught up.

In any case:

https://www.google.com/#q=cns+"oxygen+toxicity"+pde5+-cheap

Alert Diver | DAN Research Updates

Alert Diver | Understanding Oxygen Toxicity

DAN | Mobile

You don't have to use Google. I searched the web site directly without it and did not find anything. None of those links say anything related to this question.

 

[brnt999]

brnt999, I wasn't there to observe the conditions for your dive, so I'll speak generally. An ill-advised dive in potentially dangerous conditions may go 'fine' much of the time. I would think this would be the case with Belize Blue Hole dives, since the practice of taking rather inexperienced people on very deep dives there keeps getting reported on this forum. As long as everyone has no problems, it's all good.

So what happens with someone nervous and new gets low on air but can't equalize going up? Reverse block can bring the pain; I've had that twice, and that's twice too many times. Or someone else gets narc'd? Or worse yet, both things happen simultaneously?

No dive op. can be ready for every conceivable scenario, and I don't know the details of how your dive was conducted or with what divers, so maybe it was fine. But there are reasons some folks are concerned about the reports we hear.

I dove with Amigos del Mar. There were about 12 divers and they split us into 2 groups. There were 2 dive masters for each group. I was required to show my AOW card before we left port. The six of us dove one of the dive masters' computers (not our own). They had oxygen tanks hanging off the boat at our 7 minute decompression stop. We had a thorough pre-dive orientation. I think they did all they could do to make the dive safe. I dove with an AL100 (it is an option). One of the divers aborted the dive a minute into it( freaked out). Another diver in my group had to use a dive masters octo to get to the rest stop( they ran out of air).

 

[flots am]

You don't have to use Google. I searched the web site directly without it and did not find anything. None of those links say anything related to this question.

It's the first listing in the google results for the search I posted:

Cerebral vasoconstriction may be mitigated by phosphodiesterase-5 (PDE5) inhibitors, such as sildenafil (Viagra) or tadalafil (Cialis), which inhibit cyclic guanosine monophosphate (cGMP) degradation, enhancing and prolonging the NO vasodilator effect. Therefore, we tested the hypothesis that administering PDE5 inhibitors before HBO2 opposes hyperoxic vasoconstriction and accelerates oxygen seizure development."

This is from one of the Alert Diver links:

"AN was contacted by a diver who experienced symptoms of oxygen toxicity after using EAN at an oxygen partial pressure of 1.3 ATA. He had done similar dives many times before without any problems. His exposure to oxygen was within limits usually considered safe, but this time he had used Cialis (a PDE-5 inhibitor) the night before his dive. These drugs cause widening of the arteries responsible for erection, but theoretically they may cross from the circulation into the brain and may increase sympathetic activity. However, it was not known whether this could affect a diver's risk of oxygen toxicity. Dr. Ivan Demchenko and his team at Duke University conducted an animal study and demonstrated that rats treated with PDE-5 seized sooner than untreated animals. The lesson for divers is that use of PDE-5 inhibitors the night before diving may not be safe"

You're being intentionally dense and antagonistic and I have no desire to join in your reindeer games, so I'll just leave these here.

If you agree, that's fine. If you disagree, that's fine too.

flots.

 

[drrich2]

brnt999:

Sounds like Amigos del Mar went beyond the measures that we sometimes read about on Blue Hole dives, and still had one diver freak out & abort the dive and another run out of air and have to breathe off the guide's octo. to reach a rest stop.

Imagine that scenario with rather inexperienced OW, not AOW, divers, no option for 100 cf tanks and no oxygen tanks hanging off the boat.

Now, it is interesting that you mentioned a 7 minute decompression stop planned as part of the group dive (I take it). Given that guides often taken divers who aren't cert.d for overhead environments through swim throughs & similar 'minor' structure penetrations, or fairly new OW divers deeper than 60 feet, I'm not going to harp on it too much, but given the animosity towards 'trust me dives' I've seen on this forum, I suspect that's one 'feature' that some people are going to balk at - taking divers with no deco. dive training or certification on a decompression dive (did I understand correctly that this is what happened?). If so, I can't really judge that, but I wonder what others who can may say. Glad the one guy freaked out & aborted before incurring a deco. obligation.

I don't have any deco. training either, for what it's worth.

Richard.