Accident on Southern Cal Oil Rigs Dive

[bullfroger]

hey I'm not speculating just I want to know the facts and wherethey come from?

 

[HalcyonDaze]

Let's start with the information we've been given:

• Based on a photo taken prior to the dive, the deceased was wearing a drysuit, back-inflation BC with weight pockets, and had a pony bottle (unknown if it was a bailout or a deco bottle, but looking at how it's rigged I would think bailout) in addition to his main tank. His main tank had a nitrox label, but we don't know what was in it.
• Based on what was presented in this thread, this was the third dive of the day - the first being the Olympic II and the second being on the Elly/Ellen complex. I do not recall if it has been confirmed he did both of the previous dives.
• The deceased was reportedly an experienced diver familiar with rig diving.
• From an earlier post in this thread, the deceased's buddy dove down to 160-170 ft in an unsuccessful attempt to recover him. According to a post on Power Scuba's Facebook page, his only issue after the ascent was a "professed headache;" he was taken for a chamber ride as a precaution.

From that we can draw some inferences, which are subject to change as more evidence becomes available:

• He had two buoyancy aids (drysuit and BC) and easily ditchable weights. He would have had several means to arrest a descent if he was able to. If he was an experienced diver familiar with the rigs, I think it unlikely he would have been grossly overweighted.
• If this was the third dive of the day and the first (Olympic II) was a max depth of 100 ft, I would think it unlikely he would have planned to go below 100 ft on this dive and very unlikely he would go as deep as 130-140. Assuming he had done the first dive and wasn't planning on reverse-profiling well below that depth, in order to get to a depth where narcosis or oxygen toxicity plays a role something else would have to go wrong first.
• If we assume his buddy had the same gas mix as he did, the buddy made it down to over 160 ft for a short duration without evident toxicity effects.

Now, what we don't know, or at least I can't recall being presented in this thread or elsewhere, were the conditions at the time of the dive. However, if they had already done the second dive at Elly/Ellen, it would seem that there were no unusually adverse conditions.

 

[Kevrumbo]

Let's start with the information we've been given:

• Based on a photo taken prior to the dive, the deceased was wearing a drysuit, back-inflation BC with weight pockets, and had a pony bottle (unknown if it was a bailout or a deco bottle, but looking at how it's rigged I would think bailout) in addition to his main tank. His main tank had a nitrox label, but we don't know what was in it.
• Based on what was presented in this thread, this was the third dive of the day - the first being the Olympic II and the second being on the Elly/Ellen complex. I do not recall if it has been confirmed he did both of the previous dives.
• The deceased was reportedly an experienced diver familiar with rig diving.
• From an earlier post in this thread, the deceased's buddy dove down to 160-170 ft in an unsuccessful attempt to recover him. According to a post on Power Scuba's Facebook page, his only issue after the ascent was a "professed headache;" he was taken for a chamber ride as a precaution.

From that we can draw some inferences, which are subject to change as more evidence becomes available:

• He had two buoyancy aids (drysuit and BC) and easily ditchable weights. He would have had several means to arrest a descent if he was able to. If he was an experienced diver familiar with the rigs, I think it unlikely he would have been grossly overweighted.
• If this was the third dive of the day and the first (Olympic II) was a max depth of 100 ft, I would think it unlikely he would have planned to go below 100 ft on this dive and very unlikely he would go as deep as 130-140. Assuming he had done the first dive and wasn't planning on reverse-profiling well below that depth, in order to get to a depth where narcosis or oxygen toxicity plays a role something else would have to go wrong first.
• If we assume his buddy had the same gas mix as he did, the buddy made it down to over 160 ft for a short duration without evident toxicity effects.

Now, what we don't know, or at least I can't recall being presented in this thread or elsewhere, were the conditions at the time of the dive. However, if they had already done the second dive at Elly/Ellen, it would seem that there were no unusually adverse conditions.

The best hypothesis for the moment is the one with the fewest assumptions. Therefore Rule Out Hypercapnia w/ or w/o associated Ox-Tox Seizure in Scuba Diving as precipitating cause. . . Primary Cause of Death: Drowning.

kevrumbo, everyone is hypercapnic?what are your references for that? Someone done underwater blood gasses or end tidal co2 measurements? just curious.

Some References:

. . .Under normobaric and hyperbaric conditions, the single factor that limits the ability to increase ventilation is the rate at which gas can be exhaled from the lungs. The ability to exhale gas is reduced during hyperbaric and diving conditions. As gas density increases, increased effort is required to exhale gas (i.e.,it takes more work to move a heavier gas). . .
Carbon Dioxide, Narcosis, and Diving | Global Underwater Explorers

". . .To give you some sense of the small changes in arterial blood levels required for these phenomena, PCO2 around 5kPa is the average normal level, 6.2kPa is the upper limit of the normal range, and over 8.5kPa sudden incapacitation is likely. Experiments show that levels between 6.5 and 7.5 are not uncommon in divers working underwater. The point is that small changes in PCO2 of 1kPa or less can have very important implications for the safety of the diver. . ."
Advanced Knowledge Series: Basic Carbon Dioxide Physiology

"Normal respiration in divers results in alveolar hypoventilation resulting in inadequate CO2 elimination or hypercapnia. Lanphier's work at the US Navy Experimental Diving Unit Answered the question, "Why don't divers breathe enough?"
http://archive.rubicon-foundation.o...le/123456789/3327/NEDU_1956_02.pdf?sequence=1
http://archive.rubicon-foundation.o...le/123456789/3362/NEDU_1958_07.pdf?sequence=1
http://archive.rubicon-foundation.o...ndle/123456789/3809/NEDU_56_05.pdf?sequence=1

 

[MaxBottomtime]

One report was that the buddy who went after him saw him unconscious with his reg spit out. It wouldn't matter what depth he was at at that time.

 

[boulderjohn]

The following comment is generic about accident and incident discussions I have observed over the years and may or may not pertain to this incident.

Nearly half of all scuba fatalities begin with a medical event, such as a cardiac arrest. When that happens, there is usually no clear sign of what happened. Unless the diver's buddy happened to be looking right at the event when it happened, it will not be witnessed--the diver will suddenly begin sinking, often disappearing from view, and be found after a frantic search. There is often no autopsy, but when there is, the results are rarely released. It is private information for the family.

I made the previous post from a purely generic point of view, covering all cases I have read about around the world. Since then I have been contacted by someone in an official capacity who told me how things are specifically in Los Angeles County.

Autopsies are performed in all dive fatalities. The incident is fully investigated, and a report is made. That report is public information. It is not, however, published. All you have to do to get the official report is ask the sheriff's department for it.

 

[yle]

• If we assume his buddy had the same gas mix as he did, the buddy made it down to over 160 ft for a short duration without evident toxicity effects.

That's quite an assumption. It will be interesting to find out what mix was in the victim's cylinder. If it was nitrox, filled on the boat, they do partial pressure fills (if I recall correctly.) Hopefully it was properly analyzed.

If the buddy was someone the victim was paired with on the day of the trip, there's no reason to assume the buddy was using the same mix. It's possible the victim was using nitrox and the buddy was on air.

 

[Kevrumbo]

• From an earlier post in this thread, the deceased's buddy dove down to 160-170 ft in an unsuccessful attempt to recover him. According to a post on Power Scuba's Facebook page, his only issue after the ascent was a "professed headache;" he was taken for a chamber ride as a precaution.

"Signs and symptoms that need to be observed are hyperventilation, shortness of breath and tachycardia (rapid heart beat), headache and excessive sweating, mental impairment and finally, unconsciousness."
CO2 Retention

". . .Rising blood CO2 (‘hypercapnia’) is a problem in diving for several reasons. First it can cause unpleasant symptoms such as headache, anxiety and shortness of breath. These can precipitate panic. If the levels get high enough CO2 can cause incapacitation and unconsciousness. . ."
Advanced Knowledge Series: Basic Carbon Dioxide Physiology

 

[HalcyonDaze]

That's quite an assumption. It will be interesting to find out what mix was in the victim's cylinder. If it was nitrox, filled on the boat, they do partial pressure fills (if I recall correctly.) Hopefully it was properly analyzed.

If the buddy was someone the victim was paired with on the day of the trip, there's no reason to assume the buddy was using the same mix. It's possible the victim was using nitrox and the buddy was on air.

It seems the assumption is being made that this was an instabuddy with him and not someone he dove with regularly. Do we know that? I'm not familiar with how Power Scuba organizes its trips. By the third dive a diver on air would have had to stay relatively shallow to remain within NDL. That would make it even less likely that oxygen toxicity was the cause.

"Signs and symptoms that need to be observed are hyperventilation, shortness of breath and tachycardia (rapid heart beat), headache and excessive sweating, mental impairment and finally, unconsciousness."
CO2 Retention

". . .Rising blood CO2 (‘hypercapnia’) is a problem in diving for several reasons. First it can cause unpleasant symptoms such as headache, anxiety and shortness of breath. These can precipitate panic. If the levels get high enough CO2 can cause incapacitation and unconsciousness. . ."
Advanced Knowledge Series: Basic Carbon Dioxide Physiology

And the buddy had just experienced an emergency, legged it down after the deceased to 167 ft, and then come up rapidly, so one would expect him to have been breathing very heavily. We cannot say the same for the deceased prior to the accident.

 

[Kevrumbo]

. . .And the buddy had just experienced an emergency, legged it down after the deceased to 167 ft, and then come up rapidly, so one would expect him to have been breathing very heavily. We cannot say the same for the deceased prior to the accident.

Yes, but again take into consideration for this buddy-pair -and all divers even at the surface experiencing exertion breathing to begin with. . .

Look again at this simple graphic demonstration of immersion work-of-breathing, exercise, and ambient pressure differential just by trying to talk and tread water at the surface at the same time:
Now this is somewhat representative and similar to a degree -of the higher stress of the live boat-drop, hard exercising surface swim through swell & current into & under the oil rig platform's boundary, and then the initial descent to depth . . . All SoCal Divers who regularly dive the Rigs experience this, with some days being relatively benign, and at other times a physical challenge just kicking out to the structure and recovering on surface for a few minutes before starting the descent.

A fair assumption and valid point of speculation is that the deceased could have been having exertion problems (Tachypnea) right at the start, as early as the surface swim, and still elected to proceed with the dive. Now under immersion and hyperbaric conditions, the vicious cycle of CO2 toxicity commences and the victim goes into Hypercapnia at depth.

 

[yle]

Let's start with the information we've been given:

• If we assume his buddy had the same gas mix as he did, the buddy made it down to over 160 ft for a short duration without evident toxicity effects.

That's quite an assumption. It will be interesting to find out what mix was in the victim's cylinder. If it was nitrox, filled on the boat, they do partial pressure fills (if I recall correctly.) Hopefully it was properly analyzed.

If the buddy was someone the victim was paired with on the day of the trip, there's no reason to assume the buddy was using the same mix. It's possible the victim was using nitrox and the buddy was on air.

It seems the assumption is being made that this was an instabuddy with him and not someone he dove with regularly. Do we know that? I'm not familiar with how Power Scuba organizes its trips. By the third dive a diver on air would have had to stay relatively shallow to remain within NDL. That would make it even less likely that oxygen toxicity was the cause.

I didn't assume anything. I was simply pointing out that your assumption was a bit of a stretch in logic. There's no good reason to assume that the victim and buddy had the same gas in their cylinders.

You stated "If we assume..." and then went on to imply that since the buddy made it to 160 feet without ill effects, we could conclude something about the gas in the victim's cylinder. Regardless of the relationship between victim and buddy, there's no reason to assume they were using the same gas.

I will agree with you that conservative planning of a third dive on air should require a shallower depth than might have been reached on the first two dives. So if the dive was planned conservatively and if the dive plan was followed, then we could expect oxygen toxicity risk would have been mitigated.

The only thing we can conclude with certainty is there are a lot of "ifs."