Question calculating NDL is difficult

[Duke Dive Medicine]

Geoff Belter was part of a group of UTD students in various stages of training under UTD instructor George Watson. That training was being done primarily at Rock Lake in New Mexico, the only true tech diving site in the region. I was part of that group, and I dived with both Geoff and George many times before I left the group in 2011 and completed my trimix training with TDI instead. Because of that act of disloyalty, I was no longer allowed to dive with that group, so I lost touch with them for several years.

By the time of this incident, I had become a tech instructor myself and was allowed to lead dive groups at Rock Lake. I happened to be leading such a group at the same time my old group was also diving there, and we had dinner together. George talked at length about the incident. After that, several of the remaining members of that original group completed their trimix training under me, and we talked extensively about their understandings of the incident.

Geoff was extremely well liked by all of us, and his death hit us all hard. A couple years after that, we met at Marianna, Florida and deposited a memorial deep in the Jackson Blue cave.

It is my understanding that the Duke Center for Dive Medicine studied this, and perhaps @Duke Dive Medicine can provide more information.

The one piece of information I was unable to gather was what they were using for an ascent profile on their planned dive to 200 feet. As I wrote earlier, I was told that only a few people in the world could plan the dive. When I was with the group, we were required to plan all decompression dives using the UTD version of Ratio Deco, which UTD insisted did not need to be adjusted for altitude, but I don't think they would use it at that altitude without making changes.

Prior to the expedition, there was an informal conversation between a member of the expedition group and several physicians with extensive training and experience in diving medicine. No specific advice was offered; the gist was that there are no established procedures for decompression diving at nearly 16,000 feet of altitude, and that it would be up to the group to define their own. I would defer to members of the expedition group to answer any other questions.

Best regards,
DDM

 

[boulderjohn]

No specific advice was offered; the gist was that there are no established procedures for decompression diving at nearly 16,000 feet of altitude, and that it would be up to the group to define their own.

...but you can open any of the multi-deco choices (V-Planner, Buhlmann options, etc.) and get a schedule for that elevation, and that schedule will be surprisingly close to the schedule you would get at a much lesser elevation, despite the fact that no one has actually done such a dive.

As I was told, planning the dive would require a high altitude decompression scientist, such as those working with NASA and the Pentagon. The one I spoke with, speaking off the top of his head, said that a short dive to 200 feet (as they planned) would require hours of decompression. I know they did not plan anything close to that.

 

[dmaziuk]

...but you can open any of the multi-deco choices (V-Planner, Buhlmann options, etc.) and get a schedule for that elevation, and that schedule will be surprisingly close to the schedule you would get at a much lesser elevation, despite the fact that no one has actually done such a dive.

Air being compressible, ambient pressure changes non-linearly with altitude: the higher you go, the less of a change in ambient pressure there is. If you simply plug the ambient pressure into ZH-L, that's exactly what you should see. And once you get to 0 ambient pressure, you can go as high as you want from there without any change in the plan.

Computers make very fast very accurate misteaks.

 

[kosokun]

Prior to the expedition, there was an informal conversation between a member of the expedition group and several physicians with extensive training and experience in diving medicine. No specific advice was offered; the gist was that there are no established procedures for decompression diving at nearly 16,000 feet of altitude, and that it would be up to the group to define their own. I would defer to members of the expedition group to answer any other questions.

Best regards,
DDM

I was just made aware of this thread and though it's somewhat dated, I thought that it would be important to respond as there seemed to be some insinuation that decompression procedures were responsible for the accident. I was there when the accident occurred. My understanding is that they ran out of bottom gas and never had time to go through proper decompression, regardless of what that may have been. That bottom gas was also their wing gas, which resulted in the loss of buoyancy control. So any hypotheses regarding decompression at altitude relative to the accident are moot and the findings of the accident report are consistent with that assessment. However, there may be valid discussions regarding breach of protocols, cognitive impairment from cold/inadequate insulation, and even perhaps cognitive impairment from some unknown factor related to the gas they were breathing at altitude.

As an asside, someone earlier mentioned the dives that Reinhard et. al. did on Licancabur in the Atacama desert as analogous. Those dives were much higher (19,400 ft) but the max depth was ~4.5m/15 ft. Quite a different environment than going 120 ft deep at 16,000 ft elevation.

Also, DDM's description of their advice to the dive team is consistent with what I heard.

Preston Sowell

 

[boulderjohn]

I was just made aware of this thread and though it's somewhat dated, I thought that it would be important to respond as there seemed to be some insinuation that decompression procedures were responsible for the accident. I was there when the accident occurred. My understanding is that they ran out of bottom gas and never had time to go through proper decompression, regardless of what that may have been. That bottom gas was also their wing gas, which resulted in the loss of buoyancy control. So any hypotheses regarding decompression at altitude relative to the accident are moot and the findings of the accident report are consistent with that assessment. However, there may be valid discussions regarding breach of protocols, cognitive impairment from cold/inadequate insulation, and even perhaps cognitive impairment from some unknown factor related to the gas they were breathing at altitude.

As an asside, someone earlier mentioned the dives that Reinhard et. al. did on Licancabur in the Atacama desert as analogous. Those dives were much higher (19,400 ft) but the max depth was ~4.5m/15 ft. Quite a different environment than going 120 ft deep at 16,000 ft elevation.

Also, DDM's description of their advice to the dive team is consistent with what I heard.

Preston Sowell

Thanks, Preston.

It was never my thinking that the chosen decompression algorithm, whatever it was, was at fault. I always understood from what George and others told me, that the problem started when they inexplicably ran out of gas because they were using it so very quickly.

I have assumed that they used it quickly because of acclimatization to altitude. As I understood it, they were understandably affected by altitude prior to the dive, but assumed that problem would go away when they were underwater using compressed air. It is the only reason I can think that would cause two such experienced divers to both use up their air that quickly. Does that make sense in relation to your memory of the events?

George's description did not indicate to me that his lack of buoyancy control was related to the loss of inflation for his wing. He told me he simply lost control, which is again hard to understand for someone with that kind of experience and previously demonstrated skill.

 

[kosokun]

Thanks, Preston.

It was never my thinking that the chosen decompression algorithm, whatever it was, was at fault. I always understood from what George and others told me, that the problem started when they inexplicably ran out of gas because they were using it so very quickly.

I have assumed that they used it quickly because of acclimatization to altitude. As I understood it, they were understandably affected by altitude prior to the dive, but assumed that problem would go away when they were underwater using compressed air. It is the only reason I can think that would cause two such experienced divers to both use up their air that quickly. Does that make sense in relation to your memory of the events?

George's description did not indicate to me that his lack of buoyancy control was related to the loss of inflation for his wing. He told me he simply lost control, which is again hard to understand for someone with that kind of experience and previously demonstrated skill.

John,

I'm not sure that further discussion of the accident or speculation as to it's cause would be appropriate for this thread, or perhaps this forum. And it might be best conducted with one or more of that dive team's participation.

If anyone wants to learn from the accident I think that the take home point is that two very trained and experienced divers, supported by two very trained and experienced divers, found themselves in a situation where they prematurely (relative to their stated dive plan) ran out of gas. The result was a tragic accident that took one's life and changed others forever. So, how do we all ensure that that never happens to us or our team members?

Hope you're well buddy,

Preston

 

[divingdayz]

ah also, did you try looking at subsurface implementation ? they have a planner able to use both Buhlman and VPM

A great source of decompression theory right there.

Good luck with your project.