Help understanding M values
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Blackwood
Contributor
Oops - sorry, didn't follow the link. It's worth referencing again, anyway 
Mr Carcharodon
Contributor
Of course you are right you want to keep M>G. Also I should have thrown in the usual caveats. The usual presentation is that M values are pressure limits like a red line on a pressure gauge that you should not go past. But in practice M values are fuzzy line in a grey zone, so caution in approaching the limit or in decompressing if you have reached, or past, the limit is indicated.
The problem with the linked Baker paper (which is wonderful specifically about M values) is that it does not put the whole picture together. You need to be able to calculate M and G and then know what to do with them.
The Chairman
Chairman of the Board
I call that SWAG mentality. In fact, no matter what you use to track your gas absorption as it relates to your limits (tables/timer or a PDC), it's all SWAG: every blessed piece of it.
Blackwood
Contributor
Mike Boswell
Contributor
The "S" may be giving it too much credit
Oh, I would say it is very S, in the sense that it is a subject of diligent study by competent researchers using scientific methods. Like most areas that science studies, the subject matter is complex and there are no easy answers.
WRT decompression science, I think it's fascinating (and instructive) that thousands of untrained Miskito lobster divers make a dozen dives a day, for weeks at a time, to depths exceeding 100 fsw, and for the most part, DO NOT get DCS. To me this is evidence of a huge and largely unexplained (to me, anyway
) variability in the DCS phenomenon. Thus, the "fuzzy line in the grey zone".The Dives
Miskito Indians dive for spiny lobster and conch in the fishing banks off of Honduras between the Bay Islands and the remote Swan Islands.
A typical lobster dive trip lasts 18 days. Boats pick up divers in Puerto Lempira and travel two to three days to reach the fishing banks. Then they do what defies imagination: They dive for 12 straight days, making between eight and 12 dives each day to depths between 100 and 140 feet. Depending on the size of the dive boat, there are 40 to 60 divers on board, which means that a single dive boat can be responsible for up to 720 dives in a single day. For each diver, there is also a cayuquero, a teenage boy who rows the diver into position. Each team (diver and cayuquero) loads a cayuco (canoe) with four scuba cylinders and sets out to dive. The diver catches as many lobsters as he can, and when he runs out of air, he returns to the surface, immediately swaps tanks and returns to the bottom. After the diver has gone through all four tanks, the team returns to the dive boat for another four tanks, drops off their catch and returns to fishing.
From ALERT DIVER magazine
Mr Carcharodon
Contributor
Do not get DCS? Paralysis is common in that group. Not after one dive usually, but the downside is severe and real.
garyd54220
Contributor
Oh, I would say it is very S, in the sense that it is a subject of diligent study by competent researchers using scientific methods. Like most areas that science studies, the subject matter is complex and there are no easy answers.
WRT decompression science, I think it's fascinating (and instructive) that thousands of untrained Miskito lobster divers make a dozen dives a day, for weeks at a time, to depths exceeding 100 fsw, and for the most part, DO NOT get DCS. To me this is evidence of a huge and largely unexplained (to me, anyway
The Dives
Miskito Indians dive for spiny lobster and conch in the fishing banks off of Honduras between the Bay Islands and the remote Swan Islands.
A typical lobster dive trip lasts 18 days. Boats pick up divers in Puerto Lempira and travel two to three days to reach the fishing banks. Then they do what defies imagination: They dive for 12 straight days, making between eight and 12 dives each day to depths between 100 and 140 feet. Depending on the size of the dive boat, there are 40 to 60 divers on board, which means that a single dive boat can be responsible for up to 720 dives in a single day. For each diver, there is also a cayuquero, a teenage boy who rows the diver into position. Each team (diver and cayuquero) loads a cayuco (canoe) with four scuba cylinders and sets out to dive. The diver catches as many lobsters as he can, and when he runs out of air, he returns to the surface, immediately swaps tanks and returns to the bottom. After the diver has gone through all four tanks, the team returns to the dive boat for another four tanks, drops off their catch and returns to fishing.
From ALERT DIVER magazine
Mike,
I'm not sure where you got the impression that the Moskito's are not experiencing DCS injuries. The truth is they are not only being injured by DCS but are suffering very serious injuries at alarming rates. That was basically the point of the Alert Diver's article.
As noted by NatGeo
In many families in La Moskitia, Honduras, decompression sickness--and the paralysis that comes from it--strikes more than one member. .... two brothers became injured on separate dives, more than a year apart. They said they knew of families with three or four brothers who all had dive-related paralysis.
The Association of Handicapped Miskito Indian Lobster Divers has more than 2,000 members. The association does not believe it represents all the Miskito Indians who struggle with some form of paralysis brought on by diving. Those who live in remote villages (some of which lack electricity and running water) rarely make it into the capital of La Moskitia, Puerto Lempira, for treatment. The association has documented more than 400 divers who survived their injuries to return to their villages, but later died at home.
Harvesting is literally costing men their lives. In La Moskitia, there are an estimated 200,000 Miskito Indians. That means approximately one percent of the total population suffers from some disability brought on by diving."
The rest of this article can be seen here:
Miskito divers risk injury and death to feed seafood markets - NatGeo News Watch
mdf
New
I think Mike's point is this: given the nature of these dives -- lingering at 30-50m for hours, repetitively, with no apparent ascent discipline -- why aren't all of these divers getting hit, if not hammered?
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