How Deep do you Dive?

[WreckWriter]

Originally posted by Uncle Pug
That is a stinker... why do you think that is the case?

I've always wondered if there isn't a glitch in the Haldane tables at that level. I've discussed it with many people (years ago) and many folks had noticed the same thing. I have no idea if this was ever decided to be true or not but I know if I calculate a 90' 30 min air dive on V-Planner I get 3 stops for a total of 16 min deco instead of a direct ascent so it seems the current tables are a bunch more conservative in this range.

Tom

 

[fredk]

our experience at the chamber in utila was most hits of dcs occured in 30-50 feet and was for the most part instructors working with students.

 

[WreckWriter]

Originally posted by fredk
our experience at the chamber in utila was most hits of dcs occured in 30-50 feet and was for the most part instructors working with students.

Caused primarily by multiple ascents I would think.

Tom

 

[fredk]

multiple ascents and rapid ascents chasing students, most cases involving students was due to lost weight belts causing rapid ascents.

 

[fredk]

of course that is besides the hits caused by dehydration or drug induced, big problem down there as drugs are everywhere and readily available at all bars and some dive shops.

 

[voidware]

One thing I haven't noticed is people referencing their deep dives to locations. For example, a dive to 130 in the warm clear water of Grand Cayman would not seem like much of a challenge. On the other hand, a cold murky open ocean dive (ie, northeast wreck) to 80 feet would be an even greater challenge. There is also the fact of greater air consumption, wetsuit compression, and greater risk of dcs in cold water.

I would be much more likely to let my computer slip into decompression (or for that matter, slip over the dive plan) in the carib. than in nasty water.

brandon

 

[Uncle Pug]

The only case of DCS that I have personal knowledge of was a friend who suffered a serious hit (that fortunately resolved after chamber treatment) from a 90 ffw dive. He was PADI instructor rated and a S&R diver but was doing a solo bounce dive to retrieve something after a first dive. Altitude was also a factor as was personal fitness (overweight.)

Personally I think the idea that *dives between 80-100 feet are no big deal* could be a contributing factor to the statistics.

 

[The Chairman]

Just for the benefit of any OW students or new divers reading this, let’s take a moment and clarify...

Your NDL (No Decompression Limit) is based on a table that tries to approximate how much nitrogen is absorbed in a worst case scenario for most divers. It is factored in a time vs. pressure format. Being a table it cannot actually measure the nitrogen you have absorbed... it is a good guestimate though.

The bends, or better termed as DCI (Decompression Illness) or DCS (Decompression Sickness), results from either violating your NDL or having some existing predisposition(s) which make the tables inaccurate for you. Things like smoking, being overweight (das me), injuries as well as other things can make those conservative tables not so conservative for you. I do not believe that there is anything such as an "undeserved hit" when it comes to DCS. No, we may not fully understand all of the factors, but they were obviously there. God did not reach down and smite you with this for no reason.

Nitrogen Narcosis or getting "narced" has little to do with NDLs or DCS. It is merely a function of the partial pressure of the Nitrogen you are breathing. This is where I may depart from what has been presented here by some...

Whether you "feel" it or not, narcosis happens! It starts when you hit the water and first becomes noticeable @ 80 ft, increases greatly by 100 ft and should be considered dangerous by the time you hit 130 ft.

:nono: Just because you don't feel it does not mean you are not affected. NO ONE IS IMMUNE. :nono:

If you were drunk on land, you would stagger when you walk and your speech would be slurred. Underwater, you are supported by your BC (no staggering) and by the time you are talking to the fishies it is too late. In other words, those areas that would normally indicate to you and others that there is a problem have been masked by your environment. People are expecting a narcotic euphoria which may or may not happen for you. I will contend that your responses will be slowed and your senses dulled. Your critical thinking and memory will be adversely affected, leading you to think you are all right and forgetting to preserve yourself. As narcosis begins and deepens it leaves you less and less competent to determine your competency to continue. I have been deeper than 130 fsw only once… and almost lost a buddy. Never again, especially since his first words to me on the surface were “I didn’t feel a thing!” There are two divers… those who get narced below 100 fsw and those who are deceived to thinking that they are immune.

End of rant… you can flame me now!

 

[WreckWriter]

While I agree with your intent in writing this I stand by my statement that narcosis is a personal thing, no two are alike. You lose your buddy at 130, others aren't quite so impaired.

You preach the party line quite strongly, some of us feel there's a bit of room for personal interpretation.

Tom

 

[Solomon]

Exactly. That was basically my point as well. People should dive within their comfort and skill level down to 130 feet (because, if done properly, can be a nodecompression dive as it is defined). If someone is debilitated at 100 feet then they should modify their diving to incorporate this factor. Myself, have suffererd no noticeable impairment at 120 feet (but that is not to say I will not be narced at 90 feet on my next dive) . There are many, however, who are taught that 100 feet is some benchmark when for some it may be but for others it si not.