computer useage in DIR ? ?
- Thread starter jeffyjak
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Braunbehrens and Uncle Pug, et al,
Okay, let's clear up some misconceptions here...
("SNIP" will be Braunbehrens--Numbered paragraphs will be my thoughts.)
(1) I asked the question to make sure I understood what your intent was. You and Uncle Pug explained. Thank you.
SNIP>No, I'm saying that the way to avoid getting bent is to understand how deco works, and what works. Not by using some fancy gizmo.>
(2) I could not agree more. If you are going to DO deco, you need to study and try to UNDERSTAND deco. It has been an on-going study of mine. (The "fancy gizmo" comment unfortunately makes you sound like one of those folks who said: "Ya wuddn't get me in one of them new-fangled ottymobeels!---insert chosen hated machine---)
SNIP>The numbers in question are all crude approximations. However, the SHAPE of the deco and a few other things, are far more important.>
(3) The numbers have ALL been crude approximations since the days of the old Goat-bender himself. Recently, however, doppler studies, chamber research, and computer analysis on a scale here-to-fore impossible (not to mention the work of some really sharp minds) have been changing the face of the map when it comes to deco. My question would have to be: "What, exactly, do you mean by the comment about the SHAPE (since you put it in capitals) of the deco?" Are you referring to the plot, or graph, of the deco times in specific situations? Or, as someone else suggested, is this one of these Dark Force Jedi mind-trick wave-of-the-hand kind of things? Or is it some emotional thing?
SNIP>For example, you mentioned (correct me if I'm wrong) that you drive some kind of rig that keeps you at a constant PO2.
(4) Correct. It is a Computer-controlled Rebreather. The O2 sensors and the logic system are set to read PPO2 in the loop and maintain it at one's requested set-point.
SNIP>This is exactly what you don't want, if you understand deco.
(5) Think about that for a moment. It is exactly what you DO want! As long as your PPO2 is within limits, maximising your oxygen fraction results in minimising your inert gas fraction (whatever that inert gas may be). Remember that you are dealing here with a (mostly) sealed system that can, unlike OC or SCR's, constantly change the fractions of your mix.
SNIP>Rather than having your PO2 high on the bottom, where the risk and danger of tox is much higher, keep it low and offset some of that oxygen with helium, which is easier to deco from.
(6) All correct. PPO2 must remain within safe limits. Also, helium has its hazards, but it is the best inert gas to choose for a lot of reasons. (I belong to the group known as the "Helium is my friend!" camp in the CCR community.)
SNIP>Once you are shallow and doing deco, go for the maximum gradient by using a PO2 of 1.6, but don't stay on it. Take frequent low PO2 breaks. The reason for this is that your ability to offgas actually decreases when breathing high PO2's for lengthy time periods. Low po2 breaks will prevent this and your deco will actually be more effective.
(7) The reason for keeping your PPO2 high (but still in the safe range) is, as you know, to steepen the off-gassing gradient and open that "oxygen window". The reason for taking air breaks is actually to keep your over-all exposure to oxygen within safe limits to avoid CNS O2 toxicity. The comment about your ability to off-gas decreasing is only true on the capillary level. Over-all, you need to maximise the gradient, and keep it there.
SNIP>Another reason to avoid high po2's on the bottom is that you only have so much "high po2 reserve". If things turn out really bad, and you need to hit the chamber, you'll be in deep trouble if you've exhausted this reserve! The treatment will be ineffective, and possibly dangerous.
(8) Unfortunately, you are a victim of a diving "urban myth" when you say what you have said above. I am not bragging here, but I want you to know that I do know what I am talking about when it comes to this. For some years, I have been a certified Diver Medic Technician. I am still current. I was trained at UTMB Galveston, by Dr. Richard Mader, a noted researcher in the field of hyperbaric medicine, and Kevin Corson (phone number on request if you wish to check), a well-known DMT Instructor of "oil-patch" medics in the Gulf of Mexico. I am still current. Trust me on this one. If you are in "bubble trouble" and you are brought to the chamber, we WILL still treat you EVEN if you have exceeded your PPO2 exposure limits. (Treatment will probably be with the Navy Table 6 treatment schedule.) An individual's tolerance to O2 exposure increases in the chamber environment for a lot of reasons. Even if you do convulse, however, that will NOT be life-threatening in the controlled environment. Leaving those bubbles alone and not crushing them back down to a manageable size will DEFINITELY limit your "well-ness" potential.
SNIP>I shouldn't even be saying all this, I'm not really the right guy to listen to on this subject. There are people who know a lot more, and understand this a lot better. Much has been written about it. I suggest you take a look at it. DO NOT DIVE BASED ON WHAT I SAY! DO YOUR OWN RESEARCH! Better yet, take a class. Sorry for the all caps, trying to keep it clear.
(9) Actually, I don't know why you feel you shouldn't be saying what you said. With a couple of exceptions (as noted), what you are saying is GOOD advice, especially your comments in this last paragraph. As you say, much has been written about the subject. I have read an awful lot of it, and in some cases, taken classes from, or spoken directly to the authors. I will continue to do so! As you say, do the research, take the classes, and, I would add, keep an open and enquiring mind!
Okay, let's clear up some misconceptions here...
("SNIP" will be Braunbehrens--Numbered paragraphs will be my thoughts.)
(1) I asked the question to make sure I understood what your intent was. You and Uncle Pug explained. Thank you.
SNIP>No, I'm saying that the way to avoid getting bent is to understand how deco works, and what works. Not by using some fancy gizmo.>
(2) I could not agree more. If you are going to DO deco, you need to study and try to UNDERSTAND deco. It has been an on-going study of mine. (The "fancy gizmo" comment unfortunately makes you sound like one of those folks who said: "Ya wuddn't get me in one of them new-fangled ottymobeels!---insert chosen hated machine---)
SNIP>The numbers in question are all crude approximations. However, the SHAPE of the deco and a few other things, are far more important.>
(3) The numbers have ALL been crude approximations since the days of the old Goat-bender himself. Recently, however, doppler studies, chamber research, and computer analysis on a scale here-to-fore impossible (not to mention the work of some really sharp minds) have been changing the face of the map when it comes to deco. My question would have to be: "What, exactly, do you mean by the comment about the SHAPE (since you put it in capitals) of the deco?" Are you referring to the plot, or graph, of the deco times in specific situations? Or, as someone else suggested, is this one of these Dark Force Jedi mind-trick wave-of-the-hand kind of things? Or is it some emotional thing?
SNIP>For example, you mentioned (correct me if I'm wrong) that you drive some kind of rig that keeps you at a constant PO2.
(4) Correct. It is a Computer-controlled Rebreather. The O2 sensors and the logic system are set to read PPO2 in the loop and maintain it at one's requested set-point.
SNIP>This is exactly what you don't want, if you understand deco.
(5) Think about that for a moment. It is exactly what you DO want! As long as your PPO2 is within limits, maximising your oxygen fraction results in minimising your inert gas fraction (whatever that inert gas may be). Remember that you are dealing here with a (mostly) sealed system that can, unlike OC or SCR's, constantly change the fractions of your mix.
SNIP>Rather than having your PO2 high on the bottom, where the risk and danger of tox is much higher, keep it low and offset some of that oxygen with helium, which is easier to deco from.
(6) All correct. PPO2 must remain within safe limits. Also, helium has its hazards, but it is the best inert gas to choose for a lot of reasons. (I belong to the group known as the "Helium is my friend!" camp in the CCR community.)
SNIP>Once you are shallow and doing deco, go for the maximum gradient by using a PO2 of 1.6, but don't stay on it. Take frequent low PO2 breaks. The reason for this is that your ability to offgas actually decreases when breathing high PO2's for lengthy time periods. Low po2 breaks will prevent this and your deco will actually be more effective.
(7) The reason for keeping your PPO2 high (but still in the safe range) is, as you know, to steepen the off-gassing gradient and open that "oxygen window". The reason for taking air breaks is actually to keep your over-all exposure to oxygen within safe limits to avoid CNS O2 toxicity. The comment about your ability to off-gas decreasing is only true on the capillary level. Over-all, you need to maximise the gradient, and keep it there.
SNIP>Another reason to avoid high po2's on the bottom is that you only have so much "high po2 reserve". If things turn out really bad, and you need to hit the chamber, you'll be in deep trouble if you've exhausted this reserve! The treatment will be ineffective, and possibly dangerous.
(8) Unfortunately, you are a victim of a diving "urban myth" when you say what you have said above. I am not bragging here, but I want you to know that I do know what I am talking about when it comes to this. For some years, I have been a certified Diver Medic Technician. I am still current. I was trained at UTMB Galveston, by Dr. Richard Mader, a noted researcher in the field of hyperbaric medicine, and Kevin Corson (phone number on request if you wish to check), a well-known DMT Instructor of "oil-patch" medics in the Gulf of Mexico. I am still current. Trust me on this one. If you are in "bubble trouble" and you are brought to the chamber, we WILL still treat you EVEN if you have exceeded your PPO2 exposure limits. (Treatment will probably be with the Navy Table 6 treatment schedule.) An individual's tolerance to O2 exposure increases in the chamber environment for a lot of reasons. Even if you do convulse, however, that will NOT be life-threatening in the controlled environment. Leaving those bubbles alone and not crushing them back down to a manageable size will DEFINITELY limit your "well-ness" potential.
SNIP>I shouldn't even be saying all this, I'm not really the right guy to listen to on this subject. There are people who know a lot more, and understand this a lot better. Much has been written about it. I suggest you take a look at it. DO NOT DIVE BASED ON WHAT I SAY! DO YOUR OWN RESEARCH! Better yet, take a class. Sorry for the all caps, trying to keep it clear.
(9) Actually, I don't know why you feel you shouldn't be saying what you said. With a couple of exceptions (as noted), what you are saying is GOOD advice, especially your comments in this last paragraph. As you say, much has been written about the subject. I have read an awful lot of it, and in some cases, taken classes from, or spoken directly to the authors. I will continue to do so! As you say, do the research, take the classes, and, I would add, keep an open and enquiring mind!
Since Paul is offline right now I will venture to answer for him:
Yes.
Braunbehrens
Guest
- Messages
- 514
- Reaction score
- 0
Honestly, I really don't care. I don't even care that much about "looking good" in the water. I'm interested in what works, and what keeps me well. Peer pressure has never been a strong factor in my life, I prefer to use my brain.
Nope, it's still a crude approximation.
No. Keep your PO2 low on the bottom, and high during deco, with on/off toggling. There are several effects happening when breathing high PO2's. This will minimize them. The idea that you can keep your inert gasses low by raising the PO2 is putting the cart before the horse. What you are doing is infringing upon your high pO2 allowance while still on the bottom.
Unfortunately people in that community have been sold on a very dangerous concept, and quite a few have paid the price.
Actually, wkpp divers go far beyond the "safe limit"of PO2 exposure (like 10 times over). The reason is that this is again a poorly understood field, and our bodies don't work the way the models have been written...otherwise they would have all toxed a long time ago. The very fact that they are able to do this, shows that their method for dealing with high PO2's is superior to yours. No offense.
I'm not going to trade credentials with you, I'm sure you have more than me. However, I look to the people who are able to do the dives, and I think I understand what I read as much as the next guy. I also know people who have experienced problems from breathing O2.
Of course you are going to treat someone who is bent, that wasn't my point. The question is how effective the treatment is going to be, and what the consequences of the treatment are. The treatement will work a lot better if the guy hasn't been on high pO2's.
I don't really want to get into a back and forth....I know where you are coming from, and I am convinced that you you're not going to give up diving the way you have been.
People should go to the source and do the reading, as opposed to listening to two guys parroting stuff that's 3 times removed from the source.
computer usage can be a plus with the right model and equipment.. I know you are against constant PO2 and computers but here is a profile I HAVE done, the explorer computer profile was almost exactly as planned (it actually cleared a few minutes ahead of my tables)..
300for 30 minutes at a constant PO2 of 1.30
first stop using RGBM is 220ft, total tts is 109 minutes, even including the bottom time this is still below noaa limits plus I can stay on He all the way up.. if I did a dil flush with a nitrogen/oxygen only mixture my TTS drops down to 99 minutes (I haven't tried this yet)
If you were on OC you would be have your first stop still at 220, but have a total TTS of 174 minutes with only about 10% less oxygen exposure..
this assumes swiches to 50% and 100% oxygen
if you use another intermediate gas say 32%oxygen and 32% helium (I dont remember the GUE recommended gas)as an intermediate step before the 50%, tts of 131.. Whats your "official" GUE profile
On my CCR I felt perfect after the dive
BTW from what I have told if this was an Ocean dive it would be against GUE recommendations since its longer than 90 minutes (not sure how true that is).
(Actually, I don't disagree with your last conclusion, except to say that, since I know some of these guys personally and talk to them on the phone, that would make it only twice removed in my case.) :doctor:
Braunbehrens
Guest
- Messages
- 514
- Reaction score
- 0
I never said that Helium is bad. I don't want to continue the back and forth, but feel that I need to set the record straight on this. I don't know where you get this.
I didn't take anything you said personally, I'm simply pointing out that I don't do what I do based on how it makes me sound or anything of the sort. You several times now have referred to how something makes you look or sound, how something is "arcane" etc.
I don't care about being cutting edge, I don't care about being cool, and I don't care about impressing others. I care about what works, and why.
Any other attitude towards diving is IMO dangerous. Wanting to use the latest and greatest is exactly what drives people to use electronically controlled CCR's. No thanks....and no, I'm not going to debate that one either.
I didn't take anything you said personally, I'm simply pointing out that I don't do what I do based on how it makes me sound or anything of the sort. You several times now have referred to how something makes you look or sound, how something is "arcane" etc.
I don't care about being cutting edge, I don't care about being cool, and I don't care about impressing others. I care about what works, and why.
Any other attitude towards diving is IMO dangerous. Wanting to use the latest and greatest is exactly what drives people to use electronically controlled CCR's. No thanks....and no, I'm not going to debate that one either.
There are a couple of very important reasons why the use of a computer is counter-indicated for decompression diving... OPEN CIRCUIT decompression diving... and it seems important to bring them up here.
To begin with, computers encourage poor planning, and poor understanding of the shape of the algorithm. Neither is a good habit to take into the world of decompression diving.
Secondly, and perhaps more importantly, computers (and I generalise here) misshape the algorithm by padding it excessively.
Allow me to explain.
The largest market for scuba equipment is the USA.
When a software company builds anything that measures things related to health and well-being... and especially when it uses a licensed algorithm... the legal department get seriously involved. In fact, they might even read the functional specs and stand behind the applications architect when she's talking to the propeller heads.
All law suits are expensive to defend -- even stupid ones, and the legal system in the USA seems to encourage stupid law suits.
OK, so we have a lawyer telling the programming department how to interpret the algorithm... Legal has already insisted that the packaging has a huge warning against using the computer for decompression diving, but that's not enough. Legal is now asking that when the computer does get into decompression mode, it keeps people in the water longer than necessary. How much longer? Well, how long would you like?
If the lawyer is in court and has to defend the company, he can get umpteen "expert" witnesses to explain decompression theory, but the jury will not understand it. All they will take away from the cross examination is that "Decompression means staying in the water." And the corollary is "Staying longer is safer!"
I know it's dumb and makes no allowances for anything remotely related to common sense. But that's the way it is.
Computer manufacturers have to pad the algorithm to please the legal department and believe me, it's important to keep the legal department happy. Board meetings are hell when there are a bunch of pissy lawyers in attendance.
So if you want to learn to dive, forget the computer. It's like training wheels.
And just in case anyone wonders, I'm not a lawyer. But do I run a software company, and for the record, have more than 500 logged trimix dives... one of them testing a trimix computer, which incidently got bent... I did not.
Doppler
P.S. I know nothing about rebreathers. So, if you're a CC or SCC user and all of the above sounds like nonsense... please let me know. Constant PO2s make for some radical profiles... but that's another thread isn't it?
Later
To begin with, computers encourage poor planning, and poor understanding of the shape of the algorithm. Neither is a good habit to take into the world of decompression diving.
Secondly, and perhaps more importantly, computers (and I generalise here) misshape the algorithm by padding it excessively.
Allow me to explain.
The largest market for scuba equipment is the USA.
When a software company builds anything that measures things related to health and well-being... and especially when it uses a licensed algorithm... the legal department get seriously involved. In fact, they might even read the functional specs and stand behind the applications architect when she's talking to the propeller heads.
All law suits are expensive to defend -- even stupid ones, and the legal system in the USA seems to encourage stupid law suits.
OK, so we have a lawyer telling the programming department how to interpret the algorithm... Legal has already insisted that the packaging has a huge warning against using the computer for decompression diving, but that's not enough. Legal is now asking that when the computer does get into decompression mode, it keeps people in the water longer than necessary. How much longer? Well, how long would you like?
If the lawyer is in court and has to defend the company, he can get umpteen "expert" witnesses to explain decompression theory, but the jury will not understand it. All they will take away from the cross examination is that "Decompression means staying in the water." And the corollary is "Staying longer is safer!"
I know it's dumb and makes no allowances for anything remotely related to common sense. But that's the way it is.
Computer manufacturers have to pad the algorithm to please the legal department and believe me, it's important to keep the legal department happy. Board meetings are hell when there are a bunch of pissy lawyers in attendance.
So if you want to learn to dive, forget the computer. It's like training wheels.
And just in case anyone wonders, I'm not a lawyer. But do I run a software company, and for the record, have more than 500 logged trimix dives... one of them testing a trimix computer, which incidently got bent... I did not.
Doppler
P.S. I know nothing about rebreathers. So, if you're a CC or SCC user and all of the above sounds like nonsense... please let me know. Constant PO2s make for some radical profiles... but that's another thread isn't it?
Later
I brought CCRs into the debate because B. stated constant PO2 was bad.. The profiles I have done on the Explorer in RGBM mode delievered some nice deco curves on both OC and CC.. and to point out even these "extreme" profiles are still below NOAA limits, I can drop the PO2 to 1.2 or 1.1 and extend my dive bottom time and keep deco in the same ball park, now the OC dive has the higher exposure.
Planning on a CCR is just as important (if not more)especially doing the dive I listed above.. I know very few OC divers who would attempt that dive especially in OW conditions. I MUST know all my bailout requirements.. I can't assume the RB will get me to the surface.. I must go into the dive ASSUMING it will faill.. Its unlikely but if its not planned for I'm probably dead.
Staying in the water is not necassarily safer.. a few extra minutes doesn't change the statistical probablilty of an accident. Any perceived safty gained ny staying longer is getting ofsset by the probability of other issues.
The profiles I listed are for RGBM profiles, haldane models especially GF dives Are MUCH longer.. The differance bewteen CC and OC get greater.
also the more tanks with different mixes you are forced to carry the greater liklihood some abnormal event may occur..
CCRs have greater training and experience requirements but every serious diver that I have ever met and gave CCRs a real chance has switched, but CCRs aren't for everyone they require the attentive diver, someone who only checks their guages once every several minutes because they know their consumption rates would probably kill themselves..
Just because you have something to breathe doesn't mean its a breathable gas!
My favorite use of a CCR is not the deep profiles but the ones that let me get long multilevel dives starting at maybe 130-150 for an hour, comming up to 100 for another 30 then cruising a reef for another 90 minutes, and having no deco reqired since it was all done at 100 and 50.... because of the rising PO2
on OC this type of dive is unpractical in Ow since it would require at least 700cu ft of gas plus deco gas , in a cave you could at least have divers staging tanks of various mixes..
One of the real advantages of a constant PO2 in CC is control of the CNS and since there's no PO2 spike, not real need to toggle upper / lower doses... at least that's the way I read it... is that the way you run it?
What sort of CNS loading do you habitually run on the long "reef" dives? Sounds like you'd be in the 40s or 50s.
And I know one day you CC guys will win me over, but I have less than a dozen CC dives and one of them was my most unfavorite experience underwater. Felt like I was driving a bus... anyway, I stay with my tanks for the time being thanks!
Similar threads
