A guide about setpoint selection for deep dives

Mdemon · 18th April 2006, 18:47

Quote: (Originally Posted by ScubaDadMiami)

I don't see why erring on the side of being somewhat overly cautious is a problem.

You have a very good point. However, you can say the same about deco, gas selection, cell checking, redundancy etc etc. Where do you draw the line?

The longer you are in the water, the longer you are at risk. I think arbitrarily changing setpoint "just in case" needs to be justified with this in mind.

Drmike · 18th April 2006, 18:57

The deeper you are the less benefit high ppo2 gives you at depth from a subsequent deco perspective. Yet the CNS loading is the same at any depth.

Toxing is more likely during the working part of the dive. You work harder at depth.

It doesnt make sense to me to consider and act upon those facts

Deep working part of the dive reduce the ppo2 down a bit, on ascent when resting on deco push it up a bit.

Air breaks? pick up a reg and breathe!

dave t · 18th April 2006, 19:04

Quote: (Originally Posted by Drmike)

Dave I think this is very dodgy and potentialy dangerous advice.

Anyone wearing a ffm with a Rebreather should have a BOV fitted to it. Not to doesnt make any sense at all.

If they convulse you just wait until they stop then turn the BOV to OC.
You will see bubbles from the OC exhaust when/if they start breathing.

Letting someone drown as a way to tell there airway is open enough to allow a 'safe' ascent is lunacy IMO. FFM+BOV.

Ah, Mike wondered why I wasnt getting any stick from you over this, hows the Boris course? give my regards to Phil

I can only speak as I find from practical experience (unfortunatly) and I didnt let him drown infact the surgeon said there was only a half teaspoon of water in his lungs and no I dont think I would have seen the gas coming out as there was not very much and I was worried that another convulsion was gonna hit. I did the best I could and formed my opinion based on that.

If you would like to explain how a FFM will stop you from dying lets say on a hypoxic incident and you are diving on your own I am willing to learn

Dave

Drmike · 18th April 2006, 19:10

Quote: (Originally Posted by Mdemon)

You have a very good point. However, you can say the same about deco, gas selection, cell checking, redundancy etc etc. Where do you draw the line?

The longer you are in the water, the longer you are at risk. I think arbitrarily changing setpoint "just in case" needs to be justified with this in mind.

Remember we are talking about deep dives here. These tend to be one-dive- a-day afairs where there is less rush to get out as it were

My aim naturaly is to get out of the water unbent and alive
The time that it takes to do that is far-far-far less important than the above.

Id rather do very long deco following models that are more man tested/verified and employ variable ppo2 setpoints to reduce risk of O2 toxing, than to get out the water a few hours quicker if I do so by increasing risk of DCS or toxing.

Other than getting sat on by elephants theres not a lot of risk in sitting in a head pool after a deep cave dive, or reading a book on a deco platform.

Its the quality of the deco that counts not the quantity (not my words but I think very wise ones)

Drmike · 18th April 2006, 19:22

Quote: (Originally Posted by dave t)

Ah, Mike wondered why I wasnt getting any stick from you over this, hows the Boris course? give my regards to Phil

I can only speak as I find from practical experience (unfortunatly) and I didnt let him drown infact the surgeon said there was only a half teaspoon of water in his lungs and no I dont think I would have seen the gas coming out as there was not very much and I was worried that another convulsion was gonna hit. I did the best I could and formed my opinion based on that.

If you would like to explain how a FFM will stop you from dying lets say on a hypoxic incident and you are diving on your own I am willing to learn

Dave

When solo a hypoxic incident will kill you no matter if you are wearing a ffm or not - you die - a O2 convulsion only kills when the divers drown afterwards. FFM = no drowning. You may (when solo) be one of those who is not responsive enough after a hit to help yourself - but you might be one of those who is......personaly Id rather have the chance to find out

Boris course was a huge amount of fun

Phil is as mad as a box of frogs!

Boris is brilliant

dave t · 18th April 2006, 19:26

Quote: (Originally Posted by Drmike)

When solo a hypoxic incident will kill you no matter if you are wearing a ffm or not - you die - a O2 convulsion only kills when the divers drown afterwards. FFM = no drowning. You may (when solo) be one of those who is not responsive enough after a hit to help yourself - but you might be one of those who is......personaly Id rather have the chance to find out

Boris course was a huge amount of fun

Phil is as mad as a box of frogs!

Boris is brilliant

well at least we can agree about Phil

Genesis · 18th April 2006, 20:41

Couple things....

I like the "Air Break (Y/N)?" thing. But if you say "N", then the smart thing for the unit to do is raise hell (and KEEP raising hell) since the reason it called for it in the first place was due to excessive CNS loading......

As for a FFM if you have one AND retain the seal AND are rescued promptly it may save your azz. On the other hand if you DON'T retain the seal OR you're not rescued promptly its likely to make little if any difference in the outcome, only in the means of your death (suffocation/CO2 breakthrough .vs. drowning.) If nobody ELSE is there to trigger a BOV on your FFM after you tox you sure as hell aren't going to do it, and if you tox and are out of it for 30 minutes or more odds are you'll tox AGAIN during that 30 minute period since the cause hasn't been remedied. If you manage to trigger the BOV AS you are about to tox without help you're even more screwed since you'll run out of gas before you come around and are "alert". While a FFM certainly helps it is not a panacea AND it appears that the effort there is somewhat misplaced - it would be better spent understanding why the hits are happening and putting a stop to it.

netmage · 28th April 2006, 17:22

Cedric,

Question from a noob....

I understand the concept of padding in a safety factor, longer time to approach the CNS limits, etc. However there doesn't seem to be an analysis of justifying why 1.0, vs. 1.1, 1.2, 0.9, etc... Deciding on 1.0 seems arbitrary.

JonnyB · 28th April 2006, 17:39

Quote: (Originally Posted by netmage)

Cedric,

Question from a noob....

I understand the concept of padding in a safety factor, longer time to approach the CNS limits, etc. However there doesn't seem to be an analysis of justifying why 1.0, vs. 1.1, 1.2, 0.9, etc... Deciding on 1.0 seems arbitrary.

There are probably many reasons for using 1.0 instead of .9 or 1.1

But one that comes to my mind straight away, using the meg that is. Is the HUD. Watching the HUD on 1.0 you will have orange, .9 you will have red and 1.1 you will have green, this makes it easy for you to see what happends with your ppO2.
This is just to justify why 1.0 instead of .9 or 1.1 not, why to use lower SP instead of higher SP as described above.

/Jonny

cedricverdier · 28th April 2006, 22:51

Quote: (Originally Posted by netmage)

Cedric,

Question from a noob....

I understand the concept of padding in a safety factor, longer time to approach the CNS limits, etc. However there doesn't seem to be an analysis of justifying why 1.0, vs. 1.1, 1.2, 0.9, etc... Deciding on 1.0 seems arbitrary.

Hi,

You're definitely right. 1.0 is only more practical to monitor on several rebreathers. It's also a good compromise between too low and too high, but 0.9 or 1.1 work as well.

Cheers

18th April 2006, 18:47	#51 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,927	Re: A guide about setpoint selection for deep dives Quote: (Originally Posted by ScubaDadMiami) I don't see why erring on the side of being somewhat overly cautious is a problem. You have a very good point. However, you can say the same about deco, gas selection, cell checking, redundancy etc etc. Where do you draw the line? The longer you are in the water, the longer you are at risk. I think arbitrarily changing setpoint "just in case" needs to be justified with this in mind. __________________ www.southwestmafia.com "small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!" The WRONG Attitude will get you killed. "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"
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18th April 2006, 18:57	#52 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,325	Re: A guide about setpoint selection for deep dives The deeper you are the less benefit high ppo2 gives you at depth from a subsequent deco perspective. Yet the CNS loading is the same at any depth. Toxing is more likely during the working part of the dive. You work harder at depth. It doesnt make sense to me to consider and act upon those facts Deep working part of the dive reduce the ppo2 down a bit, on ascent when resting on deco push it up a bit. Air breaks? pick up a reg and breathe! __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
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18th April 2006, 19:04	#53 (permalink)
dave t Custom Title Allowed! Current Rebreather/s: Inspiration Classic Inspiration Vision Evolution Sport Kiss Classic Kiss Dolphin Ray Azimuth Home Build Other Rebreather/s: Dolphin Ray Azimuth Home Build Join Date: May 2005 Location: UK Posts: 654	Re: A guide about setpoint selection for deep dives Quote: (Originally Posted by Drmike) Dave I think this is very dodgy and potentialy dangerous advice. Anyone wearing a ffm with a Rebreather should have a BOV fitted to it. Not to doesnt make any sense at all. If they convulse you just wait until they stop then turn the BOV to OC. You will see bubbles from the OC exhaust when/if they start breathing. Letting someone drown as a way to tell there airway is open enough to allow a 'safe' ascent is lunacy IMO. FFM+BOV. Ah, Mike wondered why I wasnt getting any stick from you over this, hows the Boris course? give my regards to Phil I can only speak as I find from practical experience (unfortunatly) and I didnt let him drown infact the surgeon said there was only a half teaspoon of water in his lungs and no I dont think I would have seen the gas coming out as there was not very much and I was worried that another convulsion was gonna hit. I did the best I could and formed my opinion based on that. If you would like to explain how a FFM will stop you from dying lets say on a hypoxic incident and you are diving on your own I am willing to learn Dave
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18th April 2006, 19:10	#54 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,325	Re: A guide about setpoint selection for deep dives Quote: (Originally Posted by Mdemon) You have a very good point. However, you can say the same about deco, gas selection, cell checking, redundancy etc etc. Where do you draw the line? The longer you are in the water, the longer you are at risk. I think arbitrarily changing setpoint "just in case" needs to be justified with this in mind. Remember we are talking about deep dives here. These tend to be one-dive- a-day afairs where there is less rush to get out as it were My aim naturaly is to get out of the water unbent and alive The time that it takes to do that is far-far-far less important than the above. Id rather do very long deco following models that are more man tested/verified and employ variable ppo2 setpoints to reduce risk of O2 toxing, than to get out the water a few hours quicker if I do so by increasing risk of DCS or toxing. Other than getting sat on by elephants theres not a lot of risk in sitting in a head pool after a deep cave dive, or reading a book on a deco platform. Its the quality of the deco that counts not the quantity (not my words but I think very wise ones) __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
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18th April 2006, 19:22	#55 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,325	Re: A guide about setpoint selection for deep dives Quote: (Originally Posted by dave t) Ah, Mike wondered why I wasnt getting any stick from you over this, hows the Boris course? give my regards to Phil I can only speak as I find from practical experience (unfortunatly) and I didnt let him drown infact the surgeon said there was only a half teaspoon of water in his lungs and no I dont think I would have seen the gas coming out as there was not very much and I was worried that another convulsion was gonna hit. I did the best I could and formed my opinion based on that. If you would like to explain how a FFM will stop you from dying lets say on a hypoxic incident and you are diving on your own I am willing to learn Dave When solo a hypoxic incident will kill you no matter if you are wearing a ffm or not - you die - a O2 convulsion only kills when the divers drown afterwards. FFM = no drowning. You may (when solo) be one of those who is not responsive enough after a hit to help yourself - but you might be one of those who is......personaly Id rather have the chance to find out Boris course was a huge amount of fun Phil is as mad as a box of frogs! Boris is brilliant __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
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18th April 2006, 19:26	#56 (permalink)
dave t Custom Title Allowed! Current Rebreather/s: Inspiration Classic Inspiration Vision Evolution Sport Kiss Classic Kiss Dolphin Ray Azimuth Home Build Other Rebreather/s: Dolphin Ray Azimuth Home Build Join Date: May 2005 Location: UK Posts: 654	Re: A guide about setpoint selection for deep dives Quote: (Originally Posted by Drmike) When solo a hypoxic incident will kill you no matter if you are wearing a ffm or not - you die - a O2 convulsion only kills when the divers drown afterwards. FFM = no drowning. You may (when solo) be one of those who is not responsive enough after a hit to help yourself - but you might be one of those who is......personaly Id rather have the chance to find out Boris course was a huge amount of fun Phil is as mad as a box of frogs! Boris is brilliant well at least we can agree about Phil
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18th April 2006, 20:41	#57 (permalink)
Genesis Bubbless Box of Death Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Oct 2005 Location: Sunny Florida Posts: 1,395	Re: A guide about setpoint selection for deep dives Couple things.... I like the "Air Break (Y/N)?" thing. But if you say "N", then the smart thing for the unit to do is raise hell (and KEEP raising hell) since the reason it called for it in the first place was due to excessive CNS loading...... As for a FFM if you have one AND retain the seal AND are rescued promptly it may save your azz. On the other hand if you DON'T retain the seal OR you're not rescued promptly its likely to make little if any difference in the outcome, only in the means of your death (suffocation/CO2 breakthrough .vs. drowning.) If nobody ELSE is there to trigger a BOV on your FFM after you tox you sure as hell aren't going to do it, and if you tox and are out of it for 30 minutes or more odds are you'll tox AGAIN during that 30 minute period since the cause hasn't been remedied. If you manage to trigger the BOV AS you are about to tox without help you're even more screwed since you'll run out of gas before you come around and are "alert". While a FFM certainly helps it is not a panacea AND it appears that the effort there is somewhat misplaced - it would be better spent understanding why the hits are happening and putting a stop to it. __________________ "A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American." http://www.denninger.net http://www.diversunion.org/liability.htm - Fix the Diving Cert racket
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28th April 2006, 17:22	#58 (permalink)
netmage Tim Owens Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Dec 2005 Location: Coconut Creek, FL Posts: 521	Re: A guide about setpoint selection for deep dives Cedric, Question from a noob.... I understand the concept of padding in a safety factor, longer time to approach the CNS limits, etc. However there doesn't seem to be an analysis of justifying why 1.0, vs. 1.1, 1.2, 0.9, etc... Deciding on 1.0 seems arbitrary.
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28th April 2006, 17:39	#59 (permalink)
JonnyB Johnny The Hatch Current Rebreather/s: MK 15.X Titan Other CCR Other SCR Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Megalodon Sport Kiss Classic Kiss Other CCR Other SCR Home Build Join Date: Jan 2005 Location: Sweden (Stockholm)/Cyprus(Ayia Napa) Posts: 970	Re: A guide about setpoint selection for deep dives Quote: (Originally Posted by netmage) Cedric, Question from a noob.... I understand the concept of padding in a safety factor, longer time to approach the CNS limits, etc. However there doesn't seem to be an analysis of justifying why 1.0, vs. 1.1, 1.2, 0.9, etc... Deciding on 1.0 seems arbitrary. There are probably many reasons for using 1.0 instead of .9 or 1.1 But one that comes to my mind straight away, using the meg that is. Is the HUD. Watching the HUD on 1.0 you will have orange, .9 you will have red and 1.1 you will have green, this makes it easy for you to see what happends with your ppO2. This is just to justify why 1.0 instead of .9 or 1.1 not, why to use lower SP instead of higher SP as described above. /Jonny __________________ A quote from Crazyduck - In remembering our own Rob Davies. "Outbound flight 777 heavy you are cleared for flight Due west into that warm red Texas sunset You have angels on your wings and divers memories on your six." Rest In Peace http://www.divetekcyprus.com http://www.diveccr.com
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28th April 2006, 22:51	#60 (permalink)
cedricverdier S21 M.I.B. Current Rebreather/s: Evolution Megalodon Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Sport Kiss Classic Kiss Join Date: Apr 2005 Location: Worldwide! Posts: 497	Re: A guide about setpoint selection for deep dives Quote: (Originally Posted by netmage) Cedric, Question from a noob.... I understand the concept of padding in a safety factor, longer time to approach the CNS limits, etc. However there doesn't seem to be an analysis of justifying why 1.0, vs. 1.1, 1.2, 0.9, etc... Deciding on 1.0 seems arbitrary. Hi, You're definitely right. 1.0 is only more practical to monitor on several rebreathers. It's also a good compromise between too low and too high, but 0.9 or 1.1 work as well. Cheers __________________ Cedric Verdier PADI Course Director, ANDI-IANTD-PSAI-TDI-DSAT-DAN-NAUI-CMAS Instructor Trainer Trimix (CCR and OC) and Cave Diving Instructor Trainer www.CedricVerdier.com DIRrebreather member
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