Is a BOW fast enough to save a life?

depth · 7th June 2007, 05:59

Thanx for all the input so far.

I actually bailed to OC at 42m in Norway a few months ago myself. I learned a valuable lesson. I was descending on the slopping wreck. At my target depth i checked my primary which was blank, operating the buttons did no difference. I decided to bailout on OC pronto for a couple of reasons:

1. I was diving with air dil. and the nitrogen pressure blocked the part of my brain that would have informed me that i had a HUD that was functioning perfectly 10cm from my eye, and that I could perform a dil. flush ;-)
2. My immediate thought was that i had not checked my PO2 for at least one minute and i did not know what i was breathing and for how long, i did not want to take any chances.

Together with my two buddy's i swam to the ascent line where i made my first stop at about 21m. Here i checked the Rebreather and now everything was working as normal. I checked both handset and compared the cell readings, they were identical. I switched to the RB again and did the deco, constantly monitoring the primary and my HUD to be safe. No more problems from here on.

I also found the problem with my Meg, before the trip, I made two new battery packs and installed them in the Rebreather. I'll never do that again, more than one connection in both packs was loose. The chain is not stronger than the weakest link! I promised myself that i would never again save a few bucks and compromise my own life. Only factory battery packs from now on!

So this is what i will do from now on:

- Train my drills so they become second nature
- Set up my equipment, and train, so I can make an OC bailout faster
- Do my trimix course on the Rebreather with Rasmus Lauritsen, so i can use tx as dil. and be less influenced by nitrogen.
- Save up for a BOV

***schford*** · 7th June 2007, 08:36

Hi Depth,

Did no one teach you Open Loop as the first stage of Bailout on your Meg - as that is Leons preferred method...

Open Loop has been explained in the posts above - which is breath out through nose and in through mouth causing the ADV to fire - to speed it up you can crush lungs and hit the ADV with yoru hand for a big whoooosh of good gas.

Stuart

depth · 7th June 2007, 08:56

Hi Stuart

Quote:

Open Loop has been explained in the posts above - which is breath out through nose and in through mouth causing the ADV to fire - to speed it up you can crush lungs and hit the ADV with yoru hand for a big whoooosh of good gas

My bad, that is what i ment with a flush. Yes i was tought this during my course! ;-)

Christian

***schford*** · 7th June 2007, 09:23

Great - Rasmus as a top Bloke and I am sure you would have been....

So back to your original post....

Quote:

If I suddently feel that something is wrong, my thoughts on OC bailout are:

- There is NO WAY I have time to reach down for my OC bailout second stage and switch

For the above as long as you have loop integrity than Open Loop should be your first option with out really thinking about it - you dont have to take anything out of your mouth - you dont need fine motor control skills to twist a BOV (with a bad hit)...

It you have too high PPO2 then Open Loop will bring it down if you have too high PPCO2 than Open Loop will bring it down - if you want it brought down quickly then crush your lungs and fire that ADV and within a second or two you will be breathing fresh gas - then you can bring your breathing under control (hopefully you have enough gas) then switch to your OC bailout.

My personal belief is that if you have your BOV blumbed into your onboard DIL then it does nothing for you over and above going Open Loop - Your BOV should be plugged into your offboard bailout so you have access to a much bigger gas supply which in the event of a CO2 hit gives you more chance of getting your breathing under control.

I would stress though I have never had a CO2 hit and only ever had to bailout twice so I dont profess to be an expert!

PCDiver · 7th June 2007, 09:40

Quote: (Originally Posted by schford)

Great - Rasmus as a top Bloke and I am sure you would have been....

So back to your original post....

For the above as long as you have loop integrity than Open Loop should be your first option with out really thinking about it - you dont have to take anything out of your mouth - you dont need fine motor control skills to twist a BOV (with a bad hit)...

It you have too high PPO2 then Open Loop will bring it down if you have too high PPCO2 than Open Loop will bring it down - if you want it brought down quickly then crush your lungs and fire that ADV and within a second or two you will be breathing fresh gas - then you can bring your breathing under control (hopefully you have enough gas) then switch to your OC bailout.

My personal belief is that if you have your BOV blumbed into your onboard DIL then it does nothing for you over and above going Open Loop - Your BOV should be plugged into your offboard bailout so you have access to a much bigger gas supply which in the event of a CO2 hit gives you more chance of getting your breathing under control.

I would stress though I have never had a CO2 hit and only ever had to bailout twice so I dont profess to be an expert!

Stuart I agree that for deeper dives you should be able to access your bailout gas via your BOV.

I do question open loop as a valid bailout method in case of a CO2 hit. During a CO2 hit, either from CO2 retention or CO2 breakthru, your breathing will be extremely rapid, uncontrolled and very shallow. Open loop only works if you can control your breathing, in via the mouth, out via the nose and lots of lung volume. This is not really the case during a CO2 hit. For me, a BOV is the only solution when CO2 rears its ugly head.

In addition, lots of divers close their ADV at the bottom part of the dive.

Peter

Drmike · 7th June 2007, 10:33

Quote: (Originally Posted by PCDiver)

Stuart I agree that for deeper dives you should be able to access your bailout gas via your BOV.

I do question open loop as a valid bailout method in case of a CO2 hit. During a CO2 hit, either from CO2 retention or CO2 breakthru, your breathing will be extremely rapid, uncontrolled and very shallow. Open loop only works if you can control your breathing, in via the mouth, out via the nose and lots of lung volume. This is not really the case during a CO2 hit. For me, a BOV is the only solution when CO2 rears its ugly head.

In addition, lots of divers close their ADV at the bottom part of the dive.

Peter

If I was having a full on CO2 hit I would go OC as fast as possible via whatever means

The point (to me at least) of open loop is to stop the runnaway respiratory train before a full on disabiliating CO2 hit makes it impossible.

Its preventative rather than a cure. If I start to feel even slightly wierder than normal (be that elevated breathing rate, confusion, stress or whatever - I imediately and now instinctively go open loop and then review - If I keep feeling weird or it gets worse its imediate bov or OC bail (im only talking about 10s of seconds here not mins). Thats my method anyway. To me the advantage is it becomes instinctive. I find myself going open loop without even thinking about it as a natural instinct/reaction to increased breathing rate/feeling of retained CO2 - even on perfectly good scrubbers - just because Im working a bit too hard. It may be uneccessary and a waste of dil - but it adds a little insurance during times of hard work/risk. I usually catch myself doing it most on descent in hard currents as I near target depth.

I have had a number of CO2 build ups to what, if left unattended to, would have likely ended up being a full on hit and so far (in my case) I had quite a bit of warning (via increased rate of breathing and feeling of confusion/stress/darkness) but I know not all hits are the same or all people react the same.

Basically - to summarise if I dont know whats wrong but sense something m,ight be its open loop to see whats wrong. If I know Im having a CO2 or O2 hit its OC bail (via BOV preferably)

I agree if you are having a CO2 hit - as in your breathing rate is aleady sky high open loop is crap, switching to an OC 2nd stage is likely not possible - bov is the best way

***schford*** · 7th June 2007, 11:02

I have had no direct experience of this but I was informed that if you have a bad CO2 hit you loose fine motor muscle control and might not be able to operate the DSV lever.

My memory is rusting Mike - but didnt you have a hit once where the only thing you could do was go Open Loop to bring your breathing back under control (my memory could be wrong here).

***schford*** · 7th June 2007, 11:14

Quote: (Originally Posted by PCDiver)

In addition, lots of divers close their ADV at the bottom part of the dive.

Peter

Thats a really really good point.....and one I had not properly considered.

Stuart

**trob09** · 7th June 2007, 11:43

Quote: (Originally Posted by schford)

Thats a really really good point.....and one I had not properly considered.

Stuart

This is part of the reason I decided that open loop wasn't really the "total answer" it's been purported to be. All of my rebreather instructors advocate closing the isolator valve upon reaching the the bottom. If fine motor skill is going to stop you from switching to OC on a BOV, it's also going to stop you from opening the isolator valve on an ADV and going open loop (Provided your unit has an isolator valve).

Open loop is a great tool and one that deserves to be in the toolbox. but just as the screwdriver doesn't do the job of a hammer/wrench/saw/etc., open loop is not the answer to every gas-need problem.

Gilles · 7th June 2007, 11:47

Quote: (Originally Posted by PCDiver)

In addition, lots of divers close their ADV at the bottom part of the dive.

Peter

In light of this discussion, should one be shutting their ADV off on bottom? Shouldn't one avoid doing so until the ascent phase begins?

Unsure about other units, but on the Meg a very simple/quick reflex completely flushes your loop in about 5 seconds (assuming your flowstop is already open).

7th June 2007, 05:59	#21 (permalink)
depth Christian Rasmussen Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Aug 2006 Location: Denmark Posts: 190	Re: Is a BOW fast enough to save a life? Thanx for all the input so far. I actually bailed to OC at 42m in Norway a few months ago myself. I learned a valuable lesson. I was descending on the slopping wreck. At my target depth i checked my primary which was blank, operating the buttons did no difference. I decided to bailout on OC pronto for a couple of reasons: 1. I was diving with air dil. and the nitrogen pressure blocked the part of my brain that would have informed me that i had a HUD that was functioning perfectly 10cm from my eye, and that I could perform a dil. flush ;-) 2. My immediate thought was that i had not checked my PO2 for at least one minute and i did not know what i was breathing and for how long, i did not want to take any chances. Together with my two buddy's i swam to the ascent line where i made my first stop at about 21m. Here i checked the Rebreather and now everything was working as normal. I checked both handset and compared the cell readings, they were identical. I switched to the RB again and did the deco, constantly monitoring the primary and my HUD to be safe. No more problems from here on. I also found the problem with my Meg, before the trip, I made two new battery packs and installed them in the Rebreather. I'll never do that again, more than one connection in both packs was loose. The chain is not stronger than the weakest link! I promised myself that i would never again save a few bucks and compromise my own life. Only factory battery packs from now on! So this is what i will do from now on: - Train my drills so they become second nature - Set up my equipment, and train, so I can make an OC bailout faster - Do my trimix course on the Rebreather with Rasmus Lauritsen, so i can use tx as dil. and be less influenced by nitrogen. - Save up for a BOV __________________ I am not qualified to make my own meg batteries!!! I am not qualified to make my own meg batteries!!! I am not qualified to make my own meg batteries!!! I am not qualified to make my own meg batteries!!! I am not.............
(Online)

7th June 2007, 08:36	#22 (permalink)
*schford* Despotic Overlord Current Rebreather/s: Megalodon Sport Kiss Other Rebreather/s: Join Date: Jan 2005 Location: London, UK Posts: 3,687	Re: Is a BOW fast enough to save a life? Hi Depth, Did no one teach you Open Loop as the first stage of Bailout on your Meg - as that is Leons preferred method... Open Loop has been explained in the posts above - which is breath out through nose and in through mouth causing the ADV to fire - to speed it up you can crush lungs and hit the ADV with yoru hand for a big whoooosh of good gas. Stuart __________________ Bailout and Kit Management account for Murphy's Law The only bad question is one you did not ask and later wish you had. Use of Rebreather World is subject to the Rebreather World Terms & Conditions of Use
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7th June 2007, 08:56	#23 (permalink)
depth Christian Rasmussen Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Aug 2006 Location: Denmark Posts: 190	Re: Is a BOW fast enough to save a life? Hi Stuart Quote: Open Loop has been explained in the posts above - which is breath out through nose and in through mouth causing the ADV to fire - to speed it up you can crush lungs and hit the ADV with yoru hand for a big whoooosh of good gas My bad, that is what i ment with a flush. Yes i was tought this during my course! ;-) Christian __________________ I am not qualified to make my own meg batteries!!! I am not qualified to make my own meg batteries!!! I am not qualified to make my own meg batteries!!! I am not qualified to make my own meg batteries!!! I am not.............
(Online)

7th June 2007, 09:23	#24 (permalink)
*schford* Despotic Overlord Current Rebreather/s: Megalodon Sport Kiss Other Rebreather/s: Join Date: Jan 2005 Location: London, UK Posts: 3,687	Re: Is a BOW fast enough to save a life? Great - Rasmus as a top Bloke and I am sure you would have been.... So back to your original post.... Quote: If I suddently feel that something is wrong, my thoughts on OC bailout are: - There is NO WAY I have time to reach down for my OC bailout second stage and switch For the above as long as you have loop integrity than Open Loop should be your first option with out really thinking about it - you dont have to take anything out of your mouth - you dont need fine motor control skills to twist a BOV (with a bad hit)... It you have too high PPO2 then Open Loop will bring it down if you have too high PPCO2 than Open Loop will bring it down - if you want it brought down quickly then crush your lungs and fire that ADV and within a second or two you will be breathing fresh gas - then you can bring your breathing under control (hopefully you have enough gas) then switch to your OC bailout. My personal belief is that if you have your BOV blumbed into your onboard DIL then it does nothing for you over and above going Open Loop - Your BOV should be plugged into your offboard bailout so you have access to a much bigger gas supply which in the event of a CO2 hit gives you more chance of getting your breathing under control. I would stress though I have never had a CO2 hit and only ever had to bailout twice so I dont profess to be an expert! __________________ Bailout and Kit Management account for Murphy's Law The only bad question is one you did not ask and later wish you had. Use of Rebreather World is subject to the Rebreather World Terms & Conditions of Use
(Offline)

7th June 2007, 09:40	#25 (permalink)
PCDiver Submerge Productions Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Belgium Posts: 962	Re: Is a BOW fast enough to save a life? Quote: (Originally Posted by schford) Great - Rasmus as a top Bloke and I am sure you would have been.... So back to your original post.... For the above as long as you have loop integrity than Open Loop should be your first option with out really thinking about it - you dont have to take anything out of your mouth - you dont need fine motor control skills to twist a BOV (with a bad hit)... It you have too high PPO2 then Open Loop will bring it down if you have too high PPCO2 than Open Loop will bring it down - if you want it brought down quickly then crush your lungs and fire that ADV and within a second or two you will be breathing fresh gas - then you can bring your breathing under control (hopefully you have enough gas) then switch to your OC bailout. My personal belief is that if you have your BOV blumbed into your onboard DIL then it does nothing for you over and above going Open Loop - Your BOV should be plugged into your offboard bailout so you have access to a much bigger gas supply which in the event of a CO2 hit gives you more chance of getting your breathing under control. I would stress though I have never had a CO2 hit and only ever had to bailout twice so I dont profess to be an expert! Stuart I agree that for deeper dives you should be able to access your bailout gas via your BOV. I do question open loop as a valid bailout method in case of a CO2 hit. During a CO2 hit, either from CO2 retention or CO2 breakthru, your breathing will be extremely rapid, uncontrolled and very shallow. Open loop only works if you can control your breathing, in via the mouth, out via the nose and lots of lung volume. This is not really the case during a CO2 hit. For me, a BOV is the only solution when CO2 rears its ugly head. In addition, lots of divers close their ADV at the bottom part of the dive. Peter
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7th June 2007, 10:33	#26 (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: 3,303	Re: Is a BOW fast enough to save a life? Quote: (Originally Posted by PCDiver) Stuart I agree that for deeper dives you should be able to access your bailout gas via your BOV. I do question open loop as a valid bailout method in case of a CO2 hit. During a CO2 hit, either from CO2 retention or CO2 breakthru, your breathing will be extremely rapid, uncontrolled and very shallow. Open loop only works if you can control your breathing, in via the mouth, out via the nose and lots of lung volume. This is not really the case during a CO2 hit. For me, a BOV is the only solution when CO2 rears its ugly head. In addition, lots of divers close their ADV at the bottom part of the dive. Peter If I was having a full on CO2 hit I would go OC as fast as possible via whatever means The point (to me at least) of open loop is to stop the runnaway respiratory train before a full on disabiliating CO2 hit makes it impossible. Its preventative rather than a cure. If I start to feel even slightly wierder than normal (be that elevated breathing rate, confusion, stress or whatever - I imediately and now instinctively go open loop and then review - If I keep feeling weird or it gets worse its imediate bov or OC bail (im only talking about 10s of seconds here not mins). Thats my method anyway. To me the advantage is it becomes instinctive. I find myself going open loop without even thinking about it as a natural instinct/reaction to increased breathing rate/feeling of retained CO2 - even on perfectly good scrubbers - just because Im working a bit too hard. It may be uneccessary and a waste of dil - but it adds a little insurance during times of hard work/risk. I usually catch myself doing it most on descent in hard currents as I near target depth. I have had a number of CO2 build ups to what, if left unattended to, would have likely ended up being a full on hit and so far (in my case) I had quite a bit of warning (via increased rate of breathing and feeling of confusion/stress/darkness) but I know not all hits are the same or all people react the same. Basically - to summarise if I dont know whats wrong but sense something m,ight be its open loop to see whats wrong. If I know Im having a CO2 or O2 hit its OC bail (via BOV preferably) I agree if you are having a CO2 hit - as in your breathing rate is aleady sky high open loop is crap, switching to an OC 2nd stage is likely not possible - bov is the best way __________________ 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 Last edited by Drmike : 7th June 2007 at 10:43.
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7th June 2007, 11:02	#27 (permalink)
*schford* Despotic Overlord Current Rebreather/s: Megalodon Sport Kiss Other Rebreather/s: Join Date: Jan 2005 Location: London, UK Posts: 3,687	Re: Is a BOW fast enough to save a life? I have had no direct experience of this but I was informed that if you have a bad CO2 hit you loose fine motor muscle control and might not be able to operate the DSV lever. My memory is rusting Mike - but didnt you have a hit once where the only thing you could do was go Open Loop to bring your breathing back under control (my memory could be wrong here). __________________ Bailout and Kit Management account for Murphy's Law The only bad question is one you did not ask and later wish you had. Use of Rebreather World is subject to the Rebreather World Terms & Conditions of Use
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7th June 2007, 11:14	#28 (permalink)
*schford* Despotic Overlord Current Rebreather/s: Megalodon Sport Kiss Other Rebreather/s: Join Date: Jan 2005 Location: London, UK Posts: 3,687	Re: Is a BOW fast enough to save a life? Quote: (Originally Posted by PCDiver) In addition, lots of divers close their ADV at the bottom part of the dive. Peter Thats a really really good point.....and one I had not properly considered. Stuart __________________ Bailout and Kit Management account for Murphy's Law The only bad question is one you did not ask and later wish you had. Use of Rebreather World is subject to the Rebreather World Terms & Conditions of Use
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7th June 2007, 11:43	#29 (permalink)
trob09 . Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Posts: 704	Re: Is a BOW fast enough to save a life? Quote: (Originally Posted by schford) Thats a really really good point.....and one I had not properly considered. Stuart This is part of the reason I decided that open loop wasn't really the "total answer" it's been purported to be. All of my rebreather instructors advocate closing the isolator valve upon reaching the the bottom. If fine motor skill is going to stop you from switching to OC on a BOV, it's also going to stop you from opening the isolator valve on an ADV and going open loop (Provided your unit has an isolator valve). Open loop is a great tool and one that deserves to be in the toolbox. but just as the screwdriver doesn't do the job of a hammer/wrench/saw/etc., open loop is not the answer to every gas-need problem.
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7th June 2007, 11:47	#30 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 762	Re: Is a BOW fast enough to save a life? Quote: (Originally Posted by PCDiver) In addition, lots of divers close their ADV at the bottom part of the dive. Peter In light of this discussion, should one be shutting their ADV off on bottom? Shouldn't one avoid doing so until the ascent phase begins? Unsure about other units, but on the Meg a very simple/quick reflex completely flushes your loop in about 5 seconds (assuming your flowstop is already open). __________________ Gilles http://www.dirrebreather.com
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