syncope ??

**fireman** · 10th August 2007, 18:46

Hey how about this: How many breaths would you have to take of air at 30ft from your OC bail out, before making an uncontrolled assent to the surface to not pass out?
Personally I would chill out for a while at depth on OC and try to figure out what just happend. Of course after frantically trying to inject O2...

AD_ward9 · 10th August 2007, 18:47

Quote: (Originally Posted by fireman)

Hey how about this: How many breaths would you have to take of air at 30ft from your OC bail out, before making an uncontrolled assent to the surface to not pass out?
Personally I would chill out for a while at depth on OC and try to figure out what just happend.

Not many. One full breath, from a fully expired lung would be enough, but the more the merrier.

Alex

**nigelh** · 10th August 2007, 19:10

Quote: (Originally Posted by AD_ward9)

You do not have an O2 tension in your blood of 0.21bar. Ever.

Agreed but 0.21bar inhaled gives 0.134bar blood but that's what I live on normally.
Everything factors from that.

Quote:

Back to the point, the oxygen saturation of your blood will fall instantly the PPO2 in your lungs falls. A lot of blood goes through your lungs every second.

Admittedly. As I said if I breathed 10% I'd be in trouble but I'm not taking in new gas to replace the old so the oxygen going into my lungs from my blood stays there.

I'm interested in the question of when do the expanding lungs start to leech oxygen from the blood because I've seen freedivers samba and this is put down to that, but that is after a high exercise period of several minutes. I just can't see blood oxygen crashing the way you describe on what is little short of a simple breath hold. I did wonder about trying a breath hold with a lung full of helium but decided it wouldn't prove anything as I would never know what the mix in the lungs was. (Also I'd have to find where I lost the finger clip blood oxy-meter first.)

I need numbers and I'm the wrong sort of physicist to have books on gas transfer across semi-permeable membranes in my workshop.

***Decodiver*** · 10th August 2007, 19:14

Quote: (Originally Posted by paulraymaekers)

euh, no!

I've sent it to you again.......

***Decodiver*** · 10th August 2007, 19:27

For me this is relatively simple.....

Take a breath of AIR at 10m on OC, remove your reg, blow bubbles and ascend and you will live. (PPO2 .42 at depth)(FO2 at surface (not counting what you metabolise) 0.21).

Christ, PADI have been doing this on their CESA from 6 metres for years.

Take a breath of loop gas at 0.21 PPO2, remove your DSV, blow bubbles and ascend to the surface and YOU WILL DIE. (PPO2 at depth 0.21)(FO2 at surface (not counting what you metabilise ) 0.105).

End of.

As Alex says, this is non-negotiable and really is CCR basics. I anally keep my PPO2 readout in front of my face when ascending from 6 metres, this really is the area where the inattentive just go to sleep............................................. ..................................forever.

If my students don't have their readouts in the same position they get a severe talking to.

Cheers,

Dave Cooper.

jasondrake · 10th August 2007, 20:40

I'm shit at maths so in the interests of science I just went diving with a willing support diver. Went to 10m on OC air, removed reg and held breath for one minute and 9 seconds, with an aim to lowering my blood pp02. This was as long as I could go at the time. Didn't hyperventilate or anything beforehand. I then took one inhale from the reg and finned hard for the surface while exhaling. I estimate I made the surface in less than 3 seconds.

I have absolutely no idea if this in any way adds anything at all to the discussion, I was just bored and wanted to test my torch so thought I'd do this too.

Nothing happened. Well, apart from me arriving at the surface feeling normal and retiring to the bar for a beer. And to dry out my flooded torch.

brinoz · 10th August 2007, 20:43

Quote: (Originally Posted by AD_ward9)

Back to the point, the oxygen saturation of your blood will fall instantly the PPO2 in your lungs falls. A lot of blood goes through your lungs every second.

Alex

I get it now. I had missed that point.

Bruno

**Dave Sutton** · 10th August 2007, 21:58

Be interesting to know the following:

Since I freedive spearfish a lot, and freedive to 15 meters pretty regularly for 60-90 seconds before ascent, what exactly is the PP02 of the gas in my lungs doing on ascent to the surface? My bet is that I surface *well* below 0.10, but anyone have any better numbers?

Basically, we hold the bottom until hypercapnia drives us to ascend, and then we're dealing with lowering PP02 as we make the surface. Metabolic levels are very low *until we leave the bottom* (we're ambush-hunting fish) and then go very high, as we drive back to the surface using our large leg muscles to push very stiff long-blade (1 metre) carbon-fiber fins (Omer C4's for other freedivers). You would think the combination of going from rest to high work, coupled with lowering PP02 on ascent after dropping F02 way down while stalking would result in shallow water blackout, yet (in our circles anyhow) we've never seen it. I do feel knackered after an hour or so of this, which is why I do it. It's wonderful physical conditioning.

So, here's the question: After a 90 second breath-hold, what's the F02 in the lung gas?

Dave

tibby · 11th August 2007, 03:21

Quote: (Originally Posted by Dave Sutton)

Be interesting to know the following:

Since I freedive spearfish a lot, and freedive to 15 meters pretty regularly for 60-90 seconds before ascent, what exactly is the PP02 of the gas in my lungs doing on ascent to the surface? My bet is that I surface *well* below 0.10, but anyone have any better numbers?

Basically, we hold the bottom until hypercapnia drives us to ascend, and then we're dealing with lowering PP02 as we make the surface. Metabolic levels are very low *until we leave the bottom* (we're ambush-hunting fish) and then go very high, as we drive back to the surface using our large leg muscles to push very stiff long-blade (1 metre) carbon-fiber fins (Omer C4's for other freedivers). You would think the combination of going from rest to high work, coupled with lowering PP02 on ascent after dropping F02 way down while stalking would result in shallow water blackout, yet (in our circles anyhow) we've never seen it. I do feel knackered after an hour or so of this, which is why I do it. It's wonderful physical conditioning.

So, here's the question: After a 90 second breath-hold, what's the F02 in the lung gas?

Dave

OK, I'll bite. So I took my MaxO2 analyzer, took a deep breath and exhaled in it. The Fo2 dropped from 21.9% to 12% without trying to hold my breath. Next I held a breath for 1min. and exhaled into the analyzer. This time it went down to 10% but by then I needed to inhale pretty badly so I stopped. It takes a while to exhale into the flow regulated tiny orifice you know!
I have no idea if this is a valid test but I've got nothing more interesting to do at the moment. How's that for anecdotal data?
Tibby

AD_ward9 · 11th August 2007, 06:32

Quote: (Originally Posted by tibby)

OK, I'll bite. So I took my MaxO2 analyzer, took a deep breath and exhaled in it. The Fo2 dropped from 21.9% to 12% without trying to hold my breath. Next I held a breath for 1min. and exhaled into the analyzer. This time it went down to 10% but by then I needed to inhale pretty badly so I stopped. It takes a while to exhale into the flow regulated tiny orifice you know!
I have no idea if this is a valid test but I've got nothing more interesting to do at the moment. How's that for anecdotal data?
Tibby

I explained the numbers for free diving and holding your breath in Post 22 of this thread. Again the maths are very simple, with the result very different from rebreather diving. Your numbers say the same thing. Incidentally, the PPO2 in your lungs drops when you exhale after a breath hold. The pressure goes from 1.1bar to 0.97. From the numbers you quote, you are typical diver fitness: the best freedivers can go 5 or 6 minutes for the same end point. Also, put your head in cold water for the test: it extends your breath holding range by slowing your metabolism.

I emphasise that a freediver is a closed system: that is the fundamental difference between holding your breath and ascending while exhaling from a rebreather. You cannot compare ascent from a rebreather with breath holding, and by making that analogy you fool yourself into taking an action that will kill you if you try it.

Moreover, Open Circuit diving is completely different again. Jason take note: your PPO2 in post 36 was 0.42 when you started your experiment, but what you did was hazardous because you hit the surface with a PPO2 of around 0.09 - with falling PPO2 you do not know how close you are to simply passing out. Rebreathers can be one breath from death machines. Read CeeBee's "Always Know your PPO2 Thread" before you go diving again - it may well save your life. The attachment to post 64 is the consequence so divers might want to think more carefully before new experiments, and the events are on the rest of the thread. CeeBee's husband died last year died doing effectively, just what you did Jason. Just like learning to drive gives a person a weighty responsibility, so does learning to dive.

This discussion has major ramifications in the Ethical Assessment for Rebreather Release which we are preparing just now. We will publish it in the near future. I puts the bar even higher for equipment designers, to have systems that do not kill untrained morons, because with all due respect, this discussion shows that a lot of sports divers are exactly that.

The training agencies need to pick up on this thread. They are failing to do their job. Meanwhile, it could save the life of any diver who could not answer this issue correctly in an instant to take a refresher course with Dave Cooper instructing.

Alex

10th August 2007, 18:46	#31 (permalink)
fireman rEvo combat swimmer Current Rebreather/s: rEvo Other CCR Other Rebreather/s: rEvo Other CCR Join Date: Nov 2006 Location: chicago Posts: 518	Re: syncope ?? Hey how about this: How many breaths would you have to take of air at 30ft from your OC bail out, before making an uncontrolled assent to the surface to not pass out? Personally I would chill out for a while at depth on OC and try to figure out what just happend. Of course after frantically trying to inject O2... __________________ Heres to you Capt. Bill Never Forget, and stay safe everyone.
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10th August 2007, 18:47	#32 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,864	Re: syncope ?? Quote: (Originally Posted by fireman) Hey how about this: How many breaths would you have to take of air at 30ft from your OC bail out, before making an uncontrolled assent to the surface to not pass out? Personally I would chill out for a while at depth on OC and try to figure out what just happend. Not many. One full breath, from a fully expired lung would be enough, but the more the merrier. Alex
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10th August 2007, 19:10	#33 (permalink)
nigelh New Member Current Rebreather/s: Inspiration Vision Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Mar 2005 Location: Brighton, Sussex, UK Posts: 838	Re: syncope ?? Quote: (Originally Posted by AD_ward9) You do not have an O2 tension in your blood of 0.21bar. Ever. Agreed but 0.21bar inhaled gives 0.134bar blood but that's what I live on normally. Everything factors from that. Quote: Back to the point, the oxygen saturation of your blood will fall instantly the PPO2 in your lungs falls. A lot of blood goes through your lungs every second. Admittedly. As I said if I breathed 10% I'd be in trouble but I'm not taking in new gas to replace the old so the oxygen going into my lungs from my blood stays there. I'm interested in the question of when do the expanding lungs start to leech oxygen from the blood because I've seen freedivers samba and this is put down to that, but that is after a high exercise period of several minutes. I just can't see blood oxygen crashing the way you describe on what is little short of a simple breath hold. I did wonder about trying a breath hold with a lung full of helium but decided it wouldn't prove anything as I would never know what the mix in the lungs was. (Also I'd have to find where I lost the finger clip blood oxy-meter first.) I need numbers and I'm the wrong sort of physicist to have books on gas transfer across semi-permeable membranes in my workshop. __________________ nigelh
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10th August 2007, 19:14	#34 (permalink)
*Decodiver* Administrator Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jan 2005 Location: Geneva Posts: 2,181	Re: syncope ?? Quote: (Originally Posted by paulraymaekers) euh, no! I've sent it to you again....... __________________ CCR/OC Trimix Instructor Trainer CCR Training to Mixed Gas in Switzerland, France, UK & Germany on Megalodon/COPIS-Megalodon/KISS/Sport KISS/Ouroboros/rEvo/Inspiration/Evolution/Sentinel www.zerogravitydiving.com Rebreather World Terms & Conditions
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10th August 2007, 19:27	#35 (permalink)
*Decodiver* Administrator Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jan 2005 Location: Geneva Posts: 2,181	Re: syncope ?? For me this is relatively simple..... Take a breath of AIR at 10m on OC, remove your reg, blow bubbles and ascend and you will live. (PPO2 .42 at depth)(FO2 at surface (not counting what you metabolise) 0.21). Christ, PADI have been doing this on their CESA from 6 metres for years. Take a breath of loop gas at 0.21 PPO2, remove your DSV, blow bubbles and ascend to the surface and YOU WILL DIE. (PPO2 at depth 0.21)(FO2 at surface (not counting what you metabilise ) 0.105). End of. As Alex says, this is non-negotiable and really is CCR basics. I anally keep my PPO2 readout in front of my face when ascending from 6 metres, this really is the area where the inattentive just go to sleep............................................. ..................................forever. If my students don't have their readouts in the same position they get a severe talking to. Cheers, Dave Cooper. __________________ CCR/OC Trimix Instructor Trainer CCR Training to Mixed Gas in Switzerland, France, UK & Germany on Megalodon/COPIS-Megalodon/KISS/Sport KISS/Ouroboros/rEvo/Inspiration/Evolution/Sentinel www.zerogravitydiving.com Rebreather World Terms & Conditions Last edited by Decodiver : 10th August 2007 at 20:23.
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10th August 2007, 20:40	#36 (permalink)
jasondrake New Member Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Nov 2005 Location: Completely homeless Posts: 76	Re: syncope ?? I'm shit at maths so in the interests of science I just went diving with a willing support diver. Went to 10m on OC air, removed reg and held breath for one minute and 9 seconds, with an aim to lowering my blood pp02. This was as long as I could go at the time. Didn't hyperventilate or anything beforehand. I then took one inhale from the reg and finned hard for the surface while exhaling. I estimate I made the surface in less than 3 seconds. I have absolutely no idea if this in any way adds anything at all to the discussion, I was just bored and wanted to test my torch so thought I'd do this too. Nothing happened. Well, apart from me arriving at the surface feeling normal and retiring to the bar for a beer. And to dry out my flooded torch.
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10th August 2007, 20:43	#37 (permalink)
brinoz New Member Current Rebreather/s: rEvo Other Rebreather/s: rEvo Join Date: Sep 2006 Location: Belgium Posts: 52	Re: syncope ?? Quote: (Originally Posted by AD_ward9) Back to the point, the oxygen saturation of your blood will fall instantly the PPO2 in your lungs falls. A lot of blood goes through your lungs every second. Alex I get it now. I had missed that point. Bruno
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10th August 2007, 21:58	#38 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Classic Kiss rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,672	Re: syncope ?? Be interesting to know the following: Since I freedive spearfish a lot, and freedive to 15 meters pretty regularly for 60-90 seconds before ascent, what exactly is the PP02 of the gas in my lungs doing on ascent to the surface? My bet is that I surface well below 0.10, but anyone have any better numbers? Basically, we hold the bottom until hypercapnia drives us to ascend, and then we're dealing with lowering PP02 as we make the surface. Metabolic levels are very low until we leave the bottom (we're ambush-hunting fish) and then go very high, as we drive back to the surface using our large leg muscles to push very stiff long-blade (1 metre) carbon-fiber fins (Omer C4's for other freedivers). You would think the combination of going from rest to high work, coupled with lowering PP02 on ascent after dropping F02 way down while stalking would result in shallow water blackout, yet (in our circles anyhow) we've never seen it. I do feel knackered after an hour or so of this, which is why I do it. It's wonderful physical conditioning. So, here's the question: After a 90 second breath-hold, what's the F02 in the lung gas? Dave __________________ "Changes in Lattitudes, Changes in Attitudes, Nothing remains quite the same".... www.nobubblediving.com Last edited by Dave Sutton : 10th August 2007 at 22:00.
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11th August 2007, 03:21	#39 (permalink)
tibby untitled Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: May 2007 Location: Salt Lake City, UT Posts: 338	Re: syncope ?? Quote: (Originally Posted by Dave Sutton) Be interesting to know the following: Since I freedive spearfish a lot, and freedive to 15 meters pretty regularly for 60-90 seconds before ascent, what exactly is the PP02 of the gas in my lungs doing on ascent to the surface? My bet is that I surface well below 0.10, but anyone have any better numbers? Basically, we hold the bottom until hypercapnia drives us to ascend, and then we're dealing with lowering PP02 as we make the surface. Metabolic levels are very low until we leave the bottom (we're ambush-hunting fish) and then go very high, as we drive back to the surface using our large leg muscles to push very stiff long-blade (1 metre) carbon-fiber fins (Omer C4's for other freedivers). You would think the combination of going from rest to high work, coupled with lowering PP02 on ascent after dropping F02 way down while stalking would result in shallow water blackout, yet (in our circles anyhow) we've never seen it. I do feel knackered after an hour or so of this, which is why I do it. It's wonderful physical conditioning. So, here's the question: After a 90 second breath-hold, what's the F02 in the lung gas? Dave OK, I'll bite. So I took my MaxO2 analyzer, took a deep breath and exhaled in it. The Fo2 dropped from 21.9% to 12% without trying to hold my breath. Next I held a breath for 1min. and exhaled into the analyzer. This time it went down to 10% but by then I needed to inhale pretty badly so I stopped. It takes a while to exhale into the flow regulated tiny orifice you know! I have no idea if this is a valid test but I've got nothing more interesting to do at the moment. How's that for anecdotal data? Tibby
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11th August 2007, 06:32	#40 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,864	Re: syncope ?? Quote: (Originally Posted by tibby) OK, I'll bite. So I took my MaxO2 analyzer, took a deep breath and exhaled in it. The Fo2 dropped from 21.9% to 12% without trying to hold my breath. Next I held a breath for 1min. and exhaled into the analyzer. This time it went down to 10% but by then I needed to inhale pretty badly so I stopped. It takes a while to exhale into the flow regulated tiny orifice you know! I have no idea if this is a valid test but I've got nothing more interesting to do at the moment. How's that for anecdotal data? Tibby I explained the numbers for free diving and holding your breath in Post 22 of this thread. Again the maths are very simple, with the result very different from rebreather diving. Your numbers say the same thing. Incidentally, the PPO2 in your lungs drops when you exhale after a breath hold. The pressure goes from 1.1bar to 0.97. From the numbers you quote, you are typical diver fitness: the best freedivers can go 5 or 6 minutes for the same end point. Also, put your head in cold water for the test: it extends your breath holding range by slowing your metabolism. I emphasise that a freediver is a closed system: that is the fundamental difference between holding your breath and ascending while exhaling from a rebreather. You cannot compare ascent from a rebreather with breath holding, and by making that analogy you fool yourself into taking an action that will kill you if you try it. Moreover, Open Circuit diving is completely different again. Jason take note: your PPO2 in post 36 was 0.42 when you started your experiment, but what you did was hazardous because you hit the surface with a PPO2 of around 0.09 - with falling PPO2 you do not know how close you are to simply passing out. Rebreathers can be one breath from death machines. Read CeeBee's "Always Know your PPO2 Thread" before you go diving again - it may well save your life. The attachment to post 64 is the consequence so divers might want to think more carefully before new experiments, and the events are on the rest of the thread. CeeBee's husband died last year died doing effectively, just what you did Jason. Just like learning to drive gives a person a weighty responsibility, so does learning to dive. This discussion has major ramifications in the Ethical Assessment for Rebreather Release which we are preparing just now. We will publish it in the near future. I puts the bar even higher for equipment designers, to have systems that do not kill untrained morons, because with all due respect, this discussion shows that a lot of sports divers are exactly that. The training agencies need to pick up on this thread. They are failing to do their job. Meanwhile, it could save the life of any diver who could not answer this issue correctly in an instant to take a refresher course with Dave Cooper instructing. Alex Last edited by AD_ward9 : 11th August 2007 at 14:48.
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