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Utrinque Paratus
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Discussion Starter · #1 ·
just a follow on from the thread deep air, as i don't want to hijack Brains thread

if your last stop on a dive was 36 minutes on O2 how would you break that up if at all?

would you count the back gas breaks as part of the deco?

if you don't break it up how long would you stay on O2 before you would have breaks?

or are you happier using the 80%?

Graham
 

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If I wanted 36 minutes personally I'd do:

12 on
6 off
12 on
6 up (staying on O2)

Whether you count it or not depends on how you feel, how aggresive the deco is, how short the O2 time is (and therefore how much as a percentage of O2 time you are missing by counting the 'off' time). If in doubt or unhappy with the pattern then do more time.

I'd happily do up to 20 minutes on O2 and then a 5 minute ascent without taking a break but a 12 on 6 off pattern is a reasonable pattern to adopt for longer exposures. Would 10 and 5 work just as well? Of course it would, so choose what suits you for your diving.
 

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Wreck and Cave Diver
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just a follow on from the thread deep air, as i don't want to hijack Brains thread

if your last stop on a dive was 36 minutes on O how would you break that up if at all?

would you count the back gas breaks as part of the deco?

if you don't break it up how long would you stay on O before you would have breaks?

or are you happier using the 80%?

Graham


Our concerns with high POP gases are the effect that the O2 has on the lungs. As we know O2 is an irritant and anything above 0.5 PPO2 has a negative effect. So it does not really matter whether you use 80% or 100% both over time will have act as an irritant to the lungs ( pulmonary toxicity)

So what we are attempting to do with air breaks is to reduce to a minimum the effect of the O2 and keep the alveoli running at full speed.

Pulmonary toxicity is time dose dependent, so if you had been running high PPO2's during the bottom phase of the dive, then additional high exposures during deco would not only increase pulmonary tox, but also the likelihood of Oxtox.

Due to the effect of the gas breaks our lungs maintain a greater level of efficiency than without - I guess the secret is the how often should the gas breaks be? (a gas break is a break to the lowest breathable PPO2 that you have with you)

Over long periods of time 20 on and 5 off seems to start frying lungs, but anecdotally 12 on 6 off does not appear to have the same impact.

So with Graham's 36 minutes on O2, you could do 12 on 6 off, 12 on and 6 up. This keeps the clock running

Andy

PS I would not use 80%, as it still contains Nitrogen, and I would still be ongassing Nitrogen.
 

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For a little more history on how they picked 20 on/ 5 off protocol to start with:

Extension of oxygen tolerance by interrupted exposure.
Clark. Undersea Hyperb Med. 2004 Summer;31(2):195-8.
RRR ID: 4009

Andy gave an excellent explanation of the development of 12 on/ 6 off here.
 

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If your worried about 36mins on 1.6 slide to 5 half your load ,

I don’t do air brakes but if I did I would not count air as part of my deco ,

the old numbers were 1min @ 1.6ppo2 = 5 mis on air

newer numbers are about 1min @ 1.6ppo2 = 2,5 0n air

so if you went with the old numbers you could still do one or two 5 min air brakes
and still have done the right amount deco to come out ok ,

but if you go with the new thinking , then you have missed a bit of deco

ps

if your running your deco with a big Safety margin then you will be o.k.
as your getting more dceo to do in the first place

hope that BS helps :teeth:
 

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Wreck and Cave Diver
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If you read the reference in Gene's post you will see that 20 on and 5 off does lead to a 4% vital capacity reduction over time.

So if we use this method we are reducing the efficiency of our lungs, for short deco times 30/40 minutes this probably does not really matter, but for longer exposures it must make a difference.

So apart from shortening the exposure times its good to have a protocol thats nice and simple to remember.

Andy
 

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If you read the reference in Gene's post you will see that 20 on and 5 off does lead to a 4% vital capacity reduction over time.

So if we use this method we are reducing the efficiency of our lungs, for short deco times 30/40 minutes this probably does not really matter, but for longer exposures it must make a difference.

So apart from shortening the exposure times its good to have a protocol thats nice and simple to remember.

Andy
:thumbsup: yes its all down to time , and milldog is diving Oc for less than 140 mis in water time i would think , Do you can class that as short exposure time
 

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Wreck and Cave Diver
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:thumbsup: yes its all down to time , and milldog is diving Oc for less than 140 mis in water time i would think , Do you can class that as short exposure time
Its time and dose dependant, so it would depend on what PPO2's are being run on the dive. 140 mins is not a long dive (its long enough in the sea !) but it makes sense to have a simple protocol, rather than keep changing it based on shorter/longer durations.

Andy
 

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Utrinque Paratus
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Discussion Starter · #9 ·
there is talk that on 100% after leaving the water you feel better than if you were on the 80% until the O2 calming effect happens and wipes you out, but thats another thread.

the sort of run times i would be looking at were in the 124 to 145 minutes with ppo2 of 1.4 bottom and 1.6 deco running on 15/55, 21/35, 50% and 100% funny but the GUE planner doesn't do air breaks? anyway this would be a short exposure.

I'm interested to see who would go straight through the 36 Min's on the 100% without breaks

Graham
 

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Its time and dose dependant, so it would depend on what PPO2's are being run on the dive. 140 mins is not a long dive (its long enough in the sea !) but it makes sense to have a simple protocol, rather than keep changing it based on shorter/longer durations.

Andy
i can live with that :teeth:
 

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there is talk that on 100% after leaving the water you feel better than if you were on the 80% until the O2 calming effect happens and wipes you out, but thats another thread.

the sort of run times i would be looking at were in the 124 to 145 minutes with ppo2 of 1.4 bottom and 1.6 deco running on 15/55, 21/35, 50% and 100% funny but the GUE planner doesn't do air breaks? anyway this would be a short exposure.

I'm interested to see who would go straight through the 36 Min's on the 100% without breaks

Graham
The dive is a bit hot for me in terms of po2's, using the full 1.4 po2 on the bottom with 15/55. I pulled it through HLplanner and you get a 25 min bottom time at 83 mtrs and 130 mins run time, so I guess that is the kind of plan you are looking at. You also go over 100% CNS on this dive plan, so breaks might need to be considered to avoid the risk of oxygen toxicity, depending on how much faith you put in the % numbers.

On the previous thread you stated the o2 time as 30 mins and I said that I would do 20 on 10 up if it was my only dive of the day and wasn't in the middle of a bunch of diving days, but this is all based on using a po2 of 1.0-1.2 on the bottom and only going to 1.6 po2 from say 36 mtrs up.

I wouldn't do 36 mins all on o2, 12 on 6 off 12 on 6 up. There's only a 6 minute break in there, but I believe this makes the deco more efficient, and should not be detrimental to your deco, staving off the oxtox demon as well.

Andy
 

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Utrinque Paratus
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Discussion Starter · #12 · (Edited)
Examples Only!!!

Plan A

Dec to 85m (4) Trimix 15/55 18m/min descent.
Level 85m 25:17 (30) Trimix 15/55 1.42 ppO2, 26m ead, 33m end
Asc to 63m (31) Trimix 15/55 -18m/min ascent.
Asc to 60m (31) Triox 21/35 -18m/min ascent.
Stop at 60m 0:37 (32) Triox 21/35 1.46 ppO2, 29m ead, 35m end
Stop at 54m 1:00 (33) Triox 21/35 1.34 ppO2, 26m ead, 32m end
Stop at 48m 3:00 (36) Triox 21/35 1.21 ppO2, 22m ead, 28m end
Stop at 42m 1:00 (37) Triox 21/35 1.09 ppO2, 19m ead, 24m end
Stop at 39m 2:00 (39) Triox 21/35 1.02 ppO2, 17m ead, 22m end
Stop at 36m 2:00 (41) Triox 21/35 0.96 ppO2, 16m ead, 20m end
Stop at 33m 2:00 (43) Triox 21/35 0.90 ppO2, 14m ead, 18m end
Stop at 30m 3:00 (46) Triox 21/35 0.84 ppO2, 12m ead, 16m end
Stop at 27m 4:00 (50) Triox 21/35 0.77 ppO2, 11m ead, 14m end
Stop at 24m 4:00 (54) Triox 21/35 0.71 ppO2, 9m ead, 12m end
Stop at 21m 6:00 (60) Nitrox 50 1.54 ppO2, 10m ead
Stop at 18m 2:00 (62) Nitrox 50 1.39 ppO2, 8m ead
Stop at 15m 7:00 (69) Nitrox 50 1.24 ppO2, 6m ead
Stop at 12m 9:00 (78) Nitrox 50 1.10 ppO2, 4m ead
Stop at 9m 13:00 (91) Nitrox 80 1.51 ppO2, 0m ead
Stop at 6m 50:00 (141) Nitrox 80 1.28 ppO2, 0m ead
Surface (147) Nitrox 80 -1m/min ascent.

Off gassing starts at 69.8m

OTU's this dive: 204
CNS Total: 80.9%


Plan B

Dec to 85m (4) Trimix 15/55 18m/min descent.
Level 85m 25:17 (30) Trimix 15/55 1.42 ppO2, 26m ead, 33m end
Asc to 63m (31) Trimix 15/55 -18m/min ascent.
Asc to 60m (31) Triox 21/35 -18m/min ascent.
Stop at 60m 0:37 (32) Triox 21/35 1.46 ppO2, 29m ead, 35m end
Stop at 54m 1:00 (33) Triox 21/35 1.34 ppO2, 26m ead, 32m end
Stop at 48m 3:00 (36) Triox 21/35 1.21 ppO2, 22m ead, 28m end
Stop at 42m 1:00 (37) Triox 21/35 1.09 ppO2, 19m ead, 24m end
Stop at 39m 2:00 (39) Triox 21/35 1.02 ppO2, 17m ead, 22m end
Stop at 36m 2:00 (41) Triox 21/35 0.96 ppO2, 16m ead, 20m end
Stop at 33m 2:00 (43) Triox 21/35 0.90 ppO2, 14m ead, 18m end
Stop at 30m 3:00 (46) Triox 21/35 0.84 ppO2, 12m ead, 16m end
Stop at 27m 4:00 (50) Triox 21/35 0.77 ppO2, 11m ead, 14m end
Stop at 24m 4:00 (54) Triox 21/35 0.71 ppO2, 9m ead, 12m end
Stop at 21m 6:00 (60) Nitrox 50 1.54 ppO2, 10m ead
Stop at 18m 2:00 (62) Nitrox 50 1.39 ppO2, 8m ead
Stop at 15m 7:00 (69) Nitrox 50 1.24 ppO2, 6m ead
Stop at 12m 9:00 (78) Nitrox 50 1.10 ppO2, 4m ead
Stop at 9m 12:00 (90) Nitrox 50 0.95 ppO2, 2m ead
Stop at 6m 12:00 (102) Oxygen 1.60 ppO2, 0m ead
Stop at 6m 6:00 (108) Trimix 15/55 0.24 ppO2, 0m ead, 0m end
Stop at 6m 12:00 (120) Oxygen 1.60 ppO2, 0m ead
Stop at 6m 6:00 (126) Trimix 15/55 0.24 ppO2, 0m ead, 0m end
Stop at 6m 12:00 (138) Oxygen 1.60 ppO2, 0m ead
Stop at 6m 6:00 (144) Trimix 15/55 0.24 ppO2, 0m ead, 0m end
Stop at 6m 10:00 (154) Oxygen 1.60 ppO2, 0m ead
Surface (160) Oxygen -1m/min ascent.

Off gassing starts at 69.8m

OTU's this dive: 210
CNS Total: 130.6%

this is the same dive but using 100% at the end if you count the run times then the 80% is better, it's also better later on once your out as the [1] calming effect isn't as bad.

adding to that you also encounter (if you get this wrong) Absorptive Atelectasis: Which occurs when high levels of O2 "washout" the Nitrogen in the alveoli, leading to collapse of these sacs (alveolar collapse = atelectasis) and decreased perfusion space leading to something called a shunt. Shunting is basically a mismatch between the sacs that should be filled with oxygen and the flow of blood around them. With collapse of airspace, improper diffusion of oxygen to the blood occurs, lung can become damaged, irreparably.

refrence above Dr Mark Sullivan and Gilbert, DL. Oxygen: An overall biological view

so whilst doing the airbreaks is good for the body and dependant if this is counted in the deco, over a few days diving this could lead to damage compounded over a few days and bend you!!

so this adds another part to the question would you over a five day dive trip adjust the air breaks for longer periods?


Graham


[1] calming effect after periods on pure O2 the body once breathing normal air will encounter a feeling of tiredness sometime's sever exhaustion due to the work the encountered on the body without N2 in the breathing air.
 

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Wreck and Cave Diver
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Plan A


this is the same dive but using 100% at the end if you count the run times then the 80% is better, it's also better later on once your out as the [1] calming effect isn't as bad.

adding to that you also encounter (if you get this wrong) Absorptive Atelectasis: Which occurs when high levels of O2 "washout" the Nitrogen in the alveoli, leading to collapse of these sacs (alveolar collapse = atelectasis) and decreased perfusion space leading to something called a shunt. Shunting is basically a mismatch between the sacs that should be filled with oxygen and the flow of blood around them. With collapse of airspace, improper diffusion of oxygen to the blood occurs, lung can become damaged, irreparably.

refrence above Dr Mark Sullivan and Gilbert, DL. Oxygen: An overall biological view

so whilst doing the airbreaks is good for the body and dependant if this is counted in the deco, over a few days diving this could lead to damage compounded over a few days and bend you!!

so this adds another part to the question would you over a five day dive trip adjust the air breaks for longer periods?


Graham


[1] calming effect after periods on pure O2 the body once breathing normal air will encounter a feeling of tiredness sometime's sever exhaustion due to the work the encountered on the body without N2 in the breathing air.
The Absortive Atelectasis is only a concern with high pulomary toxicity due to continued long exposure to O2.

Apart from the high PPO2 on the bottom as And suggested I would use a max of 1.2 probably lower, as I would always assume I was working at depth - cold etc.

I would continue on multi-day exposures to run 12 on 6 off, and have done this on a regular basis. The whole CNS % measuring system is suspect to say the least, after all there are some out there who have dived exposures in excess of 1000% according to the measurements and are very much still with us.

The cycling mechanism seems to prevent most of the problems associated with Pulmonary Toxicity and CNS Tox.


Andy
 

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Utrinque Paratus
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Discussion Starter · #14 ·
The Absortive Atelectasis is only a concern with high pulomary toxicity due to continued long exposure to O2.

Andy
I disagree here completely there are cases of this occurring in O2 bars in Florida!! and they don't open 24 hours.

this can manifest in 1 minute or 5000 minutes

Graham
 

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PS I would not use 80%, as it still contains Nitrogen, and I would still be ongassing Nitrogen.
I'm not sure I understand this statement. Say you're at 6m doing the long stop on 80%. That's 20%N2 or a PPN2 of 0.32 (1.6*0.2). Surely then the only way you're net ongassing N2 is if the compartment value PPN2 is lower than 0.32 (and I'd contend it's not, unless you're diving heliox. Even if it is then I reckon I'm clean to come to the surface given that my compartment ppN2's are going to be 0.8 after saturation at the surface (provided I've offgassed any He, of course))?

So I don't think there's any net ongassing of N2. I will concede however, that you are offgassing N2 less efficiently since the gradient is going to be reduced compared to being on something with no N2 in it.....

Just curious as to if you meant that or if I'm going mad

Rich
 

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I disagree here completely there are cases of this occurring in O2 bars in Florida!! and they don't open 24 hours.

this can manifest in 1 minute or 5000 minutes

Graham
Hi

Did a google on this and the only mention I saw of oxygen bars was that the guy didn't think it would be a risk as exposure is low (unless you are an o2 addict I guess :) )

If the condition is caused by alveoli getting clogged up/ destroyed by mucus etc. then it sounds very much like the medical name for what we call pulmonary toxicity, which probably includes a whole host of specifically named maldies, but which does only occur after prolonged exposures.

Here is the link I found, which has the paragraph you quoted verbatim

Re: Re: effects of breathing 'pure' Oxygen

It seems to me that it is more beneficial to keep the o2 exposures to relatively short, but intense periods, rather than maintaining a relatively high exposure for a longer period of time over the whole dive.

Andy
 

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Utrinque Paratus
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Discussion Starter · #17 ·
sorry for the delay breathing O2 :D

i used this link and went throught the archives good refrence for all breathing gasses

NCBI HomePage

Graham
 

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Wreck and Cave Diver
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I'm not sure I understand this statement. Say you're at 6m doing the long stop on 80%. That's 20%N2 or a PPN2 of 0.32 (1.6*0.2). Surely then the only way you're net ongassing N2 is if the compartment value PPN2 is lower than 0.32 (and I'd contend it's not, unless you're diving heliox. Even if it is then I reckon I'm clean to come to the surface given that my compartment ppN2's are going to be 0.8 after saturation at the surface (provided I've offgassed any He, of course))?

So I don't think there's any net ongassing of N2. I will concede however, that you are offgassing N2 less efficiently since the gradient is going to be reduced compared to being on something with no N2 in it.....

Just curious as to if you meant that or if I'm going mad

Rich

Rich

Yes I did mean that fast tissues offgas/ongass very quickly and will start on-gassing during the ascent, so if at 6m using 100% I cannot ongas any inerts and my off-gassing is maximised, due to the O2 Window. But if I use 80% or any gas containing Nitrogeen I wll still on-gas the fast tissues.

If you look at any of the deco programmes that produce a tissue pressre graph, you will see this effect.

Andy
 

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Atelectasis in divers

The Absortive Atelectasis is only a concern with high pulomary toxicity due to continued long exposure to O2.
Just a few references of Atelectasis in divers.

Alveolar-arterial O2 differences in man at 0.2, 1.0, 2.0, and 3.5 Ata inspired PO2.
Clark and Lambertsen, J Appl Physiol. 1971 May;30(5):753-63.
NOTE: JAP has a US and UK site. I know this is free on the US site but not sure about the UK.

Report of Nine Four Hour Exposures to 100percent Oxygen at 11-13 Feet of Seawater.
Alexander and Flynn, 1971 NEDU report
RRR ID: 3351

Positive-pressure oxygen breathing and pulmonary atelectasis during immersion.
Dahlback and Balldin, 1983 UBR
RRR ID: 2951

Pulmonary atelectasis formation during diving with closed-circuit oxygen breathing apparatus
Dahlback and Balldin, 1985 UBR
RRR ID: 3011

Pulmonary mechanics and atelectasis during immersion in oxygen-breathing subjects.
Baer, Dahlback and Balldin, 1987 UBR
RRR ID: 3079

I stand with Andy on this one, this is not something we really see in operational diving until the exposures get fairly long.

If anyone has not seen it, my talk on Diving Medical Literature is available here. It is constantly changing as I come across new resources. If you see something I am missing, please PM me. I would love to include it.
 

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Utrinque Paratus
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Discussion Starter · #20 ·
Just a few references of Atelectasis in divers.

Report of Nine Four Hour Exposures to 100percent Oxygen at 11-13 Feet of Seawater.
Alexander and Flynn, 1971 NEDU report
RRR ID: 3351

Positive-pressure oxygen breathing and pulmonary atelectasis during immersion.
Dahlback and Balldin, 1983 UBR
RRR ID: 2951

Pulmonary atelectasis formation during diving with closed-circuit oxygen breathing apparatus
Dahlback and Balldin, 1985 UBR
RRR ID: 3011

Pulmonary mechanics and atelectasis during immersion in oxygen-breathing subjects.
Baer, Dahlback and Balldin, 1987 UBR
RRR ID: 3079

I stand with Andy on this one, this is not something we really see in operational diving until the exposures get fairly long.

If anyone has not seen it, my talk on Diving Medical Literature is available here. It is constantly changing as I come across new resources. If you see something I am missing, please PM me. I would love to include it.
CHEERS

Graham
 
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