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"Three sheds"
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Discussion Starter · #1 ·
Over on Burgerworld, there are a few people, who have been guinea pigs in a study that looks at post-dive bubbles. [1]

Now, as a result of those studies, some of the guinea pigs have reduced their GF high from ~85 to around 70. This has lead to significantly reduced bubbling on the ascent.

Just wondering what people's thoughts were.

Janos

[1] - I realise that there is no evidence that links increased bubbles to an increased risk of
 

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"Three sheds"
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Discussion Starter · #6 ·
Here's the original post and link to the thread. It was originally about O2 toxicity but drifted:

Down4Fun said:
I just finished a up a week participation in the DAN field study here at innerspace and learned some things about my own physiology and decompression. We did two dives a day typically in the 300 foot range. After the dives we had a TTE done every 20 minutes for two hours post dive. They were willing to share with us what they saw and we were allowed to make changes based on those results. The TTE would show bubbles in either side of the heart and they were scored according to a scale (cant remember the name now) from 0-7. 0 being none and 7 basically a white out. During the study I never had any left sided bubbles. Day one and two i had some 3-4's at the peak of my topside off gassing on the right side. I had been running a a GF of 30/85 and staying at rest during deco. After the presentation by Dr. Pollock and my own personal results I changed my GF to 30/75 and began swimming slowly during my entire deco obligation. The change resulted in mostly 0's some 1's and only one 2 during the remaining 4 days of diving. I also noticed less fatigue post dive with the changes i made. And I run my po2 at 1.4-1.58 during the deco at 20 feet.
And THE LINK

Janos
 

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Fettlin'
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Over on Burgerworld, there are a few people, who have been guinea pigs in a study that looks at post-dive bubbles. [1]

Now, as a result of those studies, some of the guinea pigs have reduced their GF high from ~85 to around 70. This has lead to significantly reduced bubbling on the ascent.

Just wondering what people's thoughts were.
Is it not obvious that reducing the high GF will increase conservatism (increasing deco time) and hence reduce the level of post-dive doppler-detectable bubbles?

I wonder how much difference the 'exercising during deco' would make; this may be quite significant.

Surely the question that each diver must ask themselves is 'how close to the edge' do I want to run and is it worth hanging around in the water longer (and carrying the extra gas volumes required) to reduce the risk of DCI v Thermal Constraints, etc.

As I get older, my deco has become more conservative; I had a session in the pot a couple of years ago, on what many would consider a pretty conservative profile, which I still attribute to the after-effects of my body being riddled with chemotherapy drugs a few months previous. I'd rather spend the extra 10-15% longer in the water these days; there's no rush, after all.
 

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A short fat well off crap cave diver. Likes wrecks
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Shock horror revalation. Doing more deco reduces body stress from decompresion diving :D

Id love to see some figures from the divers doing agressive deco like 10/125GF who claim its all cleen and eficient.

70 is realy soft deco. A dive to 50m for 60min on 20-70GF will result in 45mins more deco (75% more) than a dive on 20/100 and 32mins more than a dive on 20/90

But the questions need to be asked as to what dive gas what deco gas what ascent rates and what time to ascend from 6m-surface to get an acurate picture.


ATB

Mark
 

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Shock horror revalation. Doing more deco reduces body stress from decompresion diving :D

Id love to see some figures from the divers doing agressive deco like 10/125GF who claim its all cleen and eficient.

70 is realy soft deco. A dive to 50m for 60min on 20-70GF will result in 45mins more deco (75% more) than a dive on 20/100 and 32mins more than a dive on 20/90

But the questions need to be asked as to what dive gas what deco gas what ascent rates and what time to ascend from 6m-surface to get an acurate picture.


ATB

Mark
As stated in the various articles recently posted, these divers changed to a more conservative profile (30/85 to 30/70) because of the doppler testing identifying specific bubble sizes performed immediately after their deep dives. Each of these divers had evidence the change helped. We could only hope that divers using a more aggressive profile submit themselves to doppler testing so we can all learn what the effects are... Not me and I'm now looking to set my Predators to 30/70.

You mention the difference in deco time but the change mentioned by two authors was 30/85 -> 30/75 and 30/85 -> 30/70.. so not a huge impact to deco time.
 

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give me convenience
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Another shock horror revelation for you. If in fact it does not increase your deco time much at all then there is probably no point in doing it as it will be about as safe as what you did before.
 

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Another shock horror revelation for you. If in fact it does not increase your deco time much at all then there is probably no point in doing it as it will be about as safe as what you did before.
"Not a huge impact" does not equal "much at all" It was enough difference to change observed bubble sizes down to 0's-1's.
 

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What sort of deco times are you talking about pre and post change?
They were not my dives. The dives mentioned in the articles were up to 300' dives. Back of the napkin difference between 30/85 and 30/70 is:

200'/30 mins bottom time 30/85 = 47 minutes deco at PPO2 1.3/0.7 90'/2, 80'/1. 70'/2, 60'/3, 50'/3, 40'/4, 30'/6, 20'/26,
200'/30 mins bottom time 30/70 = 58 minutes deco at PPO2 1.3/0.7 100'/1, 90'/1, 80'/2. 70'/2, 60'/4, 50'/4, 40'/5, 30'/8, 20'/31

An extra 11 minutes added to the shallow stops.
 

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Silent Knight
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On a 40 mins at 60m dive on a setpoint of 1.3 I'd have around 126 mins Total Runtime on a GF of 15/85

I usually +5 mins at 6 for a bit more conservatism and then 1m/min ascent from 6metres effectively adding another 5 mins. This looks to be more in line with a finishing GF High of 75.

The difference between the GF Low 15 and 30 stops is only 3 metres deeper for 1 minute - so not much at diff at all with the majority of the overall difference in deco on the GF high (as you would expect)

So I guess the question, at least for me is, are these test divers just ascending from 6m directly to the surface, +5 ? or 1m/min ? something else which would lower the GF High number still further.

G
 

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are these test divers just ascending from 6m directly to the surface, +5 ? or 1m/min ? something else which would lower the GF High number still further.
G
Just to be clear - These are just "regular" divers like you and I who submitted themselves to doppler bubble testing... and their "immediate" reaction to the initial results (big bubbles) was to change their GF conservatism with positive effects. Not really a scientific study but very interesting.

Somewhat related was a discussion about VPM and positive effects of deeper stops and reference to a Navy study which showed no benefit. All very interesting and I need to find the Navy deep stop study.
 

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Jesus don't want me for a sunbeam
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Without reconciling it against risk then I'm not entirely sure what the relevance is. If, as I suspect, the risk of doing GFHi's of 85 or better isn't producing a significant incidence of DCI then the benefit is questionable. If there is evidence that 85 is contributing to more DCI then it is useful. It's the question of whether doing more deco is better than doing enough deco.

At the moment it's useless: more deco is going to give less bubbling, it's just stating the obvious. Until what sort of bubbling noticeably adds to the risk is established then what else can you say?
 

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At the moment it's useless: more deco is going to give less bubbling, it's just stating the obvious. Until what sort of bubbling noticeably adds to the risk is established then what else can you say?
As a new OC diver, I really did not focus much on the last 15' and there were a number of post dives I felt I needed to sleep real bad.

Since I started to take care not to rush the top of my ascents - especially the last 30'-0', I have felt great at the end of my OC dives... One of the bubble study authors basically stated the same thing - Post dive felt "better"/less sleepy following the change to their algorithm/evidence of smaller bubbles.

We all bubble - But researchers do believe the size of the bubbles increase our risk of a DCI. The divers in this study essentially self medicated when presented with evidence of specific bubble sizes post dive.

Really the question is what would you do if presented with such evidence... Personally, I would adopt a more conservative deco profile.
 

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Jesus don't want me for a sunbeam
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Really the question is what would you do if presented with such evidence... Personally, I would adopt a more conservative deco profile.
It's a bit like someone saying to you, it's cold today so put on another layer. If I didn't have any realistic chance of hypothermia to start with then putting another layer on isn't making me any safer, it's just making me warmer. Without knowing where your hypothermia risk is then it just comes down to a decision based on comfort.

There's nothing wrong with doing what makes you feel better but without knowing what that bubbling is actually doing, whether it is causing damage or not, whether it is increasing your risk profile or not, etc., then it is just personal preference. I don't generally notice any fatigue or anything else on 20/85, the loop pO2 is usually stabilised at the last stop, I've got nothing to indicate that I'm not doing enough deco. I've had four bends so I tend to be a bit watchful.

I just can't help thinking that there is a big chunk of information missing before I can make a proper judgement on how I see it affecting my diving.
 
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