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Loving Africa Chaps
Dec 3, 2007


We had not left it yet, but when I would wake in the night, I would lie, listening, homesick for it already.



Sir Winston Beehill posted:

This is something I'm actively practising when I find myself in a pool. This may be a noob question but something I've noticed is that when I exhale underwater, I float upwards for a second before sinking. Is this normal or am I doing something wrong?

That ill be the momentum from when you've inhaled, the trick is to start exhaling before you start rising significantly. Do some finn pivots in the pool and then try and see how small you can get the movement. If you concentrate on finding that point when you're bouyancy is about to flip you should be able to keep pretty much still in the water.

When i was diving in the red sea the boats would hang a tank at 5m and i'd play a game with myself and see just how still i could get on my safety stop using the tank as a reference point. I found it helped alot although i still have a long, long way to go till this:https://www.youtube.com/watch?v=mfcEcCoIvKs

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Trivia
Feb 8, 2006

I'm an obtuse man,
so I'll try to be oblique.


After you've achieved neutral buoyancy, it also helps to play around with your breath sizes so you know how much air you need in your lungs to rise / fall. This helps you to maintain depth without a point of reference, or if you're busy dicking around with your equipment or taking photos.

It all became much more manageable and intuitive after I started using my lungs for buoyancy, rather than my BCD.

Bishop
Aug 15, 2000


Sir Winston Beehill posted:

This is something I'm actively practising when I find myself in a pool. This may be a noob question but something I've noticed is that when I exhale underwater, I float upwards for a second before sinking. Is this normal or am I doing something wrong?
There is a bit of a delay between inhaling/exhaling and your change in buoyancy. That upwards movement probably comes from having full lungs a second or two before. Also don't take huge breaths or exhale completely unless you are going for a buoyancy change.

Recognizing this delay applies to any type of buoyancy adjustment. Using your lungs is absolutely the way to do fine tune buoyancy when underwater, but if you are descending and adding air to your BC, do it in short bursts and wait for a few seconds to see how you react instead of just jamming down the inflator button. Same goes for surfacing and dumping gas.

Tomberforce
May 30, 2006


Bishop posted:

Same goes for surfacing and dumping gas.

I totally agree - on a few OW courses I've been DMTing on the instructor I'm working with is teaching students to empty all their air from their BCD and kick themselves up - I guess safe from a runaway ascent perspective, but not how I was taught in my OW, and I think potentially dangerous considering they're all massively overweighted (18 - 21 lbs) and some are going to be taking their diving to South Asia straight away, where the dive sites on drop offs etc can be significantly deeper than anything in our local area (shore dive max 22m, boat dive max 40m on maybe 2 sites).

I haven't said anything to the instructor - as he's the instructor and I'm the DM, but I was thinking of asking someone about it.

Aquila
Jan 24, 2003



Mr.AARP posted:

What part of California are you diving? I'm in OC.

Los Angeles I guess, but I haven't done anything past my cert and some dives in Australia.

SlicerDicer
Oct 31, 2010

PAILOLO CHANNEL

East gales to 35 kt. Wind waves 17 ft. Scattered showers.

Its time to DIVE


Bishop,

I figured I should let you know the petrels performed great and I love the entire package

Iconic Racism
Apr 8, 2009


Thanks for all the advice on buoyancy. Will have to try them out later this week. When I started diving I would take massive breathes of air since I mentally reasoned that the longer the sound of inhaling, the better off I was. In my first week I would empty a 250 bar tank in about 20 mins. Currently I can make one last up to 40 mins.

Baby steps I guess.

Loving Africa Chaps
Dec 3, 2007


We had not left it yet, but when I would wake in the night, I would lie, listening, homesick for it already.



Sir Winston Beehill posted:

Thanks for all the advice on buoyancy. Will have to try them out later this week. When I started diving I would take massive breathes of air since I mentally reasoned that the longer the sound of inhaling, the better off I was. In my first week I would empty a 250 bar tank in about 20 mins. Currently I can make one last up to 40 mins.

Baby steps I guess.

I was the same when I started and had to us 15l tanks for my first few dives but once I got my buoyancy sorted I could go an hour on a normal 12 no problem.

Mr.AARP
Apr 20, 2010

I was born after Kurt Cobain died. Now you feel old.



Aquila posted:

Los Angeles I guess, but I haven't done anything past my cert and some dives in Australia.

Let me know if you wanna go diving with another relative beginner sometime. I usually do shore dives in Laguna but would love to do some L.A. beaches.

I'm also looking forward to my first boat dive/Catalina trip.

Crunkjuice
Apr 4, 2007

That could've gotten in my eye!
*launches teargas at unarmed protestors*

I THINK OAKLAND PD'S USE OF EXCESSIVE FORCE WAS JUSTIFIED!


Sir Winston Beehill posted:

Thanks for all the advice on buoyancy. Will have to try them out later this week. When I started diving I would take massive breathes of air since I mentally reasoned that the longer the sound of inhaling, the better off I was. In my first week I would empty a 250 bar tank in about 20 mins. Currently I can make one last up to 40 mins.

Baby steps I guess.

Also know depth is a factor in how long you can last on a tank. That 40 minute tank of yours at x depth will last you differently at y depth.

Just get comfortable in the water. Thats the biggest thing that will help buoyancy/air consumption. Once you get over the "OH gently caress I"M BREATHING UNDERWATER THERES A FISH OH MY GOD" feelings, and you get acclimated, everything sort of falls into place.

Stay calm, breath easy, and it'll come along with experience.

pupdive
Jun 13, 2012


Crunkjuice posted:

Once you get over the "OH gently caress I"M BREATHING UNDERWATER THERES A FISH OH MY GOD" feelings, and you get acclimated, everything sort of falls into place.

I am glad to say I have never gotten over these two things, or the fact that I weigh nothing underwater.

My air consumption, not surprisingly, sucks.

On the other hand, air consumption is also just a thing. Some people use more than others. Going diving with some Japanese people, one becomes convinced that they are simply not breathing sometimes: 3200 PSI to start, 2500 PSI to end on a 30 minute dive to 60 feet is a real head scratcher.

(220 Bar 166 Bar 18 meters depth 11.1 liter tank for those playing along in foreign lands).

Bishop
Aug 15, 2000


SlicerDicer posted:

Bishop,

I figured I should let you know the petrels performed great and I love the entire package
I would expect nothing less from Sherwater Research. They loving rule and I hear their customer service is great too. The Predator has a cooler name though! It's probably my favorite piece of dive equipment. When I finally get a rebreather of my own (any day now I swear), I'll probably use all sherwaters as controlers/monitors.

I had a friend from West Palm Beach come down yesterday and we did a nice shallow reef dive off my boat. Maybe 20ft with a 90 minute downtime? I dunno because neither of us had computers or watches because you could stay down indefinately without getting bent. Great fish life. I don't know if there have been studies or anything done but I'm completely convinced that the reef in the Keys has rebounded a ton over the past decade.

Bishop fucked around with this message at 18:05 on Dec 16, 2012

Crunkjuice
Apr 4, 2007

That could've gotten in my eye!
*launches teargas at unarmed protestors*

I THINK OAKLAND PD'S USE OF EXCESSIVE FORCE WAS JUSTIFIED!


Anyone watch the 60 minutes on the salvaging of the Costa Concordia? They had a 3-4 minute segment on the salvage divers that was pretty cool, except for something that i can't wrap my head around unless its just them screwing up facts.

They said that even with being down a lot every day, the divers had a max bottom time of 45 minutes per dive. They had 5 minutes to get up from a DEPTH OF 40 FEET to get into a chamber. They showed a dude stripping off a wetsuit and rushing into a chamber.

Things i saw. They had surface supplied air and standard commercial diving helmets. They were all wearing a full length wetsuit, with a john style or second wetsuit layer (no drysuits). I'm guessing the news reported the numbers wrong, because i can't fathom any reason why a 45 minutes dive to 40 feet would constitute an immediate chamber trip.

Tomberforce
May 30, 2006


Crunkjuice posted:

Anyone watch the 60 minutes on the salvaging of the Costa Concordia? They had a 3-4 minute segment on the salvage divers that was pretty cool, except for something that i can't wrap my head around unless its just them screwing up facts.

They said that even with being down a lot every day, the divers had a max bottom time of 45 minutes per dive. They had 5 minutes to get up from a DEPTH OF 40 FEET to get into a chamber. They showed a dude stripping off a wetsuit and rushing into a chamber.

Things i saw. They had surface supplied air and standard commercial diving helmets. They were all wearing a full length wetsuit, with a john style or second wetsuit layer (no drysuits). I'm guessing the news reported the numbers wrong, because i can't fathom any reason why a 45 minutes dive to 40 feet would constitute an immediate chamber trip.

Must be 40 metres?

TLG James
Jun 5, 2000

Questing ain't easy


Tomberforce posted:

Must be 40 metres?

Yea it's at about 120 feet right now, with a danger of it slider further down.

Crunkjuice
Apr 4, 2007

That could've gotten in my eye!
*launches teargas at unarmed protestors*

I THINK OAKLAND PD'S USE OF EXCESSIVE FORCE WAS JUSTIFIED!


Tomberforce posted:

Must be 40 metres?

I thought that first as well, but thats only 130 feet. Commercial divers with surface supplied air stay down WAY deeper for way longer than that on a regular basis. That can't be right though since the Concordia had a depth of 46 feet 6 inches, and as i understand it, it ran aground and rolled. I'm chalking this up to a news reporting error. I'll try to find a copy of the segment and post it here though.

On a more intersting note. The divers/salvage crew live on a constructed barracks site on the water. Its a makeshift platform with a shitload of cargo containers/walkways.

Bishop
Aug 15, 2000


That segment sounds interesting but you're right... Serious commercial divers could dive 40ft (or meters) all loving day if they wanted. I guess they were doing saturation diving if getting to a chamber after surfacing was involved but it's odd because of how shallow it is.

They're probably doing saturation diving because they are diving the wreck every day. Still, that's pretty shallow. Did they live in a pressurized habitat when they weren't diving? If not that means they were just decoing in a chamber every day which is a bit strange, but maybe for liability reasons that's how commercial divers do things?

e: more thoughts... Let's assume 130ft because why not. If I was diving that EVERY DAY for a month I might go with saturation diving because that would mean one or two long decompressions instead of 30. Still, a maximum 45 minute down time has to be wrong unless I'm missing something. Has anyone told the Italians about helium?

Bishop fucked around with this message at 13:17 on Dec 17, 2012

DarkHorse
Dec 13, 2006

Vroom Vroom, BEEP BEEP!

Nap Ghost

Can someone explain surface-supplied air for me? Someone I trust with a ton of diving experience told me they used a surface unit and therefore didn't need to worry about decompression limits. I may be way off, but my understanding of the mechanics involved tells me it shouldn't make a difference: you're still breathing air at the same ambient pressure, your body should absorb it the same.

Is there something I'm missing? I didn't get the impression he was talking about using a heliox or nitrox gas mix or anything like that, just a surface compressor.

Bangkero
Dec 28, 2005

I baptize thee
not in the name of the father
but in the name of the devil.


DarkHorse posted:

Can someone explain surface-supplied air for me? Someone I trust with a ton of diving experience told me they used a surface unit and therefore didn't need to worry about decompression limits. I may be way off, but my understanding of the mechanics involved tells me it shouldn't make a difference: you're still breathing air at the same ambient pressure, your body should absorb it the same.

Is there something I'm missing? I didn't get the impression he was talking about using a heliox or nitrox gas mix or anything like that, just a surface compressor.

Yep, your friend is way wrong. Decompression sickness can happen anytime you breathe compressed air at depth. For compressor diving, that air is still getting compressed to make it down to depth. edit: Caveat being shallow dives are pretty safe (eg < 30ft) - just found the thread I remembered from SB - http://www.scubaboard.com/forums/ask-dr-decompression/119678-unlimited-dives-shallower-than-30-ft-min-s-i-2.html. If your friend is not going that deep, that's probably why he hasn't been hit, not because compressor diving transcends diving physics.

In fact, freedivers can be subjected to the bends as well, however, most DCI cases in freedivers are after hours of repeated dives to 100ft or greater (http://www.skin-diver.com/departments/scubamed/FreedivingCauseDCS.asp?theID=626)

Human Planet has a fantastic piece on compressor diving and the bends: http://youtu.be/c8jlazU0rkM?t=32m48s (the behind the scenes is a lot more interesting: http://youtu.be/c8jlazU0rkM?t=49m21s)

Bangkero fucked around with this message at 16:44 on Dec 17, 2012

DarkHorse
Dec 13, 2006

Vroom Vroom, BEEP BEEP!

Nap Ghost

Thanks, that's what I thought. I figured the reason they had essentially no limit was because their depth was under 1 ATM, not because of the source of the air. The guy was adamant about it, though, and it felt weird to contradict someone with literally thousands of dives.

Crunkjuice
Apr 4, 2007

That could've gotten in my eye!
*launches teargas at unarmed protestors*

I THINK OAKLAND PD'S USE OF EXCESSIVE FORCE WAS JUSTIFIED!


Heres the segment. The whole thing is pretty interesting and worth the watch, but the diver part starts at about 5:50. The dive supervisor mentions going past 30 meters, and i guess what she said isn't technically wrong. It sounds like she's saying max depth, but she says "they have 5 minutes to get from 40 feet to get into the chamber". Not the clearest

http://www.cbsnews.com/video/watch/?id=50137223n

egyptian rat race
Jul 13, 2007

Lowtax Spine Fund 2019


Ultra Carp

Crunkjuice posted:

Heres the segment. The whole thing is pretty interesting and worth the watch, but the diver part starts at about 5:50. The dive supervisor mentions going past 30 meters, and i guess what she said isn't technically wrong. It sounds like she's saying max depth, but she says "they have 5 minutes to get from 40 feet to get into the chamber". Not the clearest

http://www.cbsnews.com/video/watch/?id=50137223n

It sounds like they are operating on surface decompression tables (sometimes referred to as Sur-D O2). A dive supervisor might elect to use this method for the sake of safety. In the case of dangerous conditions or cold water, the diver completes a minimum of decompression while exposed in the open water. He is brought to the surface on an accelerated in-water decompression table then ascends directly to the surface from 40 feet (what the CBS story referred to). He is not technically decompressed yet... The diver then has 5 minutes to exit the water, get his gear off and get into a chamber where he will be blown back down to depth (usually 40 feet). He will then most likely take in pure oxygen through a mask in ten-minute intervals while being brought up to the surface. The number of intervals and time of decompression will vary based on his dive profile. If the diver were to break that 5-minute limit, he will incur extra decompression time.

This may sound crazy, but this kind of decompression is very common in offshore applications. It keeps the diver productive for the maximum amount of time, minimizes his exposure while surfacing, and keeps the diver warm and dry during longer decompressions. If there is a medical issue, he is already in the chamber.

E: yep, just watched this again. The divers have a max dive time allowed of 45 minutes to do whatever they are tasked with at depth. 40 feet is just their last in-water decompression stop, not their max depth.

egyptian rat race fucked around with this message at 21:28 on Dec 17, 2012

Bishop
Aug 15, 2000


DarkHorse posted:

Can someone explain surface-supplied air for me? Someone I trust with a ton of diving experience told me they used a surface unit and therefore didn't need to worry about decompression limits.
Don't trust this person. Just wanted to say that this was a real interesting post. You were the guy I was hoping would chime in on this. Doing deco in a chamber because of cold water makes a lot of sense. Also in theory what you described is pretty much in water recompression, which is a terrible idea unless you know what you are doing and have good support but I've used it before. You can surface and know that you are way way short on deco and have a few minutes to gather yourself before descending again.

Bishop fucked around with this message at 22:23 on Dec 17, 2012

pupdive
Jun 13, 2012


Bishop posted:

Also in theory what you described is pretty much in water recompression, which is a terrible idea unless you know what you are doing and have good support but I've used it before. You can surface and know that you are way way short on deco and have a few minutes to gather yourself before descending again.

Here's why it is not even close to in-water recompression. In a chamber, breathing 2.8 ATA PPo2 is standard fare. In the water, that's deadly.

Recompression without insanely high PPo2 is just plain stupid, because it is treating DCS with more nitrogen.. In water compression with insanely high PPo2 is also stupid, because Tox hits in water kill. Tox hits in a chamber are just good clean fun for the chamber driver.

So Sur-D is not even slightly like inwater recompression.

SlicerDicer
Oct 31, 2010

PAILOLO CHANNEL

East gales to 35 kt. Wind waves 17 ft. Scattered showers.

Its time to DIVE


pupdive posted:

Here's why it is not even close to in-water recompression. In a chamber, breathing 2.8 ATA PPo2 is standard fare. In the water, that's deadly.

Recompression without insanely high PPo2 is just plain stupid, because it is treating DCS with more nitrogen.. In water compression with insanely high PPo2 is also stupid, because Tox hits in water kill. Tox hits in a chamber are just good clean fun for the chamber driver.

So Sur-D is not even slightly like inwater recompression.

Tell that to Richard Pyle

http://www.daneurope.org/c/document_library/get_file?folderId=13501&name=DLFE-121.pdf

Not that I advocate it but you can bet your rear end if I was bent and far enough from medical... I would do IWR over died.. Its also covered in many of my official govt publications.. There is also data and tables out of Australia for it!! Its sound science to some degree but recreationally its not considered good practice or even viable.

Loving Africa Chaps
Dec 3, 2007


We had not left it yet, but when I would wake in the night, I would lie, listening, homesick for it already.



SlicerDicer posted:

Tell that to Richard Pyle

http://www.daneurope.org/c/document_library/get_file?folderId=13501&name=DLFE-121.pdf

Not that I advocate it but you can bet your rear end if I was bent and far enough from medical... I would do IWR over died.. Its also covered in many of my official govt publications.. There is also data and tables out of Australia for it!! Its sound science to some degree but recreationally its not considered good practice or even viable.

It's all about risk vs benefit as with any medical intervention. If you're in the middle of nowhere, missed a huge amount of deco and the nearest chamber is 3 days away then IWR becomes much more attractive. If you just did a dive on the chambers house reef the balance swings somewhat.

Bishop
Aug 15, 2000


pupdive posted:

Here's why it is not even close to in-water recompression. In a chamber, breathing 2.8 ATA PPo2 is standard fare. In the water, that's deadly.

Recompression without insanely high PPo2 is just plain stupid, because it is treating DCS with more nitrogen.. In water compression with insanely high PPo2 is also stupid, because Tox hits in water kill. Tox hits in a chamber are just good clean fun for the chamber driver.

So Sur-D is not even slightly like inwater recompression.
Aren't you going to start seizing almost immediately with a 2.8ppo2? I know they do tests and such where they intentionally give you an o2 toxx hit in chambers but is it so common that it's just "good clean fun"? Honest question. That sounds insane to me but then again I'm not a commercial diver.

Also "it's just treating DCS with more nitrogen" dosen't make any sense to me either because I'm "treating DCS" when I'm doing regular in water deco and my ppo2 is usually 1.4-1.6 or whatever. Going back down and getting on an o2 rich mix is no different than switching to one on the way up. (this last point assumes you are asymptomatic, just like the guy running to the chamber is)

Over time I've become convinced that in-water recompression gets a worse reputation than it deserves. For advanced decompression divers, surfacing, getting another o2 bottle or whatever, and going back down is not all that risky if you have proper support and have not developed DCS symptoms. If I misjudge how much deco gas I'm going to need by 10 minutes, I'll absolutely do it if the circumstances are correct. Remember I'm not talking about situations where someone has bolted to the surface and is so bent that their blood is foamy.

E: to clarify a couple things, surfacing and being at 1 atmosphere of pressure is going to make nitrogen bubbles expand, but the same thing is happening when the guy surfaces and runs to a chamber to be recompressed. That's why I compared it to in water recompression.

Bishop fucked around with this message at 22:32 on Dec 18, 2012

Bishop
Aug 15, 2000


Once again I've driven the thread into things we don't talk about territory. As long as we are here let's talk about solo diving!

egyptian rat race
Jul 13, 2007

Lowtax Spine Fund 2019


Ultra Carp

I support discussions that go beyond PADI-approved territory. A lot of tech diving is seen from the outside as the stuff of wizards. It is often homebrew rules, and I enjoy people pushing the limits and exploring techniques. As long as a diver is educating himself on the subject and being realistic about the risks he/she is taking, who cares?

Solo diving, deco diving, and even recreational diving within the RDL set by agencies are inherently risky activities that share the same territory as skydiving and mountain climbing. Things can happen that are completely outside the diver's control. It is the diver's responsibility to mitigate that risk with training and equipment to a level they are comfortable with. Lightning can still strike despite anything one does to assure otherwise. I'd like to think I'm careful with my own life, but I've still had DIR-level outrage leveled at me over my choice of wetsuit or kit.

The rules set by my company are very good. We usually only dive surface-supplied beyond 75ft. We have a chamber on site for any dive beyond 100ft. The divers have the ultimate discretion on wether or not to proceed in difficult conditions. Just have fun, and learn your limits. Heed the advice of your experienced peers.

egyptian rat race fucked around with this message at 00:02 on Dec 19, 2012

Crunkjuice
Apr 4, 2007

That could've gotten in my eye!
*launches teargas at unarmed protestors*

I THINK OAKLAND PD'S USE OF EXCESSIVE FORCE WAS JUSTIFIED!


Bishop posted:

Once again I've driven the thread into things we don't talk about territory. As long as we are here let's talk about solo diving!

Haha, i say go nuts. The more info the better.

I've always been curious about commercial diving as a career, but have never actually done more than tour a commercial diving school (Ocean Corp) and never really thought about it.

Diver Dick, if you wanted to write a whole bunch of words about how you got into commerical diving/the industry, that would be an awesome read. got any job openings?

egyptian rat race
Jul 13, 2007

Lowtax Spine Fund 2019


Ultra Carp

Crunkjuice posted:

how you got into commercial diving/the industry, that would be an awesome read.

I'll try and put something together this week if you're curious. My corner of the industry is pretty small and specialized, but I've got friends from all kinds of backgrounds within the "commercial" dive world. I'll try and dig up some horrifying good photographs to go with it.

Bishop
Aug 15, 2000


Crunkjuice posted:

Diver Dick, if you wanted to write a whole bunch of words about how you got into commerical diving/the industry, that would be an awesome read.
Seconded. Also for anyone: if you think I'm making dumb posts lay into me like pupdive, thats better for everyone and makes for more productive conversation.

Bishop fucked around with this message at 04:41 on Dec 19, 2012

SlicerDicer
Oct 31, 2010

PAILOLO CHANNEL

East gales to 35 kt. Wind waves 17 ft. Scattered showers.

Its time to DIVE


Bishop posted:

Once again I've driven the thread into things we don't talk about territory. As long as we are here let's talk about solo diving!

Solo diving? Whats wrong with that?

I have done it I feel safer solo than having some useless idiot diving with me that likely I will need to save or in the event something happens to me I will be worse off. This is what happens when you dive on boats with tourists and just ignore them.

Its a odds game.

Bishop
Aug 15, 2000


Mostly I'd rather do deep wreck penetration alone because I have redundancy and can run my own line.I carry three lights, three knives, and two reels. Two divers create a lot more silt than one. That said a friend of mine had to bail out of his rebreather at around 200ft a couple weeks ago and if I wasn't there he might not have made it. The bailout incident was in open water and I think I made a post about it.

Bishop fucked around with this message at 05:22 on Dec 19, 2012

Trivia
Feb 8, 2006

I'm an obtuse man,
so I'll try to be oblique.


Does anyone have any opinion on diver's insurance? I'm going to be leaving on a diving trip soon as am playing around with the idea of getting some, especially since I have another diving trip planned for March of next year.

I only dive recreationally and rarely if ever go below 31-32 meters. Anyone use DAN?

Bishop
Aug 15, 2000


DAN is amazing. I think the deluxe package is $70 a year and that will cover a chamber ride and even covers things like lost dive gear on trips. I can't recomend DAN enough.

Bishop fucked around with this message at 05:03 on Dec 19, 2012

Trivia
Feb 8, 2006

I'm an obtuse man,
so I'll try to be oblique.


Does coverage begin as soon as you sign up, or is there a long period where medical / whatever background checks are necessary?

rockcity
Jan 16, 2004


There is zero reason not to have DAN. A trip to the chamber will set you back way more than you think uninsured and your health insurance probably won't pay for a penny of it. It will also cover an airlift if necessary and even pay for gear lost in the accident. We had one of their reps speak at my dive club and I'm really glad he did.

Finch!
Sep 11, 2001

Spatial Awareness?

[ ] Whaleshark

404 Not Found


DAN are even covering knee surgery for a friend who barely dives (not because of the knee).

I've also heard good things about most other dive insurance companies, but DAN are the best known and probably the largest organisation.

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pupdive
Jun 13, 2012


Bishop posted:

Aren't you going to start seizing almost immediately with a 2.8ppo2? I know they do tests and such where they intentionally give you an o2 toxx hit in chambers but is it so common that it's just "good clean fun"? Honest question. That sounds insane to me but then again I'm not a commercial diver.

Also "it's just treating DCS with more nitrogen" dosen't make any sense to me either because I'm "treating DCS" when I'm doing regular in water deco and my ppo2 is usually 1.4-1.6 or whatever. Going back down and getting on an o2 rich mix is no different than switching to one on the way up. (this last point assumes you are asymptomatic, just like the guy running to the chamber is)

Over time I've become convinced that in-water recompression gets a worse reputation than it deserves. For advanced decompression divers, surfacing, getting another o2 bottle or whatever, and going back down is not all that risky if you have proper support and have not developed DCS symptoms. If I misjudge how much deco gas I'm going to need by 10 minutes, I'll absolutely do it if the circumstances are correct. Remember I'm not talking about situations where someone has bolted to the surface and is so bent that their blood is foamy.

E: to clarify a couple things, surfacing and being at 1 atmosphere of pressure is going to make nitrogen bubbles expand, but the same thing is happening when the guy surfaces and runs to a chamber to be recompressed. That's why I compared it to in water recompression.

SlicerDicer posted:

Tell that to Richard Pyle

http://www.daneurope.org/c/document_library/get_file?folderId=13501&name=DLFE-121.pdf

Not that I advocate it but you can bet your rear end if I was bent and far enough from medical... I would do IWR over died.. Its also covered in many of my official govt publications.. There is also data and tables out of Australia for it!! Its sound science to some degree but recreationally its not considered good practice or even viable.


Things:

Re 2.8 PPo2
2.8 PPo2 used to be the excursion depth/PPo2 for Navy o2 rebreathers. It's changed now, but that was actually in water diving. In chambers, 2.8PPo2 is operational standard; it might be less at times but it is best to ride right on that line because bruises heal but DCS does not really do as well for well and truly hosed people who are paralyzed when they enter the chamber.

2.8 PPo2 is 60 foot on 100 o2 (more or less), which is a pretty standard treatment table for full o2 environment chambers. 2.8 PPo2 also the standard test done on inside tenders, and inside tenders run right at that often, especially when cycling through a team of inside tenders who have to minimize their n2 exposure because they are not doing a saturation dive like some of the truly badly off patients are.

There is an enormous difference between preventing bubble formation, and getting rid of bubbles that have already caused paralysis, and other CNS symptoms. If you have DCS, treating it with anything other than 100% o2 is treating DCS with more nitrogen, (or like treating a poisoning victim with more poison etc. etc.) Any additional nitrogen is just simply going to make things worse, because anything that eliminates the maximal o2 window is just misunderstanding decompression, and DCS treatment. It's not pressure, it's the relative PP of the inert gas.

Read the linked file of Richard Pyle and he says exactly that:

Richard Pyle posted:

At least three formal methods of IWR have been published. All of them prescribe breathing 100% oxygen for prolonged periods of time at a depth of 30 feet (9meters), supplied via a full face mask

In other words this is not in water recompression as most people bandy it about, and thus is a ways from what most divers think it is. It is absolutely not going in with a 60% o2 mix, or any kind if Nitrox at all; it is going in with 100 o2 and breathing it in water at a PPo2 of 2.0 with a full face mask. And it often results in seizures. And it works because treating DCS with nitrogen is silly, and the Richard Pyle version of IWR is absolutely not doing that. It is accepting o2 hits as the price of doing business.

It's important to read the point Michael Menudo says in that article:"The solution for the technical community is to expect and plan for DCS and be prepared to deal with it". When you are doing dives far from a chamber then those divers are planning to use IWR. They are not doing it as a last resort, it is simply a planned part of the mission.

(That article was originally published more than 20 years ago, and was published secondarily in AquaCorps. There has to be a newer article to cite on it.)

Regarding gov't publications giving credence to what technical divers should do:

Remember soldiers (and navy divers) have signed up to risk their lives performing their duties. Lots of military divers die diving, just like lots of soldiers die soldiering. Just like the o2 rebreathers used to run to 60 ft excursion depth and the death of some divers was just considered part of the risk of being in the military.

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