pure o2...

[fishhound]

New to the forum so hello to all! Been freediving for around a year now and always practice safety. I dive in 30-50ft(usually 30) and have some questions about breathing up with pure o2. The depths im diving shouldn't have any toxicity implications based on everything I've read and as I understand it the main reason for swb is LACK of o2. I've heard breathing up pure o2 can dramatically increase your bottom time and am thinking about experimenting with it under supervision. My question is have you done it, know anyone that has, know of any risks, etc. Sorry if this has been brought up before or a stupid question but I don't see any risks based on what ive read and wanted some other opinions since I'm no expert. Thanks for the help and insight.

 

[Mullins]

I dive in 30-50ft(usually 30)... The depths im diving shouldn't have any toxicity implications based on everything I've read

Umm, what have you been reading??

 

[cdavis]

Hi Fishhound, Welcome to DB. I used to launch out of Hudson and dive the Bayport area. Great stuff.

Probably a good idea to read some more. Symptoms of 02 toxicity can start a lot shallower than 50 ft. Convulsions are a prime symptom. Fairly high price for protection from B0.

Also, need to breath is modulated primarily by c02, not 02. Breathing pure 02 will help purge c02 from the body and raise 02 concentration, but c02 will still kick in the breathing response fairly quickly. Well trained divers can resist the breathing urge and make use of the extended time 02 allows(in very shallow water), but it ain't comfortable.

i.e., it won't help most divers much and is dangerous as hell.

Also remember, there are no stupid questions.

Connor

 

[fishhound]

just going off posts from 3 different forums and my scuba training. I'm not interested in this to push any limits and try for crazy breath holds. I am curious if this would help me in shallow depths(50ft or less) to stay a little longer 230 or less more comfortably and also help prevent swb since that is caused by low o2. The only real negative I have read about so far that is not opinion is the risk of dwb by high co2. But if Im staying down 230 or less is that a real risk? Not sure just wondering.

 

[fishhound]

connor, thanks for the info. Not argueing with you since I don't know but why is o2 toxic at shallow depths? I've read alot of posts on it(maybe they are wrong) but most say its only a factor at over 200ft which I have no intentions of doing. And yea bayport and hudson has some cool stuff especially in shallow. We got some nice gags in 15ft last weekend up to 29 inches. Would love to hook up and dive together if your in the area. I run a 22 ft lake n bay.

 

[Mullins]

why is o2 toxic at shallow depths? I've read alot of posts on it(maybe they are wrong) but most say its only a factor at over 200ft

They'll be talking about air. Pure O2 gives you five times the partial pressure of oxygen, so you'd hit the 2atm threshold much earlier - at 30ft.

 

[Kars]

In my Scuba class I was told that going beyond 7m (21ft) on pure O2 is suicidal.
And old submarine rescue Dräger breathing apparatus apparently supplied the diver with pure O2, but had the warning not to beyond 7m.

Maybe enriched air is better?

But I wouldn't go into the bottle direction. If you want to stay down a bit longer, practice With a comfortable setup my 43 year old friend with a dynamic pb of 60 can do a 2'30" dive with covering ~25m

Also with taking in different mixes of gas you make your bodily warning sensory act differently than you expect.
Having more O2 makes you body USE more, producing more CO2. I think the plants grow fast enough at the moment

 

[trux]

This is really a very bad idea! Not only because of the O2 toxicity, but especially because of CO2 toxicity. When breathing pure O2 or Nitrox, hypercapnia reaches much higher levels than with normal air, which then leads to a CO2 blackout, which (unlike classical BO) is very difficult to revive. Stay away from any tank breathing, and better learn diving safe instead (especially diving always together with a buddy, who waits with his dive at least 30s after you surface).

 

[fishhound]

good info and thanks...not planning on doing this at all but there must be benefits to it as well as risks. reading some old threads there were people(world record holders) that stated they dramatically increased their bt and there have been bh records on pure o2 as well. Its just an interesting subject I want to learn more about. I'm perfectly happy doing what im doing now and getting better every day...trux, if u were to use o2 and didn't push the limits then the co2 buildup wouldnt be an issue right? I mean say you did it and only stayed down 230? If you never stayed down longer than that is it fair to say co2 levels and dwb wouldn't be an issue? I don't know just wondering and you seem like you are very educated on this. Thanks

 

[fishhound]

They'll be talking about air. Pure O2 gives you five times the partial pressure of oxygen, so you'd hit the 2atm threshold much earlier - at 30ft.

ok..so for conversation sake it would be safe from a toxicity standpoint in under 30ft?

 

[trux]

Breath hold records on pure O2 are something completely different. First of all they are static records done on the surface (or just under it); they require special preparation; and most importantly they are done under medical surveillance, with advanced CPR being ready to use.

If you do not push limits, then there is no point in using O2 - you can quietly and more safely dive normally. Secondly, the O2 is toxic anyway, regardless of the depth. It is toxic even on surface, just that the effects take much longer. It means it is preferable avoiding breathing oxygen when it is not necessary (i.e for deco or for medical reasons). And then, when you start using O2 or Nitrox, you will push your limits anyway, regardless what you think or tell now. And then, the O2 completely changes your sensations, reactions, as well as the physiology - you won't be able to rely on body signals, which alone may be sufficiently dangerous

 

[Rik]

There are a lot of different examples and questions making this a bit confusing.

The original question was if it is safe to use 100% oxygen as a tool for breath-hold diving between 30 en 50 feet because it might help to avoid an ascent black-out due hypoxia.

As some of the other posters explained, breathing 100% oxygen can be dangerous. Acute toxicity can occur as shallow as 23 feet and repeated use of 100% oxygen can have a toxic effect on lung tissue. Carbon dioxide can also be an issue during repeated and long dives. It is important to know that carbon dioxide toxicity causes impaired judgment, resulting in unsafe behavior.

But, what is the scientific evidence?

There is not much published research on this particular topic, except an unpublished trial in the late 90's (Vann et al. oxygen enhanced breath-hold diving). The test subjects improved their dive time under controlled circumstances, but suffered from altered consciousness at the end of the dive due hight carbon dioxide levels. One test subject lost consciousness. During this trial, there where no other harmfull effects noted, although it is important to point out that these where dry breath-holds and dry breath-holds with exercises.

This trial proofs that by using oxygen you would swap one possible problem (ascent black-out) with one sure problem (carbon dioxide poisoning).

So, why would you want to use 100% oxygen at all? If it isn't even safe to perform out of the water, don't increase your risks in the water. It isn't worth it.

I would recommend Trux's advice to spend time and money on improving your technique and find a reliable safety diver or buddy instead.

 

[fishhound]

There are a lot of different examples and questions making this a bit confusing.

The original question was if it is safe to use 100% oxygen as a tool for breath-hold diving between 30 en 50 feet because it might help to avoid an ascent black-out due hypoxia.

As some of the other posters explained, breathing 100% oxygen can be dangerous. Acute toxicity can occur as shallow as 23 feet and repeated use of 100% oxygen can have a toxic effect on lung tissue. Carbon dioxide can also be an issue during repeated and long dives. It is important to know that carbon dioxide toxicity causes impaired judgment, resulting in unsafe behavior.

But, what is the scientific evidence?

There is not much published research on this particular topic, except an unpublished trial in the late 90's (Vann et al. oxygen enhanced breath-hold diving). The test subjects improved their dive time under controlled circumstances, but suffered from altered consciousness at the end of the dive due hight carbon dioxide levels. One test subject lost consciousness. During this trial, there where no other harmfull effects noted, although it is important to point out that these where dry breath-holds and dry breath-holds with exercises.

This trial proofs that by using oxygen you would swap one possible problem (ascent black-out) with one sure problem (carbon dioxide poisoning).

So, why would you want to use 100% oxygen at all? If it isn't even safe to perform out of the water, don't increase your risks in the water. It isn't worth it.

I would recommend Trux's advice to spend time and money on improving your technique and find a reliable safety diver or buddy instead.

YEa great advice. I do have a safety partner and never dive without him. I was more interested in this from a physiology standpoint not a common sense one. I have alot to learn and that's why I'm asking questions. Thanks for your input

 

[trux]

There is also another risk that I forgot to mention. CO2 strongly amplifies narcotic effects and DCS risk. Well with pure oxygen you do not have nitrogen in the lungs, but unless you breathe exclusively pure oxygen all the time on the surface for prolonged time, there will be N2 dissolved in your body, and combined together with high CO2, fast ascents, and longer bottom times, it still can cause a DCS accident. There are even suspicions CO2 alone may be behind some DCS accidents, so perhaps even very little N2 is needed in some cases.

This exact scenario is little studied, so I cannot show you any study for backing these claims, but I would not recommend doing the research on your own (unless you have a team of physicians who would monitor you, and could quickly help in case of complications).

 

[Rik]

You ask, we answer

 

[fishhound]

There is also another risk that I forgot to mention. CO2 strongly amplifies narcotic effects and DCS risk. Well with pure oxygen you do not have nitrogen in the lungs, but unless you breathe exclusively pure oxygen all the time on the surface for prolonged time, there will be N2 dissolved in your body, and combined together with high CO2, fast ascents, and longer bottom times, it still can cause a DCS accident. There are even suspicions CO2 alone may be behind some DCS accidents, so perhaps even very little N2 is needed in some cases.

This exact scenario is little studied, so I cannot show you any study for backing these claims, but I would not recommend doing the research on your own (unless you have a team of physicians who would monitor you, and could quickly help in case of complications).

trux, one more thing...if you were staying down 230 or less is it even possible to build up enough co2 to do any damage?

 

[cdavis]

fishhound,

I sympathize with your approach. don't care much for general rules and, in truth, it is often possible to find an exception to a general rule that works and makes sense. However, in this case, pure 02 is so toxic, the effects of diving with it are so hard to predict, and the possible consequences so fatal, that you might want to give up on this idea.

By the way, check out exhale (frc) divng. It is quite possible to do spearfishing dives in your depths with 2:30 times and you don't need anything special to accomplish it. I come very close to that at 60 and not in great shape.

Take a course.

Connor

 

[trux]

You still did not give up the idea? I supposse you mean 2'30", but the time is little relevant. There are more factors involved - the breath-up, the physical effort, stress, temperature, your physical condition, the extent of physilogical changes while breathing O2 combined with the diving (which is little studied), ... On my mind it is simply not worth of taking the risks.

 

[fishhound]

You still did not give up the idea? I supposse you mean 2'30", but the time is little relevant. There are more factors involved - the breath-up, the physical effort, stress, temperature, your physical condition, the extent of physilogical changes while breathing O2 combined with the diving (which is little studied), ... On my mind it is simply not worth of taking the risks.

Guys, seriously...I'M NOT GOING TO DO IT..lol I appreciate the tone in wanting me to stay safe and respect everything that's been said. But whether I take a course or not, it still would not answer the questions I asked on this subject...it was a recreational conversation...some of it made sense to me and I was curious...some of you brought up great points and science for not doing it which is what I was looking for. To be honest though I have asked these questions on a few different forums and what I am certain of from the number of differing opinions is that noone really can say for sure if its safe or not. There are risks associated with foloowing the "rules" as well. Some risks are worth it and some are not. With that being said only an moron would do it without having some science to back it up. It was just fun to think about...sorry I asked

 

[trux]

Fishhound, it is nice to hear you are not serious about going to freedive in this way. However, I still have the feeling you did not understand all the risks involved, so I feel obliged repeating the warning targeted not only to you, but also to others who may get inspired by this idea after reading your comments.

... and what I am certain of from the number of differing opinions is that noone really can say for sure if its safe or not.

Not sure if you really have read all the replies you received here, but I believe they all listed more than enough of arguments to tell you that it involves much more risks than normal diving, so I would tell that this question was fixed pretty sure.

The question whether you can dive safely 2:30 on O2, and whether you can limit all the risks is simply wrong. It is as if you asked whether you can avoid blackout if you limit you plain-air dives to 1 minute. There is simply no such guarantee in either case. Depending on conditions you can blackout at 1 min even if you are able to pull 3 minutes dives otherwise. You will certainly manage to do a shallow 2:30 dive with oxygen without a harm, but it does not mean it is safe.

And the main problem is that there are more variables, and the risks are more numerous and higher than at normal diving. With sufficient knowledge, precaution, and technique, you can reduce some of the risks, but you still remain in a more risky zone than with standard freediving.