 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeArticlesDiving DestinationsLearning Scuba DivingMarine LifeMiscellaneousDiscussion GroupsGeneralScuba EquipmentScuba LocationsAustralian ScubaUK ScubaDirectoryScuba Clubs |
Scuba Forum / General / July 2005question (for doc or physiologist) about oxygen deprivation
For a human at rest at atmospheric pressure, breathing the standard atmosphere at a normal breathing rate, if his breathing gas is abruptly switched to 100% helium, which will occur first, unconsciousness or brain damage? And a followup question: IF the answer to the previous question is "it depends on when oxygen is restored", then if the breathing gas is switched back to the standard atmosphere (not to elevated oxygen) at or immediately prior to the onset of unconsciousness, then will brain damage occur? > For a human at rest at atmospheric pressure, breathing the standard > atmosphere at a normal breathing rate, if his breathing gas is abruptly [quoted text clipped - 6 lines] > immediately prior to the onset of unconsciousness, then will brain > damage occur? I think there's too many variables for any type of coherent answer, and you'd certainly have to quantify "brain damage", since it could involve ten brain cells or a trillion. I'm sure I did in a few hundred thou last night with no helium involved. But to your base question, from my perspective of ignorance, assuming 100% O2 starvation, you'd almost certainly pass out first. Sounds like your planning on torturing someone? Who do you have tied up in your basement? > For a human at rest at atmospheric pressure, breathing the standard > atmosphere at a normal breathing rate, if his breathing gas is abruptly [quoted text clipped - 6 lines] > immediately prior to the onset of unconsciousness, then will brain > damage occur? > which will occur first, unconsciousness or brain damage? Since helium, in and of itself, doesn't cause brain damage unconsciousness would occur before any brain damage caused by O2 deprivation. It takes a few minutes for brain damage from complete O2 deprivation, but unconsciousness can result in a matter of seconds. Not only does inhaling pure helium deprive you of new O2, it results in loss of O2 already in your blood. If your lungs are full of any gas that has no O2, any O2 in the blood passing through the lungs will outgas, further lowering the arterial O2 pressure. Brain damage resulting from trauma that results from losing consciousness is a possiblity even if the O2 deprivation isn't long enough to cause damage. There's also the possibility of lung damage or AGE (that can result in brain damage) if the helium is inhaled from a pressurized source. > if the breathing gas is > switched back to the standard atmosphere (not to elevated oxygen) at or > immediately prior to the onset of unconsciousness, then will brain > damage occur? Possibly. People have died from breathing helium, but probably not in any cases where they stopped before passing out. As I understand it, pure helium has an effect that is somewhat similar to CO, in that it can interfere with subsequent O2 uptake. If you breathe too much pure helium you may cause enough O2 starvation to do damage. I'm not sure what the actual mechanism is, but it may be related to the loss of arterial O2 pressure mentioned above. People have died from breathing helium, but probably not in any cases where they stopped before passing out. What is it you have in mind?  SignatureSteve The above can be construed as personal opinion in the absence of a reasonable belief that it was intended as a statement of fact. If you want a reply to reach me, remove the SPAMTRAP from the address. > It takes a few minutes for > brain damage from complete O2 deprivation, but unconsciousness can result in a matter > of seconds. Not only does inhaling pure helium deprive you of new O2, it results in > loss of O2 already in your blood. If your lungs are full of any gas that has no O2, > any O2 in the blood passing through the lungs will outgas, further lowering the > arterial O2 pressure. I've read this elsewhere as well, but I'm asking here because my experience differed from this explanation. I will give as much information here as I can. Unfortunately I can't give any additional information about the circumstances, even though this is going to sound strange: I hooked a regulator to a tank and began breathing on it at atmospheric pressure (I was on dry land, not in the water). I also had a mask on, so I was breathing exclusively from the tank. However, the tank contained 100% helium. After several minutes (at least five, and I estimate about 10), I began to feel very faint. I dropped the regulator from my mouth and thus began breathing the standard atmosphere again. Note that I spent several MINUTES breathing pure helium without losing consciousness; I don't understand why I didn't pass out within the few seconds normally cited as the standard timeframe. I estimate that I consumed somewhere around 100 liters of helium at a normal resting breathing rate. I of course realized that it would have been very preferable to immediately go on 100% oxygen, but unfortunately none was available at the time, nor were there even any tanks available with a higher than standard oxygen percentage, but they probably wouldn't have mattered anyway, since I felt so weak that I probably wouldn't have even been able to stand up and go get one; all I could do is lie down and breathe the atmosphere. Anyway, relatively quickly (within about 20-30 minutes or so) I recovered, apparently completely. However, more than 24 hours later, I fell extremely ill, with a fully-body "nausea" that I can't really describe, except to say that I really felt it throughout my entire body and not just in my head, which lasted for about 24 hours, after which I recovered with no further problems. No diving occured during these events, and the most recent dive was far enough in the past that it couldn't have caused any complications with the effects of the helium. So my primary concern is what permanent effects this event might have had on my body and especially on my brain, and my secondary concern is about the particular symptoms which I experienced, and especially the fact that I went several minutes on 100% helium without passing out. Can anyone enlighten me? > I hooked a regulator to a tank and began breathing on it at atmospheric > pressure (I was on dry land, not in the water). I also had a mask on, > so I was breathing exclusively from the tank. However, the tank > contained 100% helium. No it didn't. >> I hooked a regulator to a tank and began breathing on it at atmospheric >> pressure (I was on dry land, not in the water). I also had a mask on, >> so I was breathing exclusively from the tank. However, the tank >> contained 100% helium. > >No it didn't. Within two breaths hypoxia would have kicked in, after three breaths you'd be on the floor with you eyes rolled back. I agree with Greg, twernt helium you were breathing. Did you at least talk funny? Signaturedillon Linux, it's not just an OS, it's a way of life. And a damn fine one, at that. > Within two breaths hypoxia would have kicked in, after three breaths > you'd be on the floor with you eyes rolled back. I agree with Greg, > twernt helium you were breathing. Then why was I sprawled out almost unconscious, suffering from nausea, so weak for several minutes that I could barely even lift my arms, and totally drenched in sweat? An 80/20 helium-oxygen mix would have no physiological effects at atmospheric pressure at all, other than to affect speech. > Did you at least talk funny? I didn't try talking. However, I noticed that the pitch of the sound of the air flowing through the regulator when I inhaled was much higher than normal. Of course, this would occur regardless of whether I was breathing 80% or 100% helium. > > Within two breaths hypoxia would have kicked in, after three breaths > > you'd be on the floor with you eyes rolled back. I agree with Greg, [quoted text clipped - 11 lines] > than normal. Of course, this would occur regardless of whether I was > breathing 80% or 100% helium. And why was it that you did such an insane thing, in the first place? >>Within two breaths hypoxia would have kicked in, after three breaths >>you'd be on the floor with you eyes rolled back. I agree with Greg, [quoted text clipped - 12 lines] > than normal. Of course, this would occur regardless of whether I was > breathing 80% or 100% helium. Given all that you've told us to date then the bad news is, Yes, brain damage has occurred, But it's safe to say it occurred BEFORE you started to breath the helium! >>twernt helium you were breathing. > > Then why was I sprawled out almost unconscious, suffering from nausea, > so weak for several minutes that I could barely even lift my arms, and > totally drenched in sweat? It could have been the result of all sorts of things that were in there in minute quantities along with the 20% O2. My guess would be that whoever filled the tank figured that nobody who wasn't already brain dead would have done more than take a few breaths off of balloons filled from the tank, and therefore wasn't all that careful about CO being introduced into the tank. BTW, do you understand that a tank can contain "pure helium" and still have other gases as well? Surely you aren't really stupid enough to believe that you can completely deplete the O2 in your lungs, blood and brain, taking 5 minutes to become merely "almost unconscious"? Then again, if you did what you say truly believing that the tank contained 100% Helium the only rational explanation I can think of is that you're not very good at suicide, or really are very, very stupid. If you were trying to kill yourself, it's a good thing you didn't put a shotgun in your mouth, because I'm sure you'd now be a really ugly guy with one eye, one ear, 2/3 of a nose and a really bad combover. Alternatively, perhaps the tank was filled with troll poison. SignatureSteve The above can be construed as personal opinion in the absence of a reasonable belief that it was intended as a statement of fact. If you want a reply to reach me, remove the SPAMTRAP from the address. <snip> > I hooked a regulator to a tank and began breathing on it at atmospheric > pressure (I was on dry land, not in the water). I also had a mask on, [quoted text clipped - 5 lines] > consciousness; I don't understand why I didn't pass out within the few > seconds normally cited as the standard timeframe. What you were likely breathing was balloon helium or rather a tank of gas used to fill balloons for KIDS. Because kids do the same stupid thing you did, they breath the stuff, "balloon" He has about 20% O2 in it - just so you don't kill yourself. If you had of been on 100% He you would have passed out and if the reg didn't come out of your mouth, you would have been dead in ~ 5 min. Horseshit. No one can go without oxygen for five minutes without significant brain injury (assuming we're not talking a cold water drowning scenario). At six minutes the brain is pretty much gone. Loss of consciousness would occur sooner. I don't believe you were breathing 100% helium. >> It takes a few minutes for >> brain damage from complete O2 deprivation, but unconsciousness can result [quoted text clipped - 45 lines] > fact that I went several minutes on 100% helium without passing out. > Can anyone enlighten me? > For a human at rest at atmospheric pressure, breathing the standard > atmosphere at a normal breathing rate, if his breathing gas is abruptly > switched to 100% helium, which will occur first, unconsciousness or > brain damage? Unconsciousness occurs before permanent damage. > And a followup question: IF the answer to the previous question is "it > depends on when oxygen is restored", then if the breathing gas is > switched back to the standard atmosphere (not to elevated oxygen) at or > immediately prior to the onset of unconsciousness, then will brain > damage occur? > Unconsciousness occurs before permanent damage. Then again, there is the issue of it being difficult to kill off brain cells when they aren't there to start with... I would think that better ingredients for suicide would be 1. oxygen tanks 2. and hydrogen tanks 3. connected to the compressor intake 4. of your recompression chamber... Bring your favorite cigar and make it look like an accident. I've been unable to find any firsthand information about this supposed 20% oxygen added to "party balloon" helium tanks. Can anyone provide links? > I've been unable to find any firsthand information about this supposed > 20% oxygen added to "party balloon" helium tanks. I don't believe that it is 20% and not every helium supplier does it... I seem to remember it being a low enough percentage that you would eventually feel somewhat lightheaded if you breathed it for a prolonged period of time... > > I've been unable to find any firsthand information about this supposed > > 20% oxygen added to "party balloon" helium tanks. [quoted text clipped - 3 lines] > eventually feel somewhat lightheaded if you breathed it for a prolonged > period of time... I think it is 16% >> I've been unable to find any firsthand information about this supposed >> 20% oxygen added to "party balloon" helium tanks. The amount of oxygen in "baloon helium" is quite variable. A couple of years ago I met a group of divers in the Florida Keys for some tri-mix diving. One of the group, a native Floridian, had secured the helium and was about to begin mixing. He was going to do the mix using partial pressure mixing with no helium analyser. He assumed that the helium bottle contained 100% He. When I noticed that the bottle was labled "baloon helium" alarms in my head went off. Fortunately I had brought my He analyser with me. Analysing the gas, I found that it contained about 75% He and 5% O2. That would correspond to a 25% air mix. Now, 5% O2 will not keep you alive for long but it will not kill you immediately either. It will really mess up your mix calculations, though, if you think the stuff is pure He. All this just points out the need to analyse your gasses. Safe diving, Cpt. Dale |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.