Blackout? Safe erotic asphyxiation - BDSM Tips & Techniques - tribe.net Blackout? Safe erotic asphyxiation topic posted Sat, November 7, 2009 - 12:04 AM by John So I am into erotic asphyxiation, I finally found someone who has an interest with me. I know the dangers but here is my situation. When I am being choked, I am completely restrained and have a blindfold and a gag. This means that I really can't tell my girl to stop; the only thing that i can do is hold something in my hand and once dropped, my girl will stop. I'm worried that I might black out, which would then cause me to drop the object and my girl would stop (as previously stated). The way my girl chokes me is by pressing on my upper throat (just under my jaw) with her hand (part between her thumb and forefinger) so that blood can still flow to my head.

I have never passed out yet, but if I do, I told her that if I do not wake after about 30 seconds, to essentially breath 2 to 3 breaths of air into my lungs (pretty much CPR) and that should bring me back relatively soon. I know that normally if a person was to be choked out in this way that they will usually awake by them them self (because the heart rate increases, increasing blood and oxygen to the brain causing the person to wake up, assuming that the persons airway is cleared and there is some oxygen left in the lungs) but a person will not awake if they are choked out to the point where the lungs completely use ALL the oxygen in the lungs then CPR is needed or death will occur. I'm wondering if anyone reading this has ever blacked out by this method or similar (gas mask) before and have awaken safely? Any tips? (Please don't tell me i'm crazy or to stop, because I won't I until i get it out of my system) posted by: Re: Blackout?

Safe erotic asphyxiation Sat, November 7, 2009 - 5:06 PM Jay Wiseman has written a lot about erotic asphyxiation. He's something of an expert on it. It is possible to die from it, but I think Jay may over exaggerate the chances of this. Still, I do recommend that you look for his article (you should be able to find it on the internet) and read it. It might not be fun for your girlfriend to be charged with manslaughter. Re: Blackout? Safe erotic asphyxiation Tue, November 24, 2009 - 8:43 PM Actually, Domina, the risks of death from this are so high that even in an emergency room setting, with people fully trained in the techniques that are essentially what are used in this sort of play, albeit for legitimate medical reasons, they always have a full crash cart right at hand, and a whole ER full of doctors and nurses. The risks are *extremely* high - *especially* if the person being choked/asphyxiated has any kind of known or hidden heart problem. Re: Blackout?

Safe erotic asphyxiation Fri, January 1, 2010 - 5:44 AM there is nothing that i find more sensual/sexy/hotter than hell.... than a hand wrapped around my throat, but i've never taken it as far as losing consciousness. i enjoy being completely and totally aware of what is happening. Re: Blackout? Safe erotic asphyxiation Sat, January 2, 2010 - 10:50 PM Thank you, KLG. I don't personally do it, because it's unsafe, but I didn't think it was as unsafe as you said it was. However, YOU would know. So thank you for the heads up. Sun, January 3, 2010 - 3:03 PM This just seems like an oxymoron to me. I also suggest learning from some experts. Jay is going to do his best to talk you out of it and he has good reason to. There are huge risks involved. We had someone locally die this way years ago. Jay has a profile on tribe so you might search for that and read his blogs.

I'm sure there is something about this subject there and you'll find out why he is an expert. Re: Safe erotic asphyxiation Fri, April 23, 2010 - 11:29 PM You're right, Kelly; it *is* an oxymoron. There is *no* such thing as "safe" erotic asphyxiation. There are only people who are lucky enough to not die from it - this time. Sun, January 10, 2010 - 1:19 AM You're welcome, Domina. The technique used medically is called "carotid sinus massage", takes very little pressure, and is used only when the heartrate is so fast as to be dangerous specifically to slow it down, and pretty much only if drug treatment fails precisely because of the risk. The risk of cardiac arrest is high indeed. I've been trained in it, but never had to use it. Re: Blackout? Safe erotic asphyxiation Tue, February 23, 2010 - 1:30 PM I'm afraid you are mistaken.

If this is "carotid sinus massage" and is as dangerous as you want to make it out to be, there should be thousands of people dieing from this everyday! Please show me the bodies stacked like cord wood from this type of partnered play gone bad. Re: Blackout? Safe erotic asphyxiation Thu, March 4, 2010 - 6:47 AM Larry, they don't all die so there aren't stacks of bodies but how many does it take? I know that I'm not willing to be the one person that dies from this type of play this week. There are plenty of other things to do. You may have been doing this for 20 years and have never had an incident but 22 year old "Dom" that tries his first time could do some damage. Is it really worth it? Sun, May 2, 2010 - 6:11 PM Hi kelly. Have you driven or ridden in a vehicle? Walled down a flight of stairs? Taken a dump? Had sex? Just to name some very common ones. People have all died doing these things so none of them are safe to do.

Kelly you are arguing about "carotid sinus massage" a subject you know little if anything about. You are arguing to defend Jay who doesn't know much if anymore than you do. If it were as dangerous as Jay and klg want to make it out to be, then yes the bodies would be stacked like cord wood. If it is only rarely happening, then why is it only happening in those rare instances? If a million people, 5 million, ten million do it and it doesn't happen what does that say about the odds on it happening? A 1 in a million shot at it happening, pretty impressive odds considering how many people die in vehicle accidents everyday and most people never give it a second thought. As you can see, safe is a relative term. " I know that I'm not willing to be the one person that dies from this type of play this week." I don't see anyone asking you to engage in this. I guess you only engage in activities that have no risk at all involved in them. Hope you enjoy them. " Is it really worth it? " If you had tried this you wouldn't be asking that question.

Those that have actually done it want to do it again, so yes it is worth it, to them. "but 22 year old "Dom" that tries his first time could do some damage." well that's why folks like me are trying to talk to newbie’s so they don't crush someone’s windpipe or break their hypoid bone. Believe it or not most Doms, who aren't psychotic, are afraid they'll hurt the sub so they go slowly and wisely so. The more information they have and better prepared they are the better they'll be. That's what I'm trying to do, put some real stuff out there. Re: Blackout? Safe erotic asphyxiation Sun, May 2, 2010 - 3:26 PM Hmmm! Well if you are a former paramedic and premed student, just like Jay, then you both better go back to school because you both missed one hell of a lot! Okay Mr. Smart ass former paramedic and premed student, if this is as dangerous as you to wanabee's make it out to be then, explain how it is that people have been choked out into unconsciousness literally millions of times with no deaths or ill effects.

For over 100 years! All ages, sexes and levels of fitness. It is done thousands of times every day. Funny neither you nor Jay can explain this! So Mr. former paramedic and premed student, explain how it is that holding your breath until passing out doesn’t cause heart attacks in healthy people? There are no reported cases of this happening and as a matter of fact go and ask your family doctor, I did! Ask a paediatrician? Tell them that your child throws a tantrum and holds their breath until they pass out. They are concerned about them falling and hurting themselves. They are concerned about the behaviour. I've yet to find one that is concerned about them having a fatal arrhythmia or cardiac arrest. Now these are the people with the big tickets! The real thing! Not some wannabe. No where have I ever said there is no risk involved in this. There is risk of dieing in everything we do! Learning how to properly manage that risk is helpful. Running around like chicken little spreading BS helps no one except for your own ego!

If you're going to hold up your "former paramedic and premed student" badge to make it look like you know what you're talking about, at least get your shit straight, because both of you know jack shit about this subject! These are only two for you to answer then, we'll get into the rest of it. Oooh! The dreaded R/t!! Oh and so much more! But explain the first two, that should be so easy for you with YOUR expertise! Jay can’t answer these, he won’t even try. He got eaten alive! I can’t wait to hear your explanation. Tue, January 12, 2010 - 7:18 PM John, I just noticed your comment about what you've told your girl to do if you black out. With all due respect, you have no idea what you're talking about, and what you've told your girl to do if you "black out" is incorrect in its entirety, at best will do nothing at all, and at worst could kill you outright, even if the choking scenario doesn't take care of that by itself. For starters, blacking out, stopping breathing, and having your heart stop are three completely different things.

Doing mouth to mouth respiration will do nothing at all by itself if your heart stops - and if you've just blacked out, you'll still be breathing, so it won't be necessary. Even if you've only stopped breathing, believe me, 2-3 breaths will *not* bring you back. Not even in your dreams. If your heart stops, you'll need full-on CPR - and you likely won't survive anyways, because these kinds of cardiac arrests are particularly difficult to resuscitate, even when witnessed and *correct* CPR is started immediately. If you're going to do this sort of play, make sure your partner is fully trained in proper CPR. And that your will and the rest of your estate are in order before you start. klg (former paramedic) Re: Blackout? Safe erotic asphyxiation Tue, February 23, 2010 - 1:08 PM Yes I have been taking women into blackout for over 20 years. Just a word of advice, there is a lot you obviously don't understand about doing this and believe me you two are unprepared for what you are getting into. I'm not telling you not to do this.

What I am telling you is that there is a lot more that you two need to know before you go down this road. Yes this can be done relatively safely when done properly. From what you've said it doesn't sound like you are at that point yet. Let me know if you want to talk about it. Be well, Re: Blackout? Safe erotic asphyxiation Sun, March 14, 2010 - 10:34 PM Ive found that if you can still breath slightly that you don't get headaches but maybe that's just me . if there is too much pressure for too long, i have also found that you get little red spots around your eyes and on your face. soft flexible, stretchy material can be good eg silk rope , spandex blends. i am by no means an expert on this it is just things i have tried myself. i have never gotten a mark on my throat yet & hopefully wont. but me and my partner are going slowly with trying it . Re: Blackout?

Safe erotic asphyxiation Tue, March 16, 2010 - 2:14 AM i have never blackout using these equipment, i have gotten close though but have always made sure there is a way for me to remove the equipment quickly , though my body does heat up a lot . i have found that the way you hold your neck can either cut off more air or allow more air to flow. when my partner strangles me i find that the closer to my chin he goes the less it hurts my neck. though he has to be extremely careful since one of his hands is the size of my entire neck. playing by myself i am more careful using pressure of a rope as close to the top of my neck as possible and then tilting my head backwards to cut off air supply, so that if i need to breath i tilt my head forward and can breath enough to remove the rope. i have never tied the rope to anything and used my weight to strangle myself i think that is way to dangerous to even think of doing. i might have repeated myself a couple of times if so i am sorry. just remember to be careful Re: Blackout?

Safe erotic asphyxiation Tue, March 16, 2010 - 6:59 PM Thank you for sharing. I have been trying to duplicate the effects of bare hands using ligatures, and have not been very successful even with a substitute rubber strip tourniquet. The problem when using ligatures, is the air passage taking the pressure away from the carotids, even though this is less of a problem nearer the chin, less risk of damaging the air passage too. Will probably experiment with a paramedic quick release tourniquet, it would provide more control over the process. and more freedom for the hands and body, no more trying to fumble with knots close to the edge. Just concerned that the plastic bit would leave markings on the neck though. Will give update on my experiments if anyone is interested. Re: Blackout? Safe erotic asphyxiation Mon, May 3, 2010 - 7:24 AM Okay so you are dealing with chokes. John the first thing anyone doing this should do is go to your doctor. Tell them you are planning on joining a jujitsu class were they practice chokes.

Ask your doctor to perform a stress test to assess your cardiovascular and respiratory fitness. Have them discuss what they think your risk factors are. Certain information in your family and personal health history can affect your risk, as can certain medications. Your doctor is the one to inform you about YOUR risk. So what if you and your partner went to the people that are experts at doing chokes? Now these people have been doing this for over a hundred years, millions of participants and no fatalities. Go find a competitive jujitsu school in your area. It is important to find a school that competes, and hopefully wins, because that helps assure competence. Then sign up for 2-3 months. You can tell the instructor you have a particular interest in applying and defending against chokes like the rear naked choke. If they ask why you can say because they win a lot of UFC matches and they look cool. Go and learn how to do it properly considering what’s at stake. Make sure the giver is CPR trained and also trained in strokes. Consider buying an AED (automated external defibrillator). Odds are you won't need it, but nothing is completely safe. Breath play has risks just like driving your car.

There is all kinds of safety equipment built into your car to try and protect you. Most drivers never need this stuff, but if someone goes through a red light and runs into you, you can't hit the hold button and make changes to prepare for the crash, it's happening right now! Hopefully your safety systems work to help protect you. Breath play is the same thing. Hopefully you will never need any of this. But if something goes wrong it's nice to have a back up plan. You've got a 3 minute window and you've used up part of that during the play. If something ever goes wrong the giver has to be able to react quickly and effectively. If they've been trained and have everything they need right there they've got a shot at saving the day. If they just call 911 and wait for the paramedics to arrive, well don't hold your breath on surviving the incident. If an AED is used immediately you have an 86% chance of survival. If they sit back and wait for the paramedics to arrive, depending on how close they are, that drops to 10% or less. Remember that 3 minute window.

They don't want to be sitting there later saying, it really wasn't that hard to do, damn why didn't I prepare for this? What’s your life worth? What’s the givers life worth? So you've learned how to do chokes properly so that you know where to squeeze and were not to squeeze. You're prepared, just in case something goes wrong. Now your ready to enjoy all of the amazing sensations this type of play can bring for both of you. "The way my girl chokes me is by pressing on my upper throat (just under my jaw) with her hand (part between her thumb and forefinger)" Look up the anatomy of the neck. Look up the hyoid bone. Learn about its importance and why you don't want to break that. " I told her that if I do not wake after about 30 seconds, to essentially breath 2 to 3 breaths of air into my lungs (pretty much CPR) and that should bring me back relatively soon." What you are talking about is called Artificial Respiration and she needs to tilt your head back and pinch your nose closed for this to work. Training would be really good here! You should be breathing on your own immediately from the A/R.

That is the important first step. If your not then she needs to react very quickly and effectively. Do you have a pulse? This can be hard to find in a tense situation especially in an untrained person. Having a pulse/oxy meter would tell her instantly what was happening for under a $100 bucks. Yes or no, do you have a pulse? Is you oxygen saturation level coming up or dropping? Don't leave her there trying to guess at what the hell is happening inside you? If you’re breathing on your own, are there any signs of stroke. Does she know what to look for? (If a stroke victim is given the proper treatment in under 3 hours the effects can be almost if not completely reversed. Another one of those time limits.) If you’ve been properly checked out by your doctor, then you know what your risks are so you can prepare for them, if something happens, if you have any issues. You are right in that so long as your airway is clear your autonomic system will kick in and restart your breathing, if you don't push it to far. That is where she becomes the wild card. Does she let go immediately and make sure your airway is clear?

Does she get caught up in the moment and it goes farther? When you're holding your own breath and you black out without any restrictions it can't go any farther. When someone else is doing it, that's a whole other story. Do they or both of you decide to push the envelope, just a little? How about the next time or the 50th time or the 500th time? If you do this with no preparation or training and all goes well, like anything else in life you gain confidence. Maybe even complacent because you've done it enough times without incident. I don't know anyone that has done this and enjoyed it that has only ever done it once by choice. They always want to do it again, especially the receivers!! It is an unbelievably powerful experience for them! Especially those that go into blackout! To walk right up to the very edge of the abyss then, take a step into freefall knowing that they may not comeback, but hoping like hell they do! I've know people who want to stay in that moment, or at least try to stay there longer. How do you suppose they go about achieving that?

With no back-up plan and pushing the envelope, do you think their risk of something going wrong jumps exponentially? Coming back is just as powerful, if not more so! That's why there are a lot more people wanting to go there than there are people willing to take them there. Instinctively as a Dom you know that if something goes wrong here and you don't know how to handle it, you are fucked! There is no time out or reset button for this broken toy. So get prepared for the event that will never happen to you two, because just like everything else in life, that risk will always be there so it could happen and 3 minutes is not a lot of time to figure out what to do next! Slams the door, puts on his seatbelt, smiles, waves and drives away. Re: Blackout? Safe erotic asphyxiation Mon, May 3, 2010 - 4:28 PM Interesting that now, all of a sudden, Larry is saying that the partner needs to be trained in CPR and that there should be a defibulator on hand... his previous posts would have you believe that it is as safe as can be...

nothing to worry about, its been being done for hundreds of years, show me the bodies and other such garbage. I did not think I would post to this thread, but finally decided i needed to add my 2-cents. I will personally tell everyone that to play with this, is to invite probable heartache into what is supposed to be enjoyable. Just as with playing with fire will sooner or later get you burned, or playing with snakes will finally get you bit, playing with this will sooner or later go too far. It may be due to a medical condition, or lack of sufficient knowledge of recovery methods, or any of a score of other possible problems. Frankly, i do not care how many times it has been done "safely" in the past, one could also ask how many strangulations have resulted in death over the ages. It is catigorically STUPID to do anything in sexual play that can possibly result in the death or dismemberment of anyone involved. Larry seems to enjoy degrading those who dissagree with him in this, and cannot accept their knowledge on the subject, considering himself to be the ultimate authority. I am curious Larry, what is YOUR medical background and training? I wil tell you mine...

I am a doctor of Traditional Chinese Medicine with over 17 years of clinical practice specalizing in sports medicine and accident trauma. I am also an upper level black belt and teacher of Ninjutsu and Juitisu in both of which we use and teach many differnet types of chokouts, many of which will not only choke you, but crush your larynix in the process. I also have at least 3rd degree blackbelts in three other punch-kick styles of martial arts as well as Tai Chi, Ba Gua and Shing-I, and am a Master of both Qi Gong and Reiki energy work. One other thing that was touched on by one of the posts... in the process of asphyxiation, the reason you black out it because oxygen isn't being delivered to the brain to keep you concious. When the brain cells lack O2 for even a short period of time, they die. Sure, you have billions of brain cells, but killing then for the fun of it is simply stupidity in the extream as you cannot regrow them.

I am aftaid that if Larry has been doing this sort of play for as long as he states, from his posts, i would say that he has lost too many brain cells already and shoud stop before he looses too many more. I repeat myself... any type of "play" that endangers the life, or limb of the participants is simply stupid in the extream. I have a very broad range of experience in the culture, but always assure my subs that my hard limits are no play that is medically contra-indicated or that may leave a permanite injury or marks (with the exception of possible tatoos). But in terms of "erotic asphyxiation", from a medical perspective, there is NO safe way to "play". Lady Tara, OMD, L.Ac., LMP/NCTMB, Shidoshi-ho Effects of Unequal Air Pressures While Scuba Diving Internet Links SECTION F Effects of Unequal Air Pressures While Scuba Diving: Ear Squeeze, Sinus Squeeze, Air Embolism and Other Forms of Barotrauma WHAT DOES BOYLE'S LAW PREDICT ABOUT UNEQUAL PRESSURES?

Once again we come to all-important Boyle's law: for a given mass of gas at a constant temperature, the product of pressure (P) and volume (V) is constant (K): P x V = K. We have already seen how, for the breath-hold diver, Boyle's law predicts that compressible air spaces will shrink on descent and re-expand on ascent, and that the situation is different for scuba divers because compressed air is continuously inhaled. Even if the scuba and breath-hold diver go to the same depth and spend the same amount of time under water (e.g., one minute), the effects of water pressure are radically different on the two divers. Because tank air is inhaled at the ambient pressure, the scuba diver's lungs and other compressible air spaces do not shrink. Consider that all the body's air-containing spaces are in contact with inhaled air. At the same time, there is a natural tendency for air anywhere in the body - in the lungs, middle ears, sinuses and other spaces - to diffuse into the blood. As air is absorbed into the blood it is replenished by fresh air inhaled from the scuba tank.

If the absorbed air was not replenished the air spaces would, over time, shrink and close. (This in fact happens in some lung diseases. Any part of a lung that becomes plugged, such as from mucus or a tumor, will shrink completely until it becomes airless.) Shrinkage and closure of an air space will not happen as long as it is in contact with a fresh supply of air. Does Boyle's law still apply to such spaces? Unequivocally, yes. When fresh air enters the diver's lungs it is at the same pressure as the surrounding water pressure. This pressure, of course, is higher than at sea level and so the air is correspondingly denser. As long as the diver continuously breathes from the scuba tank, the density of inhaled air will change with ascent and descent. For this reason the "given mass of air" stipulated in Boyle's law, which is really the number of air molecules, changes as the depth changes. On descent the "given mass" increases as the inhaled air becomes denser; on ascent the "given mass" decreases as the inhaled air becomes less dense.

Stated another way, when breathing compressed air under water, the actual number of air molecules, in the lungs and all other air spaces, increases on descent and decreases on ascent. Assume two people dive from a boat to a depth of 99 feet; one diver holds his breath and the other diver uses compressed air (scuba). Also assume that the lungs of each diver contain 10 billion air molecules and the lungs behave like balloons. Table 1 shows the physical changes in air in the lungs of each diver at 33, 66 and 99 fsw. (Actually, the breath-hold diver's lungs, being tethered by a rib cage, don't behave exactly like balloons. Also, some gas exchange takes place even with breath holding, since oxygen is taken up from air in the lungs while a smaller amount of CO2 is added to that air; as a result, the number of molecules does not remain exactly the same.) TABLE 1. Change in mass of gas, lung volume and air density with depth: breath-hold vs. Scuba. Mol. = no. of air molecules in lungs (billions); vol. = volume of air in lungs. See text for discussion.

breath-hold diver SCUBA DIVER depth(ft.) mol. vol. den. mol. vol. den. sea level 10 8 1 10 8 1 33 10 4 2x 20 8 2x 66 10 3 3x 30 8 3x 99 10 2 4x 40 8 4x For the breath-hold diver, the mass of gas (the number of molecules) in the air spaces remains about the same during the dive, so as water pressure increases the lungs must shrink (Boyle's law). For the scuba diver, however, the mass of gas (number of molecules) increases along with the increase in water pressure, so the lungs do not shrink. Thus the lungs (and other air spaces) of a scuba diver at 33 fsw contain twice as many air molecules as at sea level, and also twice as many air molecules as a breath-hold diver at the same depth (allowing for slight variation due to absorption of oxygen into the blood).

Since the volume of air in the scuba diver's lungs doesn't change, the density of air (how close the molecules are to one another) must be greater (see Table 1). At 99 fsw the breath-hold diver's lungs contain about the same number of molecules as on the surface, but in only 1/4 the volume; hence the air, being compressed by the increased pressure, is four times denser than on the surface. At 99 fsw the scuba diver's lungs are filled with air just as dense, but since there are four times the number of molecules as on the surface the lung volume is preserved (Table 1). As long as there is good communication with inhaled air, the scuba diver's compressible air spaces will fill up with the air extra molecules and will not shrink. 1. Based on the sea level values provided in Table 1, what would be the number of molecules and volume of air in a scuba diver's lungs at 132 fsw? 2. Using Boyle's law, describe what would happen to each of the following if a scuba diver holds her breath at 66 fsw and attempts ascent to the surface. a.

number of molecules in the lungs b. density of air in the lungs c. volume of air in the lungs TEST YOUR UNDERSTANDING Answers Everything described so far fits with Boyle's law. 'Pressure times volume' is a constant value when the mass of gas (number of gas molecules) is fixed; it is not constant if the gas density changes, as occurs with changes in depth, because then the mass of gas in any space also changes. The most critical result of Boyle's law occurs when the mass of gas is fixed, as would occur in the lungs of a scuba diver if breath is held. If the scuba diver was to breath-hold and ascend, the fixed mass of gas at the time of breath-hold would inexorably expand in volume (as predicted by Boyle's law) until the diver exhaled or the lungs ruptured. This, of course, is why a breath-hold ascent from any scuba dive is so dangerous. 3. A scuba diver breath-holds at 66 feet and then rises to the surface. Assuming her lung capacity is 6 liters at the point of breath-hold, what would be her lung capacity at the surface? a. 6 liters d.

Her lungs would rupture before reaching the surface. TEST YOUR UNDERSTANDING Answers WHAT IS THE DIFFERENCE BETWEEN SCUBA DIVING WITH THE GLOTTIS CLOSED AND OPEN? The glottis is the voice box, located just under your chin inside the neck. Also called the larynx, it leads directly into the trachea (the "windpipe") which then leads to the lungs (see Chapter 3). We "close" the glottis when we hold our breath, which is why you can't speak and hold your breath at the same time. (The universal sign of someone choking on food is fingers to the throat and inability to speak.) What happens when the glottis is open or closed relates directly to the difference between compressible and non-compressible structures, as was discussed in Chapter 5. Non-compressible structures include the blood, bones and all solid organs; compressible structures include the lungs, sinuses, middle ear, and the hollow organs such as the stomach and intestines. Figure 1 shows effects on the lungs from increased ambient pressure when the glottis is closed ("Closed"), and when air is replenished from scuba apparatus ("Scuba").

A scuba dive with breath held (glottis closed) is tantamount to a breath-hold dive (Table 1); the lungs will be squeezed by the increased ambient pressure. An initial volume of 6 liters (e.g., after taking in a regular breath) could theoretically shrink to only one 1.2 liters at a depth of 132 feet (Figure 1). However, the scuba diver has the option (which should always be exercised) to continuously breathe compressed air, in which case lung volume will stay the same at all depths (allowing for slight variation with regular breathing). In both situations (glottis closed and breathing compressed air) the density of air in the lungs will increase with increasing depth. Air in the tank is highly pressurized, approximately 3000 psi (equivalent to 204 atmospheres) for an 80 cu. ft. tank filled to capacity. The two-stage regulator allows compressed air to be inhaled at the ambient pressure, so the scuba diver can maintain normal lung volume at all depths.

(The increased density of the inspired air at depth is seldom great enough to impair work of breathing during recreational diving.) Tank pressure should be at least 500 psi before beginning any ascent (ideally, one should arrive at the safety stop with no less than 500 psi). Five hundred psi are equivalent to 34 atmospheres. Since the maximum RSD depth of 130 feet equals only about five atmospheres, there should always be a large gradient for air to flow from the tank to the diver's lungs. Figure 1. Effects on lungs with glottis open and closed. WHAT IS BAROTRAUMA? 'Baro' refers to pressure (e.g., a barometer is an instrument for measuring pressure). Barotrauma is physical damage to any part of the body as a result of unequal air pressures; it is from either compression or expansion of a body part. The tissues may rupture, blood supply may be compromised, or swelling may occur. All conditions discussed in this chapter are forms of barotrauma. In the case of diving, the unequal pressures are between some cavity of the body (the middle ear, the sinuses, the lungs, etc.) and the ambient air pressure.

The consequences of barotrauma may range from mild discomfort in the affected area (e.g., ears or sinuses), to various levels of pain, to rupture of an organ, such as the ear's tympanic membrane or a part of the lung. Rupture of an organ while diving is particularly hazardous because of the risk of drowning. Barotrauma is one of three pressure-related problems encountered in scuba diving; the other two are decompression sickness and nitrogen narcosis (Table 2). Barotrauma problems (including the most severe, arterial gas embolism), are physiologically explainable by Boyle's. Non-barotrauma, pressure-related problems are physiologically explainable by the laws of Dalton and Henry, as will be discussed later. WHAT BAROTRAUMA PROBLEMS CAN OCCUR ON DESCENT? Most problems on descent relate to inadequate communication between the upper airway and the middle ears and sinuses. The most frequently en-countered problem on descent is middle ear "squeeze," an ear discomfort or pain from shrinkage of the middle ear space (Figure 2). This problem may begin at only a few feet depth.

The earliest symptoms are similar to the "ear stuffiness" we sometimes feel when a plane rapidly descends. Unchecked during a dive, the feeling can rapidly progress to actual pain and ear damage. The pathologic result of continued squeeze in any space is engorgement of the mucosal lining, swelling, fluid buildup and finally hemorrhage into the space. In unchecked middle ear squeeze, the tympanic membrane or round window can collapse inward and burst, leading to extreme dizziness (vertigo) and an emergency situation. In a compilation of 1001 disorders referred to an otolaryngology (ear, nose, throat) diving specialist, the middle ear accounted for 399 (40%); 314 of the total (31%) were manifested by pain on descent (Roydhouse 1985). WHAT IS THE CAUSE OF MIDDLE-EAR SQUEEZE AND HOW CAN IT BE PREVENTED? Squeeze on the middle ear is prevented by making sure inhaled compressed air travels from the back of the nose (nasopharynx) into the middle ear spaces.

The only route of passage into the middle ear is through a tiny, compressible canal called the eustachian tube (after its discoverer, the Italian Bartolommeo Eustachi, 1524-74). Anatomically, this is a soft and flexible canal that functions as a one-way flutter valve; it easily opens up when pressure in the middle ear is higher than in the nasopharynx, but tends to close shut when pressure in the nasopharynx is higher than in the middle ear. As a result, gas flow is passive from the middle ear to the nasopharynx on ascent (you don't have to think about it), but "active" on descent (you have to make it happen). TABLE 2.

PRESSURE RELATED PRBLEMS IN DIVING 1) Barotrauma (explained by Boyle's Law) On Descent Ear/sinus squeeze Tympanic membrane rupture Alternobaric vertigo Barodontalgia On ascent Reverse ear/sinus squeeze (usually associated with inflammation in upper airway) Alternobaric vertigo Pulmonary barotrauma and sequelae, e.g., pneumothorax, pneumomediastinum, air embolism (see text for discussion) Miscellaneous; barodontalgia; gastrointestinal expansion distress 2) Non-barotrauma (explained by Dalton's and Henry's Laws) Nitrogen narcosis ("martini effect") Decompression sickness (DCS) Principal manifestations of DCS: TYPE I cutaneous musculoskeletal (the "bends") TYPE II pulmonary (the "chokes") vestibular neurological cardiovascular Figure 2. Middle ear squeeze. The external ear canal leads to the flexible tympanic membrane or eardrum, which is exposed to the ambient pressure. Behind the ear drum is the middle ear air space, which will be compressed at depth unless pressure is equalized, via the eustachian tube, with inhaled air.

If the eustachian tube is blocked � as may happen without equalization after descending just a few feet � fresh air cannot enter the middle ear space and the ear drum will bulge inward, causing pain. If the diver descends too quickly without equalization, the tympanic membrane can rupture. If the diver continues to descend slowly without equalization, blood and fluid from surrounding tissue will be forced into the middle ear space. Thus the diver has to consciously work to keep the eustachian tube open on descent, or else it will seal shunt and prevent compressed air from reaching the middle ear. This is done by one of several maneuvers, including blowing against a closed mouth and nose, swallowing, yawning, or the Valsalva or Frenzel maneuvers. (The Valsalva is a forced exhalation with nose pinched, lips closed against mouthpiece, glottis open.

The Frenzel is accomplished with nose pinched and lips closed against the mouthpiece; the back of tongue is thrust against soft palate, gently pushing air through the eustachian tubes.) Whichever method is used, it must be done frequently on descent because at some point no maneuver will work; this is the situation when the pressure keeping the tube shut is too great. If the pressure gradient across the tube (nasopharynx to middle ear) exceeds 90 mm Hg - a gradient reached at only about 4 feet depth - none of the maneuvers will open the eustachian tube and the diver must ascend to relieve the pressure. Scuba divers are universally taught to prevent middle ear squeeze by forcing air through the eustachian tubes before symptoms occur, just before or at the beginning of descent and then every few feet. "Equalize early and often" is the universal advice. WHAT IS THE TREATMENT OF MIDDLE EAR SQUEEZE? Treatment of middle ear squeeze depends on its severity. Mild cases often to respond to decongestants. Antibiotics may be indicated if there is tympanic membrane rupture, but such a problem should be referred to an otolaryngologist.

In all cases diving should be avoided until the ear has returned to normal. WHAT OTHER FORMS OF BAROTRAUMA OCCUR ON DESCENT? The inner ear can also be affected, with rupture of the round or oval windows, cochlear damage and permanent hearing loss. Tinnitus, vertigo, and deafness after a dive are the classic symptoms of inner ear barotrauma. In such cases antibiotics and bed rest are indicated, with surgical repair if there is no improvement (Neblett 1985; Davis & Kizer 1989). External ear squeeze may occur if the ear canal is blocked with ear wax or ear plugs; divers should never wear ear plugs for this reason. Another common cause of external ear squeeze is a tight-fitting wetsuit hood. The sinuses have no natural one-way valve by which to vent expanding air, but as long as there is no sinus blockage the diver can avoid "sinus squeeze." Sinus squeeze is accompanied by a painful feeling behind the cheekbones, between the eyes, in the upper teeth area, or over the forehead.

A blockage from outside the sinuses (as from nasal polyps) may produce sinus squeeze on descent, as air cannot enter the sinuses and equalize the pressures. In severe cases the diver can experience sinus hemorrhage and a bloody nose. Decongestants and analgesics are used for mild cases of sinus squeeze. Antibiotics may be needed if there is evidence of fluid or blood in the sinus cavities. Diagnosis of this problem may require a CT scan of the sinuses. WHAT BAROTRAUMA PROBLEMS CAN OCCUR ON ASCENT? Closed air spaces pose a serious threat on ascent from a dive. Boyle's law predicts that closed air spaces will expand as the ambient pressure decreases on ascent. As long as the eustachian tube and sinus passages are not blocked, the middle ears and sinuses will vent expanding air into the nose, from where it will be exhaled along with expanding air from the lungs. "Reverse squeeze" can occur if the eustachian tube and nasal passages are blocked on ascent. This is much less common than squeeze on descent, for if compressed air can get into these spaces it usually can get out.

However, sometimes with an infection divers can get air into the spaces but then the air is blocked coming out. The sinus and/or middle ear spaces attempt to expand as the air in their spaces expands; the result is pain on ascent. In a worst-case scenario, middle ear expansion without adequate venting could lead to rupture of the tympanic membrane outward, resulting in severe pain, vertigo, and drowning. For these reasons people with upper respiratory infection, sinus or nasal congestion, or middle ear infection should not dive until the problem is resolved. Alternobaric or "pressure" vertigo is a feeling of disorientation and spinning caused by a sudden, and unilateral, pressure difference between the middle and inner ear (Farmer 1990). It usually occurs during or immediately after an attempt to equalize middle ear pressure by the Valsalva maneuver. Alternobaric vertigo has been described on both ascent and descent, but is more common on ascent. If symptoms persist on the surface treatment is with decongestants, although surgery (a myringotomy � placing an opening in the tympanic membrane) may be necessary. Any unvented space can cause discomfort or pain on ascent.

Gastric discomfort is rare because of the ease of venting the stomach and intestines but does occur (Weeth 1965; Edmonds 1976). Barodontalgia (tooth pain), usually from an improperly or incompletely filled tooth, can occur on ascent when air in the cavity expands. 4. Ear pain on descent cannot be cleared without ascending because (choose all that may apply) a. The eustachian tube will not respond to any maneuver. b. Any forceful attempt might rupture the ear drum. c. You could develop vertigo. d. The air pressure is too dense. 5. The best time to begin clearing your ears is: a. Before you enter the water. b. When you begin your descent. c. At 5 feet depth. d. At any point within the first ten feet. TEST YOUR UNDERSTANDING Answers WHAT IS PULMONARY BAROTRAUMA? Pulmonary barotrauma is any damage to the lungs from unequal air pressures. The greatest danger to the diver on ascent is from pulmonary barotrauma, a risk greatly increased if breath is held. The consequence can be serious, even fatal.

The potential for pulmonary barotrauma is why the first rule of scuba diving is never hold your breath. Continuous breathing allows the lungs and communicating spaces to maintain equilibrium with the increased ambient pressure. If breath is held on ascent, air in the lungs will try to expand against an essentially fixed chest volume; depending on the vertical distance of a breath-hold ascent, the result can be anywhere from simple over inflation to lung rupture and passage of air into the blood stream. A maximum safe rate of ascent in RSD is considered to be 60 feet a minute (the slower the better); at all times the diver should continuously breathe. Should a diver run out of air and have to make an emergency ascent, proper technique requires continuous exhalation under water (by saying "Ahh...") in order to vent the expanding lung volume. This maneuver keeps the glottis open and allows continuous exhalation of expanding air, so the lung volume does not increase. For an equivalent change in depth the risk of expansion barotrauma is greatest near the surface, a fact explainable by Boyle's law.

A breath-holding scuba diver rising from 33-feet depth to the surface experiences a change in ambient pressure from two to one atmospheres absolute; if the lungs fully expand within the chest cavity lung volume will try to double. By contrast, a 33-foot rise from 99 to 66 feet depth (i.e., from 4 to 3 atmospheres) would maximally increase a breath-holder's lung volume only 33 percent, posing much less risk of barotrauma (Figure 3). The Greatest Risk of Expansion Barotrauma is Near the Surface. Barotrauma correlates with both increase in pressure in the lungs and 'over stretching' of the lung tissue. Experiments in dogs undergoing rapid ascent in a chamber showed that the lungs can withstand much higher pressures (before barotrauma occurs) if the chest cavity is bound and 'over stretching' is prevented (Schaefer 1958). Although both over stretching of lung tissue and the pressure of expanding air are factors favoring lung trauma, pressure seems to be the major one.

The pressure difference across the lungs (from inside to outside) that is the threshold for experimental barotrauma is about 80 mm Hg; this can occur with a breath-hold ascent from only four feet! The pressure difference (and risk of barotrauma) is obviously much greater with breath-hold from greater depths. During a breath-hold ascent from 33 feet the lung volume would try to double, almost guaranteeing barotrauma if breath were held at or near the diver's total lung capacity (Figure 3). If the lungs could not vent expanding air they would be subjected to a distending pressure of nine times the barotrauma threshold! Figure 3. Ambient pressure and percentage change in lung volume with equivalent depth change (33 feet). In each instance the diver is breathing compressed air at the point of breath-hold. Pulmonary barotrauma usually manifests immediately after ascent but may be delayed for several hours. It may also recur after an initial period of improvement (Krzyzak 1987). People suffering pulmonary barotrauma should be treated with a high inspired oxygen concentration, 100% if available.

Oxygen "denitrogenates" the blood and hastens absorption of bubbles (see Section H). 6. With scuba, pulmonary barotrauma is most likely to occur (choose one): a. With rapid drop in a vertical current from 60 fsw to 80 fsw. b. By breathing from a free-flowing regulator at a depth of 60 feet. c. By rapid up and down motion below the surface and near the shore, from heavy wave action. d. From coughing at a depth of 60 feet. 7. All of the following except one can result from pulmonary barotrauma: a. pneumothorax d. air around the heart TEST YOUR UNDERSTANDING Answers HOW DOES PULMONARY BAROTRAUMA OCCUR? The presumed mechanism of pulmonary barotrauma is as follows. With ascent, if the expanding air cannot be properly vented, the lungs (or some portion of them) expand in response to the increase in pressure; if they expand too much, individual alveoli are prone to rupture.

If the lungs are structurally normal, i.e., there are no blebs, bullae, or areas of abnormal tissue (which are more prone to rupture), barotrauma should not occur until a transpulmonary pressure of around 80 mm Hg is reached (Schaefer 1958). Above 80 mm Hg the alveoli are prone to tear and vent air into the surrounding space (called the interstitial space). This transpulmonary pressure should not occur in healthy lungs unless breath is held on ascent. From the interstitial space, escaped air can take one of three paths (Figure 4): between the two lungs (mediastinal air), around one of the lungs (pneumothorax), or into the blood stream (air embolism) (Macklin 1944). 1) Escaped air can dissect along tissue layers into the area known as the mediastinum, the large space between the two lungs. Once in the mediastinum, the air can go into spaces around the heart (but not in it), into the neck, and into spaces around the abdominal organs.

2) Escaped air can rupture through the visceral pleura (thin membrane that lines the lungs), resulting in a pneumothorax, which is an abnormal air collection between the chest wall and the lung. This air collection can compress or collapse the lung. 3) Escaped air can enter the pulmonary veins, from where it can travel to the arterial circulation as an air embolism (traveling air bubbles). This is by far the most serious complication of a ruptured lung, since the air embolism can block blood vessels to the brain or heart and be fatal. Figure 4. Three pathways air can take once there is a rupture of lung tissue. WHY DOES PULMONARY BAROTRAUMA OCCUR? There is no doubt that pulmonary barotrauma results from unequal air pressures across the lung. But why does it occur in some people and not others. Is it always from a breath-hold ascent? Although breath-hold ascents account for some cases, there are also cases of barotrauma where the divers are certain they never held their breath. There are two explanations for this latter group. First, some divers probably have abnormal lungs and don't know it.

Such changes as subpleural blebs and bullae (abnormal air pockets in the lungs) can often be demonstrated by chest CT scanning or even a plain chest x-ray in people with no respiratory symptoms or problems. After one diver suffered major barotrauma, a chest x-ray that was done before the dive was reviewed; it showed a large bulla, or abnormal air space with thin walls. Probably a certain percentage of people have such "weak lungs" (for want of a better term); these weak lungs may cause them no difficulty except when exposed to slight pressure changes that would not affect normal lungs. Still, there are apparently other divers with completely normal lungs, who are confident breath was not held, yet who still suffered pulmonary barotrauma. These events are difficult to explain, and are fortunately rare (as is pulmonary barotrauma in general). Pulmonary barotrauma remains a definite, albeit small, risk of scuba diving. A hyperbaric chamber is not used for pulmonary barotrauma unless there is suspicion of air embolism (discussed below). Chest tube placement for pneumothorax follows the same guidelines as without diving.

Pneumothorax is particularly dangerous if the patient is to be transported by air or receive hyperbaric therapy (which might be needed for decompression sickness or air embolism, not the pneumothorax). The decreased barometric pressure of altitude, as well as the decompression phase of hyperbaric therapy, will further expand the pneumothorax space and increase the risk of compressing the lung (and, if very severe, the heart). WHAT IS ARTERIAL GAS EMBOLISM? Arterial Gas Embolism (AGE) is the most serious medical problem related to pulmonary expansion barotrauma. It is a major cause of sport diving deaths (Arthur 1987; Kizer 1987). AGE accounts for about 40% of the case load at active dive accident treatment centers in the U.S. (Kizer 1987). AGE is thought to occur when alveoli rupture and air enters the pulmonary veins, from where it travels through the left heart chambers and into the arterial circulation.

Despite this presumed mechanism AGE victims usually do not usually show obvious evidence of lung rupture when their chest x-rays are examined (Kizer 1987; Gorman 1989; Williams 1990). AGE characteristically manifests within minutes of surfacing. In cases of AGE reported to the national Divers Alert Network in 1988, 78% had their first symptoms within five minutes and 88% within 10 minutes (DAN 1988). The early onset of symptoms is in contrast to decompression sickness (discussed in Section G). Decompression sickness is caused by a different type of bubbles (pure nitrogen) and causes symptoms that come on more gradually than AGE. The brain is the most commonly affected major organ in AGE, although air emboli can also block coronary arteries and lead to heart attack (Kizer 1987). Cerebral air embolism can present with sudden unconsciousness or acute neurologic deficit (stroke). Other neurologic symptoms include severe headache, difficulty speaking, and visual loss (Dick 1985).

The major alternative diagnosis to AGE is decompression sickness but treatment is the same for both conditions: recompression in a hyperbaric chamber. WHAT IS TREATMENT OF AGE? First aid treatment of suspected AGE requires putting the patient in comfortable position; usually this will be supine and flat. The head-lower-than-the-body position (so-called Trendelenburg position) was once thought to prevent embolism to the brain, but this has not been substantiated and is no longer recommended (Butler 1988). Other first aid includes administering a high concentration of oxygen (see Section H) and plenty of fluids. Arrangements should be made to transport the victim to the appropriate medical facility (See Appendix A). Although symptoms of AGE may improve after first aid, recompression in a chamber is still considered mandatory (Kindwall 1983; Kizer 1987; Green 1987), for two reasons. First, patients with AGE can relapse after initial improvement. Second, AGE may be accompanied by decompression sickness, a condition more insidious in onset and which also responds to recompression therapy.

One review found a 12% prevalence of both conditions in seriously ill patients referred for recompression therapy (Green 1987). Once AGE is suspected, the patient should be referred to a hyperbaric chamber. 8. Arterial gas embolism can occur from conditions explained by: a. Boyle's law Answers to TEST YOUR UNDERSTANDING 1. 50 billion molecules; volume of 8 liters. 2. Number of molecules would stay about the same; density would decrease with ascent; volume of air would increase with ascent. 3. d. Her lung would attempt to expand to three times their initial volume, to 18 liters; this is an impossibly large lung volume so there would be lung rupture become she reached the surface. 4. a, b, c 5. a or b 6. c. Rapid up and down motion increases risk of pulmonary barotrauma if breath is held, which it might be in a stressful situation. If breath is not held, mild, non-sustained coughing should not lead to barotrauma. 7. c. 8. a. Boyle's law.

The other laws have nothing to do with the pulmonary barotrauma that leads to arterial gas embolism. 9. a and b. Note that the lungs do not have to be weak or diseased for arterial gas embolism to occur. If breath is held on ascent, normal lungs can rupture and lead to air embolism. At the same time breath does not have to be held for embolism to occur; under some conditions weak or diseased lungs (as from asthma or blebs) can spontaneously rupture. 10. False. Arterial gas embolism is due to bubbles of air; decompression sickness is due to bubbles made up, at least initially, of almost pure nitrogen. 11. False. They may be treated the same (with recompression in a hyperbaric chamber), but the causes are different. 12. c and e. The other conditions are not accompanied by bubbles in the blood and tissues, and would not respond to recompression therapy. REFERENCES AND BIBLIOGRAPHY Quoted sources and general references are listed by section or sections, in alphabetical order. An asterisk indicates references that are especially recommended. Medical textbooks and journal articles can be obtained from most public libraries via inter-library loan.

For a list of companies that distribute free catalogs of diving books and videos, see Appendix D. SECTION F. Effects of Unequal Air Pressure Underwater: Ear Squeeze, Sinus Squeeze, Air Embolism and Other Forms of Barotrauma

Question: If someone holds their breath, chokes, or in some other way suspends external breathing, the term is what?
Answer: Apnoea