Why does injecting air into your veins kill you?
452331
This is sort of a myth, with some exceptions.  I remember as a kid hearing that a single bubble of air would kill you.  This is simply not the case.  A small bubble in your vein is not harmful.  Now if you send a large bubble of air back to your heart, you create an air embolism.  Air takes up space and in an enclosed area, like a blood vessel it can get lodged and can prevent blood getting past it.  Even then it may not kill you, but it could cause an infarct (lack of blood/O2 supply causing cellular death)
127795
I'd think at zero pressure you'd get dissolved gases coming out of solution in liquids (blood, urine, etc) and tissues, causing a general expansion of body contents.  The head being a relatively unflexible container, you'd have bulging eyes, brain leakage and hemorrhage.  Blood vessels in the lungs, being thin-walled and directly exposed to the vacuum, would rupture and leak.  This all happens while your body remains at normal body temperature, which wouldn't be very long, since you're dead.  Ultimately you'd freeze and the fluids would slowly sublime out of your body.\nEDIT:\nOogs's listed site and another I found (ref.) provide the following:\nGenerally the problems relate more to existing pockets of gas expanding and dissolved gas coming out of solution, rather then liquids boiling\nYou lose consciousness in ~10 sec due to loss of blood oxygen via the lungs\nBlood doesn't boil, vapor pressure of water at body temp is only 47 mm Hg (0.9 psi) which normal blood pressure can contain\nGas in the digestive tract will expand possibly causing pain and shock\nYou might get the bends\nYou don't explode\nYou die in a couple of minutes\nIn rapid decompression, forcefully holding the breath will overexpand the lungs causing ruptures and capillary tearing
1022189
Excercise more, it increases your blood flow, vein capacity and thus increases your size of veins.  You sort of want your veins to be able to allow for higher volumes of blood, it allows the heart to work less.
1161017
HCO3 is a natural buffer in your body.  Sneezing might be worst case, but be sure in the process of snorting the stuff it does not go down the lungs.  By the way, why would you want to do that?
897315
For a very short time, yes. People tend to forget about what's called "dead air spaces". Yes, you're exhaling some co2, but a good deal of that exhalation is still o2 ( it's not all used in a breath) and even more so in dead air spaces. These are areas in your body from the top of your lungs to the tip of your lips, that don't do any gas transfer to or from the blood stream. It's still normal, oxygen rich air in there.\n I also disagree with what one person has stated here, that artificial respiration is only a method to get the lungs moving. \n It IS in fact a method of oxygenating the blood stream and keeping a victim viable in the absence of their breathing on their own.
1028850
yeah, cuz it traps oxygen, and if u inject oxygen in someone's vein, they could instantly die.
1109852
On June 3, the bodies of two college students were found in a giant helium balloon in Florida. The week before, a 10-year-old in New Jersey collapsed at a birthday party after sucking helium from a balloon. Is helium really that dangerous?\n\nIt can be. Breathing in pure helium deprives the body of oxygen, as if you were holding your breath. If you couldn't breathe at all, you'd start to die in minutes—as soon as your body exhausted the supply of oxygen stored in the blood. But helium speeds up this process: When the gas fills your lungs, it creates a diffusion gradient that washes out the oxygen. In other words, each breath of helium you take sucks more oxygen out of your system. After inhaling helium, the body's oxygen level can plummet to a hazardous level in a matter of seconds.\n\nYou don't have to worry about fatal asphyxiation if you're sucking from a helium balloon at a party. At worst you'll keep going until you get lightheaded and pass out—at which point you'll stop inhaling helium and your body's oxygen levels will return to normal. Of more concern is the possibility that you'll hurt yourself when you fall down. (The boy in New Jersey bumped his head and needed three stitches.) It's far more dangerous to suck helium out of a pressurized tank: If the gas comes in too quickly, your lungs might burst and hemorrhage.\n\nOf course you're putting yourself in grave danger anytime you climb inside a giant helium balloon. The college kids in Florida weren't the first to attempt this stunt. In 2002, a case report from a Japanese medical journal described a similar episode: A drunken adolescent poked his head into an advertising balloon and asphyxiated. Several authors have also reported cases of suicide by helium inhalation. \n\nDeath by helium still seems to be quite rare. U.S. Poison Control Centers reported only two fatalities between 2000 and 2004. There's still an outcry from concerned parents whenever helium inhalation makes its way into popular culture. Federal Express had to pull a commercial that depicted the munchkins from The Wizard of Oz sucking balloons to keep their voices at a high pitch. Geoffrey, the Toys "R" Us giraffe, got a slap on the hoof for doing the same. \n\nAt the same time, doctors use a mixture of helium and oxygen (called "heliox") to help patients with upper-respiratory blockages. The treatment works because the helium is a very light gas, and it's easier to push it through an obstructed airway. (We get funny voices when we inhale helium because the lighter gas changes the resonant frequencies of our vocal tract.*)
834051
Depends how seriously the vein gets punctured.  Essentially it's puncturing the vein all the way through both sides.  If it doesn't heal quickly (or well) you get a bad bruise from all the blood that seeps out of the punctures, and it can cause nasty internal infections as well.  If the vein is already weak, it can collapse, severely damaging blood circulation and purification in the body.
1045845
YES!  \nAbsolutely it does!\nYou are not taking in the proper amount of oxygen therefore not oxygenating your blood stream/muscles/lungs properly.
467845
how indepth do you want this?\n\nbasically caused by a pressure differential in your lungs (the diaphragm inflates the lungs)...the oxygen molecules are forced through alveoli (sacs) into the bloodstream because fo this pressure differential...at the same time...Carbon Dioxide flows in the opposite direction from the blood to teh lungs to be exhaled...the oxygen attaches itself to hemoglobin..which is found in the red blood cells...and is then transported throughout the body by the heart (arteries pump blood away from the heart to teh body..veins take the blood back)\n\nhope thats good enough lol
166416
you should never inject plain water in the vein. It would have to be some type of saline. Which is used in the hospital for electrolyte replenishment. \n\nRegular tap water has a bunch of things in it. When we drink it our body breaks it down. It you inject it there is a possiblity you could come up ill.
563777
Not too much longer because the liquid that you intake does not have a way to dispose of itself therefore the fluid just builds up all over your body.  Slowly our body starts to shut down.  Its a very painful death.
654675
I think your body is trying to force you to go to sleep.\n\nit's like you can never kill yourself by holding you breath because you body just compensates by passing out, therefore causing you to breath again.
894662
Well break the words down. Capillaries are closer to the surface of the skin, that is where gases exchange and where waste is disposed of. Veins are a little deeper and have more pressure on them, they are returning blood back to the heart.\nSee you have arteries, veins, and capillaries.\nThe arteries are the pipes going out of the heart, they have the most pressure on them. Because they have to deliver all the blood with the o2 in it to the capillaries all over your body. After the gas exchange at the capillary level, it then turns in to your veins, that return to the heart.
605386
More to the point, to allow complete injection of the drug- When giving injections intraperatoneally or intramuscularly(in the gut or butt) we take a tiny bit of air into the syringe so that there isnt any drug left over-to make sure you have your full dose.  This isnt done in IV injection because of the (low) risk of air embolism blocking a vessel.\nBut, the first answerer was correct as well, and they got here first...
832732
incison it on your arteries veins on the neck\nit squirts out more blood
225438
It is caused by a vasovagal reaction where your heart beat slows down and your blood pressure drops causing less blood flow to the brain. Happens to me with needles and its kind of embarrassing.