Murder by nitrogen

If you were to attempt to asphyxiate someone by flooding their room with nitrogen gas:

  1. Would they become aware that they were being asphyxiated? i.e. would they feel short of breath, or that they were suffocating? Or would they just feel increasingly weak and dizzy until they passed out, but not feel specific respiratory distress?

  2. If this was done to a sleeping person, would they wake up?

  3. If you killed someone in this manner, what would an autopsy be able to find out?

Note to self: Politely decline invitation to matt’s sleep-over.

They would not feel short of breath and may not know anything is wrong at all until they pass out. Most of the symptoms we associate with suffocation are not actually symptoms triggered by a shortage of oxygen, but by a buildup of carbon dioxide. In the scenario you describe, CO[sub]2[/sub] won’t build up.

I posted a story in another thread a while back about two NASA workers who wandered into an area filled with nitrogen. They both died, apparently without realizing anything was wrong. I have been unable to confirm the story, however.

You remember correctly bibliophage. Two workers entered an inert gas environment area (it prevents combustion of the liquid hyrogen or oxygen) and died before they even knew what hit them.

I believe these were two of the first fatalities in the entire space shuttle program.

As for you matt, don’t you have anything better to do than sit around plotting someone’s untimely demise? I’m amazed that this thread isn’t locked already.

Zenster said: "As for you matt, don’t you have anything better to do than sit around plotting someone’s untimely demise? I’m amazed that this thread isn’t locked already."

Relax, I’m not planning a murder, although I do like to write stories about them occasionally!

I have a list of thoughts in my Death-and-destruction\Nasty-ideas folder which are considerably more unpleasant, and some of which I wouldn’t dare let see the light of day…

Well, at least we know you’re still firing on most of your cylinders.

okay, Heres the answers to your questions

  1. it would be very similar to CO poisoning, they would experience symptioms from the hypoxia, but nothing else

  2. no they would most likely not wake up.

  3. an autopsy would be able to trace it if done in some sort of a timely manner. The concentration of nitrogen in the blood would be through the roof. Your lungs work by simple diffussion. There would be a signifiant ammount of nitrogen dissolved in the victom’s blood with very little oxygen or carbon dixoide. That would be a little odd.

"3) an autopsy would be able to trace it if done in some sort of a timely manner. The concentration of nitrogen in the blood would be through the roof. Your lungs work by simple diffussion. There would be a signifiant ammount of nitrogen dissolved in the victom’s blood with very little oxygen or carbon dixoide. That would be a little odd"

Not so sure about that. The air that you’re breathing is 79% nitrogen anyway. If I flooded a room with nitrogen it would have to be at one bar unless the room was some kind of pressure chamber. If you could breathe this for several minutes without dying, the best you could do would be to elevate your blood nitrogen by ~20%. Measuring blood nitrogen would also be rather difficult - I doubt it’s a commonplace practice.

The lowered blood oxygen might be suspicious, and there are standard oxygen sensors which could measure it. But as soon as the guy has died, he stops breathing and so stops flushing oxygen and carbon dioxide out of his body. I had the impression that the brain is rather more sensitive to oxygen deprivation than the rest of the body and so death would occur before all the oxygen was lost.

In any case, don’t the cells in your body keep using your blood oxygen until they have all individually died, irrespective of whether or not brain death has occurred? Isn’t a low blood oxygen level normal in a corpse? I’m guessing here.

Looks like the real giveaway would be lowered carbon dioxide levels and again they are measurable, either directly or by changes in blood acidity. I know a way to fix that, but I think I’ll keep it to myself.

The really hard part is working out how the detective is going to solve this…

if you are tying to kill someone with nitrogen, I assumed you would place them in an environment of 100% nitrogen. This means that the only thing diffusing into the blood would be nitrogen. I don’t know if it nitrogen is checked on an ABG, I can check when I go to the NMOMI later next week. I can also check what are the normal levels of O2 and CO2 in a corpse.

The level of the nitrogen in the blood would near 100% as a person first passes out due to hypoxia (this would happen rather quickly, the brain is the most senstive organ in the body to hypoxia)and would continue to breath untill the medulla ceased to function. There would be a steady decrease of oxygen in the system (none coming in, rest getting used up) but CO2 would continue to be exhaled until apenia occured. Some CO2 would build up there after, and how much I cannot say. It would cause a change in blood ph to below 7.3 as the blood buffer system is overwhelmed.

My WAG would be that a death lacking physical trauma, lacking any sort of intoxicating drug, then a blood gas would be done to see what the person was breathing. Levels of CO2 and O2 would be close to normal, but level of N would be signifiantly too high.
Thanks for making me think throught that again.

matt, you don’t have to go all the way back to the beginning of NASA or the Space Shuttle program to find notable examples to this unfortunate cause of death.

Just this summer one or two maintanance workers in a NYC (Queens?) hospital died this way. They were in a small room/shed fixing some equipment near some leaky Nitrogen tanks.

You should be able to locate an article or two about it online. I’m also pretty sure there was one or more threads right here on the SDMB asking about it… I’d check the search feature here before looking any deeper.

Nitrogen in the air does not really diffuse into the blood, nor does it move much in the lungs. It is considered to “take up dead space” and is not measured in standard arterial blood gas measurements, but it would lead to both acidosis (as mentioned) and a change in partial pressure between the lung and the arterioles.

Less oxygen would get to the cells, and less carbon doxide would be exhaled. This differs from carbon monoxide, CO, which is poisonous since it diffuses across lung tissue into the blood 100 times better than oxygen and does a better job of binding to hemoglobin, which normally carries most of the oxygen and some of the carbon dioxide wastes in the blood. Carbon monoxide poisoning may present with cherry red lips, but some symptoms of hypoxia and acidosis would be present even though carbon doxide is being exhaled.

In nitrogen poisoning, I suspect the acidosis would occur more quickly and would present with symptoms of hypoxia. These include cyanosis occuring peripherally (fingers turn blue) and centrally (pale under the tongue), use of chest muscles to breathe better, subjective feeling of shortness of breath, breathing which is rapid and shallow (due to the Kussmall breathing), tachypnea and tachycardia (heart beats fast to try to compensate for low oxygen, also breathe faster), anemia and hyperreticulocytosis, and lots of other changes. Unlike many of the posters, I do think the hypoxia would be quite evident. It is easy to measure nitrogen concentrations in the blood, but hard to think of something like that after working for 12 hours… the ER doc might not figure it out, but I do think the forensics team probably would.

This was demonstrated in Dr Jonathon’s Miller’s seminal TV series “The Body In Question” a couple of decades ago. On-screen he had a device rigged that allowed him to re-breath his own exhalations, after filtering out CO2 using a soda system similar to a submarine (it is CO2 that triggers the choking reflex). After a few minutes he simply collapsed into unconciousness. The off-screen Doctors rushed on to revive him. Cut to credits.

      • IIRC the inhabtants of Biosphere 2 suffered nervous system damage from long-term exposure to elevated nitrogen levels. I don’t know how high for how long but at the time, they were also having trouble growing enough food and were on what were basically starvation diets. Everybody thought that everybody was stumbling around just because they were tired for lack of calories, but after they came out and could eat again, they found that the damage was permanent. - MC

Crunchy Frog: "Note to self: Politely decline invitation to matt’s sleep-over."

Noone’s slept over at my place since I suggested the spider experiment
kinoons: "I can also check what are the normal levels of O2 and CO2 in a corpse."

That would be great! Thanks!
stuyguy: "Just this summer one or two maintanance workers in a NYC (Queens?) hospital died this way. They were in a small room/shed fixing some equipment near some leaky Nitrogen tanks."

That’s pleasing to know considering that I’m sitting in a lab full of nitrogen tanks right this minute, and one of them is cheerfully bubbling through a solution as I type…
Dr_Paprika: "Nitrogen in the air does not really diffuse into the blood, nor does it move much in the lungs."

I’m sure SCUBA divers would be fascinated to hear that!
You’re right of course, in that with normal air breathing the nitrogen dissolved in your blood will be equilibriated with the 0.8 bar partial pressure in air. Since your body doesn’t consume or produce nitrogen there is no net movement of nitrogen into or out of the bloodstream through your lungs.

What I’m proposing however is to elevate the nitrogen partial pressure to 1 bar, which will cause nitrogen to diffuse into your bloodstream through your lungs. If you could breath it for long enough without dying, you could in theory elevate your blood nitrogen by about 20% although I think you’d die long before you got that far.

"In nitrogen poisoning, I suspect the acidosis would occur more quickly and would present with symptoms of hypoxia."

Ah, but I plan to mix in CO[sub]2[/sub] with the nitrogen at the same partial pressure as it’s found in exhaled air! So, no acidosis - deal with that, you forensic types!

"Unlike many of the posters, I do think the hypoxia would be quite evident."

Now you’re spoiling my story! As a matter of interest, when a person dies of, say, heart failure, do they present symptoms of hypoxia?

"It is easy to measure nitrogen concentrations in the blood, but hard to think of something like that after working for 12 hours."

How is that done? Do you take a sample and run it through a mass spectrometer or something? I’m familiar with electrochemical sensors for oxygen, but electrochemistry doesn’t get you very far with nitogen.
bmorey: Interesting! I don’t think that show made it to this side of the Atlantic, which is a pity.

Where did you hear that? I worked there spanning the two year “mission” and never heard of long term damage. There were high concentrations of nitrous oxide but not N2.

The biospherians were “stumbling” around due to low oxygen levels. The partial O2 pressure was so low that candle flames couldn’t be sustained and the crew could barely manage stairs. Management decided to pump in additional oxygen. When the Biospherians went into the lung structure where the oxygen had been pumped in they perked up most dramatically.

The Oxygen loss was discovered to be because of the concrete. It was sealed with a layer of steel inside so wasn’t fully permeable but the concrete sequestered CO2. There was plenty of carbon to go around but this absorbed a lot of the available O2.

At higher pressures, more nitrogen would diffuse into the blood. The diffusion capacity depends on many other factors independent from partial pressure. I don’t know if a 20% rise would cut it. Ask a SCUBA diver. I ain’t never had the bends.

Heart failure has lots of different causes. I presume you mean congestive heart failure when the heart pumps inefficiently and the lungs fill with fluid, which does indeed cause symptoms of hypoxia, especially when lyig down. If you mean an arrhytmia causing a heart attack… there is usually a subjective feeling of shortness of breath. There is also usually chest pressure (someone sitting on my chest) which may radiate to the jaw, neck or left arm. Light-headedness, vomiting, profuse sweating, nausea and palpitations are also common; these symptoms should be investigated with an ECG and cardiac enzymes.

A person dying of heart failure can present hypoxia symptoms.
My SO died of a massive coronary. When his heart failed, his lungs began to fill with fluid. I was told he was drowned in his own body fluids.

      • I read an interview (don’t recall which magazine, sorry) of the older bald guy and at the time he exhibited symptoms of some type of neuromuscular damage that was said to be permanent. I seem to remember his name as Story Muskgrove, but that name or spelling might be incorrect. The article said that his present condition was from prolonged exposure to elevated levels of nitrogen in Biosphere 2, though I suppose if you’ve got too much nitrogen then you don’t have enough of something else. The article said that the other people there also suffered, but didn’t elaborate. - MC

Moderators, the fact is that most of the suggestions here are incorrect. Thas fact notwithstandig, do you allow to ask and give advice on murder but guard against personal verbal attacks? I’d close AND delete the thread. If he kills anyone, you may be charged as accomplices.

What if he’s researching for a murder mystery?
You’re a tad paranoid, peace.