Murder by nitrogen

[matt]

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?

[Crunchy Frog]

Originally posted by matt
2) If this was done to a sleeping person, would they wake up?

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

[bibliophage]

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, CO2 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.

[Zenster]

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.

[matt]

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...

[Zenster]

Originally posted by matt
...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.

[kinoons]

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.

[matt]

"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...

[kinoons]

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.

[stuyguy]

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.

[Dr_Paprika]

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.

[bmorey]

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.

[DougC]

- - - 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

[matt]

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 (http://boards.straightdope.com/sdmb/showthread.php?threadid=13271)


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 CO2 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.

[Padeye]

Originally posted by MC
- - - IIRC the inhabtants of Biosphere 2 suffered nervous system damage from long-term exposure to elevated nitrogen levels.

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.

[Dr_Paprika]

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.

[dragonlady]

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.

[DougC]

...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.... - Padeye
- - - 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

[peace]

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.

[Kyberneticist]

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

[Padeye]

"The older bald guy" would have been Dr. Roy Walford. No one by the name of Story Muskgrove or anything similar was in either of the two biosphere 2 crews.

[Dr_Paprika]

I don't think this is a particularly good way to kill someone. I don't think I could be successfully prosecuted as an accessory, either. What if we were talking about which kitchen knives we liked to cook with?

Concentrations of oxygen, carbon dioxide and nitrogen can be measure by electrical probes. They had a few in the lab where I was doing my biomechanical engineering thesis, but I couldn't give you the details.

[kinoons]

okay, I'm going to kill you via the use of nitrogen

sure, no problem, I'm just going to put you in a relatively air tight room and flood it with nitrogen in order to drop the concentration of oxygen below the level needed to sustain life

Sure peace, no problem, excuse me as I get started on the room. Know a good place to buy a large amount of nitrogen?


I'd also like to hear your spin on things sense you've decided that all of our opinions on this subject are wrong.

[manhattan]

Originally posted by peace
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.

Ain't easy, is it? We don't like to close threads very much. When we do so, we weigh factors including "how likely is someone to actually do this" and "how helpful are the responses here."

Not only do I trust that matt will not actually try to kill someone by nitrogen poisoning, I am confident that lurkers will also not take this as inspiration to do anything of the sort.

Accordingly, I am leaving this thread open.

But if anyone kills anybody with nitrogen poisioning from ideas in this thread there's gonna be big trouble!

And yes, insulting fellow members is still prohibited in this forum.

[Tristan]

Hehehehe..... If it were to happen, a truly dedicated Doper would post the results, whether or not the person noticed it occuring, and how long it took...

Personally, if I've got access to a bunch of Nitrogen, I would just mix up some Ammonia, and try for a big ol' ANFO bomb.

But that's me, King of the Bodycounts!!

[[hijack]]

I'd seen old newsreel-class footage of CO2 and N2 tests they made on dogs in the 50's. They were testing for a number of things, but the key one was what to watch out for in high-flying fighter jets of the day.
The footage showed that going from 1/2% CO2 in a sleeping dog would wake him up with reddened tissues. Conversely, going from 80% N2 to 90% would put him to sleep and eventually kill him.

[peace]

OK, Man, since now on, I'll trust you experience and judgement more and will post no more cautions. Nobody's gonna kill nobody.
I'll actively participate in the thread instead.
I can think of many "cons" in nitrogen killing. Despite its relative availability (compared, say, to highly poisonous halogen gases), I have never heard of "nitrogen" murder. As a matter of fact, liquefied or compressed gases are not popular in this country as murder weapons. Even ubiquitos, accessible heating gas. On the other hand, numerous "perfect" or hardly traceble ways to kill a human being are known. A skillful executioner is hard to find, though.

[matt]

Time to come clean:

I've gotten into the habit of watching Diagnosis Murder every day when I eat my lunch. I'm not proud of it, okay? But that's British daytime TV for you. Gets me thinking along murder mystery lines, anyway.
(My question a couple of weeks ago about whether you could be charged with murdering a corpse was lifted from the show, although their scenario was rather different.)

The nitrogen question stems from the use of nitrogen in my lab, which is usually bubbling through solutions all day long. Nobody's going to use our nitrogen tanks to kill anyone though - they're five feet tall, weigh 250 lbs and hiss like hell if you open the regulators up. (Well, I guess you could drop them out the window on someone!) We have quite enough cyanide and thallium for the truly murderous to indulge themselves.

Peace: from your answers in the neck-cracking thread, I'm guessing you have some expertise in forensics and/or medicine. I'd be grateful if you could elaborate on the mistakes in the previous posts in this thread?

[Dr_Paprika]

Mixing carbon dioxide in the air at the same concentration as in exhaled air would still cause acidosis, since the levels of carbon dioxide would still be higher in the blood due to the hypoxia. In fact, if anything it would diffuse out of the lungs less quickly.

[DrMatrix]

Originally posted by matt
Nobody's going to use our nitrogen tanks to kill anyone though ... We have quite enough cyanide and thallium for the truly murderous to indulge themselves.I was a bit worried, but now I'm releived that we don't have to worry about you killing anyone with nitrogen.

Thanks for clearing that up.

[Padeye]

Originally posted by MC
- - - 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

I knew that name seemed familiar, Story Musgrave (http://vesuvius.jsc.nasa.gov/er/seh/musgrave.html) is an older, bald NASA astronaut. AFAIK he was never associated with Biosphere 2 let alone did he ever live inside the apparatus.

[donnydon]

I think that murder via Nitrogen was the idea behind the Robin Cook book "Coma" in the 70's. It was later made into a movie with Michael Douglas and Genvieve Bujold (spelling?). The eye-catching thing was the bodies hanging by strings in a warehouse-like environment...

[donnydon]

or maybe it was carbon dioxide or carbon monoxide?

[matt]

Dr Paprika: "Mixing carbon dioxide in the air at the same concentration as in exhaled air would still cause acidosis, since the levels of carbon dioxide would still be higher in the blood due to the hypoxia. In fact, if anything it would diffuse out of the lungs less quickly."

My mistake, I was thinking along different lines. Specifically, I was thinking that lowered levels of blood CO2 would occur, since you could still breathe it out but your body would be running short of the oxygen necessary to produce more of it. So my suggestion was to prevent CO2 depletion rather than its build-up, which I'm guessing is the cause of acidosis.

donnydon: carbon monoxide was the gas used in coma. Good movie! Not so great book though. Robin Cook has some truly nasty ideas, but I don't like his writing much.

DrMatrix: glad to set your mind at rest!

[djbdjb2]

The original point seems to be mostly settled, so perhaps I can hijack the thread. I too think of wierd ideas that might someday be incorporated into crime stories/murder mysteries.

One that I had thought of before is back in my mind because of the current stunt by magician David Blaine: Will someone die if they are left in a room full of ice? Let's say an ice floor 1 m. , 1m thick walls 5m high, with or without some kind of ice roof.

Do people that get locked into walk-in freezers (what are those, 10 degrees F?) die if they are not rescued in X hrs?

Would liquid N2 make a better murder weapon, since you could pour it/pump it (?) without it hissing like a gas and waking up the victim?

[Dr_Paprika]

We probably see more hypothermia in Canada than in the US.

Tissue freezes at -4 degrees. When it thaws, it ain't the same. There is some debate on how cold to keep experimental cadavers without changing physical properties.

With a central temperature below 28 degrees celsius, the old heart gives way.

A central temperature below 32 degrees celsius is dangerous. Craziness sets in (cold people remove all their clothes!) and the heart rhythms become funny.

So it depends on how long it takes for the central temperature (rectal) to go below 35 degrees celsius, which can be approximated by Newton's law of Cooling. The rate of change in temperature is proportional to the difference between the body and ambient temperatures.

[peace]

Matt, you asked you question correctly and almost answed it, too. I read about one half of the thread, then the authors began to discuss their wrong answers, I lost interest. Anyway, one does not have to know forensics to understand your scenario. Just one thing: forensic experts do no work in vacuum. Actually, the autopsy is one of the last steps in forensic investigation. The cause of death will be evident to the first officer at the sceen, the one who discovers the (compressed or liquid) nitrogen tank. In general, the case of death could be mysterious in cases of natural death.In cases of violent death police tells the medical examiner what the cause of death was, not the other way around. The medical examiner must confirm that the actual cause of death is, e.g. that the person drowned, and was not poisoned before the body was dumped in the river, etc.
In you scenario, I assume that the victim was breathing room air in a regular room. The concentration of nitrogen would probably, be ~90-95%. Therefore, the oxygen concentration would be 5-10%. This is incompatible with life. The victim will die of asphyxia, before any acidosis will develop (experts here assumed that there will be acidosis; why?). So, to answer your questions:
1) Yes. Newcomers to Lima, Peru, cannot walk more than a few hundred yards without shortness of breath. The partial pressure of oxygen is lower there. Not exact analogy, but lack of oxygen is perceived as such ("lack of air").
2)Yes, they will.
3) The autopsy findings would be those of asphyxia.

I can understand your interest in detective books and TV shows, but take them with a grain, no, with a sack of salt. They are not documentaries, their purpose is to keep your attention. They can do that.

[kinoons]

just a followup I promised I would give info on. Yesterday per my paramedic program requirements I spent a day at OMI. I asked about the concentrations of O2 and CO2 in the blood post death.



Given you find the body before the blood has clotted...


levels of O2 would be low, levels of CO2 would be high

this is due to the fact that cellular death and death of the organism do not occur at the same time. Once apena (respatory arrest) and then caradic arrest occur the body continues to function at the cellular level. This means that the O2 reserves held in the blood get used up, CO2 is created but cannot be blown off by the lungs.

[matt]

Many thanks, everyone!

[Fiver]

Padeye :I worked there [Biosphere 2] spanning the two year "mission"

Padeye, I'd be very interested in reading more about your experience (probably not in this thread).

I was never very interested in Biosphere 2, but then at the 1999 Mars Society convention I met one of the Biospherians, the attractive fortyish blonde ocean lady. She participated in a panel about colonies on Mars.

And then still later I read Roy Walford's book The Anti-Aging Plan (http://www.walford.com), which discusses many of the Biospherians' (dietary) experiences.

So, if you start an MPSIMS or IMHO thread about Biosphere 2 from your perspective, I'm there.