I was a military flight nurse for many years, so I have more than a passing familiarity with issues related to partial pressure of oxygen, and time of useful consciousness in high altitude decompressions, in addition to my anesthesia background. (And my kids and their friends love to suck helium from balloons, so I regale them with stories of gas embolisms and hypoxic asphyxiation to scare them from doing helium too much! See what happens when your parents are science nerds?!)
So, what youre referring to is inert gas asphyxiation. CO is carbon monoxide, and I dont think it would ever be seriously considered as an execution method (its too slow). CO2, carbon dioxide, I think, would cause too much physiological distress to be seriously considered as an execution method for humans, but has been used for lab animals like rats.
However, nitrogen asphyxiation for judicial execution has been briefly discussed off and on since the mid 1990's. Oklahoma is currently in the infancy of discussions about looking into this method, after the prolonged Clayton Lockett execution.
http://www.csmonitor.com/USA/Latest...-little-to-aid-anti-death-penalty-cause-video
Not content with just the upgrades to the prison and lethal injection equipment, though, Oklahoma's Republican-led House conducted a study on the use of nitrogen gas to execute inmates and is expected to consider legislation early next year that would make Oklahoma the first state to adopt hypoxia by gas the forced deprivation of oxygen as a legal execution method.
I was surprised to find a wiki entry for inert gas asphyxiation, that has a really good explanation, as well as references at the end. Its been used in the meat processing/ humane slaughter on a small scale, apparently.
http://en.wikipedia.org/wiki/Inert_gas_asphyxiation
A few more references:
https://veenga.wordpress.com/2014/09/16/nitrogen-gas-for-executions/
This one is the "think tank" proponent for nitrogen asphyxiation execution methods:
International Humanitarian Hypoxia Project: Introduction to Nitrogen Asphyxiation
http://www.gistprobono.org/ihhp/id1.html
http://web.archive.org/web/20070203...ety_publications/docs/SB-Nitrogen-6-11-03.pdf
http://videosift.com/video/How-to-Kill-a-Human-Being-in-search-of-a-painless-death (oops-- the video doesn't work on this link, but I'll leave it in case someone else can find another working version.)
While I think inert gas asphyxiation could be a very humane, painless, and rapid method of execution, I would forsee at least 10-20 years of very strident debate in the media and state legislatures before it could be seriously considered for implementation within a state department of corrections for judicial execution.
First, the description of the method includes the words gas and asphyxiation, two words that are LOADED with emotional and political meaning, and could even evoke comparisons to Nazi extermination camps by activists trying to abolish the death penalty. Contrast that with lethal injection, which most people compare to drifting off to anesthetic sleep for surgical procedures, or euthanizing a beloved pet. Surgery is something we do to living people for humane and curative purposes, so the subtle implication is that anesthesia must be painless and humane, or we wouldnt commonly anesthetize regular, non-condemned people.
Mostly, I think people, even supporters, want to forget that we are actually killing someone with lethal injection. I think a lot of people dont want to think about it too deeply or too long, and just consider that the condemned inmate is just going to sleep for a looooong time, like when we compassionately euthanize our beloved pets. (In the same way most people, IMO, dont like to think of the meat in the Styrofoam tray at the grocery store as coming from a once- living animalonce its on Styrofoam, its just dinner.) Asphyxiation, on the other hand, is associated with terrible accidents, suicides, and murders, like the Nazi atrocities. So, for that reason alone, I think it would be an uphill battle to present this method of execution to the public as desirable and humane. I don't know if the average person would understand the difference between gas poisoning, versus inert gas asphyxiation, or would associate "asphyxiation" with "suffocation".
And then theres the practical discussion of how to do it, whether by mask delivery, flooded room, flooded small box-like chamber, with or without pre- delivered sedation, etc. (It could take up to a minute or so for unconsciousness, which is actually a very long time, and could be distressing for observers. With general anesthesia and properly applied judicial lethal injection, unconsciousness usually takes only about 10 seconds.)
And on top of all that, then there would be numerous mechanical considerations, engineering designs, and OSHA and other safety issues for the corrections department and staff.
It could definitely work, but I think there are just too many political and practical issues to overcome to realistically implement this in the U.S. in the next 20 years. Perhaps if the meat packing industry embraces this on a larger scale for humane slaughter of large animals like cows and pigs, they will do a lot of the research on delivery methods and industrial safety, which could jump start a public discussion on the matter.
And who knows the death penalty could be abolished again in the U.S., with the proper proportion of anti- death penalty leaning justices on the Supreme Court. So for now, if were going to do this thing called lethal injection for judicial execution, my opinion is that we should carefully study the issue and do it the best, fastest, and most humane way we can. Id personally like to see a national think tank coalition be formed of experts to study the issues and make recommendations in support of various methods of judicial execution, just like the Death Penalty Information Center does for anti-DP issues. What troubles me personally is the wide discrepancy between how each of the participating states have developed their individual protocols and statutory language. There should be more uniformity, IMO. (And for the record, I currently live in a non-death penalty state, but I have lived in other states and countries where judicial execution was practiced.)