Nitrogen asphyxiation

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Nitrogen asphyxiation is a theoretical method of capital punishment advocated by Stuart A. Creque in a 1995 article in National Review, "Killing with kindness - capital punishment by nitrogen asphyxiation". The painful experience of suffocation is not caused by lack of oxygen intake but rather because of a buildup of carbon dioxide in the bloodstream which is exhaled under normal circumstances.

When a human (or any other mammal) breathes in pure nitrogen, they exhale carbon dioxide without resupplying oxygen. Nitrogen is a colorless, odorless and tasteless gas that comprises approximately 80 percent of the Earth's atmosphere. As such, the subject would detect no abnormal sensation. This leads to asphyxiation without the painful and traumatic feeling of suffocation. Therefore, it is viewed by some as a more humane way to end a human life in a controlled setting. As the principal component in air, nitrogen poses no significant risk upon discharge. Dying by nitrogen asphyxiation is similar to death by carbon monoxide. Execution by nitrogen asphyxiation does not require the arguably unethical use of medical skill.

1 Overview
- 1.1 Comparable accidental death
- 1.2 Awareness of impending death
2 Physiology
3 Technology
4 References
5 Related Links
6 External links

There are substantial moral arguments against and in favor of capital punishment by any means.[1] Although execution by nitrogen asphyxiation was discussed briefly in print more than 10 years ago (Creque 1995) and circulates in various online forums, it is not presently used by any nation. Switching to this procedure would require a change of law. Legislative debate on such a proposal could focus public attention and provide opponents a forum to argue for abolition (Seitz 2001).

As breathing is an absolute requirement for human life, no physical condition of a living subject can prevent the prompt completion of this procedure. Properly condemned individuals could be executed without physical trauma and without the arguably unethical use of medical skill, essentially by withdrawing life support. Some people experience claustrophobia when presented an anesthetic gas mask before surgery, and some subjects might react similarly.

Execution by lethal injection, in contrast, requires medical skill and has occasionally been prolonged when it was difficult to insert the injection needle into an open vein.[2]

Accidental nitrogen asphyxiation causes about 8 deaths per year in the United States,[3] which is asserted to be more than from any other industrial gas. For example in 1981, shortly before the launch of the first Space Shuttle mission, two technicians lost consciousness and died after they walked into a space in the Shuttle's Mobile Launch Platform that was pressurized with pure nitrogen as a precaution against fire.[4] A laboratory assistant died in Scotland in 1999, apparently from asphyxiation, after liquid nitrogen spilled in a basement storage room.[5]

Death by accidental hypoxia can occur in confined spaces or depressurized aircraft. Accidental asphyxiation from compression of the chest or abdomen, which prevents inhalation, has occurred in some police restraint positions [6] and in crowding or stampede disasters. Some toxic gases, such as hydrogen cyanide, prevent cells from aerobically producing ATP for energy and cause death by asphyxiation. Carbon monoxide binds to hemoglobin, which reduces oxygen transportation in the blood stream and causes death by asphyxiation.

Every condemned individual is aware of impending death in general, as a result of court proceedings, transport to the execution site, and preparation of the execution equipment. At the shortest time scale, however, nitrogen asphyxiation provides little warning of the moment when final unconsciousness arrives. The flow rate, pressure, humidity, and scent of both supplied gases could be made identical. The exchange valve could be designed for silent operation out of the subject’s sight, and it might be operated at the moment of some other distraction, such as opening a screen between the subject and any legal witnesses. This minimal warning before final unconsciousness, combined with the absence of painful physical trauma, make this procedure arguably humane.

A typical human breathes between 12 and 20 times per minute at a rate primarily influenced by carbon dioxide concentration, and thus pH, in the blood. With each breath, a volume of about 0.6 liter is exchanged from an active lung volume (tidal volume + functional residual capacity) of about 3 liters. Normal air is about 78 percent nitrogen, 21 percent oxygen, and 1 percent argon, carbon dioxide, and other gases. After just two or three breaths of nitrogen, the oxygen concentration in the lungs would be low enough for some oxygen already in the bloodstream to exchange back to the lungs and be eliminated by exhalation. Crude simulation of oxygen transport through the lungs and blood stream suggests that the partial pressure of oxygen in arterial blood would be about 50 percent of saturation 1 minute after switching gases and would reach zero within 3 minutes.

Unconsciousness in cases of accidental asphyxia can occur within 1 minute. Loss of consciousness results from critical hypoxia, when arterial oxygen saturation is less than 60% (Fisher n.d.). “At oxygen concentrations [in air] of 4 to 6%, there is loss of consciousness in 40 sec and death within a few minutes” (DiMaio & DiMaio 2001:231). As this procedure provides an atmosphere completely devoid of oxygen, the sequence of effects should be expected to occur even more quickly. At an altitude greater than 43,000 ft, where the ambient oxygen concentration is equivalent to 3.6% at sea level, an average individual is able to perform flying duties efficiently for only 9 to 12 seconds without oxygen supplementation (Fisher n.d.). The US Air Force trains air crews to recognize their individual subjective signs of approaching hypoxia. Some individuals experience headache, dizziness, fatigue, nausea, or euphoria, but some become unconscious without warning (Fisher n.d.). Equivalent training is unlikely for a condemned individual, making unconsciousness without warning probable, although as much as 30 sec warning is possible.

Loss of consciousness may be accompanied by convulsions (Fisher n.d.) and is followed by cyanosis and cardiac arrest. About 7 minutes of oxygen deprivation causes death of the cerebral cortex and presumably the medulla oblongata, which controls breathing and heart action.

Industrial breathing apparatus for workers in hazardous atmospheres is a well developed technology. With trivial modifications, the same equipment could be used for executions. The subject would be restrained, wearing a respirator supplied with normal air, which would then be switched to a pure nitrogen supply. As humans cannot sense the absence of oxygen, normal breathing would continue until unconsciousness and ultimately death.

Air-supplied respirator, mask, or other breathing chamber that the subject is unable to remove when restrained. A device that allows the subject clear verbal communication is recommended. A large volume device would delay delivery of the pure nitrogen atmosphere.
Supplies of air and nitrogen, in pressure tanks, for example.
For each gas, pressure regulators and a device to measure the flow rate.
Exchange valve, to switch the flow of the two input gases between outputs to the respirator or a vent.
Sensor to measure the oxygen concentration in the respirator supply line.
Humidifier or fragrance source in the respirator supply line to further obscure any sensible difference between the supplied gases.
Sensors to measure the subject’s heart and respiration rates.
Blood oxygen monitor.

Restrain the subject, for example in a sturdy chair without support for the head.
Attach sensors to monitor heart and respiration rates and blood oxygen.
Set the exchange valve to route air to the respirator and nitrogen to vent.
Start the flow of both gases, adjusting to equal flow rates and confirming normal oxygen concentration in the respirator supply line.
Place the respirator on the subject.
Complete all formal communications, such as pronouncement of sentencing and any final statement by the subject.
Reset the exchange valve to route nitrogen to the respirator and air to vent.
Observe the decreasing oxygen concentration in the respirator supply line and the occurrence of unconsciousness, when the subject becomes unable to support the head, followed in sequence by cessation of breathing and cardiac arrest.
Confirm death by medical examination.

All aspects of the procedure can be monitored electronically to allow full control by the staff, information to witnesses, and a reviewable record. At fixed intervals of one minute or less, a computer could record: