International Humanitarian Hypoxia Project

Introduction to Nitrogen Asphyxiation

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Nitrogen asphyxiation is an occasional cause of accidental death and a theoretical method of capital punishment advocated in a National Review article, "Killing with kindness – capital punishment by nitrogen asphyxiation." (Creque 1995) 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 breathes in pure nitrogen, they exhale carbon dioxide without resupplying oxygen. Nitrogen is a colorless, odorless and tasteless gas that comprises approximately 78 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. This effect occurs in humans, but may be very unpleasant for burrowing animals such as rodents or rabbits, which have better function of the carotid body receptors for hypoxia.

For this reason, accidental nitrogen asphyxiation is a possible hazard where large quantities of nitrogen are used. Also, deliberate nitrogen asphyxiation 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.

Other inert asphyxiant gases such as helium or argon produce identical effects, but nitrogen is least expensive.

Overview of capital punishment proposed use

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).

In a televised documentary in 2007 [2], the right-wing UK political commentator (and former Member of Parliament United Kingdom), Michael Portillo examined execution techniques in use around the world and found them unsatisfactory ; his conclusion was that nitrogen asphyxiation would be the least-worst method. If reintroduction of the death penalty were ever to return to the political agenda in the UK, this would be a significant contribution to the debate.

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 with an anesthetic gas mask before surgery, and some subjects might react similarly. Nitrogen could be introduced into a standard gas chamber, however, without difficulty.

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.[3]

Evidence from cases of accidental death from nitrogen asphyxiation

Accidental nitrogen asphyxiation causes about 8 deaths per year in the United States,[4] 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 entered the Orbiter aft compartment which was pressurized with pure nitrogen as a precaution against fire.[5]

A laboratory assistant died in Scotland in 1999, apparently from asphyxiation, after liquid nitrogen spilled in a basement storage room.[6]

Awareness of impending death

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.

Physiology

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 liters 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 seconds 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 (13,000 m), 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 a 30 second 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.

References

Credit: http://en.wikipedia.org/wiki/Nitrogen_asphyxiation