Maybe due to conflict of interests or inability to assess information adequately, or both.
pmc.ncbi.nlm.nih.gov
In opposition to any stated opinion that the death penalty and state execution are somehow humane, we demonstrate herein that the latest method, nitrogen anoxia, invoked by the state of Alabama is inherently inhumane.
TL;DR: the only thing they actually demonstrated is that a lack of oxygen may induce some dyspnea. No any decent evidence of significant distress associated with that dyspnea during the execution process is presented in the entire document.
Ernsting found that breathing pure nitrogen induced collapse, convulsions and unconsciousness within 17–20 s (Ernsting, 1963) which was accompanied by a 5‐ to 6‐fold elevation in ventilation and increase in heart rate and blood pressure.
In the experiments conducted by Ernsting, the subjects were instructed to hyperventilate, so elevation in ventilation was implied primarily by the design of the experiments rather than by the natural physiological response:
During the period of breathing nitrogen the subject was instructed to breathe as deeply as possible at a rate of about 20 breaths per minute.
...
1. Brief profound hypoxia was induced by voluntary over-ventilation whilst breathing nitrogen. Unconsciousness ensued when this procedure was performed for longer than 16 sec. Voluntary over-ventilation with nitrogen for 16 sec reduced the end-tidal oxygen tension to below 10 mm Hg for 8 sec.
tesble.com
As for increased heart rate and blood pressure, these effects can also be produced by voluntary hyperventilation alone (even if you breathe plain air containing 21% oxygen), hence the given case is not very informative regarding cardiovascular changes produced specifically by nitrogen-induced hypoxia, without comparing them against the changes that could be produced by the same breathing pattern with normal air.
Copeland et al. (2015) based their report, in part, on the work of Ernsting (1963) and posited further that 'inhalation of only 1–2 breaths of pure nitrogen will cause a sudden loss of consciousness'. Considering that the one to two breaths were normal tidal volumes of 0.5 L, these would dilute the initial ∼16% O2 in the lungs to 14% on the first breath and 12% on the second breath. This might lower arterial 𝑃O2 from its normal 95–100 mmHg to ∼50 and 36 mmHg, respectively, but would certainly not reduce the arterial O2 to the level that might result in a loss of consciousness.
As for unconsciousness from 1-2 breaths, Copeland et al. refer to European Industrial Gases Association:
Without oxygen present, inhalation of only 1-2 breaths of pure nitrogen will cause a sudden loss of consciousness and, if no oxygen is provided, eventually death. (European Industrial Gases Association, 2009, p. 3).
CopelandReport_NitrogenHypoxia.pdf
They can be blamed for omission of the fact that those breaths must be very deep in order to achieve LOC and that you'd probably need to wait for LOC, holding your breath (so there would be no 3rd breath), and that the LOC is not really sudden for the subject (you can actually feel how it's coming), although the unresponsiveness may seem sudden for an external observer; but the presented wording is not entirely wrong.
The report by Copeland et al. (2015) seems very concerned that the carotid bodies are not stimulated by respiratory acidosis as breathing continues to offload carbon dioxide. But, crucially, they fail to appreciate that low arterial 𝑃O2 provides its intensely dyspnoeic response via the carotid bodies in and of itself.
I don't see any mentioning of carotid bodies (or peripheral chemoreceptors) in the Copeland's report. In this report, the authors focus on hypercapnia as a realistic cause of distress:
Unlike asphyxiation, hypoxia via the inhalation of nitrogen allows the body to expel the carbon dioxide buildup that is normally associated with the respiratory cycle. This helps prevent a condition known as hypercapnia an accumulation of carbon dioxide in the blood. The result of this buildup of carbon dioxide is respiratory acidosis a shifting of the ph levels in the blood to become more acidic. Some of the symptoms of respiratory acidosis are expected to be present in cases of asphyxiation, but not expected to be present under pure hypoxia are anxiety and headaches, (Merrick Manuel, 2013).
Copeland et al. (2015) also cited Ernsting (1963) that 'there was no reported physical discomfort' and went so far as to opine that 'low levels (sic) of hypoxia' produce euphoria and that the anxiety that presents with asphyxiation (a proposed alternative that could be achieved simply by placing a plastic bag over the victim's head) would not be present. The latter point is disingenuous, because Ernsting (1963) did not comment at all on physical comfort or lack thereof.
In case if those 3 men had experienced any somewhat significant distress, it would be strange if symptoms like dimness of vision and generalized convulsion were mentioned, but the distress was not. As if dimness of vision were a more important symptom that is worth mentioning, while the distress is just a minor thing. Besides, Copeland et al. don't base their conclusions solely on data from Ernsting. The Copeland's report points to way more explicit evidences regarding the level of comfort:
Perhaps one of the greatest testaments to both the humanity of nitrogen induced hypoxia as well as the ease of administration, is its rapid popularity as a self selected means of suicide. Suicide by hypoxia using an inert gas is the most widely promoted method of human euthanasia by right to die advocates (Howard, M.O. et. al., 2011, P. 61).
The trend toward using an "exit bag" filled with an inert gas such as nitrogen or helium likely started with a publication of Final Exit: The Practicalities of Self Deliverance and Assisted Suicide for the Dying. The authors of the publication sought to identify methods of death that were swift, simple, painless, failure proof, inexpensive, non disfiguring and did not require a physician's assistance or prescription (Howard, M.O. et. al., 2011. p 61).
...
Reports of deaths observed via this method suggest that it is painless. Jim Chastain, Ph.D. President of the Final Exit Network of Florida described the process this way: In the several events I have observed the person breathes the odorless, tasteless helium deeply about three or four times and then is unconscious, no gagging or gasping. Death follows in 4-5 minutes. A peaceful process.
Derek Humphrey, current chair of the Final Exit advisory board is quoted as saying:
In the approximate 300 cases which have been reported to me there has never been mention of choking or gagging. When I witnessed the helium death of a friend of mine it could not have been more peaceful (Final Exit, 2010).
Why didn't this cited text deserve any comments from David C Poole et al.? Maybe because it would be inconvenient to address in their propaganda against inert gas asphyxiation?
More importantly, those physiologists among us who have studied the effects of breathing nitrogen anoxia know that it is an intensely disturbing and discomforting experience.
"Know" from where? A serious PubMed article should have mentioned at least one actual experiment with description of the relevant symptoms from the subject(s) undergoing inert gas asphyxiation, because just "knowing" is a level of yellow journalism.
Rather than becoming unconscious within a few breaths and dying within 1 min as stated in the Copeland Report, Smith would have been expected to show signs of severe discomfort and distress with intolerable air hunger for ∼1 min and dying within 5–6 min had he been switched to 100% nitrogen in his mask. Although the exact timing is dependent, in part, upon his breathing pattern and the rate of decreased brain O2 supply and metabolism, the eyewitness reports that claim otherwise raise the possibility that the inspired gas was not pure nitrogen, either because the gas cylinder supplying nitrogen did not contain 100% nitrogen or because leaks in the system permitted the entry of O2.
Another very probable reason: he resisted and held his breath as long as he could, which resulted in hypercapnia, causing discomfort. Comfortable euthanasia with the given method needs some cooperation between the subject to be killed and the staff. If the subject doesn't want to cooperate, then he can experience some significantly unpleasant sensations, and he becomes responsible for his distress.
Also I don't get where that "dying within 1 min" comes from. The actual text of the report suggests a different estimation:
Most electrochemical brain activity should cease shortly after loss of consciousness, and the heart rate will begin to increase to varying degrees until it stops beating 3 to 4 minutes later.
Note that cardiac arrest is not death yet.
This one doesn't offer direct evidences of distress from inert gas asphyxiation either, just vague speculations around air hunger in general.
