I couldn't find any resources that would confirm use of nitrous by Exit or more or less systematic use of it in assisted suicides in general.
That point is not proven. People have died from helium asphyxiation without continuous gas flow. For example,
tesble.com
As for nitrous, I just have more evidences that it works in closed setups without complications when some conditions are met.
That may happen due to
hypoxic ventilatory response. Nitrous can cause it too. In order to reduce the chances of getting unpleasant perceptions or minimize such perceptions, one should:
1) avoid setups that would make them breathe in a restricted manner, with a significant effort,
2) prefer breathing through mouth to nasal breathing,
3) avoid too much oxygen that would significantly delay loss of consciousness.
Probably, because they did it in an optimal way.
Some amount of nitrous will be dissolved in the bloodstream and tissues and thus removed from the system. Inert gases like helium and nitrogen have a smaller solubility in blood than nitrous and their elimination from the system this way will be smaller too.
Hypoxia caused by nitrous does make you wanting to breathe more intensively than usually. If something restricts respiration, unpleasant perceptions can be experienced according to F. Hewitt:
Should the apparatus possess valves which do not work easily, or should the channels through which the gas is made to pass be too small, or should the patient from want of confidence or knowledge breathe in a shallow and restricted manner, or through the nose, an unpleasant experience may result.
The question is: how can COâ‚‚ buildup make you feel uncomfortable if you lose consciousness within about 20 - 60 seconds (even if you use a plain inert gas like helium)? As for nitrous, its suppressive effect on hypercapnic response has been studied:
By the way, alprazolam can also be helpful at suppressing COâ‚‚-induced fear:
tesble.com
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