As you point out yourself in the thread, the nitrous used in medicine is delivered as a mix with 30 to 50% oxygen - Earth’s atmosphere is only about 20% oxygen. If you were in danger of asphyxiation due to partial breathing obstruction or something, the nitrous mask might actually be a reasonable source of oxygen-enriched air.
There might be other untoward effects from overdoing the nitrous, but asphyxiation isn’t a danger.
