The way I loint it, "depriving them of air" was suffocation. Asphyxiation was disrupting (poisoning) the body's ability to process the oxygen in the air.
Thus, carbon monoxide does not suffocate, carbon monoxide asphyxiates by poisoning the hemoglobin. Carbon dioxide suffocates but does not asphyxiate.
I strongly suspect this is another case of misuse of a word (in this case, two words) which has resulted in corrupted definitions promulgated by the internet.
Anyhow, that's the way I learned the difference between the two, wayyyy before the internet.
Sorry, but popular corruption of meanings (especially on the internet) has been kind of a bugaboo with me lately, so if I'm wrong, then I'm wrong in my current usage of the two words.
Terry, 230RN