When one person engages in asphyxiation play by themselves it is called autoerotic asphyxiation.
More About Asphyxiation Play
Asphyxiation play can pose a significant danger to participants especially when practicing alone. Autoerotic asphyxiation is particularly dangerous because there is no one to assist if the person who is being deprived of oxygen loses consciousness. Additionally as people engaging in asphyxiation play alone may create a complicated set-up for depriving themselves of oxygen, they may become incapable of releasing themselves.
This is a form of edge play.