Asphyxia (from Greek meaning ‘without pulse’, or ‘heartbeat’) is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs.

A simple explanation is that lack of oxygen can cause lightheadedness, reducing inhibitions and enhancing the sexual experience. Masochistic and castration fantasies are common and other psychological factors also play a role.