Teens often discover the practice on their own, rather than learning it from others. Its sensations are similar to the "choking game" played by young children, who get a thrill from the dizziness created by holding their breath.
Divers have also reported a "high" from oxygen deprivation, according to Coleman. "For some people that may be pleasant or something associated with sexual arousal."
"This has been around long before the Internet.We have no idea how they would discover this," said Coleman. "It's not something they learned. It was a puzzlement and we concluded they were learning it on their own."
"We can only start to piece this together from people who have actually survived," he said.
Coleman, who did not consult in the Carradine case, speculates that many, like the actor, have practiced AEA for years.
"It becomes for them a fetish kind of thing and that is what it really takes for them," he said. But often their activities escalate in risk for the thrill, resulting in accidents.
But in the case of teens, accidental death often happens because they are inexperienced in the practice. "For those who have done it a long time, they know the limits and are pretty careful," Coleman said.
He added that people, particularly young teens, need to learn about the dangers of AEA.
"There are a lot of things on the Internet and we have no idea how this is impacting people," he said. "We are certainly concerned that [the Carradine case] might lead to an increase.
"We need to educate people about the risks rather than shield people from the information," Coleman said. "A lot of people are engaged in this activity and they don't know the risk."
Carradine's ex-wife Anderson also said in divorce documents that her "pleas for him to get counseling" were ignored.
Carradine is best known for his role in the 1972-'75 television series "Kung Fu," playing an orphan, Kwai Chang Caine, who was raised by Shaolin monks and fled China after killing the emperor's nephew in retaliation for the murder of his kung fu master.
In recent years, he played "Bill," the worldly father figure of a pack of crack assassins, in Quentin Tarantino's 2003 film, "Kill Bill."
ABC senior researcher Sheelagh A. McNeill contributed to this report.