Prevention has to start early, before the behavior does.

Choking means the airway is blocked from the inside, by food, water, or an object. What happens during sex is pressure on the outside of the neck. Medicine, forensic examiners, and courts all call that strangulation.

Pressure on the neck can close the vessels that carry blood to the brain without touching the airway at all. Someone can be seconds from unconsciousness without coughing, gasping, or struggling to breathe.

“Doing it right” assumes there is a threshold a careful person can stay under. No one has ever established one. The pressure that causes damage varies from person to person, changes with position and circumstance, and neither experience nor technique can find it in advance.

About 11 pounds of pressure can close the carotid arteries; unconsciousness follows within seconds. The UK’s Institute for Addressing Strangulation reviewed the evidence and published its position under the title “There Is No Safe Way to Strangle.”

In a review of 300 strangulation cases reported to San Diego police, half the people strangled had no visible neck injuries at all. The damage that matters most is internal and shows nothing on the surface: bruised vessels, deep swelling, small tears in an artery wall.

A yes only counts if it can be taken back, and taking it back requires the ability to decide and to communicate. Strangulation can cause unconsciousness in five to ten seconds, before a safe word or hand signal can be used.

The yes doesn’t spread the risk evenly, either: the danger lands almost entirely on the person being strangled. In a survey of 4,702 Australians aged 18 to 35, people who strangled their partners and people who were strangled did not give the same account of the consent between them. And under the Training Institute’s guidance, legal consent to strangulation does not exist at any age.

Swelling inside the neck can develop several hours after strangulation and can close the airway. A stroke from a torn artery can arrive days or even weeks later. Clinical guidance lists thirteen findings that call for a CT scan of the neck vessels, and several of them surface after the person has gone home; the same guidance tells people to come back if symptoms appear.

In one study, 40 young women took memory tests. The ones who had been choked frequently scored the same as the ones who hadn’t, but the scans showed their brains working differently to produce those scores.