In some less extreme cases, a person may regain consciousness when wrapped in warm blankets, taken inside, or treated with a machine that blows hot air across the body. But once a person’s heart and breathing have stopped, the best way to revive the person, doctors say, is by using a process known as extracorporeal rewarming — taking the blood from a person’s body, warming it externally, enriching it with oxygen, and pumping it back.

Patients who survive this procedure often have little or no cognitive damage, doctors say.

Hermann Brugger, a physician and vice head of the Institute of Mountain Emergency Medicine in Bolzano, Italy, described one case in which doctors using this method were able to revive a climber rescued during a thunderstorm who did not have his own blood circulation for more than eight hours. In another case, a man buried in an avalanche for 100 minutes survived. Neither had any neurological damage, he said.

More than 100 people suffering hypothermia have survived after being resuscitated using similar techniques over the past few decades in Central Europe, according to one study.

But not all emergency medical workers and doctors are familiar with the warming technique, Dr. Brugger said. He cited one case in which a 16-year-old girl found without a pulse after hours in the cold had been declared dead before extracorporeal warming was attempted. “An emergency physician tried to resuscitate on site, but this does not make sense, because if you don’t rewarm the body, you can resuscitate as long as you wish and it’s completely useless,” he added, noting that had the girl’s blood been rewarmed externally, she most likely would have survived.

In the case of the TV “corpsicle,” Dr. Zafren said that the men appeared very stiff, but not frozen. If they had been exposed to the cold for more than 24 hours, he added, they would have had little chance of surviving, and would not have spontaneously recovered without an external source of heat.

Also, he said, the officer could not possibly have snapped through a man’s arm bone, frozen or not.

“Being mostly dead is being somewhat alive,” Dr. Zafren said. So far, doctors have been unable to pinpoint the precise point of no return, he added. “But what we do know is if you’re dead for too long, you don’t come back.”