“You should only be feeling for a pulse for 10 seconds, while people fumble around trying to feel a pulse for one minute or more,” said Dr. Stephan Mayer, the director of neurocritical care at the Mount Sinai Health System.

Doctors and nurses also tend to give up too soon. CPR is typically performed for 15 to 20 minutes, but research shows that longer attempts at CPR, up to one hour, can lead to survival. These patients ultimately may fare as well those who are resuscitated more quickly. In patients with a chance of recovery, experts now advise attempting CPR for at least 45 minutes.

If no pulse returns after 20 minutes, however, experts say more powerful interventions should be considered. Often they are not.

“Doing CPR is like today driving a Model T Ford that itself isn’t even being operated properly much of the time,” said Dr. Sam Parnia, the director of resuscitation research at Stony Brook Hospital. “When it struggles to go uphill, we should switch to a more modern car — say a Ferrari with a powerful engine.”

One alternative to CPR is extra corporeal membrane oxygenation (ECMO), a procedure in which blood is drawn from a patient in cardiac arrest through a catheter placed in a central vein, circulated through an oxygenated filter, and then returned to the body carrying oxygen.

ECMO is more widely used in countries like Japan and South Korea than in the United States. “They routinely bring people back to life who would remain dead here,” Dr. Parnia said.

Once circulation is restored, a chain of interventions must occur to prevent further injury to the body and brain. But there’s no guarantee that patients will receive these treatments, which include avoiding toxic amounts of oxygen, maintaining normal carbon dioxide levels and high blood pressure, and sometimes a cardiac catheterization procedure.