FACTBOX: How does cooling therapy work?

NEW YORK (Reuters Health) - How cooling works:

Cooling machines can be used to chill patients after cardiac arrest, and some doctors have also tested them on stroke and heart attack patients. None of these uses has been approved by the U.S. Food and Drug Administration. Some devices cool the body from the outside, via pads that circulate ice water; others use cold intravenous saline to chill the patient from within. To date, there is no consensus about the best cooling method.

Other common tools for fixing the heart:

Automated external defibrillators (AEDs) are briefcase-sized devices that let non-experts check a person's heart rhythm via patches glued to the chest. If the heart is beating too fast (ventricular tachycardia) to pump out enough blood, or just quivering chaotically (ventricular fibrillation), the AED can jolt it back to its normal rhythm. The American Heart Association supports placing AEDs in public areas such as offices and shopping malls.

Coronary angioplasty is a common procedure to open clogged blood vessels in the heart. The doctor guides a long, thin plastic tube (a catheter) to the heart via an artery, then inflates a balloon at the end of the tube to break up the buildup of cholesterol plaques. A fine wire-mesh tube called a stent is left in the coronary artery to keep it open.

Pacemakers can be placed in the chest to help control heart-rhythm disturbances such as tachycardia, which causes fatigue and other problems. They send small electric pulses to the heart, and newer models can also monitor blood pressure and other vital signs. Implantable cardioverter-defibrillators (ICDs) are similar to pacemakers, but can also shock the heart back to normal in case of cardiac arrest.

How many people can be saved by cooling?

Studies examining two types of cardiac arrest (ventricular fibrillation and tachycardia) show that one extra patient will survive without brain damage for every four to six people cooled. If all suitable patients were cooled, that means an additional 2,300 Americans would be able to leave the hospital with little or no brain damage every year, according to a government-funded study from 2008 -- the only published estimate. But some experts say the number could be much higher. Dr. Graham Nichol of the University of Washington puts it at 6,600, while Columbia's Dr. Stephan Mayer's calculations show it could be as many as 20,000.