Cardiac arrest can strike without warning: That's one reason why thousands of volunteers have learned cardiopulmonary resuscitation (CPR). Although the chest-pumping technique moves air into the lungs and blood through the body, it is difficult to perform correctly; a few minutes of lifesaving exertion can exhaust even the burliest paramedic. Overall, only 15 percent of cardiac arrest victims survive.

Cardiologics Systems, a tiny research outfit in Baltimore, Md., is lab-testing a portable, inflatable vest that could provide a safer, easier way to do CPR. The nylon vest wraps around the victim like a big blood pressure cuff; a battery-powered pump drives 10 liters of air into the vest every second. Cardiologics faces competition in the portable-CPR niche from several other R&D outfits. Before the devices become a common sight at poolsides and in ambulances, however, developers must prove they outperform manual CPR in clinical tests.