RALEIGH, N.C. — Many hospitals warn against using cell phones inside, but many people still use them. Some doctors say it is causing problems.

Janet Orr has a cell phone and she said it helps her keep in touch with family members during her granddaughter's surgery at

Rex Hospital

.

However, Rex Hospital does not allow cell phones inside the facility.

Doctors and nurses must use cell phones that operate on a lower frequency.

Steven Bowers, the manager of Rex Hospital Biomedical Engineering Department, said many visitors making cell phone calls when they should not.

"It is a real problem," Bowers said.

As part of his job, Bowers inspects and repairs medical equipment at Rex Hospital. He said he often is called when cell phones interfere with medical equipment.

"When you put the two together, obviously you run into problems," Bowers said.

Cell phones transmit signals that interfere with certain pieces of medical equipment, Bowers explained. If a stray cell phone signal interferes with a heart monitor device, it can lead to the wrong diagnosis.

"It's very hard to discern sometimes when a device has been interfered with," said Bowers. "It may go unnoticed, so therein lies another danger."

Operating rooms, emergency departments and the intensive care unit are also dangerous areas for cell phones. But Bowers said they must come extremely close to cause major problems.

"Usually within a few inches, a few feet," he said.

However, hospitals said visitors should always obey the cell phone signs.

Bowers added that newer equipment often is equipped with shields to block cell phone signals.