When you enter most health care facilities, the first thing you see is usually a sign asking you to turn off your cell phone.

But calls made on cellular phones have no negative impact on hospital medical devices, dispelling the long-held notion that they are unsafe to use in health care facilities, according to Mayo Clinic researchers.

In a study published in the March issue of Mayo Clinic Proceedings, researchers say normal use of cell phones results in no noticeable interference with patient care equipment. Three hundred tests were performed over a five-month period in 2006, without a single problem incurred.

Involved in the study were two cellular phones which used different technologies from different carriers and 192 medical devices. Tests were performed at Mayo Clinic campus in Rochester.

The study's authors say the findings should prompt hospitals to alter or abandon their bans on cell phone use.

Mayo Clinic leaders are reviewing the facility's cell phone ban because of the study's findings, says David Hayes, M.D., of the Division of Cardiovascular Diseases and a study author.

Cell phone bans inconvenience patients and their families who must exit hospitals to place calls, the study's authors say.

The latest study revisits two earlier studies that were done 'in vitro' (i.e., the equipment wasn't connected to the patients), which also found minimal interaction from cell phones used in health care facilities. Dr. Hayes says the latest study bolsters the notion that cells phones are safe to use in hospitals.