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Study: Cell Phones Interfere With Medical devices
Wireless NewsFactor
Journalist: Jay Wrolstad
January 9, 2001

The most severe interference related to cell phone use: A mechanical ventilator shut down and restarted when a cell phone was held within two inches of a communication port on the ventilator.

Mobile phones cause limited interference in the operation of medical monitoring devices, and additional testing of such phone use in hospitals is needed, according to a study released by the Mayo Clinic.

The findings could lead to more stringent regulations regarding mobile phone use in hospitals.

In an editorial that accompanied the study, published in the January issue of Mayo Clinic Proceedings, clinic physicians recommended that cell phone use in the vicinity of medical electronic devices be restricted or banned, especially in areas where patients are particularly vulnerable, such as the intensive care unit and the operating room, until there is reasonable proof of safety. Banning the use of mobile phones in patients' rooms or in medical procedure areas is proposed as a precaution.

Proximity Matters
After conducting 526 tests using 17 mobile phones, clinic researchers reported that the most serious interference occurred when a mobile phone was held one to two inches from the most sensitive area of external cardiopulmonary monitoring devices.

Interference of some type was measured in 41 percent of the tests and was found to be "clinically important" in 7.4 percent of the tests. "Clinically important" was defined as any interference that might adversely affect interpretation of data or cause a malfunction in monitoring equipment.

Malfunctioning Monitors
Cell phone-related interference was detected in electrocardiographic (ECG) tracings displayed on monitors when phones were placed at a distance of 6 to 33 inches from the medical devices. Phones held beyond a radius of five feet would not affect ECG displays, researchers hypothesized.

The most severe interference related to cell phone use was detected when a phone was held near a mechanical ventilator. The ventilator shut down and restarted when the phone was held within two inches of a communication port on the back of the ventilator.

Other findings indicate that digital phones produce noise and some movement on baseline readings, while analog phones cause movement on monitor readings. Mobile phones used at a distance of 60 inches from electrical equipment within a patient's room or a central nursing station are unlikely to cause serious equipment malfunctions, the researchers said.

Additional Testing Needed
While much research has been done regarding the effects of wireless technology on medical implants, and bans have been imposed on mobile phones in hospitals, studies using external medical equipment have thus far been inconclusive and based on theoretical concerns without scientific testing, according to the study.

"When additional testing is completed, policies regarding cellular phone usage within the hospital environment can be constructed objectively," said David L. Hayes, a Mayo Clinic cardiologist and an author of the study.

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