Originally Published MDDI April 2005

NEWSTRENDS

Cell Phone Interference with Hospital Equipment Is Still Controversial

Maria Fontanazza

With recent discussion about hospitals lifting their cell phone bans, there has been talk about whether the phones really do interfere with medical equipment. Past and present studies have shown that interference can occur when cell phones are in close proximity to equipment. However, the issue has not been completely resolved. In fact, experts say that certain kinds of medical instruments cannot be built to resist signals from cell phones.

“A cell phone doesn't generate a lot of energy, and if it does have an effect, it's not going to have much range,” says William Kimmel. Kimmel is principal at Kimmel Gerke Associates Ltd. (St. Paul, MN). “But there are certainly cases where cell phones pose a definite threat, and that's been tested and documented,” he explains.

When a cell phone is turned on, it transmits signals even if it's not in use. So, if a person puts a phone on top of a sensitive electronic instrument, it can interfere, says Kimmel.

While hospitals can make zones where the phones are permitted, Kimmel says the issue is identifying and enforcing those areas to the general public. “Although medical staffs routinely use cell phones in hospitals, and it would appear to be a double standard, they're trained. They know enough to keep their phones away from sensitive instruments. You can control the staff, because they're knowledgeable about it, but you can't control a patient visitor.”

Researchers at the University of Melbourne in Australia reviewed studies on digital cell phones and electromagnetic interference (EMI) with medical equipment. The studies were conducted between 1966 and 2004 and involved equipment used to monitor or treat patients, excluding implantable devices. The researchers found that all of the studies advised restricted use of equipment that interfered, such as cell phones, in hospitals. They concluded “medical equipment needs to be manufactured to resist EMI from mobile phones, with standards that take into account new phone technology.”

“Once you get into the scientific, medical, and industrial areas, you get into very sensitive instruments that cannot readily be made immune to radio frequency interference,” says Kimmel. “There is a different set of requirements for devices that monitor physiological effects because they pick up signals that are very tenuous. If you demand the immunity be there, you're effectively disallowing the equipment from being built in the first place. These systems can't be made bulletproof from ordinary radio forces, such as a cell phone.”

Equipment can be at risk when operating at close proximity (6 ft or less) to a cell phone. However, a cell phone's presence doesn't necessarily mean interference will occur. “There's a risk of interference that can't be controlled, so rather than take a chance, hospitals are conservative,” says Kimmel. “At minimum, if you're going to try to relieve that, then you'll have to establish a safe perimeter for the equipment to be operated.”

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