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Interference: The truth about cell phones and medical devices

By John Kirisits, clinical engineering specialist, TriMedx

Q: Do cell phones still interfere with medical devices?

A: The quick answer is maybe.

Back in the late 1980s when cellular phones started becoming popular, they were quite a bit different than today. When cell phones were first accessible and affordable, they were analog-signaled phones. You may remember the most common one called the bag phone affectionately known as a "brick." This monstrosity of electrical circuits was quite large and cumbersome – usually mounted permanently in the vehicle and definitely not kept in your pocket or strapped to your head like cell phones today. These phones typically transmitted close to 5 watts of power with fuzzy reception and would interfere with various types of electrical equipment.

Fast forward a few years later and the bag phone was "so 1980s." In the 1990s it was replaced with a portable phone, the hand-held cellular phone. A small hand held unit with lower wattage, but still an analog device that interfered with electrical equipment. Carried by the owners everywhere, it didn't take long for people to start carrying them into hospitals. At the time, cellular phones were blamed for causing ventilators to malfunction, bedside monitors to detect weird frequencies and to make public address speakers around the hospital click. Thus, it wasn’t long before hospital administrators banned mobile cellular phones.

Telecommunication today is an era of advanced, ever-changing technology. Cell phones are smaller, operate on a digital frequency, and transmit less wattage. In fact, staff in most hospitals use communication devices similar in looks and operation to cell phones. Most hospitals operate wireless networks within the facility. With the onslaught of new technology, not only in cell phones but also digital, networked medical equipment most hospitals have relaxed a complete ban on cell phones. Many have a cell phone policy that is less stringent than 15 years ago. For example, some healthcare providers have gone from total bans to use in common areas only. This means you are usually free to use your cell phone in public areas, and possibly general patient rooms. However, don't even think about using it in an ICU or a surgical room. There is too much uncertainty involved when using a cell phone in a critical care area.

Why the change of heart? Is it because the new phones are digital instead of analog? Is it because they are so small, it would be to hard to enforce a "whole house ban"? Is it because most people use cell phones as their only source of communication? Is it because here in the midwest when a family member goes to the hospital, it turns into a family reunion with cheese cake within 20 minutes? Is it because the newer equipment is designed with more internal shielding? It is really hard to tell why the big culture change.

Let’s go back to the original question, "Do cell phones still interfere with medical devices?" The short answer remains – maybe. The safe bet is to stay 3 feet away from every device while talking on your cell phone or two way radio. The closer you get, the more chance you will have some sort of interference.