Concern that the signals could disrupt telemetry or other medical equipment are based on outmoded studies using older cell phone designs, said A. Joseph Anderson, M.D., of the University of Mississippi Medical Center in Jackson, and colleagues, at the American College of Emergency Physicians meeting here.
They tested cell phone use in the ED, and found that when the phones were used as intended the signals didn't disrupt electrocardiograms or set off alarms, they reported.
"As ubiquitous as cell phones are, if they were significant interference there would be daily noticeable disruptions," the investigators wrote.
The authors noted that while cell phones are off limits in patient care areas, other wireless devices, such as Blackberries, personal digital assistants, and wireless internet cards are often used with impunity.
They noted that many of the original studies used to justify a cell phone ban were conducted in the early 1990s, when cell phones used analog signals only, could not adjust their power output, and when medical equipment was not shielded from radio interference.
In addition, many of the early studies had cell phones touching the devices with which they were found to interfere, which is not how they were used then or now.
Many, if not most cell phones in use today are digital, and the widespread reach of cell towers means that newer devices need much less power than older phones, and are therefore less likely to cause undue interference, they said. Newer medical equipment is also shielded from stray radio frequencies.
The investigators decided to examine the potential of various wireless communication devices -- including cell phones and police walkie-talkies -- to produce clinically significant interference or impair the ability to monitor patients within their emergency department.
They used three different types of digital cell phones transmitting over two different networks (at 824 MHz and 894 MHz), and a walkie-talkie used by the police department. The devices were used at distances of two feet and 14 feet from a cardiac monitor, connected to a Laerdal Heart Sim 200 ECG simulator in the emergency department while rhythm strips were recorded.
The ECG monitors were programmed to sound an alarm if the heart rate fell below 50 or rose above 150, or if the signal was lost due to interference.
The investigators examined the printed ECG strips for changes in heart rate, PR interval, QRS width, dysrhythmias, or evidence of electrical interference. The strips were read by a group of physicians, nurses, and paramedics blinded to whether cell phones were on or off.
They found that there were no monitor alarms when the cell phones and walkie-talkie were in use, and there were no obvious changes in heart rate or arrhythmias.
The readers suspected baseline interference on five out of 31 strips recorded, but this suspected interference was considered to be too small to warrant changes in management. One of the five strips flagged for interference was recorded when neither the cell phones nor the police radio were on or in operation
They also questioned whether cell phones could wreak havoc with medical equipment when they don't seem to have hurt cash registers, automotive electronics, wireless computer networks, or garage-door openers.
"With recent improvements in technology it appears reasonable to allow for the limited use of cell phones in the waiting areas and the hallways of the ED," the authors wrote.
- Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco
American College of Emergency Physicians Annual Scientific AssemblySource Reference: Anderson AJ et al. "Does Cell Phone Use Cause Electromagnetic Interference with the Function of ECG monitors in the Emergency Department?" Abstract 107, presented Oct. 15.