Cellular phone interference with the operation of mechanical ventilators

To determine whether a cellular phone would interfere with the operation of mechanical ventilators.

Laboratory study.

University medical center.

Fourteen mechanical ventilators.

We evaluated change in operation and malfunction of the mechanical ventilators.

The cellular phone (Nokia 6120i) was computer controlled, operating at 828.750 MHz analog modulation. It was operated at 16, 40, 100, 250, and 600 mW, 30 cm from the floor and 30, 15, and <3 cm from all sides of each ventilator. Six of the 14 ventilators tested malfunctioned when a cellular phone at maximum power output was placed < or =15 cm from the device. None of these responses were considered immediately life threatening except for the response of the Puritan Bennett 840, which stopped ventilating when the cellular phone at maximum power output was placed < or =30 cm from the ventilator. One ventilator doubled the ventilatory rate and another increased the displayed tidal volume from 350 to 1033 mL. In one of the infant ventilators, displayed tidal volume increased from 21 to 100 mL. In another ventilator, the high respiratory rate alarm sounded but the rate had not changed.

In a controlled laboratory setting, cellular phones placed in close proximity to some commercially available intensive care ventilators can cause malfunctions, including irrecoverable cessation of ventilation. This is most likely to occur if the cellular phone is <30 cm from the device and ringing. Based on our data and the available literature, we believe it is reasonably safe to permit the use of cellular phones in the intensive care unit, as long as they are kept > or =3 feet from all medical devices. The current electromagnetic compatibility standards for mechanical ventilators are inadequate to prevent malfunction. Manufacturers should ensure that their products are not affected by wireless technology even when placed immediately next to the device.