2006 OPEN FORUM Abstracts
THE EFFECT OF TWO WIRELESS PHONES ON THE FUNCTION OF THE VIASYS AVEA VENTILATOR DURING SIMULATED INFANT VENTILATION
Robert DiBlasi RRT-NPS, Anne M Green, John W. Salyer RRT-NPS, MBA, FAARC. Respiratory
Care Department, Children's Hospital and
Introduction: We sought to assess the
effects of electrical magnetic interference (EMI) on the Viasys Avea ventilator.
Recently, we
experienced monitored values that were out of range on several mechanical
ventilators and questioned if these erroneous measurements might be caused by
the electromagnetic interference (EMI) from wireless phones carried by the
respiratory staff or by visitors in the ICU. Our respiratory therapists rely on the Spectralink WTS wireless phones
for communications across all inpatient areas.
Methods: 9 ventilators were tested at the following settings VT
=6 ml/kg, RR=20, TI= 0.35 sec, FIO2 0.21 and flow
trigger 0.5 L/m during simulated ventilation using an infant test lung. Tests
were conducted in a training room immediately adjacent to the Pediatric
Intensive Care Unit (PICU). Two different phones were tested; a Spectralink WTS
410 wireless and Samsung SGH X475 cellular phone. An outgoing call was made to
the PICU while the phone was held against the ventilator screen. As the call continued, the phone was moved
about the body of the ventilator and then moved 5 cm, 20 cm, and 40 cm away. At the same time, another investigator was
navigating the touch screen hierarchy. This procedure was repeated for both types
of phones. Observations included any audible or visual alarms, the function of
the touch screen, and the stability of ventilator settings and measurements.
Results: There were no observed alarms,
changes in the performance of the touch screen, or observed variability in
ventilator settings or measurements with either type phone on any of the 9
ventilators tested. The ventilator also did not have any effect on the overall
function of either phone.
Discussion:
In hospitals, restriction
on the use of wireless telephones in the clinical setting has become common
practice. The risk of interference between wireless phones and medical devices
mainly depends on transmission power, distance to the transmitter, and
construction of the medical device, but signal characteristics, such as
frequency and modulation (pulsing), are also important (Anaesthesia
2003;58:353-7). There are reports that the use of some wireless
devices in a laboratory setting has resulted in serious and sometimes
potentially life threatening malfunctions with certain types of ventilators. The Spectralink phones are specifically designed for industries
using equipment sensitive to EMI, and thus transmit at a relatively low power
(12.5 mW). The Samsung phone is a typically commercially available cell phone
and operates at approximately 50 times the transmission power of the
Spectralink. The power density of a
radio wave is inversely proportional to the square of its distance from the
source. Thus, we tested phones as close to the devices as
possible. If the ventilator was
sensitive to EMI emitted by wireless communications devices, it would more
likely have been demonstrated using the Samsung phone. However, the ventilator is clearly not
sensitive to EMI of the type created by either phone. This may be related to strict
manufacturer standards and reinforced casing within the ventilator body and
monitor. Radio frequency emitted by these different types of wireless phones
appears to be well tolerated by the Viasys Avea ventilator in this clinical setting.