The Science Journal of the American Association for Respiratory Care

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 Regional Medical Center, Seattle WA


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.

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