Influence of second-generation and third-generation mobile phones on critical care medical equipment
© BioMed Central Ltd 2006
Published: 21 March 2006
The restricted use of cellular phones in patient areas in hospitals seems hard to enforce considering the growth in use and the decrease in size of these devices. The electromagnetic incompatibility of the first-generation mobile phones (i.e. GSM) with medical equipment has been described. Information on the safety of new mobile communication technology (second-generation GPRS and third-generation UMTS) is scarce. A recent paper showed minor interference with GRPS and UMTS suggesting improved safety with new networks .
We hypothesized that GPRS and UMTS have adverse influences with clinical relevance on critical care equipment.
Sixty-one medical devices used in the critical care environment were tested (i.e. nine ICU ventilators, 13 critical care monitors, seven syringe and four volumetric pumps, five hemofiltration/dialysis equipment). All were tested during full operation; a simulator was connected if necessary. A signal generator (HP/Agilent E4433B/ESG-D Digital RF) was used to generate the GPRS signal I and II (with different time slot durations both at carrier frequency 900 MHz) and the UMTS signal. Their power level was controlled at 2 W for GRPS and 0.2 W for UMTS, corresponding with maximal transmit performance of cellular phones in daily practice. The distance from the antenna to device during the tests varied from 500 to 0 cm. Incidents were classified according to an adjusted critical care adverse events scale: 'hazardous' (direct physical influence on patient by unintended change in equipment function), 'significant' (influence on monitoring significant level of attention needed with distraction from patient care) or 'light' (influence on monitoring significant level of attention needed without distraction from patient care).
A total of 49 incidents were found in 26 devices (43% of all tested devices). Seventeen incidents were classified as 'hazardous', 20 as 'significant' and 12 as 'light'. The hazardous incidents occurred in 26% with GPRS-1, in 6% with GRPS-2 and in 2% with the UMTS network. Hazardous incidents occurred at a median distance of 3.0 (0–300) cm.
Despite safety requirements of electronic medical equipment as stated in international standards, ICU devices are still vulnerable for electromagnetic interference by new-generation wireless telecommunication technology. Restricted use of cellular phones in ICUs is still warranted.