Electromagnetic Interference of External Pacemakers by Walkie-Talkies and Digital Cellular Phones: Experimental Study

A number of experimental and clinical studies have documented the risk potential of interference with implanted pacemakers by various types of cellular phones. Radiofrequency susceptibility of external medical equipment has also been reported in experimental studies. The purpose of this experimental study was to evaluate electromagnetic interference of external pacemakers by walkie-talkies and digital cellular telephones. External bipolar pacing was monitored using a digital oscilloscope to record pacemaker pulses and electromagnetic interference separately. Tests with the walkie-talkie, Private Mobile Radio (PMR) (160 MHz, 2.5 W) were conducted during the calling phase. Tests with the cellular phones, global system for mobile communications (GSM) (900 MHz, 2 W) and Digital Cellular System (DCS) (1,800 MHz, 1 W) were conducted in the test mode. Nine widely used external pacemakers from four manufacturers were tested. Various disturbances including pacing inhibition and asynchronous pacing were observed in eight pacemakers by the PMR, in four by the GSM phone, and in two by the DCS phone. The maximum distance that interference persisted ranged from 10–200 cm. This experimental study shows a potential risk of interference of external pacemakers by walkie-talkies and cellular digital phones. Appropriate warnings should be issued against the potentially serious risks of using communication devices in the vicinity of acutely ill patients treated with temporary transvenous cardiac pacemakers.     

Electromagnetic compatibility of electronic implants--review of the literature.

The aim of the article was to provide an overview of published studies regarding the electromagnetic compatibility (EMC) of electronic implants. The available literature was sorted according to combinations of implant types and sources of interference. Several experiments concerning the susceptibility of pacemakers to mobile phones have been performed. The results of these experiments suggest measures that may be used to prevent the disturbance of pacemakers. For instance, instead of carrying the activated mobile phone in the breast pocket it is recommended that a distance of 30 cm be maintained between the pacemaker and the mobile phone, and that the mobile phone be used on the contralateral side of the pacemaker's location. Similar measures may be recommended for patients with implantable cardioverter defibrillators when using mobile phones. Patients with electronic implants should walk rapidly through anti theft-devices because some of these devices are liable to disturb implants. Patients with cardiac pacemakers should not be subjected to magnetic resonance imaging as far as possible. For a variety of combinations of implants and interference sources, e.g. cardiac pacemakers and base station antennas, no studies were found in the literature. It is strongly recommended that trials be carried out to evaluate the potential risk for patients in these settings.     

Cellular phone interference with external cardiopulmonary monitoring devices

OBJECTIVES: To determine the potential effect (electromagnetic interference) of cellular telephones on external cardiopulmonary monitoring devices. METHODS: For this study, we tested 17 different medical devices with 5 portable telephones (4 digital, 1 analog) to assess the potential for electromagnetic interference. The telephones were tested in a normal operating mode to simulate a typical hospital environment with patients or their families using their cellular phones. The medical devices were connected to the appropriate simulators for proper operation while the tests were under way. The screens and alarms of the medical devices were monitored while the telephones were maneuvered in the y and z planes near the devices. Clinically important interference was defined as interference that may hinder interpretation of the data or cause the equipment to malfunction. RESULTS: Any type of interference occurred in 7 (41%) of the 17 devices tested during 54.7% of the 526 tests. The incidence of clinically important interference was 7.4%. CONCLUSIONS: Cellular telephones may interfere with the operation of external cardiopulmonary monitoring devices. However, most of the test results showed that the interference would rarely be clinically important.     

Clinical testing of cellular phone ringing interference with automated external defibrillators

OBJECTIVE: This study examined cellular phone ringing interference with automated external defibrillators (AED). METHODS: The phone systems tested were two single band handheld telephones: (1) a Global System for Mobile Communication (GSM) receiver; and (2) a Personal Communication Services (PCS) receiver. The ringing phase of a digital cellular phone includes a brief burst of peak-emitted power. The GSM had a maximum power output of 2 W, operating on a 900 MHz carrier frequency, and the PCS had a maximum output of 1 W, operating on a 1800 MHz carrier frequency. During AED monitoring, the digital cellular telephone was placed successively in three positions: (1) on the AED; (2) on the patient's chest between the electrodes; and (3) on the connector between the electrodes and the AED cable. After positioning the cellular phone, calls were placed during the AED analyzing phase. RESULTS: Three AED models were tested using their original electrodes: (1) LifePak 20 monitor/defibrillator device; (2) Lifepak 20 P monitor/defibrillator/stimulator (Medtronic Emergency Response Systems, Redmond, WA, USA); and (3) HeartStart XL M4735A monitor/defibrillator (Philips Medical Systems, Andover, MA, USA). The first two devices had Quik-Combo electrodes and the third device had Adults Plus multifunction electrodes. Ninety-one tests were performed on 13 patients. The only disturbance provoked by testing was noise emitted by the AED speaker when the receiver was close to the device. The noise began 2-4 s before the first audible ringing tone and persisted throughout the ringing phase. The distance at which this effect could be prevented was 15 cm. CONCLUSION: Clinical testing during ECG monitoring by an AED during call from a cellular phone did not show any analysis dysfunction during unshockable rhythms and provoked only transient dysfunction of the speaker device.     

Do Mobile Phones Pose a Potential Risk to Autonomic Modulation of the Heart?

Background: It has long been speculated that mobile phones may interact with the cardiac devices and thereby cardiovascular system may be a potential target for the electromagnetic fields emitted by the mobile phones. Therefore, the present study was designed to test possible effects of radiofrequency waves emitted by digital mobile phones on cardiac autonomic modulation by short‐time heart rate variability (HRV) analysis. Methods and Results: A total of 20 healthy young subjects were included to the study. All participants were rested in supine position at least for 15 minutes on a comfortable bed, and then time and frequency domain HRV parameters were recorded at baseline in supine position for 5 minutes. After completion of baseline records, by using a mobile GSM (Global System for Mobile Communication) phone, HRV parameters were recorded at turned off mode, at turned on mode, and at calling mode over 5 minutes periods for each stage. Conclusion: Neither time nor frequency domain HRV parameters altered significantly during off mode compare to their baseline values. Also, neither time nor frequency domain HRV parameters altered significantly during turned on and calling mode compared to their baseline values. Short‐time exposure to electromagnetic fields emitted by mobile phone does not affect cardiac autonomic modulation in healthy subjects. (PACE 2011; 34:1511–1514)     

Effect of digital cellular phones on tachyarrhythmia analysis of automated external defibrillators.

OBJECTIVES: Emergency services personnel, family members, laypersons or patients often carry and use mobile phones on sites of emergencies. As there are reported effects on implanted pacemakers and cardioverter defibrillators, the influence of digital cellular phones on automated external defibrillators was studied. METHODS: Twelve automated external defibrillator models were bench tested for their correct decision to or not to advise a shock, while being exposed to electromagnetic interference from a handheld cellular phone with 2 W or a portable cellular phone with 8 W transmitting power. The phones were programmed by a special subscriber identity module card to maximum output power with a carrier frequency of 906.2 MHz. The tests were conducted with a burst frequency of 217 Hz in speech mode and 2-8 Hz in discontinuous transmitting exchange mode. The sensitivity and specificity of electrocardiogram analysis systems were tested, with shockable and non-shockable rhythms provided by an electrocardiogram simulator and on two human subjects with normal sinus rhythm. RESULTS: A total of 8640 tests were recorded, each automated external defibrillator was tested a total of 720 times. The automated external defibrillators demonstrated a sensitivity of 100% and a specificity of 100%, representing a positive likelihood ratio of 8641 and a negative likelihood ratio of 0.000. In this setting all automated external defibrillators analysed correctly even under worst-case testing conditions, and performed excellently without any single failure. In some devices, voice prompts were distorted beyond comprehension, as the coil of the automated external defibrillator speaker received the pulsed signals. CONCLUSION: Shock advisory systems of automated external defibrillators are not susceptible to electromagnetic interference of 900 MHz cellular phones. Voice prompts, however, could be distorted by the operation of nearby digital mobile phones. During automated external defibrillator training this issue needs to be addressed.     

Cellular telephone interference with medical equipment

OBJECTIVE: To assess the potential electromagnetic interference (EMI) effects that new or current-generation cellular telephones have on medical devices. MATERIAL AND METHODS: For this study, performed at the Mayo Clinic in Rochester, Minn, between March 9, 2004, and April 24, 2004, we tested 16 different medical devices with 6 cellular telephones to assess the potential for EMI. Two of the medical devices were tested with both new and old interface modules. The 6 cellular telephones chosen represent the different cellular technology protocols in use: Code Division Multiple Access (2 models), Global System for Mobile communications, Integrated Digital Enhanced Network, Time Division Multiple Access, and analog. The cellular telephones were tested when operating at or near their maximum power output. The medical devices, connected to clinical simulators during testing, were monitored by observing the device displays and alarms. RESULTS: Of 510 tests performed, the incidence of clinically important interference was 1.2%; EMI was Induced in 108 tests (21.2%). Interference occurred in 7 (44%) of the 16 devices tested. CONCLUSIONS: Cellular telephones can interfere with medical equipment. Technology changes in both cellular telephones and medical equipment may continue to mitigate or may worsen clinically relevant interference. Compared with cellular telephones tested in previous studies, those currently in use must be closer to medical devices before any interference is noticed. However, periodic testing of cellular telephones to determine their effects on medical equipment will be required.     

Influence of mobile phones on accuracy of ECG interpretation algorithm in automated external defibrillator.

BACKGROUND: Automated External Defibrillators (AED) are a recommended tool for out-of-hospital emergency medical services. Mobile phones (GSM) are a potential source of electromagnetic interference which may cause failure of ECG interpretation and subsequent inappropriate action of AED's. METHODS: We evaluated the influence of 900 MHz GSM phones on the accuracy of automatic ECG interpretation with a GSM Mobile Station Tester with adjustable power and mode of transmission (Hewlett-Packard HP5515A), GSM phones (Alcatel, Ericsson, Nokia, Panasonic), ECG simulator (Metron) and four AEDs (Fore Runner-Hewlett-Packard, Heartstart 3000-Laerdal, Cardio-Aid 100-Artema, Heartstream XLT-Agilent). The protocol included 18 different ECG patterns, different ECG voltages, and different power and mode of transmission. RESULTS: The first stage of the protocol included minimal power of signal transmitted from GSM Mobile Station Tester and maximum power of GSM phone's signal--hence maximal potential interference to AED. The protocol was based on close direct contact between the GSM phone and the AED device. Regardless of the ECG pattern, with both 0.5 and 1.0 mV ECG voltage, and the GSM phone placed on various parts of AED device or at the patient cable, no failure of AED algorithm occurred. No detectable noise was seen at AED's ECG display. CONCLUSION: AEDs seems to be well protected against clinically significant failure caused by noise from 900 MHz GSM phones.     

Interference by new-generation mobile phones on critical care medical equipment

Introduction  

The aim of the study was to assess and classify incidents of electromagnetic interference (EMI) by second-generation and third-generation mobile phones on critical care medical equipment.     

Influence of D-Net (European GSM-Standard) Cellular Phones on Pacemaker Function in 50 Patients with Permanent Pacemakers

The widespread use of cellular phones in the last years has prompted some recant studies to suggest an interference of pacemaker function by cellular phone usage. To determine the risk of pacemaker patients using D-net cellular phones, we tested 50 patients with permanent pacemakers after routine pacemaker check by short phone calls using a cellular phone (Ericsson, D-net, frequency 890–915 MHz, digital information coding, equivalent to the European Croupe Systemes Mobiles standard). A six-channel surface ECG was continuously recorded from each patient to detect any interactions between pacemakers and cellular phones. Phone calls were repeated during the following pacemaker settings: (1) preexisting setting; (2) minimum ventricular rate of 90 beats/min and preexisting sensitivity; and (3) minimum ventricular rate of 90 beats/min and maximum sensitivity without T wave oversensing. Only 2 (4%) of 50 patients repeatedly showed intermittent pacemaker inhibition during calls with the cellular phone. Both pacemakers had unipolar sensing. Therefore, although interactions between cellular phone use and pacemaker function appear to be rare in our study, pacemaker dependent patients in particular should avoid the use of cellular phones.     

Third‐Generation Mobile Phones (UMTS) Do Not Interfere with Permanent Implanted Pacemakers

Aims: Third‐generation mobile phones, UMTS (Universal Mobile Telecommunication System), were recently introduced in Europe. The safety of these devices with regard to their interference with implanted pacemakers is as yet unknown and is the point of interest in this study. Methods and Results: The study comprised 100 patients with permanent pacemaker implantation between November 2004 and June 2005. Two UMTS cellular phones (T‐Mobile, Vodafone) were tested in the standby, dialing, and operating mode with 23 single‐chamber and 77 dual‐chamber pacemakers. Continuous surface electrocardiograms (ECGs), intracardiac electrograms, and marker channels were recorded when calls were made by a stationary phone to cellular phone. All pacemakers were tested under a “worst‐case scenario,” which includes a programming of the pacemaker to unipolar sensing and pacing modes and inducing of a maximum sensitivity setting during continuous pacing of the patient. Patients had pacemaker implantation between June 1990 and April 2005. The mean age was 68.4 ± 15.1 years. Regardless of atrial and ventricular sensitivity settings, both UMTS mobile phones (Nokia 6650 and Motorola A835) did not show any interference with all tested pacemakers. In addition, both cellular phones did not interfere with the marker channels and the intracardiac ECGs of the pacemakers. Conclusion: Third‐generation mobile phones are safe for patients with permanent pacemakers. This is due to the high‐frequency band for this system (1,800–2,200 MHz) and the low power output between 0.01 W and 0.25 W. (PACE 2010; 860–864)     

Cellular phone interference with the operation of mechanical ventilators

OBJECTIVE: To determine whether a cellular phone would interfere with the operation of mechanical ventilators. DESIGN: Laboratory study. SETTING: University medical center. SUBJECTS: Fourteen mechanical ventilators. INTERVENTIONS: We evaluated change in operation and malfunction of the mechanical ventilators. MEASUREMENTS AND MAIN RESULTS: 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. CONCLUSIONS: 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.     

Cellular Phone Interference Testing of Implantable Cardiac Defibrillators In Vitro

An in vitro study was undertaken to investigate the potential for cellular telephones to interfere with representative models of presently used ICDs. Digital cellular phones (DCPs) generate strong, amplitude modulated fields with pulse repetition rates near the physiological range sensed by the 1CD as an arrhythmia. DCPs with Time Division Multiple Access (TDMA) pulsed amplitude modulation caused the most pronounced effect—high voltage firing or inhibition of pacing output of the ICDs. This electromagnetic interference (EMI) occurred only when the phones were within 2.3–5.8 cm of the ICD pulse generator that was submerged 0.5 cm in 0.18% saline. ICD performance always reverted to baseline when the cellular phones were removed from the immediate proximity of the ICD. Three models of ICDs were subjected to EMI susceptibility testing using two types of digital phones and one analog cellular phone, each operating at their respective maximum output power. EMI was observed in varying degrees from all DCPs. Inhibition of pacer output occurred in one ICD. and high voltage firing occurred in the two other ICDs. when a TDMA11 Hz DCP was placed within 2.3 cm of the ICD. For the ICD that was most sensitive to delivering unintended therapy, inhibition followed by firing occurred at distances up to 5.8 cm. When a TDMA-50 Hz phone was placed at the minimum test distance of 2.3 cm. inhibition followed by firing was observed in one of the ICDs. EMI occurred most frequently when the lower portion of the monopole antenna of the cellular phone was placed over the ICD header.     

Do European GSM Mobile Cellular Phones Pose a Potential Risk to Pacemaker Patients?

BARBARO, V., et al .: Do European GSM Mobile Cellular Phones Pose a Potential Risk to Pacemaker Patients? A series of in vivo trials were carried out in order to verify whether the electromagnetic field radiated by GSM (Groupe Systemes Mobiles) mobile cellular phones might affect implanted pacemakers. Two European GSM phones of 2-watt power were tested and trials conducted on 101 pacemaker implanted outpatients attending day hospital for routine check-up, who volunteered for trials. Forty-three pacemaker models from 11 manufacturers were tested in all. When the sensing threshold of the pacemakers was set at a minimum and the antenna of the phone was in direct contact with the patient's chest, interference was detected for 26 implanted pacemakers. Specifically, pulse inhibition in 10 of 101 cases, ventricular triggering in 9 of 46 DDD-VDD pacemakers, and asynchronous pacing in 4 of 52 devices. Pulse inhibition was also observed combined with asynchronous pacing in 1 of 52 cases and with ventricular triggering in 2 of 46 cases. Minimum effect duration was ca. 3 seconds but in 6 cases effects continued as long as the interfering GSM signal was on. No permanent malfunctioning or changes in the programmed parameters were detected. Whenever interference was detected, trials were repeated to determine the maximum sensing threshold at which interference persisted (with the antenna in contact with the skin over the pacemaker). Then maximum distance between antenna and pacemaker at which interference occurred was determined at pacemaker maximum and minimum sensing threshold. Under our experimental conditions electromagnetic interference effects were detected at a maximum distance of 10 cm with the pacemaker programmed at its minimum sensing threshold. When the phone antenna was in direct contact with patient's skin over the implant, electromagnetic interference effects occurred at maximum ventricular and atrial sensing thresholds of 4 mV and 2.5 mV, respectively.     

Electromagnetic Interference of Digital and Analog Cellular Telephones with Implantable Cardioverter Defibrillators: In Vitro and In Vivo Studies

The present study examines the potential electromagnetic interference effects induced by cellular telephones on ICDs. We developed ad hoc protocols to conduct both in vitro and in vivo trials on most of the implantable cardioverter defibrillators available on the international market. Trials were conducted with three cellular telephones: two GSM (Global System for Mobile Communication) and one TACS (Total Access Communication System). A human trunk simulator was used to carry out in vitro observations on six ICDs from five manufacturers. In vivo tests were conducted on 13 informed patients with eight different ICD models. During the trials in air, GSM telephones induced interference effects on 4 out of the 6 cardioverter defibrillators tested. Specifically, pulse inhibition, reprogramming, false ventricular fibrillation, and ventricular tachycardia detections occurred, which would have entailed inappropriate therapy delivery had this been activated. Effects were circumscribed to the area closely surrounding the connectors. When the ICD was immersed in saline solution, no effects were observed. Three cases of just ventricular triggering with the interfering signal were observed in vivo.     

Cell Phone Use in the Post Anesthesia Care Unit Best Practice Project

PurposeEach year cell phones have evolved in capability and sophistication enticing society to become more dependent on them. Presently, our hospital policy states there is no cell phone use allowed in the postanesthesia care unit (PACU) for patients or family members. However, given the almost addictive use of the mobile phone today, a patient connecting with family and friends during a very anxious and personally vulnerable time triggered us to re-evaluate this policy.DesignThis was a quality improvement project.MethodsA literature review of published research on cell phone use in the recovery room in five databases was conducted. Two hundred seventy six articles were screened for eligibility, and seven articles were critically appraised and synthesized.FindingsEvidence supported that cell phone electromagnetic radiation interference with the mechanics of the medical equipment at bedside is negated by distance.ConclusionThe sustainability of cell phone use in the PACU will be determined by quality indicators of patient compliance with respectfulness to the atmosphere of the quiet zone of surgery recovery bays, and satisfaction indicators of patient care not being negatively impacted.     

Electromagnetic interference in critical care

Mobile communication and wireless data transmission are playing an increasing role in health care. Reports describing medical device malfunction related to cellular phones have raised awareness about the problem of electromagnetic interference. Although initial institutional responses were to ban cellular devices in hospitals, these restrictions are relaxing as the knowledge base in this area expands. Medical device malfunction is extremely rare if the distance from the transmitting device is greater than 1 m. This article reviews the current understanding of electromagnetic interference as it applies to the technology-rich critical care environment.     

Is There a Risk for Interaction Between Mobile Phones and Single Lead VDD Pacemakers?

Mobile phones may cause pacemaker interference. Patients with a single lead VDD pacemaker might be at special risk, since the atrial sensitivity is often programmed to low (high sensitivity) threshold values and the majority of patients are pacemaker dependent due to the underlying high degree AV block. We evaluated 31 patients with three types of single lead VDD pacemakers: 12 Unity, 292–07 (Intermedics, Inc.); 10 Thera VDD, 8948 or 8968i (Medtronic, Inc.); and 9 Saphir 600 (Vitatron, Inc.) for interference from a cellular mobile phone with a power of 2 W (D-net). For this purpose, atrial and ventricular sensitivity settings were programmed to their most sensitive values (A: 0.1–0.25 mV; V: 1.0 mV) and ventricular sensing was programmed to unipolar. With the ECG continuously monitored, the phone's extendable antenna was brought in direct contact with the patient's skin at the right sternal border, with the tip of the antenna in skin contact just below the clavicle, within 5 cm of the pacemaker connector. Then multiple phases of phone calls were performed, and the effects on the pacemakers recorded. In our group of patients with three different types of single lead VDD pacemakers, no interference could be detected using a 2-W mobile phone in the digital D-net. The programmed values remained unchanged after the interference test. Therefore, the risk of interference seems to be low for the VDD pacemakers tested, although our study design does not allow to entirely exclude the possibility of interference from a mobile phone.     

Electromagnetic Interference of an Implantable Loop Recorder by Commonly Encountered Electronic Devices

De COCK, C.C., et al. : Electromagnetic Interference of an Implantable Loop Recorder by Commonly Encountered Electronic Devices. Electromagnetic interference of pacemaker systems has been well established and can lead to an inappropriate function of these devices. Recently, an implantable loop recorder (ILR) (REVEAL, Medtronic Inc.) has been introduced to evaluate the possible arrhythmic etiology of patients with recurrent syncope. We evaluated the interference of this device in two patients with implantable ILR and in three nonimplanted ILRs with four electromagnetic sources: cellular phones (GSMs), electronic article surveillance systems (EASs), metal detector gates (MDGs), and magnetic resonance imaging (MRI). The GSM did not affect appropriate function of the ILR whereas radiofrequency (RF) EAS could interfere with normal function in implanted and nonimplanted systems. The MDG had no influence on ILR function. The magnetic field induced by the MRI resulted in an irreversible error in one nonimplanted ILR. Therefore, although interference between electromagnetic sources and ILRs appears to be rare in our study, physicians should be aware of possible malfunctioning of these devices.     

Mobile communication devices causing interference in invasive and noninvasive ventilators

PURPOSE: The aim of this study was to assess if common mobile communication systems would cause significant interference on mechanical ventilation devices and at what distances would such interference occur. MATERIALS AND METHODS: We tested all the invasive and noninvasive ventilatory devices used within our region. This consisted of 2 adult mechanical ventilators, 1 portable ventilator, 2 pediatric ventilators, and 2 noninvasive positive pressure ventilatory devices. We operated the mobile devices from the 2 cellular communication systems (digital) and 1 2-way radio system used in our province at varying distances from the ventilators and looked at any interference they created. We tested the 2-way radio system, which had a fixed operation power output of 3.0 watts, the Global Systems for Mobile Communication cellular system, which had a maximum power output of 2.0 watts and the Time Division Multiple Access cellular system, which had a maximum power output of 0.2 watts on our ventilators. The ventilators were ventilating a plastic lung at fixed settings. The mobile communication devices were tested at varying distances starting at zero meter from the ventilator and in all operation modes. RESULTS: The 2-way radio caused the most interference on some of the ventilators, but the maximum distance of interference was 1.0 m. The Global Systems for Mobile Communication system caused significant interference only at 0 m and minor interference at 0.5 m on only 1 ventilator. The Time Division Multiple Access system caused no interference at all. Significant interference consisted of a dramatic rise and fluctuation of the respiratory rate, pressure, and positive end-expiratory pressure of the ventilators with no normalization when the mobile device was removed. CONCLUSIONS: From our experiment on our ventilators with the communication systems used in our province, we conclude that mobile communication devices such as cellular phones and 2-way radios are safe and cause no interference unless operated at very close distances of less than 1 meter.