Electromagnetic Interference From Electronic Devices Used in the Management of Type 1 Diabetes Can Impair the Performance of an Avalanche Transceiver in Search Mode

Introduction

The avalanche transceiver (or beacon) is considered to be an essential component of backcountry safety equipment and should be carried by all persons who venture into avalanche-prone terrain. Although there is evidence to show that use of an avalanche transceiver can reduce duration of burial and improve mortality among avalanche victims, ¹ observational studies have demonstrated variable adherence to avalanche transceiver use among backcountry recreationalists. In both the United States and Europe, avalanche transceiver use has been reported by 11% to 98% of persons upon entry into the backcountry.^2,3 Those participating in backcountry skiing (89% to 98%) are significantly more likely to carry a transceiver than backcountry snowboarders (90%), snowmobilers (57%), and those using snowshoes (11% to 25%). Of considerable concern are persons who access the backcountry from within a resort area, with only 9% to 36% avalanche beacon use reported at point of entry into avalanche-prone terrain.

The influence of avalanche transceivers on life-saving medical electronic devices has been investigated previously. Although interference has been observed during telemetric communication with permanent cardiac pacemakers or implantable cardiac defibrillators, the function of the pacemaker or implantable cardiac defibrillator itself is unaffected by the use of an avalanche transceiver when both devices are in close proximity. ⁴ Conversely, avalanche transceivers have themselves been shown to be susceptible to electromagnetic interference from commonly used personal electronic equipment such as global positioning satellite (GPS) locators, cell phones, MP3 players, and two-way radios when these devices are held adjacent to a transceiver. ⁵ The signal transmitted by a transceiver is not affected; however, the ability of an avalanche transceiver in search mode to accurately determine the proximity and direction of a transmitting transceiver can be significantly impaired. These observations have led to the recommendation that all portable electronic devices be kept at least 30 cm away from an avalanche transceiver while in search mode so that a companion rescue scenario is not compromised.

Portable electronic devices play an important role in the management of type 1 diabetes mellitus. ⁶ A real-time continuous subcutaneous glucose monitoring system (rtCGMS) gives the user a continuous estimation of interstitial fluid glucose concentration (which approximates that of blood glucose). A thin wire sensor inserted into the subcutaneous interstitial space (usually in the abdomen) is attached to a small transmitter and worn for as long as 2 weeks at a time. Every 5 minutes or so, the interstitial fluid glucose concentration is determined and transmitted wirelessly to a handheld receiver that informs the user of the current reading. An insulin pump constantly delivers rapid-acting analogue insulin at a variable rate as determined by the user. Often, an rtCGMS and insulin pump are used together, with some devices being able to communicate with each other. Together, these devices allow the experienced operator to maintain near-normal glycemic control (and are likely to become more prevalent with time ⁷ ).

With appropriate preparation, a diagnosis of type 1 diabetes should not be seen as an impediment to participation in backcountry activities. Accordingly, some persons with type 1 diabetes who use an insulin pump and rtCGMS will also use avalanche transceivers while in the backcountry, in line with expert recommendation. The influence of electromagnetic interference from an insulin pump and rtCGMS on the performance of avalanche transceivers is unknown, and was assessed.

Methods

In an open field (away from buildings and overhead or underground structures), the performance of two widely available and commonly used triple antenna digital avalanche transceivers—the Mammut Pulse Barryvox (Mammut Sports Group, Switzerland), and the Arva 3 Axes (Arva Nic-Impex, Annecy, France)—was investigated. The ability of each transceiver in search mode to determine the proximity and direction to the other (in transmit mode) was examined at set distances (45 m, 30 m, 15 m, 10 m, 5 m, and 1 m). The most distant point at which the receiving transceiver was able to accurately determine both the distance from and direction to the transmitting (source) beacon was recorded (effective search range). Both transceivers were investigated in digital mode.

In turn, portable electronic devices—Baofeng UV-5R two-way radio (Baofeng, Quanzhou, China), iPhone 4 and iPhone 5 (Apple, Cupertino, CA, USA), Dexcom G4 rtCGMS (Dexcom, San Diego, CA, USA), Medtronic Guardian rtCGMS (Medtronic, Minneapolis, MN, USA), and Animas Vibe insulin pump (Animas, West Chester, PA, USA)—were then held underneath either the transmitting or receiving beacon, and the recordings were repeated to assess the influence of the electronic device on transceiver function. All devices (including the avalanche beacons) had either fresh batteries or a more than 95% charge.

Results

The greatest distance at which the searching transceiver could accurately determine the direction to and distance from the transmitting transceiver was 30 m. Identical results were obtained when either avalanche transceiver was used in the transmitting or searching position. There was no interference observed when any electronic device was in close proximity to the transmitting transceiver or more than 30 cm away from the searching transceiver. Avalanche transceivers did not influence the function of the diabetes devices (data not shown).

When the electronic devices were held within 30 cm of the searching transceiver, the distance at which the searching transceiver could accurately determine the direction to and distance from the transmitting transceiver was reduced (Figure). The magnitude of effect was different depending on which device was used. The devices that impaired beacon function most were the iPhone 4, the iPhone 5, and the Animas Vibe pump. These all reduced the transceiver’s effective search range to just 5 m. The Dexcom G4 rtCGMS did not produce any apparent interference.

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Figure

Avalanche transceiver performance when in close proximity to personal electronic devices. The vertical axis indicates the distance (in meters) from the transmitting transceiver when the device indicated on the horizontal axis is held underneath the receiving transceiver in search mode. “Control” indicates results obtained with no interfering personal electronic device. Results were the same regardless of which avalanche transceiver was transmitting or searching, and no effect was seen when the device was held more than 30 cm from the receiving transceiver. Data reflect the mean of 3 identical experiments. CGMS, continuous glucose monitoring system.

Discussion

These data confirm that electronic diabetes devices can interfere with avalanche transceiver function. The cause of this effect is presumed to be electromagnetic interference. The resulting reduction of the transceiver’s search range from 30 m to 5 m is significant, and has potential to delay recovery of a buried avalanche victim (and thus reduce chances of the victim’s survival). Therefore, this important information should be shared with persons (and their advising physicians) with type 1 diabetes who also use an avalanche transceiver.

In these experiments, the Animas Vibe insulin pump produced the most interference. That may be due to the presence of moving parts (electric pump motor). The Dexcom G4 rtCGMS did not produce any electromagnetic interference, whereas the other rtCGMS examined (Medtronic Guardian) caused an intermediate level of interference. It is, therefore, not safe to assume that all devices of similar function will result in identical interference effects. A more comprehensive analysis of all available continuous glucose monitoring systems and insulin pumps (with additional avalanche transceivers) would be required to fully appreciate the extent of this effect.

The magnitude of effect was similar to that observed (and previously reported) with other commonly used electronics (such as cell phones, MP3 players, and so forth). Diabetes electronic devices per se, therefore, do not lead to additional risk compared with other portable electronics when they are used alongside avalanche transceivers alone. This study did not examine the combined effect of multiple devices simultaneously in close proximity to an avalanche beacon. As a person with type 1 diabetes may carry several devices (eg, insulin pump and continuous glucose monitoring system in addition to cell phone, radio, GPS, MP3 player, and so forth), the potential effects of electromagnetic interference on an avalanche transceiver may be additive. This research question warrants further investigation.

No interference was observed when the electronic diabetes device was held more than 30 cm from the receiving beacon, which is in line with current recommendations for other personal electronic devices (15 to 50 cm). This study would, therefore, recommend that persons with type 1 diabetes be advised to keep their rtCGMS or insulin pump 30 cm or more from an avalanche transceiver while in avalanche-prone terrain in the backcountry.