Thursday, July 12, 2012

Tablet Computer May Interfere With Shunt Valve Settings

Janis C. Kelly
July 10, 2012 — Researchers are reporting that proximity to a tablet computer can interfere with settings of magnetically programmable shunt devices, which are often used to treat children with hydrocephalus.
The Apple iPad 2 (Apple Inc.) contains magnets that can change valve settings in the shunt if it is held too close to the valve — within about 2 inches.
Such a change may result in shunt malfunction until the problem is recognized and the valve is readjusted to the proper setting. Patients and their caregivers should monitor use of the tablet computer to ensure that no change is made to the valve settings, researchers say.
Cormac O. Maher, MD, a pediatric neurosurgeon and senior author of the report, said he hopes to raise awareness of this potential interaction through publication of this study.
This is not to say that the iPad 2 cannot be used safely in the vicinity of patients with programmable shunts, they write. "With proper precautions to keep a tablet device away from close proximity to the valve, the continued use of these devices, even in the general vicinity of patients with programmable shunt valves, appears to be safe," they conclude.
A variety of magnets can be found in households today, and the authors state that the magnetic field strength of the iPad 2 lies within the range of these everyday magnets. Patients and caregivers should regard precautions surrounding use of the iPad 2 to be the same as those taken with other household magnets.
These results were published online June 26, and appear in the August issue of the Journal of Neurosurgery: Pediatrics.
Shunt Malfunction
Researchers initiated the study after a tablet computer seemed to affect a programmable shunt in one of their patients, a 4-month-old girl with hydrocephalus.
Three weeks after the baby received the shunt, she was examined for shunt malfunction due to a changed setting in the magnetically programmable valve that regulates the flow of cerebrospinal fluid. The baby's mother stated that she had held an iPad 2 while holding the infant.
Programmable shunt valve settings can be altered by exposure to magnetic fields. Indeed, specialized magnets are used by physicians to adjust the settings on these valves. Because in this case no other environmental factor could be identified that would have led to a shift in the valve settings, the authors decided to test whether the iPad 2 might be implicated. Unlike the initial iPad, the iPad 2 contains several magnets and is often used with an Apple Smart Cover, which contains additional magnets.
The researchers tested 10 programmable shunt valves with a variety of settings. They exposed the valves to an iPad 2 with and without the Smart Cover at different distances: less than 1 centimeter (cm), 1 to 2.5 cm, 2.5 to 5 cm, 5 to 10 cm, and greater than 10 cm. Each exposure lasted 10 seconds.
Overall, the valves were tested 100 times for each of the 5 distances during exposures to the iPad 2 with the Smart Cover closed, and 30 times for distances less than 1 cm for the tablet computer without the cover.
After exposure of the programmable valves to the iPad 2 and Smart Cover at distances of 0 to 1 cm, researchers found that the settings had changed in 58% of the valves. After exposure at distances of 1 to 2.5 cm, the settings had changed in 5% of the valves, and after exposure at distances of 2.5 to 5 cm, the settings had changed in only 1% of the valves.
No changes in valve settings were identified after exposures at higher distances.
After exposure of programmable valves to the iPad 2 without a cover, which was tested only at distances of 0 to 1 cm, researchers found that the settings had changed in 67% of the valves.
Although no change in setting was found past a distance of 5 cm (2 inches), the authors caution that patients and caregivers should be made aware of the potential for a change in the settings of a magnetically programmable shunt valve if an iPad 2 is placed very near.
The authors have disclosed no relevant financial relationships concerning the materials or methods used in this study or the findings specified in this paper.
Journal of Neurosurgery: Pediatrics.2012;10:118-120. Published online June 26, 2012. Abstract.

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