AEP Implanted Medical Device Procedures

AEP Process Highlights • No official Company “Policy” on the issue, but a pragmatic approach outlined in a White Paper issued by the Industrial Hygiene Group • Recognizes two types of devices and events: – Pacemakers - Increased or decrease heart rate – Defibrillators – Firing of defibrillator – Does not address other medical devices

• Establishes a level of concern at 1 Gauss • Standard sign to mark areas where 1 Gauss can be exceeded • Does not set a monitoring requirement or frequency

Process Highlights (continued) • Monitoring has been conducted by Corporate IHs • Areas of concern are primarily generator leads/bus work, large motors and MCCs • No known events related to heart rate or firing of defibrillators • One recent event related to induction heating…

Implanted Medical Devices (High Electromagnetic Field Exposures) Louis O. Hosek, Ph.D. April 3, 2008 There are generally two types of heart-regulating implanted medical devices which could be worn by workers at our facilities. One is an implanted pacemaker (Implantable Pulse Generator or IPG) the other is an implanted defibrillator (Implantable Cardioverter Defibrillator or ICD). The pacemaker keeps the heart within a certain pace while the defibrillator shocks the heart to reverse fibrillation. Both may be affected by power frequency electric fields over 6,000 volts/meter or modulated magnetic fields over 1 Gauss. These devices are designed and tested to operate normally during a patient’s exposure to electric and magnetic fields commonly encountered in the work and home environments. There are areas within the electric power industry where these fields can be exceeded. When the field is over the suggested limit for the device, it doesn’t matter if, for instance the magnetic field is slightly over 1 gauss or 20 gauss, the risk of interference is the same; the units can over-sense. For the pacemaker the most likely occurrence is the unit can over-pace. This means there could be extra heart beats caused by the over-pacing. Generally the wearer would not notice it occurred. It would not be harmful nor would it be uncomfortable. Once the wearer left the field, the unit would return to normal. There would be no permanent harm to the unit or individual.

Another possibility, even though it is remote, would be a lower heart-rate outcome resulting in dizziness or lightheadedness. In the event of this occurrence, the wearer could leave the area and the unit would return to normal as well. Risk is extremely small for the under-pacing, but even with the small risk, jobs should not be assigned to the individual where high electric or magnetic field exposure might result in a safety hazard because of the dizziness. Example: use of ladders, scaffolding or chainsaws, etc. So, there really is not much indicated in terms of restrictions for wearers of the pacemaker. Wearers can function fine in our work setting with some education of situations to avoid. Implanted defibrillators are at the same risk to high fields as stated above except that triggering of the device could result in the unit firing and a defibrillation shock administered when not needed. This is extremely painful and is described as literally “it knocks the person down”. This risk is unacceptable and a wearer of the implanted defibrillator should not be assigned to any job where the field levels could be exceeded.

Signs posted in areas where monitoring indicates an issue.

Induction Heating of Scaffold Structure

Eddy CurrentsWhen conducting specimens are subjected to a time-varying magnetic field (or motional induction in a static field), currents tend to be induced in the specimen. They flow in closed paths (e.g. circular paths perpendicular to the inducing field) in the specimen and are called eddy currents. In accordance with Lenz's law, the eddy current tends to oppose the change in the field inducing it. These induced currents will have a magnetic field associated with them. Eddy currents result in joule heating (I^2R) in the conducting specimen. In fact, the technique of induction heating is an application of heat resulting from induced eddy currents.

Photo of Scaffold Pole Heated by Induction from Generator

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