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The Physical Lab - Problems with Power

Problems with Power

     It is easy to assume that the power hookup in a hospital will be free from problems and that you will always have a steady consistent flow of energy when you connect a device to a hospital plug. In many labs, this is not the case. It is not uncommon for a facility to experience any of a number of power issues. Many times, these issues are relatively simple and can be corrected with a little effort.       


          One of the more frequently encountered power issues is the availability of plugs. As technology has been developed that provides us with more powerful tools, we find that we need access to more power outlets to run all the extra pieces of equipment that this new technology requires. In many cases, the outlets are too far away or there simply are not enough of them available. To overcome this difficulty, many labs turn to multiple plug power strips. By doing this, they are overcoming one problem, but introducing another. In exchange for sufficient power outlets, they risk introducing significant noise levels to any equipment hooked up to these poorly insulated pieces of equipment. I know it would make sense to assume that if a manufacturer makes a multi-plug electrical outlet they would takes steps to ensure that they would be grounded sufficiently well to prevent noise from being introduced to the equipment plugged in to these devices. Remember, however, that the multistrip plugs are designed for home use and were never intended to be used with extremely sensitive medical equipment. In a medical facility, you are only supposed to use additional outlets if they meet very strict standards. Your Biomedical Engineering Department should be able to verify if any multiplug outlet you have or wish to use are up to proper specifications to use in the lab.

Power Drain

          Another power situation occurs when insufficient power is delivered on one or more circuits in the lab. This is a difficult problem to identify as most people who work in a Lab would have no idea how to determine that they are dealing with a low power problem. While I am in no way, an expert on the subject, I have learned that there is usually a very specific event that suggests that you may be dealing with brown outs.

          Many of the systems used in the EP Lab are complex computer driven devices that do extensive processing. These devices are very sensitive to power and must have a constant supply of electricity to maintain normal function. If the power supply is constant, there is no problem. But when the electrical current powering the device drops below a critical threshold, the computer that controls the device will simply shut down due to multiple circuit failure. When this happens, it is easy to assume that the problem lies within the device that shut down. While this may, in many cases, be correct, you need to reevaluate what is going on when they device checks out OK yet the problem continues to occur.

          I was involved in an incident in a lab that was adding some new equipment to their program. One device in particular was shutting down on a regular basis. In my investigation of what was causing this problem, it became apparent that the problem was specific to on circuit within the lab. This was determined by switching the device in question to a different plug. Once this was done, there were no further problems. There was, however, a limited number of plugs available and using the one where we had no problems placed the device involved directly in the way of the circulating nurse. So the device was returned to its original location and the problems returned. Once this happened, a power meter was hooked into the circuit in question. The data from the power meter showed frequent drop offs in the current delivered to that specific outlet. With the power meter inline, it was easy to correlate the device shutdowns to signifcant drops in current. A new plug was pulled and the problems were resolved.

          It should be noted that a power surge may also cause havoc with computer driven systems in the lab. This is, however, a fairly rare problem. Power spikes do occur, yet most medical systems today have surge protectors to prevent damage from happening when a spike occurs. Keep in mind that, while these surge protectors do offer a fair amount of protection, there are instances when there is little you can do to protect the systems in your lab. I was witness to one situation where a lightning strike caused significant problems with multiple systems in the lab. It wasn't really a suprise to anyone as the facility had taken a direct hit from a lightning strike. What was a bit of a suprise was that most of their systems returned to normal opporation after they were powered down and rebooted.

In-Line Noise

          Another problem that can occur in the lab is electrical noise. All cables used in an EP lab generate an electrical field that surrounds the cable along its entire length. While this field is not very strong, it can cause problems when two or more of these fields interact over a sufficient area. This occurs when ever two cables run in parallel. Given the shear number of cables in the EP lab, noise is almost inevitable. The trick is to minimize the amount of noise by following a few simple guidlines.

- Try to avoid running cables parallel to each other. Seperate them when possible and if they do need to cross, have them cross at right angles.
- Make sure each system is properly grounded. The easiest way to achieve this is to avoid using the little powerstips mentioned above.
- Keep systems that periodically emit large amounts of energy seperate from other systems in the lab. Specifically, place your RF generators on a seperate cart away from other equipment whenever possible.

          Following these guidelines should help minimize system noise. If you follow these steps and are still having problems, start listing which systems are having noise and what the circumstances of operation are in effect when the noise happens. One of the best tools you can have against noise are good troubleshooting skills. Keep a written list of what systems have noise, what other systems are active at the time, where the system was plugged in and was there any obvious triggers that started on ended the noise. Also try to determine if the noise is present in other rooms in the lab area. This information will be a valuable tool in determining the source of any noise you may be having.

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