PubMed · 11437796
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
J M Chapman. 2001. Complete power failure.. https://doi.org/10.1046/j.1365-2044.2001.02137-15.x
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Explore the source record for details and available documents.
Problems involving electromagnetic interference (EMI) with electronic medical equipment are well-documented. However, no systematic investigation of EMI has been done. We have systematically investigated the causes of EMI. The factors involved in EMI were determined as follows: 1) Electric-field intensity induced by invasive radio waves from outside a hospital. 2) Residual magnetic-flux density at welding points in a building. 3) Electric-field intensity induced by conveyance systems with a linear motor. 4) The shielding capacity of hospital walls. 5) The shielding capacity of commercial shields against a wide range frequency radio waves. 6) The immunity of electronic medical equipment. 7) EMI by cellular telephone and personal handy-phone system handsets. From the results of our investigation, we developed a following practical procedure to prevent EMI. 1) Measurement of electric-field intensity induced by invasive radio waves from outside the hospital and industrial systems in the hospital. 2) Measurement of residual magnetic-flux density at electric welding points of hospital buildings with steel frame structures. 3) Control of the electromagnetic environment by utilizing the shielding capacity of walls. 4) Measurement of the immunity of electronic medical equipment. And 5) Installation of electronic gate equipment at the building entrance to screen for handsets.
In recent years various studies proved that electrical stimulation can improve contractile capability and restore muscle function in long-term denervated degenerated muscles. The low excitability of the muscle cells at the initial stage of training and surrounding connective tissue, acting as an electrical shunt, require special stimulation parameters. Until now, no appropriate devices (stimulators) are commercially available. Therefore, we were forced to design our own stimulators. The control unit of the stimulators is based on a microprocessor for maximum flexibility regarding the generation of the parameters such as pulse amplitudes, pulse width, frequency, stimulation times, ramps, and so on. In addition, the microprocessor design allows recording of compliance data such as stimulation date, time, duration, and used programs. The constant voltage output stage of the stimulator is able to generate biphasic charge balanced stimulation impulses with a pulse width of 1 to 300 ms, voltage amplitudes up to +/-80 V (160 VPP), and stimulation currents up to 250 mA. To prevent direct current due to inexact charge compensation, the electrode outputs are decoupled capacitively. Simultaneous 2 channel stimulation with independent intensity levels is possible. The stimulators are programmed using a notebook or a personal digital assistant via infrared serial interface. This concept guarantees the application of correct stimulation parameters because the patient has only access to parameters that are preprogrammed for him in the outpatient clinic. For the home based training, access is limited to variation of intensity within preprogrammed limits. For safety reasons, the portable unit is powered by an internal rechargeable battery. High efficiency switched voltage regulators are used to provide the different required voltage levels while ensuring an acceptable operating time of the stimulator.