Utah Medical Products FINESSE +, Руководство по обслуживанию

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10
Service Manual
Complications
When an appreciable electrical current is caused to flow through the patient's body, as in all
monopolar electrosurgery, the common undesirable physiological effects of electric current must
be considered. In the above discussions of electrosurgical theory, such words as cutting, cell
explosion, burning, sparking, and searing have been used. Any of these phenomena occurring too
strongly or at the wrong places are undesirable. In addition to these, there is also electric shock,
which has not yet been considered.
Electric shock, or faradic effect, results from the depolarization of nerve or muscle cells by a non-
physiologic electric voltage. In electrosurgery, this effect is avoided by using voltage waveforms of
such high frequencies that the ions, which must migrate across a cell membrane to depolarize a
cell, are only caused to vibrate over very small magnitudes. Heat is dissipated, but shock does not
occur. To avoid electric shock, frequencies above 300,000 cycles per second (300 kHz) must be
used. The system operates at 450 kHz, which is well above this limit.
The other undesirable effects of electrical current, such as burns, are avoided by proper design of
the generator, careful application of the dispersive electrode, maintenance of the patient contact
with the dispersive electrode, and avoidance of all metallic contacts to the patient that may allow
alternate paths for the electrosurgical current. The system has been designed with iso-
lated patient leads which minimizes the potential for currents to seek alternative routes. It also
provides error indicators to signal when the dispersive electrode's connections are broken and
patient contact possibly compromised.
There remains the possibility that the isolation may be destroyed by inadvertent direct or capaci-
tive grounding in the patient connections outside the generator. The warnings and precautions
given in the
Operational Safety Notes and Warnings section of this manual must be strictly heeded.
Smoke Evacuation and Filtration
The smoke produced during electrosurgery has an odor that is unpleasant, strong, and persistent.
It consists of organic gases, water vapor, visible and sub-visible solid particles and virus particles.
It is generally considered good practice to remove the smoke from the surgical field and filter it.
A system for this purpose is provided as part of the system.
Filtering of the smoke is accomplished using a HEPA (High Efficiency Particulate Air) pre-filter, a
layer of activated charcoal, and a third-stage ULPA (Ultra Low Penetration Air) particulate filter.
The effectiveness of the two stages of particle filtering has been measured on several filters using
spherical latex particles. The combined particle filtration efficiency of both filters was found to be
equal to or better than 99.999% efficient on 0.1 micron particles.
The vacuum motor used in the system produces sufficient pressure reduction to pull
approximately 70 liters per minute (2.5 cfm) at the normal setting through a 30cm long smoke
tube with a 6mm inside diameter. This rate is effective in removing smoke from an enclosed sur-
gical field as required by the LETZ procedure. It should be noted that a smaller diameter tube will
significantly reduce the flow rate. Also, it is easier for smoke to escape from an open surgical
field. It may be necessary to switch to the "high" flow setting to achieve effective smoke removal
under these circumstances.