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| Electrosurgery \ |
CITECH Report - Comparison of Electrosurgical Units
| Aaron Medical Industries, Inc.
St. Petersburg, Florida
March 17, 1997
CITECH #490-262
Comparison of Physician's Office Electrosurgical Units
Aaron Medical Industries, St. Petersburg, Florida, contracted with CITECH to compare the human factors and construction of two small electrosurgical units designed for physician's offices. The first unit is the ConMed (formerly Birtcher) Hyfrecator Plus, Model 7-797. The second unit is marketed both as the Delasco Model 734 and as the Aaron Model 800 High Frequency Desiccator. Aaron Medical shipped to us unopened boxes, containing one new sample of each unit. Both included standard handpieces and active electrodes, as well as optional patient plates and footswitches.
Both units are very similar in size, although the ConMed Hyfrecator Plus is about 1 4/z inches greater in height than the Aaron 800. The ConMed unit is about 25% heavier than the Aaron, although both weigh less than 3 kg. As both units are intended for wall or pole mounting, the height and weight differences are not significant. Both units plug into conventional grounding power receptacles and have their power switches on the right side panel. Both units have rated outputs of 30 W.
Both units are intended to be oriented with the front panel vertical; this requires mounting the unit on a wall or a mobile stand. The power cord exiting on the bottom of both units (as well as a cable connector on the ConMed unit) allows operation on a table only with the unit placed on its back (i.e., front panel horizontal). The manual for the Aaron unit specifically states that the unit is not to be used in a horizontal position, as liquids may spill into it. While the ConMed manual states the correct operating position, it does not warn against operating it on a table. [We believe that both units are subject to damage from spillage on a horizontal front panel.] Unfortunately, both units seem to invite casual use in this position, although more frequent users would probably use the wall mount or mobile stand.
The Aaron unit is labeled for a duty cycle of 30 sec on, 30 sec off; while the ConMed is labeled for 10 sec on, 30 sec off. Because it is unlikely that a physician will notice or heed this limitation, it suggests that the Aaron unit will have a lower failure rate.
Description of ConMed Hyfrecator Plus
The ConMed unit is housed in a gray plastic case, with a slightly textured surface. The case is a two-piece shell, with a wide groove forming the seam between them. The front panel of the unit has three grooves, similar to that one, that are purely decorative. These grooves, about 1/32" wide, could trap dirt; the textured surface of the case could also make the unit more difficult to clean. The power switch on the right side panel has its off position at the top, contrary to common convention.
The Hyfrecator Plus has a green two-digit power display, labeled in watts, as well as two green front-panel buttons for increasing or decreasing power. A green LED indicates when the unit is activated. The handpiece is available in two versions, one includes an activation button and buttons for increasing or decreasing the selected power; the other requires a footswitch and has no buttons. The switching handpiece has a 5-pin connector that plugs and screws into the bottom of the unit; it has a pigtail with a banana plug that connects to the appropriate output along the lower front edge of the unit. Thus, two connections must be made to use the switching handpiece, which is much more common than the footswitch-controlled handpiece. The footswitch cable has a S-pin connector, identical to that of the switching handpiece, that plugs and screws into the bottom of the unit.
The lower edge of the front panel includes a mechanical slide switch with three positions: Hl, LO, and Bl (bipolar). Moving the switch to the appropriate position exposes either a single banana jack (one for the Hl position, a different one for the LO position) or two other banana jacks (for the Bl position); the switch closes off access to the unused jacks.
The low-output jack allows the output power to be adjusted from O to 15 W, with 0.2 W increments up to 5 W and 1 W increments to- 15 W. The high- and bipolar-output jacks allow the power to be set from O to 30 W in 1 W increments. The unit retains its power setting when turned off, but resets to zero when it is unplugged.
The output power display on the Hyfrecator Plus consists of two digits and a decimal point behind a window in the front panel. While the digits are roughly centered vertically behind the window, the decimal point is somewhat lower, with the bottom of the decimal point being approximately flush with bottom of the window. Therefore, if the unit is mounted with the display window even a little above the user's line of sight, the decimal point cannot be seen. This permits confusion at power settings below 5 W because, for example, 1.2 W looks the same as 12 W.
A patient plate may be used with the ConMed unit; its connecting cable attaches to the plate with a rigid, bulky connector. When the plate is used, the banana plug connectors for the handpiece and the return electrode are plugged into thebipolar terminals. There is no indication of this unusual connection on the unit itself, and the instruction manual discusses it only under Section 6, "Terminology for Systems Configurations."
The activation-tone volume is adjusted with a small screwdriver in a hole in the rear panel. The volume increases by turning the control counterclockwise, contrary to common convention.
Description of Aaron 800
The Aaron 800 unit has a one-piece, smooth, white plastic case that forms five sides of the unit, and a metal back plate; there are no grooves or other places for dirt to collect. The front panel has a large rotary power adjustment knob with rubberized grip, a two-digit red power display (with larger digits than on the Hyfrecator Plus), and a blue activation light. It has banana jacks for the monopolar electrode cable (two jacks for a molded, polarized plug), a patient plate, and the bipolar electrode cable (two banana jacks, spaced further apart than the monopolar jacks). The footswitch connects with a right-angled phone plug that will not fit into any other receptacle. Icons on the front panel clearly identify each jack. Inserting an active electrode plug (monopolar or bipolar) into its front-panel jack moves a shutter to partially close the other electrode jacks, making it impossible to use both electrodes at once. [The three-position slide switch on the front of the ConMed unit serves the same purpose, but it must be adjusted manually.] When the footswitch is connected, it is possible to activate the handpiece from either the handpiece button or the footswitch.
The power display on the Aaron 800 is very clear and can easily be seen from a distance and from a wide viewing angle. The power may be read to the nearest 0.1 W through 9.9 W; the decimal disappears at settings of 10 W and higher.
The power is increased by turning the rotary knob clockwise (as users would expect). The knob provides much finer adjustment at lower power levels; about half of its rotation adjusts the power from O to 10 W, with the remaining half increasing the power to 30 W.
A two-position slide switch on the back panel of the Aaron unit adjusts both the volume and the pitch of the activation tone. One position (lower in both pitch and volume) is barely audible. While we recognize that some users may prefer this, we consider a clearly audible activation tone a necessary safety feature of electrosurgical units.
A patient plate may be used with the unit; there is a clearly marked jack on the front panel for its cable. The plate is somewhat smaller than ConMed's, although this is not significant. The cable attaches to a corner of the plate with a simple, small connector.
Comparison of Active Handpieces
The ConMed switching handle has three green buttons—one to activate it, one to increase the power setting, and one to decrease it. The activation button has a raised dot for easy identification. The other two buttons are labeled UP and DN, although the markings are subject to wear. When not in use, the gray handle stores in a slot in the front panel of the unit; two flanges on the handpiece slide into two grooves on the unit.
The Aaron handpiece has only one button; it activates the unit. When not in use, the handpiece rests in a slot in the front panel, where it is held away from the panel itself, minimizing contamination of the front panel. [Of course, the power control must be touched by the surgeon or an assistant, which could compromise sterile procedure. The ConMed handle cannot be sterilized by means readily available in a physician's office, so the cross-contamination issue is academic.]
The body of the Aaron and ConMed handpieces are about the same length. However, the single-use removable tip is much longer on the ConMed electrode. This places the end of the tip (where contact is made with tissue) much further from the physician's hand, which provides slightly less fine control of the tip position. The stiffer, heavier cable of the ConMed handle (whose power selection buttons require additional conductors) makes it a bit more difficult to maneuver. The Aaron cable is also about one foot longer than the ConMed, adding to its ease of use. The ConMed cable has a slightly more rubbery insulation that might make cleaning more difficult. The ConMed nonswitching handle (which is less commonly used) has a cable that is even thinner and more flexible than that of the Aaron handle (possibly because it does not include a switching conductor), with smooth insulation.
The ConMed handpiece accepts two types of single-use electrodes: a blunt one and a very sharp pointed one. The Aaron unit comes with only one style of electrode, a reusable one with a fairly dull point. However, the Aaron handpiece also accepts ConMed electrodes.
The Aaron handpiece may be autoclaved or cold-sterilized; the ConMed pencil can only be sterilized by ethylene oxide, which is not available at most physician's offices.
Interior
We opened both units to examine their construction. Both units are easily opened by removing several screws from the back. The plastic housing (shell) of the ConMed unit comprises two halves. Its circuit is more complex than that of the Aaron, and it is divided between two circuit boards, one attached to each half of the shell. A fan-folded ribbon cable connects the two halves and provides adequate room for working on both boards. Each of the circuit boards has a number of nicely sized test points. All components are well marked. The components appear to be of good quality, although clearly not state-of-the-art, and construction practices are good.
The metal back plate of the Aaron unit comes off to show a single circuit board, with significantly fewer components than the ConMed; components include one large microchip. A large toroidal transformer is mounted to the metal back plate of the unit; the volume-adjustment switch for the audible activation tone is also on the back plate. The leads from the transformer and the switch to the circuit board are too short to allow the back plate to be laid flat for servicing the unit; however, they can be unplugged from the circuit board. The components appear to be of good quality and well marked, and construction practices are good. There are a number of test points on the circuit board.
Manual
The greatest difference between the two units is in their manuals. We recognize that manuals are seldom read; nevertheless, the ConMed manual is much more complete, better organized, attractive, well-illustrated, and durable than the Aaron manual. One shortcoming of the ConMed operating instructions is in describing the use of a return electrode (dispersive plate): the need to connect the plate and the handpiece to the bipolar jacks is not as clear as other instructions. The Aaron manual includes no illustrations, product specifications, or ratings, and is extremely brief; its small-type text occupies only four small pages.
Summary
In summary, we found a number of differences between the human factors and construction of the ConMed (Birtcher) Hyfrecator Plus and the Aaron Medical Model 800 (Delasco 734). However, the units are relatively simple medical devices and both offer virtually identical features. Therefore, lacking an egregious violation of good or conventional design practices (and there were no such violations), it simply isn't possible for one unit to stand out dramatically above the other.
The body of this report describes both units and points out a number of favorable and unfavorable aspects of each. This section summarizes the differences that we considered more significant than the others. It must be remembered that, in most cases, a given difference can be considered either an advantage for one unit or a disadvantage for the other. In preparing this summary, we tried to ascribe each characteristic to the unit in which that feature stood out from the normal; however, this was not always possible. The attributes are not listed in any particular order or ranking.
Aaron 800 |
ConMed Hyfrecator Plus |
Advantages
Housing is smooth; no seams to collect dirt
Simple, unambiguous front-panel connections
Automatic blocking of unused frontpanel jacks
Easy power adjustment; expanded control at low power levels
Shorter active electrode (tip) allows finer control of tip
Handpiece can be sterilized by steam or cold solution
Fewer components in circuit
Circuit allows higher duty cycle
Disadvantages
Poor manual
Audible tone can be adjusted too low
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Advantages
Circuit can be serviced easily because of ribbon cable between halves
Disadvantages
Decimal point in power setting not visible from below
Dirt-catching grooves on housing
Two power ranges for monopolar output unnecessarily complex
Handpiece can be sterilized only by ethylene oxide
Use with return electrode confusing
On/off switch, audible tone volume adjustments counter-intuitive
Handpiece Up/Dn legend subject to wear
Switching handpiece cable shorter and less flexible
Lower rated duty factor could affect reliability
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Conclusions
ClTECH's comparison of the human factors and construction of the Aaron 800 and the ConMed Hyfrecator Pius electrosurgical units was done on the bench, rather than in clinical use. The two devices are fairly basic in their capabilities: they are turned on and off, and their power level is adjusted. Thus, major differences between them in terms of human factors (i.e., user friendliness) are simply not possible. We found that each unit had some advantages over the other, with none of them, even in the aggregate, suggesting an overwhelming preference for either one.
Overall, we judged the Aaron 800 somewhat better in its ease of use. This was based primarily on the well-designed power adjustment (one easily turned knob, with expanded control at the lower end, and a good power display) and a simpler handpiece. Also, the Aaron 800 gave more consideration to cross-contamination, with a readily sterilized handpiece and smooth cabinet. A higher duty factor rating and fewer electronic components suggest greater reliability, although we did not confirm this. The major disadvantages of the Aaron 800 were a poor manual and the ability to adjust the activation tone to be almost inaudible. The major advantage of the Hyfrecator Plus is its manual. Its main disadvantage is more complex and confusing operation, the result of the two output power ranges, the Hl/LO/BI switch, and the hard-to-see decimal point in the display.
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