Electrosurgical accessory testing

CITECH tests electrosurgical accessories (cables, monopolar and bipolar electrodes and return electrodes) more frequently than it tests any other devices. We are familiar with the content and philosophy of the ANSI/AAMI standard, HF18, and also with IEC 60601-2-2 and 60601-2-18. Our testing has been used in 510(k) submissions and to justify CE Marking. Still, testing some electrosurgical devices remains as much an art as a science.

The following articles discuss some of the tests, as they relate to standards. If you have any questions about testing your electrosurgical accessory, please call us; we'll be glad to discuss them with you.

Meeting Two Standards for Active ESU Accessories

There are two standards that cover electrosurgical units (ESUs) and their accessories. The domestic standard is ANSI/AAMI HF18; the current edition is dated 1993. The international standard is IEC 60601-2-2; the second edition is currently being used. [Another international standard, IEC 60601-2-18, for endoscopic equipment, has not come into widespread use in this country.] This article focuses on the requirements of the two standards for active accessories.

Manufacturers seeking FDA clearance to market these accessories in the U.S. should meet HF18, while those marketing in Europe should meet the IEC standard. There are many similarities between the two standards, but there are also some significant differences. To help firms looking toward both markets, CITECH can develop a test program that demonstrates compliance with both standards without duplication.

Requirements of the IEC standard are at least as severe as those of the ANSI/AAMI standard, where they cover similar tests. However, ANSI/AAMI HF18-1993 includes several tests of accessory cables that are not found in the IEC document, which is why FDA expects conformance with HF18. [There is also a cable test in IEC 60601-2-2 that has no counterpart in the domestic standard.] There are two other areas where the differences between the standards are especially noteworthy—the dielectric withstand test voltage and the material used to wrap the active accessory for testing.

Both standards require that the dielectric withstand capabilities of the electrode be tested at 150% of a particular voltage, but there's an ocean of difference between them as to which voltage this is. The ANSI/AAMI standard requires that the electrode manufacturer specify a maximum voltage rating for the device (with testing at 150% of that value). This can be less than the maximum setting of the ESU, and it reflects the typical clinical use of the particular device. The IEC standard requires that the electrode withstand 150% of the maximum output of the ESU with which it is intended to be used. Although there are valid arguments for both approaches, the IEC requirement is usually much more difficult to meet, especially with the thin insulation required of laparoscopic electrodes.

The first (1986) edition of ANSI/AAMI HF18 required that the electrode be wrapped in foil for the dielectric withstand test. However, as the standard was used, it was noted that the foil would not conform well to the electrode; the inevitable creases in the foil caused stress points for high-voltage breakdown, causing inconsistent and unrealistic results. Therefore, the 1993 edition of HF18 requires that the electrode be wrapped in a conductive, conforming material, such as saline-moist cloth; it specifically warns against the use of foil. The IEC standard, on the other hand, requires that the electrode be wrapped in foil; no alternative is allowed, and no rationale is offered. Based on our experience, we believe that this is wrong for the same reason that AAMI did.

The ANSI/AAMI standard has one test on the accessory that is not found in the IEC standard—60 Hz dielectric withstand. While the test is easier to conduct than the high-frequency dielectric withstand test that both standards require, we have never found a device to pass the high-frequency test but fail the 60 Hz test. Therefore, the 60 Hz test is a good initial screening test, but eliminating it will not affect safety.

CITECH has worked with many clients to test electrosurgical electrodes against the requirements of the ANSI/AAMI and IEC standards. Below, we have prepared a table that compares the active accessory requirements of the two standards. If you would like to discuss your testing needs or have any questions pertaining to the comparison table, call CITECH.

CITECH, 5200 Butler Pike, Plymouth Meeting, PA 19462-1298. Tel: 610-825-6700; Fax: 610-834-1275.