POWER WHEELCHAIR RF INTERFERENCE: FDA AUDITING ALL U.S. MANUFACTURERS

POWER WHEELCHAIR RF INTERFERENCE: FDA AUDITING ALL U.S. MANUFACTURERS following reports of uncontrollable wheelchair movement in the presence of certain radiofrequencies and microwave radiation. The facility inspections, which are part of a wider FDA investigation that began in June 1992, will focus on manufacturer adverse incident report files in an effort to determine the cause of the malfunctions. Since the beginning of the year, FDA has inspected 11 firms and plans to inspect the remaining 23 U.S. manufacturers in the next several months. Twelve foreign manufacturers also will be inspected. The agency issued a letter alerting manufacturers to the potential problem on May 10. Electro-magnetic compatibility tests conducted by FDA on "several brands of power driven wheelchairs" revealed that when the chairs were exposed to "common RF radiation, including frequencies emitted from police or fire department radios, the chairs moved uncontrollably," FDA says. The agency notes that "such EMC-induced brake release and wheelchair movement poses a potential injury risk to the user." Testing the chairs across a range of frequencies from 1 MHz to 1,000 MHz, FDA found that they are "susceptible to interference from many different RF and microwave frequencies." The agency concluded that "consistent wheel movement" occurs at an approximate field strength of 10 V/m, which it says "can be encountered at a distance of more than three (3) feet from a medium-power hand-held 'walkie-talkie' type radio operating at 450 MHz, such as those used by police and security guards." The agency says that, based on the reports received to date, it is difficult to determine whether the reported problems were caused by RFI, a component malfunction or user error. The letter requests that manufacturers "provide any information that you have concerning this matter such as incident reports, complaints, studies, etc. We would also appreciate receiving technical information on how this problem, if observed, has been addressed by your firm." Recipients have 20 working days to respond. FDA also plans to send a letter to consumer groups representing power wheelchair users. The letter will alert the groups to the agency's findings and request any additional information they may have, FDA says.