Steve Hughes, REO UK, explains the importance of electrical isolation and good product design in medical devices.
Steve Hughes, managing director of REO UK
The increased complexity of medical device setups is causing concern in the medical industry. As more and more healthcare professionals use a variety of electrical equipment as part of their diagnosis and measurement regime, there is a knock-on effect on the stability of the mains power supply. Here,
Notepads have been replaced with iPads, mechanical beds with electrically adjustable beds and traditional film imaging has been substituted with the latest digital picture archiving and communication system (PACS). Add to this other innovations, such as endoscopy cameras and new dental systems, and the mains power supply certainly has a lot to deal with.
The increasing electrification of devices creates problems on the mains power supply. AC to DC power conversion by the device's power supply introduces voltage distortion, current harmonics, electrostatic discharge, power surges and electromagnetic interference (EMI) into the supply. These power quality problems can affect the calibration and sensitivity of diagnostic devices used by doctors and healthcare professionals. Erroneous test results can result in misdiagnosis and potentially harmful treatment plans for patients.
European legislation has focused on tackling this issue by introducing minimum requirements for the electrical isolation of various medical equipment. The IEC 60601-1 medical device standards govern the essential performance, basic safety and design requirements for new medical devices.
The directives classify devices into three areas based on how closely they are used to the patient's body. Type B devices operate within a six foot vicinity of the patient without bodily contact. Type BF makes physical contact with the body and Type CF makes physical contact with the heart. Each of the categories outlines the level of isolation, insulation, creepage, clearance and leakage allowed.
Most large equipment used in a clinical setting, such as magnetic resonance imaging (MRI) machines, anaesthesia units and ventilators, contain an embedded transformer or are disconnected entirely from the mains by using battery packs. However, devices in patient environments don't usually contain a transformer and it's not always cost-effective, practical or necessary to use battery packs. It's for this reason that we developed the Reomed isolation transformer which aims to provide safe galvanic separation between primary and secondary circuits, double and strengthened isolation, a very low leakage current and strict air and leakage clearances.
For users looking to isolate medical devices in patient environments, the Reomed has been designed to offer an easy way to meet European electrical isolation standards by simply retrofitting the transformer into an existing setup. However, it's important to remember that the legislation also goes further in stipulating requirements for ergonomic design.
In the USA the Food and Drug Administration (FDA) recalled nearly 200 products that had failed due to electrical problems, mechanical faults due to poor design, bacterial contamination during manufacture and device software issues.
At REO we've found that sustainable design is only achieved through a consultative process between doctors, regulatory bodies, original equipment manufacturers (OEMs) and patients. By undertaking thorough design testing, manufacturing controls, and post installation servicing, OEMs can hope to provide the successful wave of next generation medical devices.