ASK THE EXPERT
Rich Nazarian is the president and CEO of Minnetronix Inc., a medical device design and manufacturing firm in St. Paul, MN. Nazarian has more than 20 years experience in the medical device development field. Prior to cofounding Minnetronix in 1996, he led product development efforts for implantable artificial heart electronic systems, cardiopulmonary - bypass systems, laser - imaging systems, and other medical and industrial devices for 3M. Nazarian is principal inventor on eight patents ranging from telemetry systems for implantable devices to networked bypass systems, and he is the principal author of numerous papers ranging from artificial heart control systems to medical device development methods. At Minnetronix, he continues to be a leader in the development of new and innovative medical devices. Nazarian earned his BS and MS in e lectrical e ngineering at Stanford University.
MPMN: How has the RoHS directive impacted the medical electronics industry?
Nazarian: As you are aware, the European Commission (EC) issued two directives in 2002-2003 with the goal of reducing toxic waste material. The legislation targets the use of lead, in particular the use of lead-bearing solder, in electrical and electronic equipment. These directives are identified as Directive 2002/96/EC of the European Parliament and of the Council of 27 January 2003 on Waste Electrical and Electronic Equipment (WEEE) and Directive 2002/95/EC on Restriction of Hazardous Substances (RoHS). Although categories 8 [medical devices] and 9 [monitoring and control instruments] are not covered, thus exempting medical device manufacturers from compliance with these directives, WEEE and RoHS do have a profound impact on medical products.
The impact that the RoHS directive has on the medical electronics business takes three principal forms:
1. Availability of components : The primary effect of RoHS on electronics manufacturers is the removal of lead from their assembly processes. Because of this, the industry is experiencing a wholesale migration to lead-free components and OEM assemblies, including single-board computers and electronics modules. In addition, significant numbers of legacy parts, which contain lead, may become obsolete if they are not sold in numbers large enough to justify migration. The combination of these factors is driving part obsolescence and revision on an unprecedented scale. The fact that medical devices are exempt from the directive does not protect manufacturers from the issues of parts modification, obsolescence, and replacement.
2. Appropriateness of processes : Many PCB assembly houses are migrating to lead-free processes. It is important that the appropriate process be used with the appropriate parts, and that these processes are properly qualified. Due primarily to process temperature constraints, leaded (non-RoHS) parts should not be used in lead-free (RoHS) assembly processes. With some notable exceptions, lead-free parts may be used in leaded processes. These process considerations may call for changes in the supply chain and requalification of designs.
3. Reliability of technologies : Leaded component and soldering processes have well-established reliability that has been demonstrated over decades of use. Lead-free components do not have a comparable track record, and the creation of reliable and repeatable processes, for both component manufacturing and PCA's, is still evolving. Known problems in lead-free assemblies include tin whisker growth, components that may age more rapidly, and soldering that is more difficult to rework and that has greater brittleness. These issues may or may not impact an individual medical device depending on the particular design and the intended use.
OEM customers and suppliers need to develop a thorough understanding of issues related to RoHS in their specific environment, and then develop an appropriate and proactive strategy to deal with them.
MPMN: What is spurring the demand for electronic implantable devices? What benefit do they have for patients?
Nazarian: Increased demand for implantable devices is being driven by a number of converging forces. These include demand-side factors such as an aging population, as well as supply-side factors such as technological advancements. More specifically, some of the leading influences motivating the increased push for implantable devices include:
1. Historical cost-effectiveness of implantable devices : Over the past 30 years, implantable devices have proven to be extremely cost-effective alternatives to hospitalization or drug therapies for the treatment of various chronic illnesses. Studies such as "The cost-effectiveness of automatic implantable cardiac defibrillators: results from MADIT. Multicenter Automatic Defibrillator Implantation Trial." (Mushlin, AI, et. al.) PMID: 9626173 [PubMed - indexed for MEDLINE] and others have demonstrated that implantable devices compare quite favorably with other therapies when measured on a cost-per-year-of-life-saved basis. In addition, this index has steadily fallen as technology has reduced implant costs and increased years of life saved.
2. Demand for new treatments : While implantable electronic technology was once largely confined to the cardiac arena with rhythm management devices, there is now a much broader array of therapies that rely on these types of products. These therapies range from drug delivery, to pain management, to hypertension treatment, to cochlear implants, to treatment of neurological disorders such as Parkinson's disease and many others. As medicine gains a greater understanding of the mechanisms and morphologies of disease processes, devices are being designed to perform very specific functions in the treatment of those diseases. This provides new ways for implantable devices to provide benefits for patients.
3. Advances in microelectronics miniaturization and technology : As microelectronics technology advances, functionality that was only dreamed of 10 or 15 years ago is quite realistic in implantable designs today. Ultralow power DSP technology, for example, allows for biological signal processing and stimulation in ways that were previously impractical. MEMS and nanotechnology are just now starting to push their way into biological interfacing, and integrated packaging, battery, and wireless technology is allowing for devices that do more in less space with less power than ever before.
4. Advances in device-tissue interfaces : Technology is enabling devices to be integrated directly into biological subsystems such as the cochlea, vascular aneurysms, and stents, and even complex structures such as the optic nerve. Some of these advanced applications serve both therapeutic and monitoring functions and may be part of a drug-device interaction that provides optimized treatment benefits. Drug delivery, for example, has traditionally been an open-loop process, limited to symptomatic feedback control. Implantable sensors monitoring specific physiologic or biochemical responses can integrate with delivery devices to tune the dosing levels to provide superior therapy with fewer side effects. These types of drug-sensor-actuator interactions will continue to drive implantable electronics development for the foreseeable future.
MPMN: Consumer electronics has spawned a craze for wireless devices. Is it inevitable that many medical devices that have traditionally operated from a power supply source will soon be wireless? What are some examples of wireless products emerging in the medical device field? What are the obstacles?
Nazarian: A number of medical technologies, both external and implantable, are migrating to wireless implementations. From wireless ECG systems to implantable pressure monitors and pulse generators, the applications and demands for wireless devices continue to grow. Device interaction with wireless in-hospital networks is increasing, particularly for limited risk diagnostic equipment such as monitors, as is acceptance of the integration of general consumer electronics standards such as Wi-Fi. Body-worn wireless technology for patient data monitoring is another field that is generating a great deal of interest. Products incorporating mini-personal-networks allow pressure, oxygen saturation, pulse, temperature and other types of data to be collected continuously for both in-patient and out-patient use.
The obstacles to wireless device adoption come in several forms, including robustness, safety and regulatory concerns, evolving technology, and international considerations. Although numerous standards exist for wireless communications, unlike consumer devices, interoperability is quite rare in wireless medical devices. For perspective, if you were to picture a world in which your PDA only talked to a certain computer brand, its wireless capabilities would be far less attractive. This level of limited interoperability is common among today's wireless medical devices. In addition, there are drawbacks related to batteries and power management for wireless devices. For low-power devices, adding wireless capability can add significantly to the power and battery requirements for a device. While power can be managed and tradeoffs explored between device size, transmission bandwidth and distance, battery impact must be considered. For higher-powered active medical devices that perform significant amounts of physical work and are in continuous use, the power required to go fully wireless can be prohibitive. Unlike consumer devices, regular battery recharging for many medical devices, such as blood pumps and temperature controllers, is often awkward and impractical. This combination of factors brings battery technology to the forefront for wireless device applications. Despite the advances in lithium chemistry, batteries are often the primary impediment to true wireless medical technology. This is not to say that tremendous progress hasn't been made, it only goes to highlight that in a world where devices are still too big, too power hungry, and not long-enough lasting, there is ample room for technology-driven improvement.
MPMN: What would you identify as the most significant trend in the medical electronics market? Why?
Nazarian: Many areas are transforming the way medical electronics are developed and perceived. Among these are demand for implantable devices, interactions between devices and drug-based therapies, demand for wireless technologies, and the increasing integration of embedded microcontrollers and software into safety critical functions for the creation of 'smart' systems. Medical electronics are currently being heavily influenced by rapidly advancing electronics technology, and by constantly expanding knowledge and advancements in all areas of medicine. As these technology areas continually expand and grow, their convergence in medical electronics implies more technically complex devices in new and expanded medical treatment areas. Along with this expansion comes increasing need for understanding and diligence in risk management and safety in medical electronics, in areas ranging from usability, to electrical safety, to electromagnetic compatibility.
MPMN: How do EMI and ESD affect electronics manufacturing? What are some ways to avoid them?
Nazarian: ESD in manufacturing has long been identified as a threat to device performance and reliability. EMI, both conducted and radiated, has grown in recent years, particularly in production environments that have heavy machinery or equipment that doesn't comply with the same standards that devices might be subjected to in use. In addition, components and subassemblies that might be extremely robust when installed in completed products may be highly susceptible in process. Most manufacturers have well-established approaches to managing these threats, a few of which are listed here.
1. Separation : Short of building EMI screen rooms, physical distance and dedicated power are the next best approaches to managing conducted and radiated emissions.
2. ESD coatings, paints, and work surfaces : Many facilities use conductive paints and coatings for flooring and work surfaces. These can be expensive and must be monitored, maintained, and managed, but can have a significant widespread impact on reducing ESD.
3. Clearly identified ESD safety zones and susceptible components : Labeling work areas and parts can substantially reduce their tendency to be exposed to ESD. It is not a good idea to label everything in this way, as it then loses its effectiveness.
4. ESD-related training : Perhaps the most important factor is proper training of personnel with respect to ESD issues. Employees must know how to use and check wrist straps, grounding pads, test equipment, and material packaging in order for any protection plan to be effective.
5. EMI and ESD mitigation monitoring : All mitigation methods must be tested on a regular basis as appropriate. Inadequate ground connections are common causes of loss of ESD protection even in well-planned environments. Additions or changes in equipment placement or power routing can have a subtle impact with respect to EMI, necessitating field testing, and power quality measurements in sensitive environments.
As with most failure mode threats, awareness and understanding of EMI and ESD in specific environments is the key to their management and mitigation.
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