Originally Published EMDM March/April 2001
TECHNOLOGY NEWS
Sensors
Pulse Oximetry Probe Achieves Noninvasive Monitoring of CO2 Tension
Sentec Inc. (Therwil, Switzerland), a sensor technology company, has produced a pulse oximetry probe that offers noninvasive monitoring of both O2 and CO2 levels. The V-Sign probe, which attaches to the earlobe, includes two different technologies: one is based on an optical measurement of O2 saturation, and the other is an electrochemical measurement of CO2 tension.
Sentec plans to distribute the digital probe with a signal analysis board as a subsystem to medical OEMs producing anaesthesia and respiratory equipment, as well as other products incorporating O2 saturation technology. "For state-of-the-art monitoring, anyone who measures O2 saturation should measure CO2 sooner or later," says Tschupp. He points out that insufficient levels of CO2 in the bloodstream lead to narrowing of blood vessels, which in turn can prevent adequate blood flow and result in damage to vital organs.
OEMs will be able to connect the V-Sign to their equipment via Sentec's multiparameter board, which is also the interface to the company's digital pulse oximeter finger probe. This finger sensor includes memory for the storage of patient information, allowing the probe to track a patient from the operating room to the bedside without any loss of data.
Tschupp describes the probe as "the world's first intelligent digital sensor of vital parameters," noting that no other such small medical sensor has a microprocessor built into its head to amplify and digitize data. He adds that this integrated design allows for the use of a thin and highly flexible four-wire cable, whereas a conventional cable for multiparameter sensors might have as many as 13 wires.
Patents are pending for the V-Sign probe in Europe and the United States. The probe has not yet been supplied to OEMs, but Sentec is in negotiations with several international monitoring technology companies, and plans to produce 5000 systems over the next year. The product was presented to potential partners at the Medica trade fair in Düsseldorf, Germany, last November. According to Tschupp, the company is willing to negotiate agreements with individual patient-monitoring companies for the exclusive use of the new probe in specific product areas.
Benjamin Lichtman
Miniature Valve System Makes Medical Applications a Snap A miniature solenoid valve system has a snap-together, modular design that markedly cuts production time and manifold size. The new valve system—developed by the Pneutronics Div., Parker Hannifin S.A. (Evreux, France)—is ideal for use in medical applications such as blood pressure devices and oxygen tanks.
"The X-system allows medical OEMs to shrink package size without losing the capabilities of much larger manifolds," says Bill Nissim, Pneutronics sales and marketing manager.
The system weighs up to 50% less than other manifolds and can cut the usual valve system production times by 70%. Utilizing a new lightweight polyurethane manifold and Pneutronics's X-valve technology, the system is more efficient than previous miniature models. The X-valves can handle flow rates at pressures from 0 to 30 psig and have a short response time. The valves were recently used by Medical Education Technologies Inc. (Sarasota, FL, USA) in patient simulators.
"In the past, few people used single CO2 probes because they required a second sensor for O2 monitoring, and they had a slow response time," says Andres Tschupp, CEO of Sentec, emphasizing that the new V-Sign probe features a CO2 response time close to its O2 response time.
Valves
The modular X-system combines a polyurethane manifold with Pneutronics's X-valve technology for a lighter, more-efficient miniature valve system.
The one-piece, 8-mm valves snap into the manifold, eliminating the mounting hardware and reducing the assembly time that it takes for traditional aluminium and brass manifold systems. A blown valve can easily be removed and replaced using the snap-in method. With an elastomer base and fewer functional parts, tolerance problems and leak potential are also reduced.
"The unique design makes the X-system ideal for portable medical applications like blood pressure equipment," says Richard Parker, a Pneutronics applications engineer. "But it can also be custom configured to meet the needs of a variety of medical applications."
Jamie Graham
Electronic Components
High-Density Packaging Reduces System Cost, Size, and Weight
Described as an alternative to single-chip packages that are assembled onto a printed circuit board, high-density packaging (HDP) uses unhoused integrated circuits or chip-size packages mounted on integrated electronic boards. The benefits to device OEMs, according to Art of Technology AG (Zürich, Switzerland), include size and weight reductions, reduced power consumption, and increased functionality. The technology also enables the development of new products, according to R&D director Etienne Hirt, for applications such as sensor systems for diagnostic and monitoring equipment, active implantable devices, and wearable home-care systems.
Companies that do opt to use the silicon chip as a bare die often only consider wire bonding the die onto a ceramic substrate, according to Hirt. "This is a reliable method and it has the advantage of being able to withstand aggressive solutions," he says, "but it also has substantial drawbacks." Among these, he cites high cost and low interconnect density. In addition, wire-bond assembly adds height to the integrated circuit. Other HDP assembly methods and substrates can satisfactorily address the requirements of medical applications, according to Hirt.
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| High-density packaging methods were used in the development of multichannel neural cuff electrodes with integrated multiplex circuitry. |
"The mechanical and electrical interconnection from the die to the substrate can also be accomplished by means of a foil, solder, or adhesive; by rerouting the pads on the chip; or by using advanced packages such as ball grid arrays or chip-size packages," explains Hirt. In addition to ceramics, substrate options include laminates, thin-film processes, and flex solutions. Encapsulation can be achieved using metal or ceramic enclosures; however, these tend to be heavy, large, and expensive. "Often, a coating or injection-moulded circuit is sufficient," says Hirt, adding that Makrolon is one such material that is suitable for implants. The long-term reliability of electronics protected in this manner must be thoroughly investigated, he cautions.
These and other options were considered in the development of an implantable microelectronic device by a leading manufacturer of these types of products. The Fraunhofer Institut IZM and Technischen Universität, both in Berlin, collaborated with the company on the project, which used HDP technology to yield a new production concept that could reduce total costs while ensuring reliability.
Art of Technology was spun off the Electronics Laboratory of the Swiss Federal Institute of Technology in Zürich in October 1999. The company's stated mission is to support OEMs with turnkey solutions for the miniaturization of electronics through the use of HDP.
Norbert Sparrow
Copyright ©2001 European Medical Device Manufacturer
