ENGINEERING INSIGHT
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An application-specific integrated circuit from AMI Semiconductor is a critical component of a blood gas monitor that is under development at Sphere Medical.
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An arterial monitor currently in development is designed to provide constant real-time measurement of chemicals in the blood such as glucose, electrolytes, drug concentrations, and blood gases. The Proxima system from Sphere Medical Ltd. (Cambridge, UK) includes a disposable sensor and an application-specific integrated circuit (ASIC) enclosed in standard IV tubing. The device can measure single chemicals or can be modified to measure a variety of blood components simultaneously. Results are output to a small bedside monitor to provide clinicians with continuous information on levels of important blood chemicals. To design and manufacture the unit’s ASIC, Sphere enlisted the help of AMI Semiconductor (AMIS; Oudenaarde, Belgium).
“Sphere found us mainly because of our involvement in the medical market,” says AMIS medical group vice president Todd Schneider. Specializing in design and manufacture of integrated mixed-signal and structured digital products, AMIS routinely develops sensors, wireless platforms, and other components for medical devices. “Our work with Sphere was very much a collaboration,” Schneider adds. “Sphere had very particular requirements and we helped them spec the chip, getting them ‘head room’ on the design and a great amount of flexibility.”
AMIS has more than 200 mixed-signal design engineers and close to 100 digital design engineers that are dedicated to ASIC development. The ASIC developed for Sphere includes a high-performance analogue subsection with a low-power analogue-to-digital convertor, temperature sensor, and power management and communications interface.
Using technology originally acquired from Siemens, Sphere’s Proxima microanalyzer initially will be used for glucose monitoring. The sensor will later be used to measure other criteria such as blood gases, electrolytes, and drug concentrations. Blood gas monitoring is critical for supervising an intensive–care patient’s respiratory system. “Each year, about 15 million patients in intensive care are artificially ventilated, and these patients need to have their blood gases measured,” notes Sphere vice president of research and development Peter Laitenberger.
Existing technologies, including portable cartridge and lab console analyzers, often require clinicians to wait for critical patient data. “The most frequently used method of testing a blood sample is to ice it up and take it to the laboratory,” Laitenberger explains. “Results are ready in 15 to 30 minutes, if you are fast. But at busy times in the hospital’s schedule, results can take several hours before they are ready,” he says. By contrast, the Sphere device analyzes the blood and provides results in 1 to 2 minutes. In addition, the disposable sensor can be used for one patient for about 3 days—the typical length of stay for intensive-care patients.
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