Sensors quicken blood tests

By: 
June 05, 2000

San Diego -Patients undergoing heart surgery and recovering in intensive care units typically require frequent monitoring of blood gases, sometimes as often as 30 times per day. Blood samples sent to hospital labs usually take up to a half-hour to process. The faster the tests are processed, the faster the doctor can intervene. Sometimes, even a few minutes can literally mean the difference between life and death. VIA Medical Corp. has developed an alternative to conventional approaches to blood gas monitoring that reduces testing time to a minute or two.

The VIA blood gas monitor uses miniature sensors that are placed inside an intravenous line. The monitor automatically draws blood into the IV tubing to cover the sensors, takes measurements, and reinfuses the blood back into the patient. The sensors continually monitor blood gas levels and provide results within two minutes, without the inconvenience of drawing blood.

In developing the monitor, VIA decided to use electrochemical sensors rather than optical sensors. Among the challenges the company faced was sterilization because the sensors were open to blood. "We incorporated six electrochemical sensors in a single sensor array," says David Wong, VIA's Chief Scientific Officer. "These sensors operate either potentiometrically, amperometrically, or by electrical conductance."

Potentiometric measurement is the measurement of voltage output of the sensor, which varies with analyte concentration of sodium, potassium, and other chemicals in the blood. Amperometric measures current. A third type of sensor measures electrical conductance.

Via found ways to make the sensors small and inexpensive enough to be sold as disposables. The sensors are sterile and are biocompatible. Although the company focuses on medical applications, the sensors also have potential applications in industrial processes, according to Wong. "Monitoring sodium is important in the beverage industry. And glucose tracking is important in the fermentation process," he says.

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