Capnography Set to Take to the Field

May 1, 2005 By: Stephanie vL Henkel, Sensors Sensors

First responders to a medical emergency immediately check the patient's airways to see if there's any action. Of additional interest would be a determination of the level of exhaled CO2, a reliable indicator of pulmonary function. Respiratory CO2 measurement, or capnography, is typically accomplished by nondispersive IR (NDIR) or colorimetric devices. But they are not built for field use. Now there's a third technique.

Nanomix has developed a CO2-specific monitor that combines carbon nanotube transistors with silicon microstructures to yield a small, disposable unit. It is designed for use by EMTs at an accident scene to verify endotrachial tube placement and to assess the effects of CPR and other life-support measures. The monitor is useful as well for anesthesiologists in the OR, and in clinics that perform sleep apnea observations and evaluations of asthma treatments.

The unit takes advantage of the previously developed Sensation detection platform. The carbon nanotube network overlying the silicon microstructures is coated with a polyethylene imine and starch polymer layer that interacts with the chemical or biological analyte of interest. The resulting electrical impedance can be measured by applying a voltage to produce a characteristic signal. The monitor's operating lifetime is 6 hr., but in actual use it could last up to a week. The estimated shelf life is a year. The dynamic range is 0%–10% CO2, and response time is <1 s.

Nanomix has received a $500,000 NSF Phase II SBIR grant to devise a collaborative development kit based on the Sensation platform. The company will work with academic and industrial partners on applications ranging from medical diagnostics to water and air quality monitoring.

Contact David Macdonald, Nanomix, Inc., Emeryville, CA; 510-428-5300,,

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