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Chapter 1: Technology Overview
The following chapter contains general descriptions about parameters, measurements, and the technology used in
EMMA.
Principles of Operation
The measurement of CO2 in the breathing gas mixture is based on the fact that different gas components absorb
infrared light at specific wavelengths. A beam of invisible infrared light is directed through the respiratory gas flow in
the EMMA Airway Adapter. As the beam passes through the EMMA Airway Adapter, some of the light is absorbed by
the gas mixture. The amount of absorbed light is measured by a miniaturized two channel spectrometer positioned to
receive the infrared light beam.
The spectrometer incorporates a filter wheel fitted with two different optical "color" filters. The wavelength ranges of
these filters are chosen such that one filters out colors where carbon dioxide has very strong absorption and the other
filters out colors where carbon dioxide has no absorption.
The spectrometer also incorporates an infrared detector that converts the light beam to an electrical signal. The
electrical signal is converted to a digital value that is fed to a microprocessor. The ratio of the light measured through
the two filters is then used by the microprocessor to calculate the carbon dioxide concentration in the breathing gas
mixture.
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