CAPNOGRAPHY WITH LEAD SELENIDE DETECTOR AND INTEGRATED BANDPASS FILTER

A capnometer (10) includes an integrated device (30, 30A, 30B) comprising a substrate (40), a lead selenide (PbSe) layer (42) or other infrared light absorbing layer disposed on the substrate, and a bandpass filter layer (50) disposed on the substrate. A temperature sensor tracks temperature of the device. A CO2 measurement cell (20) has light source (28) arranged to emit light (L) that passes through a flow path (F) and then through the bandpass filter layer of to reach the PbSe or other infrared light absorbing layer. Electronics (32) connected with the PbSe or other infrared light absorbing layer measure a photoconductivity signal. The electronics includes signal processing circuitry to convert the photoconductivity signal to a carbon dioxide partial pressure or concentration value. The electronics also includes the temperature sensor to enable accurate and fast temperature control of the device and instant temperature compensation for the temperature change.