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Abstract

An side stream infrared gas analyzer for detecting the concentration of a gaseous component of a substantially gaseous flow stream such as the expired air of a patient under anesthesia. The infrared gas analyzer comprises an infrared energy detector, a sample cell, and an infrared energy source which are designed to be small and to consume relatively little electrical power. The infrared energy detector converts the received incident radiation into at least one electrical signal representative of the received incident radiation and is preferably mounted directly onto a printed circuit board containing signal processing circuitry which processes the electrical detection signals provided by the infrared energy detector. The infrared energy detector also has a first infrared transmissive window on a detection side thereof through which the incident radiation passes for detection. The sample cell is preferably mounted on the detection side of the infrared energy detector and receives at least a portion of the substantially gaseous flow stream from the patient and directs the received portion to a detection volume which shares the first infrared transmissive window of the infrared energy detector on one side thereof. The infrared energy source is then mounted on the side of the sample cell opposite the infrared energy detector so that emitted infrared energy passes through a second infrared transmissive window which is shared by the infrared energy source and a side of the detection volume opposite the infrared energy detector. After passing through the second infrared transmissive window, the infrared energy from the infrared source passes through the detection volume for absorption by the gaseous component and then through the first infrared transmissive window for detection by the infrared energy detector. The concentration of the gas constituent is then calculated from the resulting absorption signal.

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First Claim