Shutterless mainstream discriminating anesthetic agent analyzer

An anesthetic agent detector for simultaneously measuring the concentrations of respective anesthetic agents in a respiratory gas stream of a patient, comprising:

• a source of infrared radiation;
• a separate infrared detector for each of said respective anesthetic agents, each detector disposed so as to receive incident radiation from said infrared radiation source and to produce first electrical signals representative of the received incident radiation and ambient temperature transients;
• means for directing at least a portion of said respiratory gas stream of said patient between said infrared detectors and said infrared radiation source;
• a separate reference infrared detector for each of said infrared detectors, each reference detector being disposed back to back with its corresponding infrared detector and connected in parallel opposed manner therewith so as to output second electrical signals representative of ambient temperature transients;
• means for shielding said reference detectors from said infrared radiation source, said shielding means being disposed between said infrared detectors and said reference detectors;
• and
• means for processing said first and second electrical signals to produce signals representative of the concentrations of said respective anesthetic agents.

A method of simultaneously measuring the concentrations of respective anesthetic agents in a respiratory gas stream of a patient, comprising the steps of:

• transmitting a beam of infrared radiation through said respiratory gas stream;
• detecting the intensity of said infrared radiation, after it has passed through said respiratory gas stream, using a separate infrared detector for each of said respective anesthetic agents, and generating first electrical signals representative of the detected infrared radiation;
• detecting ambient temperature transients in a region adjacent said infrared detectors using a separate reference infrared detector adjacent each of said infrared detectors, each reference detector being connected in parallel opposed manner with its corresponding infrared detector and being shielded from said infrared radiation, and generating second electrical signals representative of said ambient temperature transients;
• generating difference signals respectively corresponding to the differences between the respective first electrical signals and second electrical signals;
• and
• processing said difference signals to produce signals representative of the concentrations of said respective anesthetic agents.

An infrared energy detector for measuring the amount of incident infrared radiation received from a source of infrared energy, comprising:

• a plurality of thermopile detectors disposed so as to receive incident radiation from said infrared radiation source via respective optical channels and to produce first electrical signals representative of the received incident radiation and ambient temperature transients;
• a separate reference thermopile detector for each of said thermopile detectors, each reference thermopile detector being connected in parallel opposed manner with its corresponding thermopile detector and outputting second electrical signals representative of ambient temperature transients;
• and
• means for shielding said reference thermopile detectors from said infrared energy source.