Patent ID: 6267928
Filing Date: 2001-07-31
Classification: A61B,Y10T

Abstract:
A capnometer comprising:a radiation source for irradiating infrared radiation to a respiratory gas;a thermal detector for sensing a transmission of said infrared radiation and for outputting a detection signal;means for turning said radiation source on and off at predetermined intervals;a memory for storing an output from said thermal detector;maximum value detecting means for detecting a maximum value of said detection signal output from said thermal detector for the present inspiration phase;minimum value detecting means for detecting a minimum output value, corresponding to an offset value, of said detection signal output from said thermal detector when said radiation source is turned off momentarily;corrected value determining means for determining a corrected value based upon said maximum value for the present inspiration phase,means for determining a density signal by calculating the difference between a subsequent detection signal, output from said thermal detector, and said corrected value;means for determining a reference value by calculating the difference between said corrected value and said minimum value for the present inspiration phase;means for determining the concentration of carbon dioxide by calculating a ratio of said density signal to said reference value.