Method for continuously measuring the CO{HD 2 {B content in breathing gases

A method of continuously measuring the CO2 content in breathing gases during inspiration and exhalation phases of breathing using a luminous source to pass infrared light rays through an interference filter accorded to CO2 and a conduit of the gas to a photodetector, comprises passing the breathing gas developed during the breathing phases through the conduit to influence the photodetector to transmit a measured value signal in accordance with the CO2 content, directing the signal to a breathing air phase recognition unit, storing the maxima and the minima of the measured value signals in each breathing phase in a maximum storage and a minimum storage, dividing the stored values under the control of the recognition unit and directing the values to a computation unit to indicate the logarithm of the values so as to give an indication of the variations of the CO2 content. The indicated value is then directed to an indicating unit to show the value of the CO2.