Arrangement and process for controlling a numerical value for patient respiration

An arrangement with a control circuit for controlling a numerical value for patient respiration as well as to a process for controlling the numerical value. The numerical value is controlled on the basis of an evaluation of the EEG (electroencephalogram) of the patient ( 1 ) by an EEG sensor ( 2 ), e.g., by determining the so-called BIS (bispectral index). A control of the inspiratory gaseous anesthetic concentrations is cascaded to the control of the EEG value in the manner of a cascade circuit. This has the advantage that a metering device ( 6 ) belonging to the arrangement meters a gaseous anesthetic mixture directly according to the patient's needs. As an alternative, the control of the numerical value is performed on the basis of an evaluation of the expiratory gaseous anesthetic concentrations resolved for individual breaths at the Y-piece ( 19 ) of the respiration circuit ( 12 ) by a gaseous anesthetic sensor ( 8 a ), preferably an infrared optical gas sensor.