Determining carbon di:oxide prodn. in respiratory gas - using only oxygen consumption and concn. measurements

• Main Authors: ALTNER, ULRICH., 2360 BAD SEGEBERG, DE, DITTMANN, RALF, 2400 LUEBECK, DE, HARMS, HEYE, 2400 LUEBECK, DE
• Format: Patent
• Language: English; German
• Published: 25.07.1991
• Subjects: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; MEASURING; PHYSICS; TESTING

(A) CO prodn. in respiratory gas is determined using a mixing chamber through which the gas flows, a first O2 sensor in the respiratory gas inlet line, a second O2 sensor at the mixing chamber outlet, a CO2 absorber upstream of the second O2 sensor, a control unit with a comparator for comparing the measurement signals of the first and second O2 sensors and a controllable O2 supply to the mixing chamber for determining O2 consumption by the compensation method. CO2 prodn. is determined by a serial measurement cycle involving (a) measuring O2 consumption (VO2) by means of the O2 supply (6) into the mixing chamber (5) and setting switch valves (13,14) to feed the measuring gas stream into a first measuring as line (19) via the CO2 absorber; (b) switching off the O2 supply (6) by means of the control unit (15); (c) measuring the O2 concn. (FIO2) in the respiratory gas inlet line (3) using the first O2 sensor (10); (d) determining the O2 concn. (FEO2) using the second O2 sensor (11); (e) controlling the switch valves (13,14) with the control unit (15), such that the measuring gas stream flows past the CO2 absorber in a second measuring gas line (20) and the O2 concn. (FEO2) is measured by the second O2 sensor (11); and (f) supplying the measurement signals (VO2, FIO2, FEO2, FEO2) to the control unit (15) and determining the CO2 prodn. (VCO2) by means of a first signal relationship (I). (B) In a similar process, steps (b) and (d) are omitted, step (e) involves determining an O2 consumption value (VO2) from the O2 supply (6) into the mixing chamber (5) instead of measuring the O2 concn. (FEO2) and step (f) comprises supplying the measurement signals (VO2, VO2 and FIO2) to the control unit (15) and determining the CO2 prodn. (VCO2) by means of a second signal relationship (II). USE/ADVANTAGE - The process is useful in routine clinical operation in hospitals, for measuring O2 consumption and CO2 prodn. without the need for CO2 concn. measuring equipment.