Method for calibration of gas measuring sensors for dissolved gasses and method for measuring the concentration of CO.sub.2 in blood with the assistance of such a calibration method
First Claim
1. A method for calibrating a sensor for measuring a concentration of gas dissolved in a fluid and for generating a measured value corresponding to the measured concentration, comprising the steps of:
- providing a predetermined, first calibration fluid having a predetermined, first concentration of a gas dissolved therein;
providing a gas phase containing the same gas as is dissolved in said first calibration fluid, said gas in said gas phase being at a partial pressure in said gas phase differing from said partial pressure of said gas in said first calibration fluid, so that a partial pressure difference for said gas exists between said gas phase and said first calibration fluid;
separating said gas phase from said fist calibration fluid by a gas-permeable wall;
forming a second calibration fluid from said first calibration fluid by modifying the concentration of said gas in said first calibration fluid to a predetermined, second concentration of said gas in said second calibration fluid exclusively by causing a material transport between said first calibration fluid-and said gas phase through said gas-permeable wall by virtue of said partial pressure difference, said second concentration being different from said first concentration;
supplying said first and second calibration fluids to a sensor to be calibrated; and
calibrating said sensor by identifying first and second measured values using said sensor corresponding said first and second concentrations.
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Accused Products
Abstract
Method for calibrating gas measuring sensors for dissolved gasses and method for measuring the concentration of CO2 in blood with the assistance of such a calibration method two or more separate calibration fluids in which a gas to be measured is dissolved with respectively different partial pressures are employed. For simplification, another (i.e., a second) calibration fluid is produced from one (i.e., a first) calibration fluid by modifying the partial pressure of the first calibration fluid to a different value, preferably by material transport between the first fluid and a gas phase. Analysis equipment operating with this method, particularly for CO2 measurement of blood, become simpler, smaller and less expensive.
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Citations
23 Claims
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1. A method for calibrating a sensor for measuring a concentration of gas dissolved in a fluid and for generating a measured value corresponding to the measured concentration, comprising the steps of:
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providing a predetermined, first calibration fluid having a predetermined, first concentration of a gas dissolved therein; providing a gas phase containing the same gas as is dissolved in said first calibration fluid, said gas in said gas phase being at a partial pressure in said gas phase differing from said partial pressure of said gas in said first calibration fluid, so that a partial pressure difference for said gas exists between said gas phase and said first calibration fluid; separating said gas phase from said fist calibration fluid by a gas-permeable wall; forming a second calibration fluid from said first calibration fluid by modifying the concentration of said gas in said first calibration fluid to a predetermined, second concentration of said gas in said second calibration fluid exclusively by causing a material transport between said first calibration fluid-and said gas phase through said gas-permeable wall by virtue of said partial pressure difference, said second concentration being different from said first concentration; supplying said first and second calibration fluids to a sensor to be calibrated; and calibrating said sensor by identifying first and second measured values using said sensor corresponding said first and second concentrations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for measuring a partial pressure of CO2 dissolved in blood using a CO2 sensor for measuring said CO2 partial pressure and for generating a corresponding measured value proportional to a logarithm of the CO2 partial pressure comprising the steps of:
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providing a predetermined, first calibration fluid having CO2 dissolved therein with a defined physiological, first partial pressure and having HCO3- dissolved therein with a defined physiological concentration having a defined physiological, first pH value; providing a gas phase containing the same gas as is dissolved in said first calibration fluid, said gas in said gas phase being at a partial pressure in said gas phase differing from said partial pressure of said gas in said first calibration fluid, so that a partial pressure difference for said gas exists between said gas phase and said first calibration fluid; separating said gas phase from said first calibration fluid by a gas-permeable wall; producing a second calibration fluid from said first calibration fluid by material transport between said first calibration fluid and said gas phase exclusively by causing a material transport between said first calibration fluid and said gas phase through said gas-permeable wall by virtue of said partial pressure difference, said second calibration fluid differing from said first calibration fluid only by having a physiological, second CO2 partial pressure therein differing from said first CO2 partial pressure and a physiological, second pH value differing from said first pH value; supplying said first and second calibration fluids successively, in an arbitrary sequence, to a CO2 sensor and to a pH sensor; providing a base line fluid having CO2 dissolved therein with a concentration corresponding to a partial pressure of less than 10 Torr and having a defined, third physiological pH value differing from said first pH value; additionally supplying said pH sensor with said base line fluid;
using said CO2 sensor and said pH sensor, producing a measured value UpCO2 (c) corresponding to the first CO2 partial pressure in said first calibration fluid, a measured value UpCO2 (C'"'"') corresponding to the second CO2 partial pressure of said second calibration fluid, a measured value UpH (C) corresponding to the first pH value of said first calibration fluid, a measured value UpH (C'"'"') corresponding to the second pH value of said second calibration fluid, and a measured value UpH (BF) corresponding to the third pH value of said base line fluid, and a measured value UpCO2 (BF) corresponding to a CO2 partial pressure of said base line fluid;generating a quantity
space="preserve" listing-type="equation">S.sub.pCO2 =K.sub.pCO2 ·
S.sub.pH
space="preserve" listing-type="equation">wherein K.sub.pCO2 =- (U.sub.pCO2 (C)-U.sub.pCO2 (C'"'"'))/(U.sub.pH (C)-U.sub.pH (C'"'"'))!
space="preserve" listing-type="equation">and S.sub.pH =(Δ
U.sub.pH (C)/(pH(C)-pH(BF))
space="preserve" listing-type="equation">wherein Δ
U.sub.pH (C)=U.sub.pH (C)-U.sub.pH (BF);supplying blood to said CO2 sensor and obtaining a measured value UpCO2 (B) corresponding to a CO2 partial pressure of said blood; calculating a logarithm of the CO2 partial pressure of said blood log(pCO2 (B)) according to
space="preserve" listing-type="equation">log(pCO.sub.2 (B))=(Δ
U.sub.pCO2 (B)-Δ
U.sub.pCO2 (C))/S.sub.pCO2 +log(pCO2(C))wherein
space="preserve" listing-type="equation">Δ
U.sub.pCO2 (B)=U.sub.pCO2 (B)-U.sub.pCO2 (BF) and
space="preserve" listing-type="equation">Δ
U.sub.PCO2 (C)=U.sub.pCO2 (C)-U.sub.pCO2 (BF); andidentifying the CO2 partial pressure in said blood from log(pCO2(B)). - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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Specification