Method for continuously measuring the CO.sub.2 content in breathing gases

• US 4,011,859 A
• Filed: 09/02/1975
• Issued: 03/15/1977
• Est. Priority Date: 09/05/1974
• Status: Expired due to Term

• Current Assignee: Dragerwerk AG
• Original Assignee: Dragerwerk AG
• Inventors: Frankenberger, Horst
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/609,564
• Time in Patent Office: 560 Days
• Field of Search: 128/2 C, 128/2 L, 128/2 R, 128/2.07
• US Class Current: 600/532
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61B 5/0873 using optical means
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis

Abstract

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.

Claims

1. A gas measuring method on the principle of infrared absorption for continuous measuring of the CO₂ content in breathing gases while using a measuring cell along with a luminous source, an interference filter accorded to CO₂, and a photodetector, wherein the measured values of the measuring cell which is placed in the breathing-air stream are processed in a signal processing unit which is controlled by a breathing-air phase recognition unit, the respective maxima and minima of the measured values in each breathing phase are stored in a maximum-value storage and a minimum-value storage, said values, controlled by the breathing-air phase recognition unit, are divided and the logarithm is taken thereof in a computation unit and, since ##EQU6##the CO₂ content at the end of the expiration phase is indicated in an indicating unit.

2. A method of continuously measuring CO₂ content in a breathing gas during the inspiration and exhalation phases of breathing and using a luminous source to pass light rays through an interference filter accorded to CO₂ and a conduit of the gas to a photodetector, comprising continuously passing the breathing gas developed during the breathing phases through a 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 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 in the breathing gases.

3. A method according to claim 2, including indicating the CO₂ content in each breathing phase in an output terminal after division by the minimum value and the minimum value storage and logarithmation in the computing unit.