Carbon dioxide detection (II)

• US 5,291,879 A
• Filed: 07/23/1992
• Issued: 03/08/1994
• Est. Priority Date: 02/26/1988
• Status: Expired due to Fees

• Current Assignee: Albert L. Babb, Gary L. Tarbox, Michael P. Hlastala
• Original Assignee: Albert L. Babb, Gary L. Tarbox, Michael P. Hlastala
• Inventors: Hlastala, Michael P., Babb, Albert L., Tarbox, Gary L.
• Primary Examiner(s): Burr, Edgar S.
• Assistant Examiner(s): Lewis, Aaron J.
• Application Number:
  US07/918,372
• Time in Patent Office: 593 Days
• Field of Search: 128/200.26, 128/205.23, 128/202.22, 128/207.14, 128/207.15
• US Class Current: 128/200.26
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61M 16/0488 Mouthpieces; Means for guiding, securing or introducing the tubes guiding or introducing with laryngoscopes A61B1/267; holding devices on the body A61M25/02
• CPC Class Codes: A61M 16/0816 Joints or connectors
• CPC Class Codes: A61M 16/085 Gas sampling
• CPC Class Codes: A61M 2016/0413 with detectors of CO2 in exhaled gases
• CPC Class Codes: A61M 2230/432 partial CO2 pressure (P-CO2)
• CPC Class Codes: G01N 31/223 for investigating presence of specific gases or aerosols G01N31/221, G01N31/222 take precedence; actuation of fire alarm by presence of smoke or gases G08B17/10

Abstract

Methods and apparatus for ascertaining whether there is at least a threshold concentration of carbon dioxide in gases being monitored. Reversible hydration of the carbon dioxide to generate excess hydrogen ions and trigger a color change in a pH sensitive indicator is employed in representative embodiments of the invention to provide an indication that the threshold concentration of carbon dioxide is present in the gases. The methods and apparatus may be used to distinguish between tracheal and esophageal intubation of human and other mammalian patients.

Claims

1. A method of confirming that an airway tube has been placed and is being maintained in the trachea of a patient, said method comprising the steps of:

preparing a detector means including an indicator which is sensitive to CO₂ at predetermined threshold concentrations occurring in exhalations of the patient and is so selected;

(a) as to undergo in cycles matching successive breaths of the patient a sustained pattern of periodic changes of color representing, in an alternating manner;

(i) the presence of a threshold concentration of CO₂ within the airway tube, and (ii) the absence of the threshold concentration of CO₂ within the airway tube but to (b) be incapable of undergoing such periodic changes of color in the absence of exhalations producing such alternating pattern of CO₂ concentrations in the airway tube;

so associating the detector means with the airway tube and thereby making said indicator responsive to gases in the airway tube that, if said tube is correctly placed in the trachea of the patient, said indicator will undergo said sustained pattern of periodic changes in contrast to the absence of a recurring pattern found when the detector means associated airway tube is mistakenly installed in the esophagus of the patient;

observing whether the detector means indicator undergoes the sustained pattern of periodic changes of color indicative of the placement and maintenance of the airway tube in the trachea of the patient or whether the sustained pattern of periodic changes is absent as is indicative of the airway tube having been dislodged or incorrectly placed in the patient'"'"'s esophagus;

employing an observation of a sustained pattern of periodic changes of color as evidence that the airway tube has been placed and is being maintained in the trachea of the patient; and

employing an observation that a sustained pattern of periodic changes of color is not present as evidence that the airway tube was not or is no longer correctly placed in the trachea of the patient.