Abstract: A method and apparatus are is disclosed for determining whether respiratory gas is present in a gaseous sample. The sample is brought into contact with an indicator which yields an indication within a diagnostically effective period of time of the presence in the sample of carbon dioxide in concentration of at least 2% while an indication of the presence of carbon dioxide or other trace acidic gas in a sample of ambient air is delayed beyond a predetermined period of time. The method and apparatus of the present invention have particular utility in determining the correct placement of an endotracheal catheter in a patient or in the direction of apnea.

Abstract: A method is disclosed for determining whether respiratory gas is present in a gaseous sample by which the sample is brought into contact with an indicator which yields an indication within a diagnostically effective period of time of the presence in the sample of carbon dioxide in concentration of at least 2% while an indication of the presence of carbon dioxide in a sample of ambient air would be delayed beyond a predetermined period of time. The method has particular utility in determining the correct placement of an endotracheal catheter in a patient or in the detection of apnea.

Abstract: A detector for rapid response, quantitative determination of carbon dioxide in a gas comprising one or more components, each of which comprises a carrier with a surface to be exposed to the gas, said surface including ane indicating element of a predetermined sensitivity which gives a rapid response signal when exposed to a given concentration of carbon dioxide, the response signals produced when the component or components are exposed to the gas providing a rapid and progresssive quantitative determination of the concentration of carbon dioxide or any change with time of said concentration in the gas.

Abstract: A rapid response device for the detection of carbon dioxide in a concentration of more than 2% in a gas mixture comprising an indicator component mounted within an enclosure with a transparent window, the component comprising a carrier having fixedly attached thereto an indicating element formed from an aqueous solution of a colorless Lewis base, a hygroscropic, high boiling, transparent, colorless, water-miscible liquid and a pH-sensitive indicator, the enclosure being sealed for storage under a carbon-dioxide free atmosphere; and a method for determining the correct placement of an endotracheal catheter using the device.