title: Gas mixing apparatus for determining cardiac output by CO2 rebreathing.
abstract: The carbon dioxide rebreathing technique is widely used for determination of cardiac output during exercise. The equilibration method of Collier et at. (J. Appl. Physiol. 9:25, 1956) is generally preferred over the exponential method of Defares (J. Appl. Physiol. 13:159, 1968). However, the equilibration method requires the volume and initial CO2 percentage in the rebreathing bag to be adjusted according to the work rate. A device for mixing two gases (100% O2 and 20% CO2/80% O2) was constructed for this purpose. Multistage regulators are attached to the gas tanks and connected to a medical gas mixer via high-pressure air hoses. A variable time-delay switch causes a solenoid valve to open for 1.0-10s to deliver a predetermined gas volume. The device was found to accurately deliver a preset volume and concentration of gas to the rebreathing bag. A gas mixing apparatus simplifies the equilibration CO2 rebreathing technique by allowing the investigator to easily select the initial volume and percentage of CO2.
authors.affiliation: University of Tennessee-Knoxville, Exercise Science Unit 37996-2700, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Bassett
authors.forename: T R
authors.initials: TR
authors.lastname: Fitton
mesh_terms: D000280:Administration, Inhalation; D002245:Carbon Dioxide / Q000008:administration & dosage* / Q000097:blood; D002302:Cardiac Output; D004582:Electronics, Medical / Q000295:instrumentation; D004867:Equipment Design; D005080:Exercise Test; D006801:Humans; D009330:Nebulizers and Vaporizers; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology*; D011312:Pressure; D013990:Tidal Volume; D013997:Time Factors; D014937:Work
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen