A COMPARISON BETWEEN FREON AND ACETYLENE REBREATHING FOR MEASURING CARDIAC-OUTPUT

  • 1 January 1980
    • journal article
    • research article
    • Vol. 51  (11) , 1214-1221
Abstract
Cardiac output (CO) was measured in 10 young, healthy male subjects during rest and submaximal exercise on a bicycle ergometer by rebreathing a 2.0-2.8/(ATPS [ambient temperature and pressure, saturated with water vapor]) gas mixture of acetylene (0.7-1.2%), freon-22 (3-4.2%), Ar (6-7%) and O2 (.apprx. 40%) in N2. End tidal gas fractions were measured by a mass spectrometer. Ar was used as an inert, insoluble gas for corrections of end tidal acetylene-, freon- and O2 fractions. The acetylene corresponded to reported CO (6.06 .+-. 0.20 l/min at rest and 15.05 .+-. 0.44 l/min at 150 W). The freon values followed those of acetylene, but were systematically lower by 0.74 l/min at rest and 1.20 l/min at 150 W. A forced respiratory rate (30-32/min) increased CO and .ovrhdot.VO2 [O2 consumption rate] during rebreathing at rest and lower exercise levels; a spontaneous respiratory rate (14/min at rest and 22/min at 150 W) did not change .ovrhdot.VO2 during rebreathing compared to Douglas measurements at steady state. Freon can be used as the inert, soluble gas in the rebreathing procedure and a spontaneous respiratory rate is recommended. This noninvasive method has applications for measurement of cardiac output in space vehicles.