SINGLE BREATH CARDIAC-OUTPUT - ENHANCED SAMPLING AND ANALYSIS TECHNIQUES

  • 1 January 1983
    • journal article
    • research article
    • Vol. 54  (11) , 1009-1014
Abstract
The single breath method for measuring cardiac output (.ovrhdot.Q) was enhanced using new computer sampling and analysis techniques. The CO2 elimination rate was measured breath by breath using computer integration of expired flow rate and CO2 concentration. The concentration of CO2 in the arterial blood was determined from the CO2 partial pressure at the end of a normal breath. The concentration of CO2 in mixed venous blood was determined with a modification of the single breath method. The variability and relative accuracy of measurement of cardiac output were evaluated using 4 healthy men who exercised at 3 work rates from 0.5 l .cntdot. min-1 (rest) to 2 l .cntdot. min-1 O2 consumption (.ovrhdot.VO2). Repeatability of measurements was assessed by making repeated measurements on 1 subject at a steady-state exercise work rate. The coefficients of variation for repeated measurements made at 0.5 l .cntdot. min-1 (rest), 1.0 l .cntdot. min-1 .ovrhdot.VO2 and 2.0 l .cntdot. min-1 .ovrhdot.VO2 were 18.2, 10.5 and 8.8%, respectively. Regression lines relating cardiac output and O2 consumption from 3 separate studies, employing the direct Fick method and the described method, were all similar. The probability of a successful breathing maneuver was increased to nearly 100%. Success was defined as a linear regression correlation coefficient (r2), relating instantaneous exchange ratio and CO2 during the breathing maneuver, of > 0.9.

This publication has 3 references indexed in Scilit: