Validation of a Modified One-Step Rebreathing Technique for Measuring Exercise Cardiac Output

A modification of the Farhi one-step rebreathing technique is described for determining submaximal exercise cardiac output (Q). Factors critical in the estimation of Q are initial rebreathing bag volume and constant bag volume during the maneuver. By substituting a high flow rate analyzer for the re...

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Bibliographic Details
Main Authors: Szlyk, Patricia C, Evans, Karleyton C, Sils, Ingrid V
Format: Report
Language:English
Subjects:
ANALYZERS
Anatomy and Physiology
AS879
BAGS
BREATHING APPARATUS
CIRCUITS
EXERCISE(PHYSIOLOGY)
FLOW
HEART
HEART RATE
HIGH RATE
Life Support Systems
LOSSES
MANEUVERS
MASS SPECTROMETERS
MEASUREMENT
OUTPUT
OXYGEN CONSUMPTION
PE62787A
RECIRCULATION
Stress Physiology
TIDES
TUBES
VALIDATION
VOLUME
WU129
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Description
Summary:A modification of the Farhi one-step rebreathing technique is described for determining submaximal exercise cardiac output (Q). Factors critical in the estimation of Q are initial rebreathing bag volume and constant bag volume during the maneuver. By substituting a high flow rate analyzer for the recommended low flow rate mass spectrometer, adding a recirculation circuit from the outlet of the analyzer to an inlet at the base of the rebreathing bag and reducing the length of sample tubing to the analyzer, we were able to recirculate the subject's expired gas and achieve no loss of bag volume. No statistically significant differences in estimate of cardiac output were noted between the mass spectrometer and LB-2 analyzer with recirculation circuit during submaximal cycling. Heart rate and oxygen uptake were highly correlated with cardiac output and agreed well with the literature, irrespective of the CO2 analyzer system used. A unique feature of our method is that the subject's tidal volume is measured prior to the maneuver and then used as the initial rebreathing bag volume. Varying the bag volume by + or - 0.2L from the tidal volume had no significant effect on the estimate of cardiac output during exercise. Now quick, reliable and noninvasive measurements of cardiac output are feasible in subjects not only in the laboratory but also in the field where a mass spectrometer is not readily portable. Keywords: Field portable, Noninvasive, Submaximal exercise, Cardiac output, Rebreathing.