Journal of Applied Physiology, Vol 53, Issue 5 1125-1132, Copyright © 1982 by American Physiological Society
Noninvasive cardiac output determination using inhaled oxygen-15-labeled carbon dioxide
N. M. Braslow, C. A. Hales, B. Hoop, D. J. Kanarek and H. Kazemi
Inhaled oxygen-15-labeled carbon dioxide (CO2*) is hydrated in the alveolar
capillary blood to produce oxygen-15-labeled water (H2O*). This allows
noninvasive delivery of a traceable indicator into the pulmonary
circulation. Removal of oxygen-15 marker from the lung is a function of
pulmonary perfusion. Two techniques were evaluated for computing cardiac
output (CO) following single bolus inhalation of CO2*: 1) continuous
monitoring of arterial blood activity through an external detector and 2)
noninvasive positron imaging of oxygen-15-label washout from the chest and
simultaneous emergence of activity in arterial blood. In seven mongrel dogs
studied using technique 1, 46 determinations of CO were made from 1.2 to
8.0 l/min and compared with simultaneous indocyanine green dye-dilution
determination. Correlation coefficient was 0.90 with slope of linear
regression of 1.05. In 12 mongrel dogs studied using technique 2, 23
determinations of CO were made from 0.9 to 9.2 l/min and compared with
simultaneous indocyanine green dye determination. Correlation coefficient
was 0.985 (P less than 0.001) with slope of linear regression of 0.898.
This noninvasive technique (2) for determination of CO is independent of
assumptions regarding regional ventilation or perfusion of the lung and
appears valid in animal studies.
