Archive for the ‘Cardiac Output’ Category


Estimation of Mixed Venous Pco2 for Determination of Cardiac Output in Children (Introduction)Study objectives: Cardiac output (Q) can be estimated noninvasively during exercise by employing C02-rebreathing techniques (equilibrium and exponential) to estimate the oxygenated mixed venous Pco2 (Pvco2). It has been found in adults and children that the equilibrium method underestimates Q as a result of overestimation of PvC02, unless PvC02 is “downstream corrected.” In adults, it has been found that the exponential method does not require downstream correction and yields values similar to those obtained by the equilibrium method with downstream correction. The objectives of this study were as follows: to test whether the exponential method gives similar results to the equilibrium method with downstream correction in children; to verify that downstream correction is required in children; and to test whether a single equation could be used in adults and children to predict Q from oxygen consumption (Vo2). asthma mist asthma relief
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  • Estimation of Mixed Venous Pco2 for Determination of Cardiac Output in Children (Discussion)We found in healthy children that PvC02 obtained using the exponential method was similar to the downstream corrected equilibrium value, but significantly different from the uncorrected equilibrium value. This is similar to what has been described in adults.’ This suggests that in children, as in adults, either the equilibrium method with downstream correction or the exponential method can be used when calculating PvC02.

    Using the PvC02 obtained by the equilibrium method with the downstream correction, we found a very high correlation, r2=0.95, between Q and Vo2 in healthy adults and children of both sexes (equation 3, Fig 2). Our results agree closely with those of dye dilution studies’ (equation 4, Fig 2). We found that there was a slight additional effect when a grouping factor, indicating whether a subject was a child or an adult, was included, but this effect disappeared when weight was included as one of the independent variables in the stepwise linear regression equation. (more…)

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  • Estimation of Mixed Venous Pco2 for Determination of Cardiac Output in Children (Results)A total of 14 children (11 boys and 3 girls), mean age 11.7±1.6 years, range 8.2 to 13.9 years, successfully underwent steady-state exercise tests in which PvC02 was measured by both the exponential and equilibrium methods. Eight were healthy children of hospital staff, four were healthy prematurely born children, and two were otherwise healthy children who had undergone testing for growth hormone secretion due to short stature. Nine other children (five boys and four girls) underwent steady-state exercise tests in which PvC02 was obtained by the equilibrium method alone. Five were children of hospital staff and four were prematurely born. The mean age of the 23 children was 11.0±1.9 years, range 7.1 to 13.9 years. Twelve adults (seven men and five women), mean age 33.6±7.2 years, range 24 to 48 years, underwent steady-state exercise tests in which PvC02 was measured by the equilibrium method. (more…)

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  • Estimation of Mixed Venous Pco2 for Determination of Cardiac Output in Children (Materials and Methods)Subjects

    Hospital staff and their children were recruited for the study. Data obtained from prematurely born children who were participating in a long-term follow-up study and from children who had undergone exercise testing for growth hormone secretion were also employed. Subjects were excluded if they had an FEVX of <80% of their predicted value based on age, race, sex, and height. The study had the approval of the Institutional Review Board of the Montreal Children’s Hospital/McGill Research Institute. For children, an informed consent was obtained from one of the parents as well as from the child. (more…)

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