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Aortic input impedance in infants and children.
M K Sharp1, G M Pantalos, L Minich
1Biofluid Mechanics Laboratory, Department of Bioengineering, University of Utah, Salt Lake City 84112, USA. m.k.sharp@m.cc.utah.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|June 14, 2000
Summary
Vascular resistance in pediatric patients is higher than in adults, decreasing with weight. A specific lumped-parameter model best described aortic impedance in children, revealing distinct resistance and compliance characteristics.
Area of Science:
- Cardiovascular Physiology
- Pediatric Cardiology
- Biomedical Engineering
Background:
- Understanding pediatric cardiovascular mechanics is crucial for diagnosing and treating heart conditions.
- Aortic input impedance is a key parameter reflecting the heart's load and systemic vascular properties.
Purpose of the Study:
- To characterize the input impedance of the ascending aorta in pediatric patients.
- To compare pediatric aortic impedance parameters with adult values.
- To identify the best lumped-parameter model for describing pediatric aortic input impedance.
Main Methods:
- Flow and pressure measurements in the ascending aortas of six pediatric patients (1-4 years).
- Calculation of input impedance from measured data.
- Evaluation of three- and four-element lumped-parameter models to fit the impedance data.
Main Results:
- Total vascular resistance decreased with increasing patient weight, being 1-3 times higher than in adults.
- Conductance per unit weight was constant but 3 times higher than in adults.
- A model with characteristic aortic resistor (R(c)) and inertance in series, followed by parallel peripheral resistor (R(p)) and compliance, best fit the data.
- R(p) and R(c) decreased with weight; R(p) was 1-3x higher and R(c) was 2-15x higher than adult values.
- Pediatric R(p)-to-R(c) ratio differed significantly from adults, with R(p) developing faster with weight.
- Compliance increased with weight but was 3-16x lower than adult values.
Conclusions:
- Pediatric aortic input impedance exhibits unique characteristics compared to adults, notably higher resistance and lower compliance.
- The peripheral resistor (R(p)) appears to develop more rapidly with patient weight than the characteristic aortic resistor (R(c)).
- The proposed lumped-parameter model provides a valuable tool for analyzing pediatric cardiovascular mechanics.