Impulse-response function of splanchnic circulation with model-independent constraints: theory and experimental validation

Munk, Ole L., Keiding, Susanne and Bass, Ludvik (2003) Impulse-response function of splanchnic circulation with model-independent constraints: theory and experimental validation. American Journal of Physiology-gastrointestinal And Liver Physiology, 285 4: G671-G680. doi:10.1152/ajpgi.00054.2003


Author Munk, Ole L.
Keiding, Susanne
Bass, Ludvik
Title Impulse-response function of splanchnic circulation with model-independent constraints: theory and experimental validation
Journal name American Journal of Physiology-gastrointestinal And Liver Physiology   Check publisher's open access policy
ISSN 0193-1857
Publication date 2003-10-01
Sub-type Article (original research)
DOI 10.1152/ajpgi.00054.2003
Volume 285
Issue 4
Start page G671
End page G680
Total pages 10
Editor M. Montrose
B.B. Rauner
Place of publication Bethesda, MD, United States
Publisher American Physiological Society
Collection year 2003
Language eng
Subject 239901 Biological Mathematics
780101 Mathematical sciences
Abstract Modeling physiological processes using tracer kinetic methods requires knowledge of the time course of the tracer concentration in blood supplying the organ. For liver studies, however, inaccessibility of the portal vein makes direct measurement of the hepatic dual-input function impossible in humans. We want to develop a method to predict the portal venous time-activity curve from measurements of an arterial time-activity curve. An impulse-response function based on a continuous distribution of washout constants is developed and validated for the gut. Experiments with simultaneous blood sampling in aorta and portal vein were made in 13 anesthetized pigs following inhalation of intravascular [O-15] CO or injections of diffusible 3-O[ C-11] methylglucose (MG). The parameters of the impulse-response function have a physiological interpretation in terms of the distribution of washout constants and are mathematically equivalent to the mean transit time ( T) and standard deviation of transit times. The results include estimates of mean transit times from the aorta to the portal vein in pigs: (T) over bar = 0.35 +/- 0.05 min for CO and 1.7 +/- 0.1 min for MG. The prediction of the portal venous time-activity curve benefits from constraining the regression fits by parameters estimated independently. This is strong evidence for the physiological relevance of the impulse-response function, which includes asymptotically, and thereby justifies kinetically, a useful and simple power law. Similarity between our parameter estimates in pigs and parameter estimates in normal humans suggests that the proposed model can be adapted for use in humans.
Keyword Gastroenterology & Hepatology
Physiology
Modeling
Mean Transit Time
Portal Vein
Spleen
Power-law Kinetics
Tracer Clearance Curves
Transit Times
Kinetics
Washout
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2004 Higher Education Research Data Collection
School of Biomedical Sciences Publications
 
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Created: Tue, 14 Aug 2007, 19:20:03 EST