Digital Computer Simulation of Cardiovascular System in Bleeding Patient for Clinical Management
A cardiovascular system model that simulates interactive responses to drugs has been developed on a small digital computer to realize virtual reality. The overall model basically consists of three models. The first is a momentum transport model that represents relations between blood pressure and flow in the cardiovascular system. In this model, the cardiovascular system is divided into Twelve components and modeled by using equivalent electrical circuits. The second is a mass transport model comprising twelve compartments corresponding to the respective components of the cardiovascular system. This model represents the distribution of the administered drug in the various cardiovascular components. The third is an interaction model that represents the relations between the momentum and mass transport models. This model causes variations in the resistance and capacitance parameters of the momentum transport model as a function of the current drug concentrations in the appropriate compartments of the mass transport model. The capacitances representing the ventricles are varied in a time- dependent fashion to simulate the beat of the heart. Simulation is performed by using the Euler method to solve a system of 24 ordinary differential equations governing the momentum and mass transport models on a 32-bit micro computer, a Macintosh IIfx.
The model was assessed by performing a demonstration of the cardiovascular response to the dopamine during hemorrhage. The effect of hemorrhage upon to the cardiovascular system is added to the models as hemorrhagic model. The hemorrhagic model affects the momentum transport model by reducing total blood volume and changing the peripheral resistance, compliance, heart contractility and rate. Hemorrhage model reduces total blood volume, cardiac output, mean arterial pressure, central venous pressure, coronary flow, cerebral flow, renal flow and other ogans’ flow by 28 %, 49%, 43%, 58%, 15%, 16%, 65% and 53% respectively and increases heart rate and systemic vascular resistance by 53 % and 14% of each value in normal cardiovascular condition.
The effect of dopamine upon the cardiovascular system is incorporated into the interaction model. Administration of dopamine as a constant infusion (10 μg/kg/min.) during hemorrhagic hypotension results in the increase of cardiac output, mean arterial pressure, central venous pressure, coronary flow, cerebral flow, renal flow, and other ogans’ flow by 11 %, 16%, 6%, 6%, 7%, 24% and 8% of each value in normal cardiovascular condition from hemorrhagic level respectively.
Simulated hemodynamics during hemorrhage and dopamine infusion was similar to real hemodynamics. We believe that it will become possible to estimate the hemodynamics of dopamine administered to the bleeding patient before actual administration of the drug by adding parameter estimation to match the model to a real patient. Also, The simulation is very useful to educate medical students for hemodynamics.
KeywordsEquivalent Electrical Circuit Total Blood Volume Mass Transport Model Heart Contractility Cerebral Flow
Unable to display preview. Download preview PDF.
- 1.Smith, N.T. Mathematical Model of Uptake and Distribution of Inhalation Anaesthetic Agents. In Anesthesia par Inhalation, ed P. Viars, Paris: Arnette Publishers, 1987; 87–118.Google Scholar
- 2.Fukui, Y A study of the human cardiovascular-respiratory system using hybrid computer modeling. Ph.D. thesis at University of Wisconsin 1972Google Scholar
- 4.Fukui Y, Smith NT. Interactions among ventilation, the circulation, and the uptake distribution of halothane—Use of a hybrid computer multiple model: I. The basic model. Anesthesiology 1981; 54 (2): 107–118Google Scholar
- 5.Fukui Y, Smith NT. Interactions among ventilation, the circulation, and the uptake distribution of halothane—Use of a hybrid computer multiple model: II. Spontaneous versus controlled ventilation and the effects of C02. Anesthesiology 1981; 54 (2): 107–118Google Scholar
- 8.Guyton AC, Coleman TG. Long-Term regulation of the circulation: interrelationship with body fluid volumes. In: Reeve EB, Guyton AC eds. Physical basis of circulatory transport: Saunders, 1967; 179–201Google Scholar
- 9.Milhom Jr HD. The application of control theory to physiological systems. Philadelphia: W B Saunders, 1966Google Scholar
- 10.Nagumo J (ed) Physiological systems (in Japanese: Seitai sisutemu). Nikkan Kogyo Shimbun, Ltd., 1971.Google Scholar
- 11.Sunagawa K. and Sugawa K Models of ventricular contraction based on time-varying elastance. CRC Crit Rev Biom Eng 1982; Feb. 1982: 193–228Google Scholar
- 13.Greenway CV. Mechanisms and quantitative assessment of drug effects on cardiac output with a new model of the circulation. Pharmacological Reviews, 1982; 33 (4): 213–251Google Scholar
- 14.Yamada K, Hojima T and Marumo H. The parmacological studies on Dopamine (1) Effects on the blood pressure and various pharmacological preparations. OuyouYakuri, 1974; 8 (6): 835–846Google Scholar
- 15.Kubo K, Hojima T and Marumo H. The pharmacological studies on Dopamine (II) Effects of dopamine on the cardiovascular system in anesthetized dogs. OuyouYakuri, 1974; 8(6): 847–864Google Scholar
- 16.Hirano S, Fujitani S, Nakamura S, Tanimura C, Adachi H, Nakagawa M and Ijichi H. Hemodynamic effects of dopamine during hemorrhagic hypotension in anesthetized rats. Cardioangiology, 1979; 6 (4): 295–302Google Scholar
- 17.Runciman WB and Skowronski GA. Pathophysiology of hemorrhagic shock. Anaesth Intens Care, 1984; 12: 193–205Google Scholar
- 18.Kimoto S and Wada T (ed). New Encyclopedia of surgical science, 1990; 5: 59–70Google Scholar