Multiple model approach to uptake and distribution of halothane: The use of an analog computer

Abstract

This paper describes a multiple analog computer model of the uptake and distribution of the anesthetic agent halothane. The model consists of two interdependent loops, one representing the blood circulation and another representing the halothane transport. Cardiac output and regional conductances are influenced in relation to the concentration of halothane in some relevant compartment of the model. Computer generated curves are given to show the response of alveolar concentration, arterial pressure and cerebral blood flow to step and pulse changes in inspired concentration. For evaluation of the model, other variables than alveolar concentration, such as, arterial pressure and blood flow may often be more useful. The present model will be used to develop an automatic control system for the administration of anesthesia.

Modelling and multi-parametric control for delivery of anaesthetic agents

“…For anaesthesia, some of the models that have been reported in the open literature are: (i) pharmacokinetic and pharmacodynamic model of Zwart et al [34] for uptake of halothane, a volatile anaesthetic, and its influence on CO and MAP, (ii) five-compartment model of Yasuda et al [29][30][31] for the distribution of isoflurane, a volatile anaesthetic, and (iii) circulatory model of Yu et al [32] for haemodyanmic repsonses to intravenous agents, dopamine (DP) and sodium nitroprusside (SNP), in case of an acute heart failure.…”

“…The controllers for anaesthesia can be broadly classified based upon their application for: (i) regulation of hemodynamic variables [2,8,12,13,16,18,26,28,[32][33][34] and (ii) simultaneous regulation of haemodynamic and other states of anaesthesia [1,11,17,20]. Control of anaesthesia is based upon reliable measurements and estimation of state variables.…”

Modelling Inert Gas Exchange in Tissue and Mixed–Venous Blood Return to the Lungs

“…If a subject is given an inhaled anaesthetic, with a constant inspired concentration, then the arterial blood partial pressure will rise from zero up to an asymptotic value with time [see, for e.g., Mapleson (1963Mapleson ( , 1973 and Zwart et al (1971)]. …”

Correlation of canine electroencephalographic activity during surgical anesthesia

“…The model was incorporated in this research as a means to utilize, in a quantitative manner, the results obtained by Zwart et al (1972). The inputs to the model were the desired halothane concentrations which were selected via adjustments on the anesthetic machine.…”

“…The nonlinear aspects of the system were accommodated through the use of a piecewise approximation. Table 3 of Zwart et al (1972) provided the volume flow rates for 2 levels of halothane. These levels were divided into 4 equal ranges, and the flow parameters were linearly interpolated at the midpoint of each range.…”