Termodinámica de la mezcla estáticaaplicaciones médicas y medio ambientales

Abstract

lntroduction: Since the 80's, the control of the infusion mechanisms has been a main goal in arder to fulfill different necessities, e.g. control of the plasmatic levels or the concentration at the target organ. To this end, three possibilities have been explored, namely: computer assisted infusion bombs - Target Controlled lnfusion (TCI)-, manual protocols -Manually Controlled lnfusion (MCI)-, which emulate what infusion bombs do, and control of the infusion through static mixing -Physically Controlled lnfusion (PhCI)-, the later not used due to the lack of information on it. At present we can consider the mixing mechanisms to be understood, but not so the influence, on these mixers, of the air chamber inside of the container in the way it has been used so far. Objective: The general goal is the study of the influence of the thermodynamic variables on the behavior of static mixture mixing devices containing two phases: liquid and gas. Material and methods: Experiments with continuous gravimetry, dynamic pycnometry, have been designad and conducted to quantify the weight and volume changes caused by the variation of both the static and dynamic pressure of the infusion system. After this experimental phase, we developed calibration procedures for the mixer, understood as a pycnometer, in arder to work without the gas phase and to be able to evaluate the density variations during the mixing process. Results: For the different variations on the pressure, we have obtained, without variation of the density; weight curves with kinetic behavior of arder one. In the pycnometric experiments we measured the variations of the density with time, resulting in a kinetic behavior of arder one as well, but not in accordance with the stablished theoretical model. Discussion: Thermodynamically, this system has been classified as isothermal, with a gaseous phase behaving as an ideal gas. We checked the existence of influences because of the existence of the gaseous phase and evaluated their physical and clinic implications, stating the necessary conditions for the design and development of devices for the intravenous administration of drugs with physical control of the infusion. One of the facts proven is that the hypothesis (that is, that this kind of systems work in a stationary state), assumed from the beginning and by the scientific community, is clearly flawed, since the weight and volume exponentials do not agree in the pycnometric experiments. Hence, the necessity of understanding better this fact with new experiments; these devices work in pseudostationary state and the concentration is not the only variable that is modified, but also the density. Conclusions: We have proven the influence of the kinematics of the mixture in the existence of a gaseous phase and the necessity of excluding it. These devices work in a pseudostationary state, so we have to study the behavior of the concentration and the density, as well as their behavior when the mixture contains several salutes and the solution is multicomponent.