11 th International Research/Expert Conference ”Trends in the Development of Machinery and Associated Technology” TMT 2007, Hammamet, Tunisia, 05-09 September, 2007. SOME CONSIDERATIONS ON OPTIMAL DIAMETER OF A MECHANICAL VALVE PROSTHESIS AND ITS QUALITY EVALUATION PARAMETERS" Ileana Rosca Transilvania University 29, Bd. Eroilor, 500036 Brasov Romania ABSTRACT Cardiovascular illness treatment constitutes a vast market, the demand being extremely various from simple drugs till supporting circulation temporary devices for implanted artificial hearts. Concerning different “philosophical” considerations from the argument point of view, it must be mentioned that treatment is rarely resolving, more often a life quality improvement is obtained. The problem of valve prosthesis diameter is a very sensitive one, because its quality must ensure not only dimensional but also physiological parameters. In this paper we propose to present the dependence between valve’s diameter and its type, patient’s homodynamic characteristics and its physical activity. Also, in order to choose the appropriate diameter of a valve prosthesis one must take into account the relationship between pressure passing through valve, the temporary evolution of the blood volume and the cardiac frequency. Further, some dimensional and non-dimensional parameters that estimate the valve’s quality function are presented: the effective passing section, the effective free section, and reflux. 1. ELEMENTS OF HEART’S PHYSIOLOGY AND PATHOLOGY Many ill human parts need mechanical or electric devices: kidney, blood and vessels, valves, heart's muscle etc. Cholesterol particles and grease deposed internally to thicken blood vessels drive flow reduction, reduced oxygenation till occlusion. If the plates are deposed on valves (Figure 1), they can produce heart attack. Growing of cholesterol plates is foreseeing by angiographies, and other tests. Figure 1. Heart’s valves. Figure 2. Valvular functions. 1083