Desenvolvimento tecnológico dos oxigenadores de membrana

Abstract

RBCCV 44205-782Desenvolvimento tecnológico dos oxigenadores de membrana Technological evolution of membrane oxygenatorsDescriptors: Oxygenators, membrane. Extracorporeal circulation.Descritores: Oxigenadores de membrana. Circulação extracorpórea. INTRODUCTIONThe first attempts of oxygenating blood outside the body were made by physiologists in the XIX century in their studies on perfusion of organs isolated from animals.The first modern studies dedicated to artificial oxygenation of blood, with the objective of maintaining the life of an organism, dated from 1937 and were performed by John Gibbon [1]. In the years that followed, Gibbon dedicated his research to the improvement of this revolutionary technique [2][3][4]. Several researchers, encouraged by the possibility of building apparatuses capable of replacing cardiopulmonary functions, started to build oxygenators [5][6][7].Oxygenators must be capable of oxygenating approximately five liters of blood per minute and to remove the carbon dioxide (CO 2 ) in order to artificially support the life of an adult. Moreover, heat exchange must be optimized in the least possible surface area, whilst the trauma caused to blood elements must be minimal. The priming necessary to operate the apparatus must also be small, in order to allow its use with acellular solutions, avoiding excessive hemodilution and unnecessary transfusions of blood or blood derivatives [8].Several forms of supplying oxygen (O 2 ) to the blood have been attempted, with more or less success, enabling the development of many models of oxygenators of which only a few have been clinically employed. DRUMMOND, M ET AL -Technological evolution of membrane oxygenatorsBraz J Cardiovasc Surg 2005; 20(4): 432-437 Later, other membrane oxygenators with similar configurations to the original project of Clowes & Neville [16] were used [5,17,18]. Kolobow et al. [19], based on the Kolff model, projected an oxygenator composed of long strips of silicon sustained by an envelope with spacers to stop the membranes from sticking together. In this model, the blood flowed inside the strips and O 2 circulated parallel to the central axis that sustained the reel of membranes. As this model functioned adequately for long periods, it was utilized in prolonged ventilatory support procedures. The Kolobow oxygenator was continuously improved and is currently produced and sold by the American Company, Avecor. It is the only oxygenator on the market recommended for prolonged use.The first-generation membrane oxygenators had great resistance to the passage of blood through the membranes which was impossible to overcome by siphoning alone. Some apparatuses were set up on the side of the positive pressure of a peristaltic pump, whilst others required an additional pump to circulate the blood in the membrane chamber. Because of the difficulties with gas exchanges and the complexity of their construction and use, the first-generation membrane oxygenators were not very well accepted. The development of technology to produce expand...