Design and performance of a new membrane lung

The evolution of cardiopulmonary bypass: lessons to be learned

John Gibbon conceived cardiopulmonary bypass (CPB) and performed the first intracardiac repair using extracorporeal perfusion in 1953. This achievement stimulated rapid development of the knowledge base and equipment necessary for accurate diagnoses and successful intracardiac operations. In the early 60s increasing evidence indicated that exposure of blood to nonendothelial cell surfaces produced bleeding and thrombotic complications and a massive inflammatory response. Early efforts to discover a synthetic, nonthrombogenic surface gave way to efforts to control the 'whole-body inflammatory response' by pharmacological means. These efforts are ongoing; progress is slow; and heparin is still required for most applications of extracorporeal perfusion technology. Nevertheless, CPB now enables over one million cardiac surgical operations each year. Future progress and the development of artificial internal organs that process blood depend upon control of the blood-surface interface without anticoagulants.

In vitro performance assessment of tubular membrane oxygenators

The definite advantage in oxygen transfer performance of staged (single, double and triple) tubular membrane oxygenators (TMO) is compared with reference to flat membrane oxygenators (Travenol or Landé Edwards). The overall construction of staged TMO with a blood mixing chamber is a very good way to destroy the blood boundary layer and modify the blood stagnant zone in the device. Four sizes of staged TMO were studied using the principle that gases dissolve in water in concentrations linearly proportional to the partial pressures of the gases when in equilibrium with the liquid. The experimental results show that the oxygen transfer rate and the corresponding overall oxygen mass transfer coefficient of staged TMO are increased by the same order as those of the reference membrane oxygenators. Furthermore the essential parameter analysis prove that oxygen transfer increases with the number of stages and decreases with the length of the blood tubular modules. The multistage design of TMO revealed an increase in the hydrodynamic resistance occurring in the apparatus. However the highest relative oxygen transfer efficiency suggests that better fluid distribution as well as better uniformity of oxygenation prevail in the staged devices.