PulsOxy – Pulsatile flows to improve function of a long-term oxygenator
State of current research
Extracorporeal lung assist is used during acute respiratory distress syndrome or chronic obstructive lung disease. Among other parts these systems include a blood pump and an oxygenator. The pump constantly supports the blood through the extracorporeal circuit, while the oxygenator ensures the gas exchange with the blood. The gas exchange occurs through a microporous membrane, which separates the gas and the blood phase. Due to diffusion the oxygen passes into and carbon dioxide is eliminated from the blood. Despite technical advancements, long-term durability of oxygenators in Extracorporeal Membrane Oxygenation (ECMO) circuits is still limited to 1 – 2 weeks, because due to protein deposition on the membrane and formation of thrombi the performance of the oxygenator gets worse. As an ECMO therapy normally endures several weeks the oxygenator needs to be exchanged during the therapy which means increased stress for the patient. For that reason it is desirable to increase the period of application of the oxygenator.
The aim of this project is the investigation of the influence of pulsatile blood flow on an ECMO circuit regarding gas transfer efficiency and hemocompatibility, and thus on a prolonged period of use. There are some cases described in literature, where pulsatile blood flow has a positive effect on patient and performance of the oxygenator . But also there are cases, which cannot confirm these statement . The hypothesis is, that the mixing of blood in the oxygenator is lower with constant blood flow than with pulsatile blood flow. Therefore, constant blood flow develops more dead water areas with negative influence on the hemocompatibility. So a better mixing of blood during pulsatile blood flow may reduce the static areas and the deposition of fibrin on the membrane. Consequently, the membrane might ensure a longer gas exchange and therefore a longer application period of the oxygenator.
During the project we evolve a laboratory prototype with well described blood flow and distribution and a pump control, which generate pulsatile flow profiles. The flow profiles are assessed and selected in regard to the technical and medical background. With the laboratory prototypes we will perform comparative, systematic, and standardized in-vitro experiments with both constant and pulsatile blood flow. The effects of blood flow conditions on gas exchange and hemocompatibility will be examined in separate experiments.
 G. Wright. Mechanical Simulation of Cardiac Function by means of pulsatile blood pumps Journal of Cardiothoracic and Vascular Anesthesia, 11(3): 299-309, 1997
 G. Chow, I. Roberts, D. Edwards, A. Lliyd-Thomas, A. Wade, M. Elliott & F. Kikham. The relation between pump flow rate and pulsatility on cerebral hemodynamics during pediatric cardiopulmonary bypass. The Journal of Thoracic and Cardiovascular Surgery, 114: 568-577, 1997.