An intra-aortic balloon pump (IABP) is used during acute cardiogenic shock (CS) to mechanically assist the heart and therewith stop or reverse the cardiac deterioration. It already has been used for many years as a fast and easily applicable therapy, although many questions are still unanswered about the exact functioning and influence on therapy outcome. This project focuses on one of these unanswered questions, with its topic being the influence of patient-posture on IABP therapy. IABP patients are mostly positioned horizontally. In this position the hydrostatic pressure is practically equal in the vascular system. Therefore the influence of gravity on the IABP therapy seems to be negligible. However, there is no clear evidence that this position gives the optimal therapy outcome or that a more comfortable semi-recumbent patient position would influence the therapy. Several investigations were done where the patient position is changed from a horizontal position to a semirecumbent position (, , ). The main outcome is that the position changes the functioning. With invitro experiments a change in IAB behavior is observed and for in-vivo experiments a decrease in mean aortic pressure and a decrease in left anterior descending flow velocity . For these in-vivo measurements it is unclear if this change occurs due to the change in hydrostatic pressure or due to the change of the IABP functioning. The goal of this project is to obtain an understanding of the influence of patient-posture ont he IABP-therapy. This includes the gravity influence on the therapy for different IAB sizing and different patient-depending parameters like aortic diameter and stiffness. The IABP system properties are investigated to obtain a proper view on its functioning and its specifications. After this an existing model, namely the 1D-wave propagation model by Kroon & Huberts , is further elaborated to include a IABP with the mentioned phenomena. This numerical model is then used to investigate the functioning of the IAB under pathological heart conditions. By varying the different parameters the influence of patient position in combination with the relevant parameters is investigated. The results of an aorta with IABP included do not represent a similar flow and pressure response as measured in patient data, since there is no clear diastolic pressure augmentation. This makes it difficult to compare the results directly with the situation without IABP. However, the results show a realistic behavior of the IAB. This means that it can be used to investigate the IAB behavior. Summarizing the results it can be concluded that the patient-position has an influence on the IABP therapy. The IAB in- and deflation is affected and causes small changes in pressure and flow at proximal and distal positions in the aorta. However, it is not possible to give a conclusion on how this affects the therapy. This because the position related effect is small and the results do not show a clear pressure augmentation, which could also influence the IAB behavior.