When cardio-pulmonary function fails, the heart and/or lung can be supported by various forms of mechanical circulatory support (MCS). The support can be temporary, prolonged or become destination therapy until an organ transplant is available. Common modes of mechanical circulatory support include extracorporeal membrane oxygenation (ECMO), ventricular assist devices (VAD’s), and intra-aortic balloon pumps. All these devices seek to augment, replace or restore the function of the heart. Not matter the device, obtaining accurate flow measurements is essential to understanding complete physiology for improved patient outcomes and management.