Pump

Centrifugal pumps use a rotating system of blades (called impellers) that are magnetically coupled to a motor. The blades spin to create a vortex, resulting in a pressure difference to drive the blood flow. This generates the suction on the inflow catheter and pushes the deoxygenated blood into the blood gas-exchange unit. Typical pump speeds are between 2000 and 6000 rotations per minute (RPM), and the rate at which the blood travels through the pump is the flow (L/min). An external interface displays the speed, flow, inflow and outflow pressures and their difference (Dp). The pump settings can also be adjusted using this interface.

Flow depends on various circuit factors, such as pump speed (RPM), blood volume, preload, downward resistance and afterload. A higher flow will be determined by higher pump speed, high blood volume or high preload. In contrast, high down- stream resistance or afterload will lead to low flows. Blood flow (L/min) is fundamental in V-V ECMO, and hemodynamic stability is necessary to run V-V ECMO, as it supports only pulmonary and not cardiac function. V-V ECMO will contribute to systemic oxygenation depending on the flow rate relative to the patient’s CO (this is the blood flow/CO ratio).