Left ventricle (LV) distension is a complication of venoarterial extracorporeal membrane oxygenation (VA-ECMO) support. The effects of Impella on the pulmonary circulatory physiology were studied in a single-center study of six consecutive patients on VA-ECMO support who had LV unloading with Impella. Right ventricular stroke volume, pulmonary hemodynamics, and partial pressure of end-tidal CO2 (PETCO2) were measured on echocardiogram, pulmonary artery catheter, and capnography, respectively. The addition of Impella CP increased total blood flow and reduced pulmonary artery wedge pressure. There was a small reduction in arterial oxygen saturation as Impella increased LV output. The increase in pulmonary artery capacitance (PCap) exceeded the reduction in pulmonary vascular resistance (PVR), thereby increasing the pulmonary artery time constant (product of PCap and PVR). The right ventricular stroke volume increased and the improvement in pulmonary hemodynamics and blood flow were associated with reduced arterial-PETCO2 gradient. The Impella CP unloads the LV during VA-ECMO support, increasing total flow, reducing RV afterload, and facilitating RV output and pulmonary blood flow with improvement in gas exchange.