01.5 Mechanical intervention of the pulmonary vessels ("pooling")

This is the direct consequence of what has happened before. On inspiration, the right ventricle is supplied with blood and produces a substantial ejection which is stored in the pulmonary circulation, which cannot be emptied because it is blocked by the downstream obstacle constituted by a rigid left ventricle. Expiratory improvement in left ventricular distensibility lifts the blockage of the pulmonary circulation, and the elastic recoil of the pulmonary circulation drives the blood towards the left chambers on expiration.