Overview
Without a shunt or extracorporeal bypass, pulmonary flow and systemic forward flow are the same circulation flow in the model. Regurgitant volume is not counted as extra useful systemic cardiac output.
Shunts introduce separate Qp and Qs, with modeled direction, recirculation and oxygen-content information. Changing resistance or support can change their relationship.
V-A ECMO is a bypass exception: venous drainage and arterial return do not pass through the pulmonary circulation. The support summary explains native flow and device contributions so pulmonary resistance is not calculated from the wrong flow.