Fig. 1. Mean values of pulmonary arterial pressure (PAP), left atrial pressure (LAP), and left pulmonary blood flow (LQ) before and during gradual right pulmonary artery occlusion (RPA occl) in an individual conscious dog during normoxia and hypoxia. The continuous left pulmonary vascular pressure–flow (LPQ) plots generated from these raw traces during normoxia and hypoxia are shown in the lower panel. Note that the LPQ plots are linear and that hypoxia caused a leftward shift in the LPQ relationship.