Fig. 1. Composite left pulmonary vascular pressure–flow (LPQ) plots in eight dogs at baseline and after U46619 preconstriction (*P < 0.01) in the conscious state and during halothane anesthesia. Compared with the conscious state, halothane had no net effect on the baseline LPQ relationship. The dose of U46619 was titrated to achieve the same degree of preconstriction in the conscious and halothane-anesthetized states.