Pulmonary Vasoconstriction in Response to Precapillary Hypoxemia*

The pulmonary arterial pressor response to acute hypoxia is generally attributed to pulmo- nary vasoconstriction (1). Moreover, the dem- onstration that the pulmonary pressor response can occur without the intervention of either the autonomic nervous system (2-4) or known neurohumoral mediators (5, 6) has led to the popular view that the pulmonary vasoconstric- tion is a consequence of local effects of acute hypoxia on the vascular wall (7).