Figure 4. Typical aortic input impedance magnitude (top graphs), phase (middle graphs), and coherence (bottom graphs) spectra obtained in the same dog on three experimental days in the control state (circles) and with high doses of isoflurane, halothane, and sodium nitroprusside (triangles). Frequency points with magnitude squared coherence less than 0.8 (dashed line) are not included in the top and middle graphs.