Pulse Wave Velocity in the Main Pulmonary Artery of the Dog

Apparent phase velocities in the main pulmonary artery were calculated from simultaneous measurements of pressure at two sites in 11 anesthetized, open-chest dogs, at heart rates ranging from 24 to 240 beat/min. The distribution of apparent phase velocity with harmonic frequency was similar to that reported previously for input impedance and frequency. Phase velocity in the absence of reflections, estimated by averaging apparent phase velocities at frequencies from 9 to 23 cycle/sec, averaged 275 cm/sec in the control state and 417 cm/sec during the infusion of 5-hydroxytryptamine (serotonin). The elastic modulus of the pulmonary arterial wall implied by these velocities was calculated to be approximately 1.2 × 106 dyne/cm2 in the controls and 2.7 × 106 dyne/cm2 during serotonin. These results are consistent with previous observations on normal pulmonary vascular input impedance in the dog under these conditions, and with the relationships predicted by the Womersley equations, and suggest that the effects of serotonin on the input impedance spectrum are due in part to an increase in pulse wave velocity.