Pulmonary hemodynamic responses to elevated cerebral spinal fluid pressure in the dog

To investigate the possibility that a pulmonary vasomotor reflex contributes to the pulmonary hemodynamic response to elevated cerebral spinal fluid pressure (PCSF), we studied 10 chloralose-anesthetized dogs in which the left lower lobe (LLL) perfusion was isolated to eliminate the influence of passive factors and of circulating vasoactive agents. Left lower lobe neural integrity was tested by electrically stimulating the stellate ganglion. This resulted in a 35.5% increase in lobar vascular resistance and a 29.1% increase in systemic vascular resistance. Elevating the PCSF to 137 Torr caused the systemic vascular resistance to increase 33.0%, but resulted in no change in LLL vascular resistance. In the intact right lung, this PCSF elevation resulted in increases in pulmonary artery and left atrial pressures, but no change in right lung vascular resistance. Because the neurally intact LLL did not respond to PCSF elevation and the responses of the right lung could be accounted for by passive mechanisms, we conclude that no pulmonary vascular reflex was elicited by PCSF elevation in this preparation.