Author's present address P. J. Fadel: Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390–8586, USA.
Haemodynamic changes during neck pressure and suction in seated and supine positions
Article first published online: 22 JUL 2004
The Journal of Physiology
Volume 540, Issue 2, pages 707–716, April 2002
How to Cite
Ogoh, S., Fadel, P. J., Monteiro, F., Wasmund, W. L. and Raven, P. B. (2002), Haemodynamic changes during neck pressure and suction in seated and supine positions. The Journal of Physiology, 540: 707–716. doi: 10.1113/jphysiol.2001.013259
- Issue published online: 22 JUL 2004
- Article first published online: 22 JUL 2004
- (Received 7 September 2001; accepted after revision 16 January 2002)
We sought to quantify the contribution of cardiac output (Q) and total vascular conductance (TVC) to carotid baroreflex-mediated changes in mean arterial pressure (MAP) in the upright seated and supine positions. Acute changes in carotid sinus transmural pressure were evoked using brief 5 s pulses of neck pressure and neck suction (NP/NS) via a simplified paired neck chamber that was developed to enable beat-to-beat measurements of stroke volume using pulse-doppler ultrasound. Percentage contributions of Q and TVC were achieved by calculating the predicted change in MAP during carotid baroreflex stimulation if only the individual changes in Q or TVC occurred and all other parameters remained at control values. All NP and NS stimuli from +40 to −80 Torr (+5.33 to −10.67 kPa) induced significant changes in Q and TVC in both the upright seated and supine positions (P < 0.001). Cardiopulmonary baroreceptor loading with the supine position appeared to cause a greater reliance on carotid baroreflex-mediated changes in Q. Nevertheless, in both the seated and supine positions the changes in MAP were primarily mediated by alterations in TVC (percentage contribution of TVC at the time-of-peak MAP, seated 95 ± 13, supine 76 ± 17 %). These data indicate that alterations in vasomotor activity are the primary means by which the carotid baroreflex regulates blood pressure during acute changes in carotid sinus transmural pressure.