| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Received February 9, 2004
Revised March 8, 2004
Accepted after revision April 6, 2004
1 University of Leeds
2 Leeds Teaching Hospitals
* To whom correspondence should be addressed. E-mail: mrpvlw{at}leeds.ac.uk.
Obstructive sleep apnoea (OSA), which is characterised by periodic inspiratory obstruction, is associated with hypertension and possibly with changes in the baroreceptor reflex. In this investigation we induced changes in inspiratory resistance and in inspiratory oxygen and carbon dioxide content, which simulate some of the changes in OSA to determine whether this caused changes in the gain or setting of the carotid baroreflex. In 8 healthy subjects (aged 21-62 years) we changed the stimulus to carotid baroreceptors, using neck chambers and graded pressures of -40 to +60 mmHg, and assessed vascular resistance responses in the brachial artery from changes in blood pressure (Finapres) divided by brachial artery blood flow velocity (Doppler ultrasound). Stimulus response curves were defined during (a) sham (no additional stimulus), (b) addition of an inspiratory resistance (inspiratory pressure -10mmHg), (c) breathing asphyxic gas (12%O2, 5% CO2), (d) combined resistance and asphyxia. Sigmoid or polynomial functions were applied to the curves and maximum differentials (equivalent to peak gain) and the corresponding carotid pressures (equivalent to "set point") were determined. The sham test had no effect on either gain or "set point". Inspiratory resistance alone had no effect on blood pressure and did not displace the curve. However, it reduced gain from -3.0 ± 0.6 to -2.1 ± 0.4 units (P<0.05). Asphyxia alone did increase blood pressure (+7.0 ± 1.1 mmHg, P<0.0005) and displaced the curve to higher pressures by +16.8 ± 2.1 mmHg (P<0.0005). However, it did not affect gain. The combination of resistance and asphyxia both reduced gain and displaced the curve to higher pressures. These results suggest that inspiratory resistance and asphyxia cause changes in the baroreceptor reflex which could lead to an increase in blood pressure. These changes, if sustained, could provide a mechanism linking hypertension to obstructive sleep apnoea.
This article has been cited by other articles:
|
|
 |
|
  V. L. Cooper, M. W. Elliott, S. B. Pearson, C. M. Taylor, M. M. J. Mohammed, and R. Hainsworth Cardiovascular Control: Daytime variability of baroreflex function in patients with obstructive sleep apnoea: implications for hypertension Exp Physiol, March 1, 2007; 92(2): 391 - 398. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. P. Moore, V. E. Claydon, L. J. Norcliffe, M. C. Rivera-Ch, F. Leon-Velarde, O. Appenzeller, and R. Hainsworth Carotid baroreflex regulation of vascular resistance in high-altitude Andean natives with and without chronic mountain sickness Exp Physiol, September 1, 2006; 91(5): 907 - 913. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. D. Monahan, U. A. Leuenberger, and C. A. Ray Effect of repetitive hypoxic apnoeas on baroreflex function in humans J. Physiol., July 15, 2006; 574(2): 605 - 613. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. V. Robinson, D. M. Smith, B. A. Langford, R. J. O. Davies, and J. R. Stradling Continuous positive airway pressure does not reduce blood pressure in nonsleepy hypertensive OSA patients Eur. Respir. J., June 1, 2006; 27(6): 1229 - 1235. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. L Cooper, S. B Pearson, C. M Bowker, M. W Elliott, and R Hainsworth Interaction of chemoreceptor and baroreceptor reflexes by hypoxia and hypercapnia - a mechanism for promoting hypertension in obstructive sleep apnoea J. Physiol., October 15, 2005; 568(2): 677 - 687. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
