Tachtsidis, I and Elwell, CE and Leung, TS and Bleasdale-Barr, K and Hunt, K and Toms, N and Smith, M and Mathias, CJ and Delpy, DT (2005) Rate of change in cerebral oxygenation and blood pressure in response to passive changes in posture: A comparison between pure autonomic failure patients and controls. OXYGEN TRANSPORT TO TISSUE XXVI , 566 187 - 193.
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The cardiovascular and cerebrovascular responses to head-up postural change are compromised in pure autonomic failure (PAF) patients because of sympathetic denervation. The aim of this study was to characterize the rate of change of systemic mean blood pressure (MBP) and cerebral haemodynamics in response to passive posture changes. Nine PAF patients and 9 age-matched controls took part in this study. MBP and oxy (O(2)Hb), deoxy-haemoglobin (HHb), and tissue oxygenation index (TOI) on the forehead were continuously monitored non-invasively using the Portapres (R) and near-infrared spectroscopy (NIRS), respectively. From visual inspection of the haemoglobin difference signal (Hb(diff) = O(2)Hb-HHb), seven distinct phases were marked (1: supine, 2: start passive tilt, 3: head up to 60 degrees degrees, 4: end of tilt, 5: tilt reversal, 6: return to supine, 7: rest); the same time points were used for all of the other signals. For each phase, the slope was calculated using a linear regression algorithm. Significant differences were found between PAF patients and controls in the Hb(diff) slope magnitude for phases 3 (P < .05) and 5 (P = .01), and the duration of phase 2 (P < .05). MBP slope magnitudes showed significant differences for phases 2 (P < .01) and 5 (P < .01). These differences in the rate of change suggest differences in blood vessel resistance related to sympathetic activation.
|Title:||Rate of change in cerebral oxygenation and blood pressure in response to passive changes in posture: A comparison between pure autonomic failure patients and controls|
|Location:||Univ Rochester, Rochester, NY|
|Keywords:||NEAR-INFRARED SPECTROSCOPY, ORTHOSTATIC HYPOTENSION|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Neurology > Brain Repair and Rehabilitation|
UCL > School of BEAMS > Faculty of Engineering Science > Medical Physics and Bioengineering
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