Does gradual change in head positioning affect cerebrovascular physiology?. Issue 3 (8th February 2018)

• Record Type: Journal Article
• Authors: Lam, Man Y.; Haunton, Victoria J.; Robinson, Thompson G.; Panerai, Ronney B.
• Is Part Of: Physiological reports. Volume 6:Issue 3(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-02-08
• Subjects: Cerebral autoregulation -- head positioning -- reproducibility; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.13603
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: We studied cerebral blood velocity (CBV), and associated hemodynamic parameters during gradual changes in head positioning in a nonstroke group. CBV (transcranial Doppler ultrasound), beat‐to‐beat blood pressure (BP, Finometer), and end‐tidal carbon dioxide (ETCO2, capnography) were recorded between lying flat (0°) and sitting up (30°) head positions, in 18 volunteers (10 female, mean age, 57 ± 16 years), at two visits (12 ± 8 days). A significant reduction was found between 5‐min FLAT (0°) and 5‐min SIT (30°) positions in CBV (visit 1: 4.5 ± 3.3%, P = 0.006; visit 2: 4.1 ± 3.5%, P = 0.003), critical closing pressure (CrCP; visit 1: 15.5 ± 14.0%, P = 0.0002; visit 2: 14.1 ± 7.8%, P = 0.009) and BP (visit 1: 8.3 ± 7.4%, P = 0.001; visit 2: 11.0 ± 11.3%, P < 0.001). For 5 min segments of data, the autoregulation index and other hemodynamic parameters did not show differences either due to head position or visit. For 30 sec time intervals, significant differences were observed in the following: (BP, P < 0.001; dominant hemisphere (DH) CBV, P < 0.005; nondominant hemisphere (NDH) CBV, P < 0.005; DH CrCP, P < 0.001; NDH CrCP, P < 0.001; DH resistance area product (RAP), P = 0.002; NDH RAP, P = 0.033). Significant static changes in BP, CBV and CrCP, and large transient changes in key hemodynamic parameters occur during 0° to 30°, and vice versa, with reproducible results. Further studies are needed following acute ischemic stroke to determine if a similar responses is present. Abstract : This study assessed the reproducibility of cerebral hemodynamic parameters before, during, and after a gradual change of head positioning in a nonstroke group. Despite significant transient changes in cerebral blood velocity (CBV) and other hemodynamic parameters, dynamic cerebral autoregulation (dCA) calculated over a 5‐min period was not affected by gradual changes in head positioning. These findings provide the necessary framework to study the effects of head positioning in patients with acute stroke and other conditions associated with cerebral or vascular perturbations.