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Middle cerebral artery blood flow velocity in response to lower body positive pressure

Perry, B.G., Schlader, Z.J., Raman, A., Cochrane, D.J., Lucas, S.J.E. and Mündel, T. (2013) Middle cerebral artery blood flow velocity in response to lower body positive pressure. Clinical Physiology and Functional Imaging, 33 (6). pp. 483-488.

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Lower body positive pressure (LBPP) has been used in the treatment of haemorrhagic shock and in offsetting g-force induced fluid shifts. However, the middle cerebral artery blood flow velocity (MCAv) response to supine LBPP is unknown. Fifteen healthy volunteers (mean ± SD: age, 26 ± 5 year; body mass, 79 ± 10 kg; height, 174 ± 9 cm) completed 5 minutes of 20 and 40 mm Hg LBPP, in a randomized order, separated by 5 minutes rest (baseline). Beat-to-beat MCAv and blood pressure, partial pressure of end-tidal carbon dioxide (PETCO2) and heart rate were recorded and presented as the change from the preceding baseline. All measures were similar between baseline periods (all P>0·30). Mean arterial pressure (MAP) increased by 7 ± 6 (8 ± 7%) and 13 ± 7 mm Hg (19 ± 11%) from baseline during 20 and 40 mm Hg (P<0·01), respectively. The greater MAP increase at 40 mm Hg (P<0·01 versus 20 mm Hg) was mediated via a greater increase in total peripheral resistance (P<0·01), with heart rate, cardiac output (Model flow) and PETCO2 remaining unchanged (all P>0·05) throughout. MCAv increased from baseline by 3 ± 4 cm s-1 (5 ± 5%) during 20 mm Hg (P = 0·003), whilst no change (P = 0·18) was observed during 40 mm Hg. Our results indicate a divergent response, in that 20 mm Hg LBPP-induced modest increases in both MCAv and MAP, yet no change in MCAv was observed at the higher LBPP of 40 mm Hg despite a further increase in MAP.

Publication Type: Journal Article
Murdoch Affiliation: School of Psychology and Exercise Science
Publisher: Blackwell Publishing
Copyright: © 2013 Scandinavian Society of Clinical Physiology and Nuclear Medicine
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