The effects of superimposed tilt and lower body negative pressure on anterior and posterior cerebral circulations

Michael M. Tymko, Caroline Alice Rickards, Rachel J. Skow, Nathan C. Ingram-Cotton, Michael K. Howatt, Trevor A. Day

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Abstract

Steady-state tilt has no effect on cerebrovascular reactivity to increases in the partial pressure of end-tidal carbon dioxide (PETCO2). However, the anterior and posterior cerebral circulations may respond differently to a variety of stimuli that alter central blood volume, including lower body negative pressure (LBNP). Little is known about the superimposed effects of head-up tilt (HUT; decreased central blood volume and intracranial pressure) and head-down tilt (HDT; increased central blood volume and intracranial pressure), and LBNP on cerebral blood flow (CBF) responses. We hypothesized that (a) cerebral blood velocity (CBV; an index of CBF) responses during LBNP would not change with HUT and HDT, and (b) CBV in the anterior cerebral circulation would decrease to a greater extent compared to posterior CBV during LBNP when controlling PETCO2. In 13 male participants, we measured CBV in the anterior (middle cerebral artery, MCAv) and posterior (posterior cerebral artery, PCAv) cerebral circulations using transcranial Doppler ultrasound during LBNP stress (−50 mmHg) in three body positions (45°HUT, supine, 45°HDT). PETCO2 was measured continuously and maintained at constant levels during LBNP through coached breathing. Our main findings were that (a) steady-state tilt had no effect on CBV responses during LBNP in both the MCA (P = 0.077) and PCA (P = 0.583), and (b) despite controlling for PETCO2, both the MCAv and PCAv decreased by the same magnitude during LBNP in HUT (P = 0.348), supine (P = 0.694), and HDT (P = 0.407). Here, we demonstrate that there are no differences in anterior and posterior circulations in response to LBNP in different body positions.

Original languageEnglish
Article numbere12957
JournalPhysiological Reports
Volume4
Issue number17
DOIs
StatePublished - 1 Sep 2016

Fingerprint

Cerebrovascular Circulation
Lower Body Negative Pressure
Blood Volume
Intracranial Pressure
Head-Down Tilt
Blood Pressure
Posterior Cerebral Artery
Anterior Cerebral Artery
Doppler Ultrasonography
Passive Cutaneous Anaphylaxis
Partial Pressure
Supine Position
Middle Cerebral Artery
Carbon Dioxide
Respiration

Keywords

  • Central hypovolemia
  • cerebral blood velocity
  • head-down tilt
  • head-up tilt
  • lower body negative pressure

Cite this

Tymko, Michael M. ; Rickards, Caroline Alice ; Skow, Rachel J. ; Ingram-Cotton, Nathan C. ; Howatt, Michael K. ; Day, Trevor A. / The effects of superimposed tilt and lower body negative pressure on anterior and posterior cerebral circulations. In: Physiological Reports. 2016 ; Vol. 4, No. 17.
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abstract = "Steady-state tilt has no effect on cerebrovascular reactivity to increases in the partial pressure of end-tidal carbon dioxide (PETCO2). However, the anterior and posterior cerebral circulations may respond differently to a variety of stimuli that alter central blood volume, including lower body negative pressure (LBNP). Little is known about the superimposed effects of head-up tilt (HUT; decreased central blood volume and intracranial pressure) and head-down tilt (HDT; increased central blood volume and intracranial pressure), and LBNP on cerebral blood flow (CBF) responses. We hypothesized that (a) cerebral blood velocity (CBV; an index of CBF) responses during LBNP would not change with HUT and HDT, and (b) CBV in the anterior cerebral circulation would decrease to a greater extent compared to posterior CBV during LBNP when controlling PETCO2. In 13 male participants, we measured CBV in the anterior (middle cerebral artery, MCAv) and posterior (posterior cerebral artery, PCAv) cerebral circulations using transcranial Doppler ultrasound during LBNP stress (−50 mmHg) in three body positions (45°HUT, supine, 45°HDT). PETCO2 was measured continuously and maintained at constant levels during LBNP through coached breathing. Our main findings were that (a) steady-state tilt had no effect on CBV responses during LBNP in both the MCA (P = 0.077) and PCA (P = 0.583), and (b) despite controlling for PETCO2, both the MCAv and PCAv decreased by the same magnitude during LBNP in HUT (P = 0.348), supine (P = 0.694), and HDT (P = 0.407). Here, we demonstrate that there are no differences in anterior and posterior circulations in response to LBNP in different body positions.",
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The effects of superimposed tilt and lower body negative pressure on anterior and posterior cerebral circulations. / Tymko, Michael M.; Rickards, Caroline Alice; Skow, Rachel J.; Ingram-Cotton, Nathan C.; Howatt, Michael K.; Day, Trevor A.

In: Physiological Reports, Vol. 4, No. 17, e12957, 01.09.2016.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - The effects of superimposed tilt and lower body negative pressure on anterior and posterior cerebral circulations

AU - Tymko, Michael M.

AU - Rickards, Caroline Alice

AU - Skow, Rachel J.

AU - Ingram-Cotton, Nathan C.

AU - Howatt, Michael K.

AU - Day, Trevor A.

PY - 2016/9/1

Y1 - 2016/9/1

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AB - Steady-state tilt has no effect on cerebrovascular reactivity to increases in the partial pressure of end-tidal carbon dioxide (PETCO2). However, the anterior and posterior cerebral circulations may respond differently to a variety of stimuli that alter central blood volume, including lower body negative pressure (LBNP). Little is known about the superimposed effects of head-up tilt (HUT; decreased central blood volume and intracranial pressure) and head-down tilt (HDT; increased central blood volume and intracranial pressure), and LBNP on cerebral blood flow (CBF) responses. We hypothesized that (a) cerebral blood velocity (CBV; an index of CBF) responses during LBNP would not change with HUT and HDT, and (b) CBV in the anterior cerebral circulation would decrease to a greater extent compared to posterior CBV during LBNP when controlling PETCO2. In 13 male participants, we measured CBV in the anterior (middle cerebral artery, MCAv) and posterior (posterior cerebral artery, PCAv) cerebral circulations using transcranial Doppler ultrasound during LBNP stress (−50 mmHg) in three body positions (45°HUT, supine, 45°HDT). PETCO2 was measured continuously and maintained at constant levels during LBNP through coached breathing. Our main findings were that (a) steady-state tilt had no effect on CBV responses during LBNP in both the MCA (P = 0.077) and PCA (P = 0.583), and (b) despite controlling for PETCO2, both the MCAv and PCAv decreased by the same magnitude during LBNP in HUT (P = 0.348), supine (P = 0.694), and HDT (P = 0.407). Here, we demonstrate that there are no differences in anterior and posterior circulations in response to LBNP in different body positions.

KW - Central hypovolemia

KW - cerebral blood velocity

KW - head-down tilt

KW - head-up tilt

KW - lower body negative pressure

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DO - 10.14814/phy2.12957

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VL - 4

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JF - Physiological Reports

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