Gravitational effects on intracranial pressure and blood flow regulation in young men: a potential shunting role for the external carotid artery

Ogoh, Shigehiko; Washio, Takuro; Paton, Julian F. R.; Fisher, James; Petersen, Lonnie G.

doi:10.1152/japplphysiol.00369.2020

Cited by 10 publications

(13 citation statements)

References 42 publications

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“…Previous reports have found that steady-state CBF was preserved during −10° HDT for 5–10 min ( 10 , 16 ) consistent with the present results of no change in mean MCAV during −10° HDT. In addition, Ogoh et al reported no changes in internal carotid artery blood flow during −10° and −20° HDT for 10 min ( 34 ). The present study showed no change in steady-state CBF during −30° HDT for 10 min.…”

Section: Discussionmentioning

confidence: 99%

Effects of −10° and −30° head-down tilt on cerebral blood velocity, dynamic cerebral autoregulation, and noninvasively estimated intracranial pressure

Kato

Kurazumi

Konishi

et al. 2022

Journal of Applied Physiology

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Background: Steady-state cerebral blood flow (CBF) and dynamic cerebral autoregulation are reportedly maintained during -10° head-down tilt (HDT) despite slight increases in intracranial pressure (ICP). However, the higher ICP during -30° HDT may alter steady-state CBF and dynamic cerebral autoregulation. The present study hypothesized that steady-state CBF and dynamic cerebral autoregulation would be altered by higher ICP during -30° HDT than during 0° and -10° HDT. Methods: Seventeen healthy participants were positioned horizontal (0°) and in -10° HDT and -30° HDT for 10 min in random order on separate days. The arterial blood pressure waveform was obtained using a finger blood pressure device and the cerebral blood velocity waveform in the middle cerebral artery was obtained using transcranial Doppler sonography (TCD) for the last 6 min in each position. ICP was estimated using non-invasive ICP (nICP) based on TCD. Dynamic cerebral autoregulation was evaluated by spectral and transfer function analysis. Results: Although nICP was significantly higher during -30° HDT (12.4 mmHg) than during -10° HDT (8.9 mmHg), no significant differences in steady-state mean cerebral blood velocity or transfer function gain in any frequency ranges were seen among all angles of HDT. Conclusion: Counter to our hypothesis, the present results suggest that steady-state CBF and dynamic cerebral autoregulation may be preserved during short-term -30° HDT despite the higher ICP compared to that during -10° HDT.

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Section: Discussionmentioning

confidence: 99%

Effects of −10° and −30° head-down tilt on cerebral blood velocity, dynamic cerebral autoregulation, and noninvasively estimated intracranial pressure

Kato

Kurazumi

Konishi

et al. 2022

Journal of Applied Physiology

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“…Hirasawa et al [71] reported a plateau in ICA flow 60 s into a 120-s unilateral static leg contraction at 30% of MVC. External carotid artery blood flow, however, demonstrated a continual rise, concurrent with small increases in MAP in the later stages, indicative of a potentially protective mechanism by directing flow extracranially during hypertension [83]. Whether this persists during dynamic exercise with larger increases in MAP is unknown, and difficult to assess with current imaging methodologies (see Measurement challenges and considerations).…”

Section: Static Resistance Exercisementioning

confidence: 99%

The Acute Cardiorespiratory and Cerebrovascular Response to Resistance Exercise

Perry

Lucas

2021

Sports Med - Open

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Resistance exercise (RE) is a popular modality for the general population and athletes alike, due to the numerous benefits of regular participation. The acute response to dynamic RE is characterised by temporary and bidirectional physiological extremes, not typically seen in continuous aerobic exercise (e.g. cycling) and headlined by phasic perturbations in blood pressure that challenge cerebral blood flow (CBF) regulation. Cerebral autoregulation has been heavily scrutinised over the last decade with new data challenging the effectiveness of this intrinsic flow regulating mechanism, particularly to abrupt changes in blood pressure over the course of seconds (i.e. dynamic cerebral autoregulation), like those observed during RE. Acutely, RE can challenge CBF regulation, resulting in adverse responses (e.g. syncope). Compared with aerobic exercise, RE is relatively understudied, particularly high-intensity dynamic RE with a concurrent Valsalva manoeuvre (VM). However, the VM alone challenges CBF regulation and generates additional complexity when trying to dissociate the mechanisms underpinning the circulatory response to RE. Given the disparate circulatory response between aerobic and RE, primarily the blood pressure profiles, regulation of CBF is ostensibly different. In this review, we summarise current literature and highlight the acute physiological responses to RE, with a focus on the cerebral circulation.

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“…the angle of tilt applied differ from that in the previous study (Ogoh et al, 2020), the possibility should be considered that the changes in the facial tissue microcirculation might differ from those in the macrocirculation at the external carotid artery level, even for the same extracranial circulation. However, the previous study by Ogoh et al (2020) and the present study together suggested that the extracranial tissue circulation varied with steeper HDT.…”

Section: Cheek Sbf and Extracranial Circulationmentioning

confidence: 72%

“…Blood flow regulation in the internal and external carotid arteries is reported to differ during gravitational changes (Ogoh et al, 2020). the angle of tilt applied differ from that in the previous study (Ogoh et al, 2020), the possibility should be considered that the changes in the facial tissue microcirculation might differ from those in the macrocirculation at the external carotid artery level, even for the same extracranial circulation. However, the previous study by Ogoh et al (2020) and the present study together suggested that the extracranial tissue circulation varied with steeper HDT.…”

Section: Cheek Sbf and Extracranial Circulationmentioning

confidence: 75%

Alteration in facial skin blood flow during acute exposure to −10 and −30° head‐down tilt in young human volunteers

Kurazumi

Kato

Konishi

et al. 2022

Experimental Physiology

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New Findings What is the central question of this study?Facial skin blood flow (SBF) might increase during head‐down tilt (HDT). However, the effect of HDT on facial SBF remains controversial. In addition, the changes in facial SBF in the cheek (cheek SBF) during a steeper angle of HDT (>−12° HDT) have not been investigated. What is the main finding and its importance?This study showed that cheek SBF decreased during −30° HDT, alongside increased vascular resistance. Furthermore, vascular impedance was suggested to be elevated, accompanied by an increased hydrostatic pressure gradient caused by HDT. Constriction of the facial skin vascular bed and congestion of venous return owing to the steep angle of HDT can decrease facial SBF. Abstract Head‐down tilt (HDT) has been used to simulate microgravity in ground‐based studies and clinical procedures including the Trendelenburg position or in certain surgical operations. Facial skin blood flow (SBF) might be altered by HDT, but the effect of a steeper angle of HDT (>−12° HDT) on facial SBF remains unclear. We examined alterations in facial SBF in the cheek (cheek SBF) using two different angles (−10 and −30°) of HDT and lying horizontal (0°) in a supine position for 10 min, to test the hypothesis that cheek SBF would increase with a steeper angle of HDT. Cheek SBF was measured continuously by laser Doppler flowmetry. Cheek skin vascular resistance and the pulsatility index of cheek SBF were calculated to assess the circulatory effects on the facial skin vascular bed in the cheek. Cheek SBF decreased significantly during −30° HDT. In addition, the resistance in cheek SBF increased significantly during −30° HDT. The pulsatility index of cheek SBF increased during both −10 and −30° HDT. Contrary to our hypothesis, cheek SBF decreased during −30° HDT along with increased skin vascular resistance. Vascular impedance, estimated by the pulsatility index in the cheek SBF, was elevated during both −10 and −30° HDT, and elevated vascular impedance would be related to increased hydrostatic pressure induced by HDT. Skin vascular constriction and venous return congestion would be induced by −30° HDT, leading to deceased cheek SBF. The present study suggested that facial SBF in the cheek decreased during acute exposure to a steep angle of HDT (∼−30° HDT).

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Gravitational effects on intracranial pressure and blood flow regulation in young men: a potential shunting role for the external carotid artery

Cited by 10 publications

References 42 publications

Effects of −10° and −30° head-down tilt on cerebral blood velocity, dynamic cerebral autoregulation, and noninvasively estimated intracranial pressure

Effects of −10° and −30° head-down tilt on cerebral blood velocity, dynamic cerebral autoregulation, and noninvasively estimated intracranial pressure

The Acute Cardiorespiratory and Cerebrovascular Response to Resistance Exercise

Alteration in facial skin blood flow during acute exposure to −10 and −30° head‐down tilt in young human volunteers

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