Cerebral blood flow velocity in humans exposed to 24 h of head-down tilt

This study investigates cerebral blood flow (CBF) velocity in humans before, during, and after 24 h of 6 degree head-down tilt (HDT), which is a currently accepted experimental model to simulate microgravity. CBF velocity was measured by use of the transcranial Doppler technique in the right middle cerebral artery of eight healthy male subjects. Mean CBF velocity increased from the pre-HDT upright seated baseline value of 55.5 +/- 3.7 (SE) cm/s to 61.5 +/- 3.3 cm/s at 0.5 h of HDT (P < 0.05), reached a peak value of 63.2 +/- 4.1 cm/s at 3 h of HDT, and remained significantly above the pre-HDT baseline for > or = 6 h of HDT. During upright seated recovery (1–5 h post-HDT), mean CBF velocity decreased to 87% of the pre-HDT baseline value (P < 0.05). Mean CBF velocity correlated well with calculated intracranial arterial pressure (IAP) (r = 0.54, P < 0.001). As analyzed by linear regression, mean CBF velocity = 29.6 + 0.32IAP. These results suggest that HDT increases CBF velocity by increasing IAP during several hours after the onset of microgravity. Importantly, the decrease in CBF velocity after HDT may be responsible, in part, for the increased risk of syncope observed in subjects after prolonged bed rest and also in astronauts returning to Earth.

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Is there any influence of breastfeeding on the cerebral blood flow? A review of 256 healthy newborns

Radiologia Brasileira ◽

10.1590/s0100-39842012000500006 ◽

2012 ◽

Vol 45 (5) ◽

pp. 263-266 ◽

Cited By ~ 3

Author(s):

Alexandra Maria Vieira Monteiro ◽

Claudio Marcio Amaral de Oliveira Lima ◽

Paula Medina

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Middle Cerebral Artery ◽

Cerebral Artery ◽

Pulsatility Index ◽

Cerebral Blood Flow Velocity ◽

Resistance Index ◽

Left Middle Cerebral Artery ◽

Mean Velocity ◽

The Right

OBJECTIVE: To investigate whether breastfeeding influence the cerebral blood-flow velocity. MATERIALS AND METHODS: The present study included 256 healthy term neonates, all of them with appropriate weight for gestational age, 50.8% being female. Pulsatility index, resistance index and mean velocity were measured during breastfeeding or resting in the anterior cerebral artery, in the left middle cerebral artery, and in the right middle cerebral artery of the neonates between their first 10 and 48 hours of life. The data were analyzed by means of a paired t-test, Brieger's f-test for analysis of variance and linear regression, with p < 0.01 being accepted as statistically significant. RESULTS: Mean resistance index decreased as the mean velocity increased significantly during breastfeeding. Pulsatility index values decreased as much as the resistance index, but in the right middle cerebral artery it was not statistically significant. CONCLUSION: Breastfeeding influences the cerebral blood flow velocities.

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Relationship between Autistic Spectrum Trait and Regional Cerebral Blood Flow in Healthy Male Subjects

Psychiatry Investigation ◽

10.30773/pi.2018.07.27 ◽

2018 ◽

Vol 15 (10) ◽

pp. 956-961 ◽

Cited By ~ 2

Author(s):

Miho Ota ◽

Junko Matsuo ◽

Noriko Sato ◽

Toshiya Teraishi ◽

Hiroaki Hori ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Regional Cerebral Blood Flow ◽

Healthy Male ◽

Regional Cerebral Blood ◽

Autistic Spectrum ◽

Male Subjects

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Hemorrhage, Phenobarbital, and Fluctuating Cerebral Blood Flow Velocity in the Neonate

PEDIATRICS ◽

10.1542/peds.82.4.548 ◽

1988 ◽

Vol 82 (4) ◽

pp. 548-553

Author(s):

Karl C. K. Kuban ◽

Helen Skouteli ◽

Allen Cherer ◽

Elizabeth Brown ◽

Alan Leviton ◽

...

Keyword(s):

Blood Flow ◽

Cohort Study ◽

Cerebral Blood Flow ◽

Coefficient Of Variation ◽

Intraventricular Hemorrhage ◽

Anterior Cerebral Artery ◽

Cerebral Blood Flow Velocity ◽

Coefficients Of Variation ◽

Movement Artifact ◽

The Right

Fifty-one sequential intubated babies with birth weights of less than 1,751 were evaluated by serial Doppler ultrasound during the first three days of life. These babies were part of a phenobarbital prophylaxis trial cohort study. Subependymal-intraventricular hemorrhage developed in 17 of the babies. Infants with subependymal-intraventricular hemorrhage, whether or not they received pancuronium or phenobarbital, had coefficients of variation comparable to those of babies without hemorrhage. Coefficient of variation values of the right were comparable to values obtained from the left anterior cerebral artery complex and did not appear to be consistently altered by the presence of subependymal-intraventricular hemorrhage. Coefficient of variation values appeared to be consistently greatest on day 1 and lowest on day 2. In addition, the values overall increased as the number of waves used to determine the coefficient of variation enlarged from five to 20. This phenomena, however, was not seen among pancuronium recipients and suggests that movement artifact may be a determinant of coefficient of variation values. We conclude that, when the best 20 waves are chosen to evaluate the coefficient of variation, no association exists between coefficient of variation values and development of subependymal-intraventricular hemorrhage or administration of phenobarbital.

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Determinants of cerebral blood flow velocity change during squat-stand maneuvers

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00291.2020 ◽

2021 ◽

Vol 320 (4) ◽

pp. R452-R466

Author(s):

Ronney B. Panerai ◽

Angus Batterham ◽

Thompson G. Robinson ◽

Victoria J. Haunton

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Flow Velocity ◽

Blood Flow Velocity ◽

Cerebral Blood Flow Velocity ◽

Velocity Change ◽

Arterial Blood ◽

Autoregulation Index ◽

End Tidal ◽

The Right

The large changes in mean arterial blood pressure (MABP) and cerebral blood flow velocity (CBFV) induced by squat-stand maneuvers (SSM) make this approach particularly suited for studying dynamic cerebral autoregulation (CA). However, the role of other systemic determinants of CBFV has not been described and could provide alternative physiological interpretations of SSM results. In 32 healthy subjects (16 female), continuous recordings of MABP (Finometer), bilateral CBFV (transcranial Doppler, MCA), end-tidal CO2 (EtCO2; capnography), and heart rate (HR; electrocardiogram) were performed for 5 min standing at rest, and during 15 SSM at the frequency of 0.05 Hz. A time-domain, multivariate dynamic model estimated the CBFV variance explained by different inputs, corresponding to significant contributions from MABP ( P < 0.00001), EtCO2 ( P < 0.0001), and HR ( P = 0.041). The autoregulation index (ARI; range 0–9) was estimated from the CBFV response to a step change in MABP. At rest, ARI values (typically 5.7) were independent of the number of model inputs, but during SSM, ARI was reduced compared with baseline ( P < 0.0001), and the three input model yielded lower values for the right and left MCA (3.4 ± 1.2, 3.1 ± 1.3) when compared with the single-input MABP–CBFV model (4.1 ± 1.1, 3.9 ± 1.0; P < 0.0001). The high coherence of the MABP–CBFV transfer function at 0.05 Hz (typically 0.98) was considerably reduced (around 0.71–0.73; P < 0.0001) when the contribution of CBFV covariates was taken into account. Not taking into consideration other determinants of CBFV, in addition to MABP, could be misleading and introduce biases in physiological and clinical studies.

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Exercise plus volume loading prevents orthostatic intolerance but not reduction in cerebral blood flow velocity after bed rest

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00427.2011 ◽

2012 ◽

Vol 302 (2) ◽

pp. H489-H497 ◽

Cited By ~ 17

Author(s):

Sung-Moon Jeong ◽

Shigeki Shibata ◽

Benjamin D. Levine ◽

Rong Zhang

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Cerebral Blood Flow Velocity ◽

Orthostatic Intolerance ◽

Bed Rest ◽

Left Ventricular ◽

Stress Index ◽

Control Group ◽

Orthostatic Tolerance ◽

Volume Loading

This study tested the hypothesis that reduction in cerebral blood flow (CBF) during orthostatic stress after bed rest can be ameliorated with volume loading, exercise, or both. Transcranial Doppler was used to measure changes in CBF velocity during lower body negative pressure (LBNP) before and after an 18-day bed rest in 33 healthy subjects. Subjects were assigned into four groups with similar age and sex: 1) supine cycling during bed rest (Exercise group; n = 7), 2) volume loading with Dextran infusion after bed rest to restore reduced left ventricular filling pressure (Dextran group; n = 7), 3) exercise combined with volume loading to prevent orthostatic intolerance (Ex-Dex group; n = 7), and 4) a control group ( n = 12). LBNP tolerance was measured using a cumulative stress index (CSI). After bed rest, CBF velocity was reduced at a lower level of LBNP in the Control group, and the magnitude of reduction was greater in the Ex-Dex group. However, reduction in orthostatic tolerance was prevented in the Ex-Dex group. Notably, volume loading alone prevented greater reductions in CBF velocity after bed rest, but CSI was reduced still by 25%. Finally, decreases in CBF velocity during LBNP were correlated with reduction in cardiac output under all conditions ( r2 = 0.86; P = < 0.001). Taken together, these findings demonstrate that volume loading alone can ameliorate reductions in CBF during LBNP. However, the lack of associations between changes in CBF velocity and orthostatic tolerance suggests that reductions in CBF during LBNP under steady-state conditions by itself are unlikely to be a primary factor leading to orthostatic intolerance.

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Cerebral hemodynamics during sensorimotor activation in humans

Journal of Applied Physiology ◽

10.1152/jappl.1994.77.6.2804 ◽

1994 ◽

Vol 77 (6) ◽

pp. 2804-2811 ◽

Cited By ~ 40

Author(s):

M. Sitzer ◽

U. Knorr ◽

R. J. Seitz

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Time Course ◽

Cerebral Blood Flow Velocity ◽

Finger Movement ◽

Vibratory Stimulation ◽

Hemodynamic Changes ◽

Movement Sequences ◽

The Mean ◽

Male Subjects

We studied the time course and magnitude of cerebral blood flow velocity (CBFV) changes in the middle cerebral artery (MCA) and the regional cerebral blood flow (rCBF) in the MCA territory during stimulation of the left sensorimotor cortex. Healthy right-handed male subjects were examined during performance of right-hand finger movement sequences, vibratory stimulation, and somatosensory discrimination. In somatosensory discrimination there were significant increases of the mean CBFV (4.8 +/- 9.9 cm/s; P < 0.01) and the mean rCBF (10.2 +/- 4.2 ml.100 g-1.min-1; P < 0.01), whereas no significant changes of the mean CBFV and rCBF occurred in finger movement sequences or vibratory stimulation. During all stimulation sessions the mean CBFV changes increased rapidly and reached a first maximum 3.3 +/- 0.3 s after stimulation onset. Simultaneous measurements of relative mean CBFV changes in both MCAs revealed left-right differences during voluntary finger movement sequences (left MCA, 14.3 +/- 10.6%; right MCA, 0.9 +/- 11.6%; P < 0.001) corresponding to a higher mean rCBF change in the left MCA territory. In the two tasks involving finger movements there was an increase of the respiratory rates (4.3 +/- 3.8 breaths/min; P < 0.05) and the pulse rates (11.6 +/- 5.5 beats/min; P < 0.05), respectively. Our data demonstrate a correspondence of mean CBFV and rCBF changes evoked by sensorimotor activation in the human brain. Furthermore, cerebral hemodynamic changes related to motor activity are accompanied by cardiorespiratory effects.

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