New Perspectives in Rheoencephalography

One of the most important advances in biomedical engineering has been the ability to inspect inside the body without opening it. In this sense, rheoencephalography (REG) is an electromedical technique used to assess the cerebral blood flow (CBF) by noninvasive electrical impedance methods, using electrodes attached to the scalp surface. This technique was first proposed by Polzer and Schuhfried (1950), and emerged as an extrapolation of impedance plethysmography applied to the head. An electric current flowing through a biological tissue causes a potential difference between any pair of electrodes that can be measured. This potential difference depends on the amplitude of the injected current, the shape of the conductor, the arrangement of the electrodes, and the electrical characteristics of the tissue. For instance, the electrical conductivity of the lung tissue is much lower than that of the cerebrospinal fluid (CSF), since alveolar sacs are nonconductive. Furthermore, the electrical conductivity depends on the frequency of the electric current, the orientation of the tissue fibers relative to the current flow, and the amount of extracellular fluid that surrounds the cells. For example, electrical conductivity is higher in the blood than in most tissues, since plasma acts as a truehighway for ions (Malmivuo & Plonsey, 1995).

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Bicarbonate ion modulation of cerebral blood flow during hypoxia and hypercapnia

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1982.243.1.h33 ◽

1982 ◽

Vol 243 (1) ◽

pp. H33-H40 ◽

Cited By ~ 7

Author(s):

R. C. Koehler ◽

R. J. Traystman

Keyword(s):

Blood Flow ◽

Cerebrospinal Fluid ◽

Cerebral Blood Flow ◽

Lactic Acid ◽

Acid Production ◽

Lactic Acid Production ◽

Extracellular Fluid ◽

Contralateral Side ◽

Relative Importance ◽

Anesthetized Dogs

The relative importance of changes in extracellular fluid (ECF) pH in mediating increases in cerebral blood flow (CBF) during hypoxia and hypercapnia was assessed by varying [HCO(-3)]ECF in pentobarbital-anesthetized dogs. Blood flow to one caudate nucleus (CNBF) that was bathed by cerebrospinal fluid (CSF) of varied [HCO(-3)] was compared with CNBF (measured by radiolabeled microspheres) on the contralateral side, which received a normal-[HCO(-3)]CSF perfusate. Raising [HCO(-3)]CSF from 25 to 60 meq/l for 150 min lowered CNBF by 16% and suppressed the slope of cNBF response to hypercapnia by 61% but suppressed the slope of CNBF response to hypoxia significantly less (22%). Lowering [HCO(-3)]CSF to 8 meq/l increased CNBF by 71% and augmented the response to hypercapnia by 126% but did not alter the slope of the response to hypoxia. These data indicate that changes in [H+]ECF can account for the increased CBF during hypercapnia but not for the entire hypoxic response. The increase in lactic acid production that would be necessary to solely account for the increase in CBF during hypoxia is much greater than what has been reported in the literature.

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Acupuncture Affects Regional Blood Flow in Various Organs

Evidence-based Complementary and Alternative Medicine ◽

10.1093/ecam/nem051 ◽

2008 ◽

Vol 5 (2) ◽

pp. 145-151 ◽

Cited By ~ 53

Author(s):

Sae Uchida ◽

Harumi Hotta

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

The Body ◽

Neural Mechanisms ◽

Uterine Blood Flow ◽

Afferent Pathway ◽

Antidromic Activation ◽

Efferent Nerve ◽

Afferent Nerves ◽

Cortical Cerebral Blood Flow

In this review, our recent studies using anesthetized animals concerning the neural mechanisms of vasodilative effect of acupuncture-like stimulation in various organs are briefly summarized. Responses of cortical cerebral blood flow and uterine blood flow are characterized as non-segmental and segmental reflexes. Among acupuncture-like stimuli delivered to five different segmental areas of the body; afferent inputs to the brain stem (face) and to the spinal cord at the cervical (forepaw), thoracic (chest or abdomen), lumbar (hindpaw) and sacral (perineum) levels, cortical cerebral blood flow was increased by stimuli to face, forepaw and hindpaw. The afferent pathway of the responses is composed of somatic groups III and IV afferent nerves and whose efferent nerve pathway includes intrinsic cholinergic vasodilators originating in the basal forebrain. Uterine blood flow was increased by cutaneous stimulation of the hindpaw and perineal area, with perineal predominance. The afferent pathway of the response is composed of somatic group II, III and IV afferent nerves and the efferent nerve pathway includes the pelvic parasympathetic cholinergic vasodilator nerves. Furthermore, we briefly summarize vasodilative regulation of skeletal muscle blood flow via a calcitonin gene-related peptide (CGRP) induced by antidromic activation of group IV somatic afferent nerves. These findings in healthy but anesthetized animals may be applicable to understanding the neural mechanisms improving blood flow in various organs following clinical acupuncture.

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