Electrical impedance plethysmography: Its use in studying the cerebral circulation of the rabbit

Colditz, Paul B.; Bartholomew, P.; Sinclair, J I; Murphy, Daniel J.; Rolfe, P.; Wilkinson, A

doi:10.1007/bf02446883

Cited by 11 publications

(3 citation statements)

References 10 publications

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“…Changes in CBF detected by LDF compare well with measurements performed with the hydrogen clearance technique, 9,17,28 microspheres, 5,12,22,29 and the [ 14 C]iodoantipyrine method. 10,14,16 The LDF test does not produce absolute values for blood flow in the microcirculation.…”

Section: Autoregulation Assessment Using Ldf and Cppsupporting

confidence: 64%

Monitoring of autoregulation using laser Doppler flowmetry in patients with head injury

Lam

Hsiang

Poon³

1997

Journal of Neurosurgery

143

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The authors studied 31 comatose head-injured patients to assess the clinical usefulness of laser Doppler flowmetry (LDF) in continuous autoregulation monitoring. The LDF probes were placed on the surface of the cerebral cortex. Data on LDF, intracranial pressure (ICP), and arterial blood pressure (ABP) were recorded and continuously entered into a computer. The data were broken down into multiple segments of 15 minutes' duration (epochs). Epochs showing rapid change in cerebral perfusion pressure (CPP), change in CPP of less than 10 mm Hg, LDF values of less than five arbitrary units, and loss of ABP/ICP waveform were excluded from further analysis. A linear relationship between LDF and CPP in individual epochs was used as an indicator of loss of autoregulation. The relationship between LDF and CPP changed with time, indicating improvement or deterioration in autoregulation. Longitudinal analysis of all the epochs measured in a patient revealed three patterns of progress: 1) intact autoregulation; 2) transient loss; and 3) persistent loss of autoregulation. All five patients with intact autoregulation had a good outcome. Ten patients experienced transient loss of autoregulation; of these four had a good outcome, five were moderately disabled and one was severely disabled. Transient impairment of autoregulation did not always indicate poor outcome, provided the impaired autoregulation responded to treatment. In 11 patients who had persistent loss of autoregulation, nine died and two were severely disabled. In five cases the LDF probe lost contact with the cerebral cortex and no useful information was obtained. Real-time measurement of autoregulation using LDF and CPP monitors was achieved and the findings were related to outcome in these patients.

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Section: Autoregulation Assessment Using Ldf and Cppsupporting

confidence: 64%

Monitoring of autoregulation using laser Doppler flowmetry in patients with head injury

Lam

Hsiang

Poon³

1997

Journal of Neurosurgery

143

View full text Add to dashboard Cite

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“…Comparing LDF with the microsphere technique is an appropriate way to validate LDF because microspheres and red cells distribute similarly in the circulation. However, previous studies did not show good absolute agreement of both methods in spite of good correlation (Lindsberg et al 1989; Colditz et al 1993). These systematically differing flow changes detected by LDF seem to occur specifically during lCBF increases while the slope of the regression line between lCBF changes obtained by LDF and 14 C‐iodoantipyrine autoradiography (Dirnagl et al 1989) or hydrogen clearence (Skarphedinsson et al 1988; Haberl et al 1989) is reported as being approximately 0.9 at a reduced lCBF in the adult rat brain.…”

Section: Discussionmentioning

confidence: 71%

Developmental changes in cerebral autoregulatory capacity in the fetal sheep parietal cortex

Müller

Löhle

Schubert

et al. 2002

The Journal of Physiology

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We validated laser Doppler flowmetry (LDF) for long-term monitoring and detection of acute changes of local cerebral blood flow (lCBF) in chronically instrumented fetal sheep. Using LDF, we estimated developmental changes of cerebral autoregulation. Single fibre laser probes (0.4 mm in diameter) were implanted in and surface probes were placed on the parietal cerebral cortex at 105 ± 2 (n = 7) and 120 ± 2 days gestational age (dGA, n = 7). Basal lCBF was monitored over 5 days followed by a hypercapnic challenge (fetal arterial partial pressure of CO 2 , P a,CO 2 : 83 ± 3 mmHg) during which lCBF changes obtained by LDF were compared to those obtained with coloured microspheres (CMSs). Mean arterial blood pressure (MABP) was increased and decreased using phenylephrine and sodium nitroprusside at 110 ± 2 and 128 ± 2 dGA. Intracortical and cortical surface laser probes gave stable measurements over 5 days. The lCBF increase during hypercapnia obtained by LDF correlated well with flows obtained using CMS (r = 0.89, P < 0.01). The signals of intracortical and surface laser probes also correlated well (r = 0.91, P < 0.01). Gliosis of 0.35 ± 0.06 mm around the tip of intracortical probes did not affect the measurements. The range of MABP over which cerebral autoregulation was observed increased from 20-48 mmHg at 110 dGA to 35 to > 95 mmHg at 128 dGA (P < 0.05). Since MABP increased from 33 to 54 mmHg over this period (P < 0.01), the range between the lower limit of cerebral autoregulation and the MABP increased from 13 mmHg at 110 dGA to 19 mmHg at 128 dGA (P < 0.01). LDF is a reliable tool to assess dynamic changes in cerebral perfusion continuously in fetal sheep.

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“…However, only weak and qualitative-rather than quantitative-correlations were found in all studies in which the Z signal was compared to other robust indicators of cerebral circulation (Jacquy et al 1974, Colditz et al 1988a, 1993.…”

Section: Introductionmentioning

confidence: 90%

Pulsatile electrical impedance response from cerebrally dead adult patients is not a reliable tool for detecting cerebral perfusion changes

et al. 2001

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The original objective of this work was to verify the possibility of using electrical pulsatile cerebral impedance measurements as a diagnostic aid for assessing the brain-death condition in adults; a subordinate target was to validate a simple method for detecting perfusional changes in the brain. To this end, impedance signals were recorded, for a comparative study, from both live subjects and brain-dead patients, using a simple four-electrode arrangement. Rather unexpectedly, pulsatile transcephalic impedance waveforms exhibiting a temporal dependance similar to those of live subjects were detected in artificially ventilated, cerebrally dead, adult subjects; distributions of the time delays between impedance peaks and ECG peaks were also recorded for the two groups (dead and live subjects). These data provided no evidence, at the 1% significance level, against the hypothesis that the two sample groups are drawn from identical populations. The detection of impedance variations from brain-dead patients can be explained by the residual persistence of blood flow through the scalp, by mechanical variations synchronous with the heart beat and by the presence of the oscillating flow and the systolic spikes that precede the final blood flow arrest. The fact that impedance variations can be traced back to a multiplicity of causes, unrelated to the normal unidirectional flow, renders the transcephalic impedance method inappropriate for detecting cerebral perfusion changes in adults. This conclusion is also strengthened by some theoretical results recently derived from a multilayer model of the head.

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Electrical impedance plethysmography: Its use in studying the cerebral circulation of the rabbit

Cited by 11 publications

References 10 publications

Monitoring of autoregulation using laser Doppler flowmetry in patients with head injury

Monitoring of autoregulation using laser Doppler flowmetry in patients with head injury

Developmental changes in cerebral autoregulatory capacity in the fetal sheep parietal cortex

Pulsatile electrical impedance response from cerebrally dead adult patients is not a reliable tool for detecting cerebral perfusion changes

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