Effect of electrode size on the contributions of intracranial and extracranial blood flow to the cerebral electrical impedance plethysmogram
- 48 Downloads
The contribution of scalp blood flow to pulses obtained by cerebral electrical impedance plethysmography (rheoencephalography) has been investigated using a four-electrode (quadripolar) montage with brass disc electrodes 1 cm, 2 cm and 4 cm in diameter. Three states of scalp perfusion were produced by the application of a tourniquet around the occipto-frontal circumference of the head, and blood flow in the scalp was monitored by means of reflection photoplethysmography and an electrical impedance technique. When scalp perfusion was occluded, cerebral impedance pulse amplitude was reduced to 80% of that obtained during normal scalp flow; in the presence of maximal scalp flow as a result of the reactive hyperaemia induced by release of the tourniquet, cerebral impedance pulse amplitude was 30% greater than during normal scalp flow. Altering electrode diameter did not affect the contribution of scalp flow to cerebral impedance pulse size. The effect of changes in scalp flow did, however, increase when a bipolar electrode montage was used instead of a quadripolar montage.
KeywordsCerebral blood flow Impedance plethysmography Photoplethysmography Rheoencephalography
Unable to display preview. Download preview PDF.
- Costeloe, K. andRolfe, P. (1980) Continuous limb blood flow estimation in the newborn using electrical impedance plethysmography,Pediatr. Res.,14, 1053–1060.Google Scholar
- James, I. M. (1979) Methods for assessment of the effect of drugs on cerebral blood flow in man.Br. J. Clin. Pharmacol.,7, 3–12.Google Scholar
- Lifshitz, K. (1970) Electrical impedance cephalography, electrode guarding and analog studies.Ann. N.Y. Acad. Sci.,170, 532–549.Google Scholar
- Markovich, S. E. andNamon, R. (1970) Monopolar rheoencephalography.Ann. N.Y. Acad. Sci.,170, 652–660.Google Scholar
- McHenry, L. C. (1965) Rheoencephalography—a clinical appraisal.Neurology,15, 507–517.Google Scholar
- Murdoch, N., Murray, P. W., Rolfe, P. andWeindling, A. M. (1981) Computer modelling of cerebral electrical impedance in the newborn baby for comparison within vivo measurements. In Proceedings of 5th Nordic Medical and Biological Engineering Conference, Sweden.Google Scholar
- Rolfe, P. (1979) Theoretic aspects of skin blood flow estimation using thermal, optical and impedance techniques.Birth Defects,15, 135–147.Google Scholar
- Salter, D. C. (1979) Quantifying skin disease and healingin vivo using electrical impedance measurements. InNoninvasive physiological measurements,Rolfe,P. (Ed.), Academic Press, London.Google Scholar
- Seipel, J. H. (1970) The influence of electrode size and material on the rheoencephalogram.Ann. N.Y. Acad. Sci.,170, 604–621.Google Scholar