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Medical and Biological Engineering and Computing

, Volume 19, Issue 5, pp 547–552 | Cite as

Evaluation of blood resistivityin vivo for impedance cardiography in man, dog and rabbit

  • F. M. Traugott
  • A. W. Quail
  • S. W. White
Article

Abstract

The accuracy of impedance cardiography for measurement of stroke volume (SV2) has been controversial. This could be, in part, due to the use in the Kubicek formula of the bench-determined blood resistivity (ϱ)-haematocrit (Hct) relationship, which does not take into account factors such as complex blood-velocity movements. In the present studyin vivo, ϱ was calculated in dog, rabbit and man from the rearranged Kubicek formula, ϱ=(SV. Zo2)/(L2. dZ/dt max T); the stroke volumes used in the calculation being derived at different Hcts in the different species from the independent techniques of electromagnetic flowmeter, direct Fick, and direct Fick and thermodilution, respectively. Thein vivo ϱ-Hct relationship is linear, inverse and nearly constant over the range of Hcts tested (dog 26–62%, man 31–48%, rabbit 37%). No significant difference exists between meanin vivo ϱ values determined for the three species at corresponding haematocrits despite different thoracic anatomy and circulatory dynamics. Thus, the best estimate of mean ϱin vivo within the normal Hct range is 135Ω cm, the use of which will result in a SV2 accuracy of better than ±10%.

Keywords

Blood resistivityin vivo Cardiac output Haematocrit Impedance Cardiography Stroke volume 

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Copyright information

© IFMBE 1981

Authors and Affiliations

  • F. M. Traugott
    • 1
  • A. W. Quail
    • 2
  • S. W. White
    • 3
    • 4
  1. 1.National Health & Medical Research Council of AustraliaAustralia
  2. 2.National Health & Medical Research Council of AustraliaAustralia
  3. 3.Faculty of MedicineUniversity of NewcastleAustralia
  4. 4.Department of AnaestheticsThe Royal Newcastle HospitalNewcastleAustralia

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