- Title
- Thoracic resistivity for stroke volume calculation in impedance cardiography
- Creator
- Quail, Anthony W.; Traugott, Frans M.; Porges, William L.; White, Saxon William
- Relation
- Journal of Applied Physiology Vol. 50, Issue 1, p. 191-195
- Publisher Link
- http://dx.doi.org/10.1152/jappl.1981.50.1.191
- Publisher
- American Physiological Society
- Resource Type
- journal article
- Date
- 1981
- Description
- Blood resistivity (p) values used in the Kubicek formula for stroke volume (SV) calculation by impedance cardiography are bench derived and do not take into account complex blood velocity movements and dynamic hematocrit changes in systole. In this study, the relevance of rho has been questioned. Thoracic resistivity (pτ) has been calculated in dogs from the rearranged Kubicek formula: pτ = (SV · Z02)/(L2 dZ/dtmax·T), where SV was measured by the electromagnetic flowmeter (EM). Hematocrit (Hct) in the dog was varied by hemorrhage and infusion. In contrast to the direct and exponential bench p-Hct relationship, pτ varies inversely with Hct, but by no more than +6.3 Ω · cm (at Hct 26%) and -11.8 Ω · cm (at Hct 66%) about a mean pτ of 135 ± 1.0 Ω · cm (at Hct 40%). Impedance SV calculated using pτ over a wide range of SV bears a linear relationship to EM values with a 95% prediction limit for a single SV estimate of ±0.84 about a mean value of 26.9 ml. The findings suggest that pτ is virtually constant during a variety of physiological disturbances.
- Subject
- noninvasive stroke volume measurement in humans; cardiac output; anemia; dogs
- Identifier
- http://hdl.handle.net/1959.13/938734
- Identifier
- uon:12664
- Identifier
- ISSN:8750-7587
- Language
- eng
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