https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12691 2 rebreathing method, however, still suffers from relatively poor accuracy at rest, and gated pool radionuclide scanning requires high levels of medical technological expertise under confined laboratory conditions. Impedance cardiography (IC) does not suffer from these disadvantages. We have evaluated the accuracy of impedance cardiography against accepted invasive methods e.g. thermodilution (TD), dye dilution (DD), the electromagnetic flowmeter (EM), in models where different degrees of experimental control could be applied. This approach was necessary due to the empirical aspects of the Kubicek formula for the calculation of stroke volume using IC. In addition, we have assessed the accuracy of the independent methods in clinical usage, as the assessment of accuracy of impedance cardiography would depend to some extent on the accuracy of the independent method used. Using regression analysis of simultaneous estimates of SV and CO, the accuracy of TD (against EM) in rabbits is 1.0% (S.E. of a single CO estimate expressed as % of mean CO (492 ± 3.5 ml), and that of IC SV measurements in the dog (against EM) is 1.7% (22.2 ± 0.4ml). In man, the accuracy of right heart thermodilution SV measurements (against DD) is 3.9% (75.4 3.0ml), and that for IC SV measurements (against TD) is 2.1 % (58.2 ± 1.2ml). These results indicate that both the invasive TD, and the non-invasive IC systems used in our laboratories have comparable and satisfactory accuracies for SV measurement, and suggest that under conditions of normal hearts and lungs, IC is useful for accurate and continuous non-invasive stroke volume measurements in exercising man, provided certain conditions of usage are satisfied.]]> Wed 24 Jul 2013 22:25:16 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12701 Sat 24 Mar 2018 08:18:25 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12700 Sat 24 Mar 2018 08:18:24 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12763 Sat 24 Mar 2018 08:18:18 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12890 Sat 24 Mar 2018 08:17:13 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12668 z) has been controversial. This could be, in part, due to the use in the Kubicek formula of the bench-determined blood resistivity (p)-haematocrit (Hct) relationship, which does not take into account factors such as complex blood-velocity movements. In the present study in vivo, p was calculated in dog, rabbit and man from the rearranged Kubicek formula, p = (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. The in vivo p-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 p values determined for the three species at corresponding haematocrits despite different thoracic anatomy and circulatory dynamics. Thus, the best estimate of mean p in vivo within the normal Hct range is 135Ωcm, the use of which will result in a SV_z accuracy of better than ± 10%.]]> Sat 24 Mar 2018 08:15:49 AEDT ]]>