Bioimpedance and Arterial Distension

Hypertension

Impedance, Electrical, Tissue, Excitation frequency, arterial distension, distension wave form

The overall objectives were to investigate if characteristic dimensions for tissue and vessels determined from measured bioimpedance spectra would provide the same values as dimensions determined from MR images of the upper arm and verify that temporal variations of impedances could be converted to blood pressure.

It is emphasized that measurements of pulse wave velocity was not a part of this trial, which implies that only uncalibrated blood pressures could be measured. The specific objectives were: 1. To determine conductivities and permittivities in the spectral region from 1 KHz to 1 MHz for persons with: (a) a normal distribution of fat and muscles, (b) exceptionally thick layers of subcutaneous fat, and (c) exceptionally thin layers of subcutaneous fat. Both sexes should be represented. 2. To verify that temporal variations synchronous with the heartbeat could be measured on all three groups. Hypotheses: A. That experimentally in vivo determined electrical parameters for tissues would differ considerably from theoretical values and from values measured in vitro experiments. B. That the variations of the electrical parameters would exhibit little variation from person to person. C. Those simple experimental relations can be established for the electrical parameters by including a simple vascularization model. D. That it is possible to measure temporal variation of the impedance, which are synchronous with the heartbeat. E. That the measured values would facilitate the calculation of the differential blood pressure with accuracies better than 10 mmHg.

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