Classification of the free fluid reservoir in the calf by electrical impedance tomography.

The Electrical impedance tomography computes images of resistivity distribution which allow to analyse the body fluid content. The Sheffield system, Applied Potential Tomography (APT) was chosen to examine fluid shifts in the calf following body postural change, saline infusion (FL), and lower body negative pressure stress (LBNP). The APT allows the detection of differently reacting regions in the tomogram. The overall images of APT showed an exponential resistivity increase after the body position change from upright to 6 degrees head down tilt (HDT). During LBNP the pattern of the APT images looked the same as during FL. Both showed a resistivity decrease in the overall images. The outer surface showed a different magnitude of resistivities compared to the inner region in all experiments. A comparison of the overall APT images with the tomograms simultaneously obtained by NMR in one test subject showed the same tendency. This leads to the conclusion that the changes in the fluid reservoir of the calf may be classified by electrical impedance tomography.