Abstract
Abstract Electrical impedance tomography (EIT) has become an accepted tool for monitoring regional ventilation. Interest is growing to derive additional information on pulmonary perfusion and ventilation/perfusion distribution. Favoured ap-proach is the impedance indicator dilution technique. Until now hyperosmolar sodium chloride solutions (5.8% and 20%NaCl) have been used as indicators in experiments which, however, may be problematic in view of side effects and are not approved for application in patients. Different radiographic contrast media (CM) approved for use in patients and five reference solutions were tested in vitro. Resistivities were measured in blood at 37°C by a conductivity meter (LF39, Meinsberg GmbH, Germany) in the indica-tor content range from 0 to 28 Vol%. Three non-ionic CM: Iodixanol, Iomeprol, Iobitridol and two ionic CM: Ioxaglate and Diatrizoate were examined. As references 0.9%, 5.8% and 20%NaCl as well as isotonic (4.5%) and hypertonic (18.2%) glucose solutions were included. Proportionality Proportionality between test solution concentration and deter-mined resistivity changes was proven by regression/correlation analysis. Non-ionic CM induced linear increases of blood resistivity by 80% (Iodixanol), 75% (Iomeprol) and 66% (Iobitridol) at the highest test concentration of 28Vol%. Ionic CM changed resistivity by 13% (Ioxaglate) and 24% (Diatrizoate). The determined r
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