The invalidity of presently available fluid distribution models (FDMs) for the estimation of intra- (ICV) and extracellular volume (ECV) with BIS has been proven. They are sensitive to changes of body posture and ion concentrations in body fluids. Tilt table experiments were conducted with 11 subjects: 30 min supine - 30 min 70° head up tilt - 30 min supine. Total ECV and ICV were estimated with a commercial BIS-system. The data changed significantly after tilting, no steady state was reached within 30 min. The changes are supposed to be artifacts due to fluid redistribution in the ECV. Errors due to ionic shifts were estimated with a kinetic model for ion exchanges during dialysis. The expected errors for the volume changes are greater than 15% for the ECV and smaller than 20% for the ICV with a standard FDM.
|Effective start/end date||1/01/96 → 31/01/00|