Observing the water handling in humans to resolve the role of the interstitium: preliminary results of the usability of deuterium oxide and bio-impedance analysis - a pilot analysis.

The aim of this research was to evaluate the relevance of using deuterium oxide (²H₂O) and bio-impedance analysis (BIA) to assess size and function of the interstitium for urological research. Nineteen volunteers were recruited to this prospective trial combining ingestion of ²H₂O and BIA. Blood samples were obtained every 10 min after ingestion of ²H₂O. Urine was collected before and after the experiment. BIA was performed every 5 min. Body position was alternated to study the effect on fluid distribution. First order kinetics were assumed for the uptake of ²H₂O from the gastrointestinal tract to the blood. Sex seemed to have an influence with a significantly slower exchange for women (p = 0.041, men: 0.052 min^-1, women: 0.038 min^-1). Impedance measured in legs (men: p = 0.012, women: p = 0.008) and trunk (both p < 0.001) decreased significantly with posture change. These changes probably reflect the orthostatic redistribution of fluid with an increase of fluid in both trunk and legs. Both methods were tested and found to be useful for further urological research. Significant gender differences in ²H₂O uptake dynamics from the gastrointestinal pool were observed. An impact of posture changes on the electrical impedance measured was observed.