Electric impedance measurements in quadriplegia.

Previous experimental studies have shown that measurements of electric impedance of the whole human body relate to body fluid volumes. Measurements using two properly selected current frequencies have been purported to be useful in determining the sizes of extracellular and total body fluids. In this study, measurements of whole body impedance were performed on 20 healthy able-bodied subjects and 20 patients with quadriplegia at the frequencies of 1.5kHz and 150kHz. Differences found between the two groups suggest that the ratio of interstitial body fluids to total body fluids in quadriplegic patients is higher than in healthy subjects. This finding is consistent with previous body composition studies conducted on quadriplegic patients using a radioisotope technique, which have suggested a relative increase of extracellular space.