Long-term electrical impedance measurements are affected by specific errors. Electrode failure, changes in its impedance due to aging, and postural changes are among the most important. The authors analyse errors due to electrode replacement and body postural changes. Electrode replacement errors can cause impedance changes up to 5% of basal value. This is one of the most important factors in data reproducibility. Body postural changes also contribute to impedance variations. The authors have proposed the use of a reference position to carry out impedance measurements as the one that shows the smallest impedance sensitivity to postural changes. In general, the authors observed that this is achieved with arms and legs slightly separated from the body. They propose the use of a ratio of impedance at two different frequencies to discern the origin of impedance changes, whether from physiological phenomena or postural errors.
All Science Journal Classification (ASJC) codes
- Biomedical Engineering
- Physiology (medical)