A portable bioimpedance instrument for monitoring residual limb fluid volume in people with transtibial limb loss: A technical note

• Published in: Medical engineering & physics Vol. 68; pp. 101 - 107
• Main Authors: Hinrichs, Paul, Cagle, John C., Sanders, Joan E.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-06-2019
• Subjects: Amputee; Bioimpedance; Fluid volume; Prosthetic fit; Residual limb; Volume accommodation; ADC; μSD; C; ρe; FPGA; Fluid volume; I; Cm; L; Zobs; Ve; Volume accommodation; Td; Q; Re; Zn; Ri; Zthigh; Residual limb; USB; DAC; CMR; Prosthetic fit; Msps; α; Amputee; VCCS; Bioimpedance; Zdistal; RMS
• ISSN: 1350-4533; 1873-4030
• DOI: 10.1016/j.medengphy.2019.04.002

•Portable system applied 26 frequency bursts per second between 3 kHz and 1 MHz.•Unit was of dimension 15 cm × 11 cm × 4 cm, weighed 3.9 N, and sampled at 30 Hz.•Mean RMS errors were 0.07% for Re, 2.23% for Ri, and 1.15% for Cm.•Errors at high frequencies were from the voltage controlled current source.
People with transtibial limb loss experience daily changes in volume of their residual limb that affect the fit of their prosthetic socket. A portable instrument was developed to monitor fluid volume changes outside of the laboratory setting. The bioimpedance system applied 26 current bursts per second at frequencies between 3 kHz and 1 MHz, and sensed voltage at up to six channels. Among six voltage-controlled current source circuits and five receive-channel amplifier topologies considered, a differential Howland current pump and a single receive-channel instrumentation amplifier proved the best combination of low noise and low power consumption. Mean RMS errors were 0.07% for extracellular fluid resistance, 2.23% for intracellular fluid resistance, and 1.15% for membrane capacitance.