A portable bioimpedance instrument for monitoring residual limb fluid volume in people with transtibial limb loss: A technical note. (June 2019)

• Record Type: Journal Article
• Authors: Hinrichs, Paul; Cagle, John C.; Sanders, Joan E.
• Is Part Of: Medical engineering & physics. Volume 68(2019)
• Page Start: 101
• Page End: 107
• Publication Date: 2019-06
• Subjects: Bioimpedance -- Amputee -- Residual limb -- Fluid volume -- Prosthetic fit -- Volume accommodation; α correction term -- μSD micro SD card -- ρe resistivity of extracellular fluid -- ADC analog to digital converter -- C mean circumference of the residual limb -- Cm membrane capacitance -- CMR common mode signal rejection -- DAC digital to analog converter -- FPGA field-programmable gate array -- I resistive component of bioimpedance -- L distance between voltage-sensing electrodes -- Msps megasamples per second -- Q reactance component of bioimpedance -- Re extracellular fluid resistance -- Ri intracellular fluid resistance -- RMS root mean square -- Td transmission delay term -- USB universal serial bus -- Ve extracellular fluid volume -- VCCS voltage controlled current source -- Zdistal impedance between the distal voltage-sensing and distal current-injecting electrodes -- Zn Impedance in channel n -- Zobs Observed complex impedance -- Zthigh Impedance between the proximal voltage-sensing and proximal current-injecting electrodes; Biomedical engineering -- Periodicals; Biomedical Engineering -- Periodicals; Physics -- Periodicals; Génie biomédical -- Périodiques; Biomedical engineering; Electronic journals; Periodicals; 610.28
• DOI: 10.1016/j.medengphy.2019.04.002
• Languages: English
• ISSNs: 1350-4533

Abstract

Abstract : 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. Abstract: 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.