Overcoming the Impedance Range Limitations of Portable Bioelectrical Impedance Spectroscopy Clinical Devices

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Medical Physics

Background:

• Portable bioimpedance spectroscopy (BIS) devices, like the ImpediMed® SFB7, have limited impedance measuring ranges, restricting their use in demanding four-electrode measurements.
• Higher impedance measurements, crucial for clinical applications such as localized skin characterization, are often not feasible with current portable BIS devices.
• Existing benchtop devices offer wider ranges but lack portability and are not optimized for human BIS measurements.

Purpose of the Study:

• To propose and validate a method to overcome the impedance range limitation of portable BIS devices, specifically the SFB7.
• To enable demanding two-electrode measurements using a portable BIS device by extending its effective impedance range.
• To facilitate novel clinical studies requiring high-impedance BIS measurements.

Main Methods:

• A fixed, known impedance was connected in parallel to the bioimpedance under investigation.
• The total measured impedance, now within the SFB7's range, was recorded.
• A post-processing algorithm was developed to calculate the original bioimpedance by removing the contribution of the known parallel impedance.

Main Results:

• The proposed method successfully extended the impedance measuring range of the SFB7 device.
• Testing on a physical model and in vivo demonstrated the practicality of the technique.
• Relative errors for resistance (R) and reactance (X) were found to be less than 2.5% and 7%, respectively.

Conclusions:

• The developed method effectively overcomes the impedance range limitations of the SFB7 BIS device.
• This advancement allows for previously impossible demanding two-electrode measurements.
• The findings enable new clinical research opportunities, particularly in localized skin characterization and other high-impedance BIS applications.