Bioelectrical impedance analysis and bioelectrical impedance
spectroscopy
(BIA/BIS) of tissues reveal important information on molecular composition
and physical structure that is useful in diagnostics and prognostics.
The heterogeneity in structural elements of cells, tissues, organs,
and the whole human body, the variability in molecular composition
arising from the dynamics of biochemical reactions, and the contributions
of inherently electroresponsive components, such as ions, proteins,
and polarized membranes, have rendered bioimpedance challenging to
interpret but also a powerful evaluation and monitoring technique
in biomedicine. BIA/BIS has thus become the basis for a wide range
of diagnostic and monitoring systems such as plethysmography and tomography.
The use of BIA/BIS arises from (i) being a noninvasive and safe measurement
modality, (ii) its ease of miniaturization, and (iii) multiple technological
formats for its biomedical implementation. Considering the dependency
of the absolute and relative values of impedance on frequency, and
the uniqueness of the origins of the α-, β-, δ-,
and γ-dispersions, this targeted review discusses biological
events and underlying principles that are employed to analyze the
impedance data based on the frequency range. The emergence of BIA/BIS
in wearable devices and its relevance to the Internet of Medical Things
(IoMT) are introduced and discussed.