Bioimpedance

1.

Bioimpedance signals
Levak Maxim BMT2-51B

2.

Introduction
● The goal of the report is to explain
what bioimpedance is and how we
measure it
● Bioimpedance is useful because
electrodes on the skin can help us
study changes inside the body

3.

What is bioimpedance
● Bioimpedance describes how strongly
body tissue opposes an alternating
current
● Current usually passes more easily
through muscle than through fat
● Impedance also depends on the
frequency of the current

4.

How do we measure it
● The device sends a small
alternating current through the
tissue
two-electrode
configuration
● In a four-electrode setup, one pair
sends current and the other pair
measures voltage
● Repeated measurements show how
impedance changes over time
Four-electrode
configuration

5.

Example of a bioimpedance signal
● During a pulse, blood volume in the
forearm briefly increases
● The measured impedance usually
falls below its baseline
● On a graph of −ΔZ, this fall appears
as an upward peak

6.

Other applications and limitations
● Changes in chest impedance can help
us monitor breathing
● Some smart scales use bioimpedance to
estimate body water and body fat
● Movement, skin contact and the amount
of water in the body can affect the
results

7.

Conclusion
● Bioimpedance shows how body tissues
respond to a small alternating current.
● The device measures voltage and uses it to
calculate impedance. Repeated
measurements show how impedance changes
over time.
● During a pulse, blood volume in the forearm
increases. The measured impedance usually
falls, so the −ΔZ curve rises.
● Bioimpedance can also help us monitor
breathing and estimate body water and body
fat.