Techniques & Measurements

This page lists techniques and measurements employed by
the easyTEL+ system for large animals, and used in the area
of measuring cardiovascular, neurological and respiratory
outcomes.

Implanted telemetry

Physiological measurements are captured, amplified and digitized by a transmitter
surgically implanted and wirelessly transmitted to a receiver within 3 to 5 meters distance.

When received by the telemetry receiver, physiological signals can directly be sent to the acquisition computer, via Ethernet.
Communication between implants and receivers is bidirectional, allowing data collections, but also implant remote control (implant state (on/off), settings and configuration).

Did you know?
Telemetry technique ensures no cross talk between transmitters, allowing animals to be implanted with two implants or to be group-housed in the same room or cage.

Biopotentials

Electrocardiogram (ECG), electroencephalogram (EEG), electromyogram (EMG) or
electrooculogram (EOG) signals can be retrieved using easyTEL+ digital telemetry  through implanted electrodes. Various configurations are available:

Single lead biopotential, using a 2-wire electrode:
To get 1-lead ECG, or 1 EEG, EOG or EMG. For ECG, Lead II placement is usually
chosen (but not necessarily).

Dual biopotential:
To get a 2-lead ECG or a combination of 2 biopotentials amongst 1-lead ECG, EEG,
EOG or EMG.

Unipolar configuration, using 3 wires electrode:
In this configuration, the reference electrode is common to both biopotentials.
Unipolar biopotential is easier for the surgery but both biopotentials must be similar (2 EEG or 2 ECG for instance).

  • Biop 1 = Electrode 1 – Electrode 2
  • Biop 2 = Electrode 3 – Electrode 2

 

Bipolar configuration, using 4 wires electrodes:
In this configuration, the biopotential is measured between the positive (red) and
negative (white) electrode, allowing to get two independent biopotentials (EEG and
EMG for instance).

  • Biop 1 = Electrode 1- Electrode 2
  • Biop 2 = Electrode 3- Electrode 4
    For ECG, lead III can be deduced by the software from leads I and II.

 

Quadruple unipolar biopotential, using 5 wires:
All biopotentials have the same reference. This configuration allows the acquisition
of 4 EEG.

Quadruple bipolar biopotential, using 9 wires:
Each biopotential is independent, which is useful for multi-purpose acquisitions,
for instance: 2 EEG + 1 EMG + 1-lead ECG. In this configuration, the reference
electrode is independent from all biopotentials.

Outcomes

ECG : wave duration, amplitude, ST elevation, QT correction , arrythmia detection,
HRV analysis.

Standard or solid tip electrodes are available. Numerous citations describe
the anatomic placement that results in good outcomes. The subcutaneous placement is the most common placement while the epicardial placement gives a signal with a better amplitude, as it is less sensitive to electrical noise and subject posture (more stable axis). Solid-tip provides an intravascular ECG with a better signal to noise ratio compared to subcutaneous placement, while avoiding the thoracotomy required in an epicardial surgery.

EMG : Temporal and spectral analysis

EEG :
• Sleep scoring
• Epileptic seizure detection
• Spectral analysis

EOG : Temporal and spectral analysis

References

Blood pressure

Intra-arterial measurement of Blood Pressure (BP) is the preferred technique for
BP measurement because of the ability to directly measure BP over an extended
period. Implants intended for blood pressure acquisition are equipped with a
catheter that will be inserted in an artery (femoral, carotid for example). Another
catheter can be added to the implants that is intended to acquire left ventricular
pressure, to assess myocardial function.

Outcomes
• Systolic • Diastolic • Heart Rate • Mean pressure • Duration of breath
References

Breathing rate

Impedance varies directly with pulmonary volume.

Therefore, breathing rate can be retrieved through 4 electrodes, implanted subcutaneously on the thorax.

Two electrodes inject a small electrical current, and the two other electrodes measure the resulted impedance.

Acceleration

A 3-axis accelerometer inside the implant measures the acceleration in the x-, y- and z-axis.

Any movement of the subject head translates in variations in the x, y, z coordinates of acceleration.

Using the three individual axis signals, IOX2 acquisition software calculates a global acceleration, making it possible to derive information about the animal’s posture (standing on hind legs, on its side etc).

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