OxyFlo Pro User Manual
Revision 1.1 | May 2015
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Calibration of a probe generates an error message and audible ‘beeps’
Please refer to section 3.6 (Probe Calibration).
Erratic Flow (BPU) values / signal artefacts
CAUTION
Certain environmental conditions and probe application and
positioning errors can affect the reliability of laser Doppler
blood flow readings.
Irrespective of the probe used, it is important to reduce the possibility of
signal artefact, noise and signal dropout in the blood flow reading.
The presence of motion artefact noise in the blood perfusion signal is often
due to relative movements of the tissue (e.g. induced by breathing) with
respect to the probe and/or probe cable movements. These artefacts can
be minimised by allowing the probe to come into contact with the tissue
such that the probe and tissue ‘move in unison’ and by ensuring the cables
do not move. It may be helpful to secure the probe cable to the table at
intervals with adhesive tape.
If the signal artefact is regular in nature (e.g. induced by breathing) try
selecting the ‘ART’ filtered analogue output (refer to section 3.8).
It is also essential to ensure that undue probe pressure is not applied to the
tissue; otherwise local occlusion of the microvasculature may result in a
corresponding reduced blood flow reading.
Excessive ambient lighting at the probe measurement site can also disturb
the blood flow reading. Avoid direct illumination of the measurement site
from external lighting sources and direct sunlight. If erroneous readings due
to excessive ambient lighting levels are suspected, cover the measurement
area with a light piece of opaque material.
In summary, avoid the following situations:
Strong ambient lighting sources such as surgical lights
Fluctuating ambient lighting
Probe movement relative to the tissue
Movement of the probe cable
Excessive physical pressure of the probe against the tissue under
investigation
Baseline blood flow values vary widely between measurements
The laser Doppler flowmetry technique provides only arbitrary, non-absolute
units of tissue blood flow since the sampling volume/depth cannot be
reliably determined and thus a probe may generate widely varying baseline
values from the same/similar tissue site/region at every placement.
The OxyFlo Pro may not therefore be suited to the non-continuous or
repeated assessment of changes in tissue blood flow over chronic time