OxyFlo Pro User Manual
Revision 1.1 | May 2015
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For the OxyFlo Pro, tissue blood flow is indicated in relative units called
Blood Perfusion Units (BPU). All OxyFlo Pro monitors have been calibrated
with a constant, known motility standard so that, for a given blood flow
situation, all OxyFlo Pro probes will read the same value of blood flow
expressed in BPU.
The standard BPU output has been optimally filtered with a time constant of
200ms to give a clean and smooth looking signal whilst able to respond to
dynamic changes and pulsatile blood flow changes.
The ‘ART’ parameter
ART is a processed version of the standard blood flow output, also
measured in arbitrary ‘BPU’ units, in which a proprietary artefact rejection
algorithm effectively filters out the presence of motion artefacts in the blood
flow signal. This substantially reduces motion artefacts or ‘spikes’ in the
blood flow data arising from regular probe cable movement and/or regular
tissue movement (e.g. due to breathing), as well as unwanted spikes e.g.,
from accidental cable movement. The ART parameter can be output on the
secondary data channel for each probe, via the touch screen (see table 4).
The ‘RAW’ parameter
The optional ‘RAW’ output is a version of the standard blood flow output
that is subject to reduced filtering. This provides faster response times to
rapid blood flow changes, at the expense of a degree more noise. The RAW
parameter can be output on the secondary data channel for each probe, via
the touch screen (see table 4).
The ‘Backscatter’ parameter
The OxyFlo Pro also generates a signal which is proportional to the total
light remitted or backscattered from the tissue. This is called the
Backscatter Signal (BS).
Backscatter is expressed as a percentage (%) fraction of the laser light
remitted from the tissue relative to the total amount of laser light incident on
the tissue.
For example, in highly perfused tissues the BS will be low due to increased
photon absorption. Situations where the BS signal is close to zero may
indicate that the probe has come into contact with whole blood, this could
cause the BPU reading to saturate since the system is no longer monitoring
microvascular blood flow.
The backscatter parameter too can be output on the secondary data
channel for each probe, via the touch screen (see table 4).