OxyFlo Pro User Manual
Revision 1.1 | May 2015
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periods. The strengths of the laser-Doppler technique lie in observing
continuous,
acute
changes in blood flow relative to a baseline (control).
What is the Meaning of Zero and Negative BPU?
The calibrated zero reading has been obtained by calibrating the system
against a special static scattering material where no movements occur. In
such cases the back-scattered light processed by the OxyFlo Pro contains
no Doppler shifted frequency components and a true zero is obtained. In a
true physical sense, ‘noise’ around zero can be both positive and negative,
thus it is possible that a small negative reading (of up to –10 BPU) can be
observed in conditions of zero perfusion.
A zero reading indicates zero motion both in the measuring volume under
examination and artefactual motion arising from relative movements
between the probe and the measuring volume. During
in vivo
measurements, rarely is an absolute zero obtained. Even during total
occlusion of tissue blood flow, there is often some small, residual motion of
blood cells trapped in the vessels, as well as some small muscle and tissue
movement in the measuring volume. Even after surgical removal of tissue,
localised red blood cell movement and Brownian motion may still occur.
5.2
Simple Probe Integrity Check
The integrity of the optical fibres within OxyFlo probes can be checked by
holding the probe end to a source of bright diffuse light (e.g. a ceiling light)
whilst visually inspecting the connector end. Two bright spots of light of
equal intensity should be visible from the two pins within the connector. The
light spots may be more obvious if the probe end is slowly waved across the
light source repeatedly.
If light is visible from just a single pin or if light from one of the pins is
obviously dimmer than the other then this indicates either a fibre-break or
fibre damage. Generally (but not in all cases) such damage can be
repaired; please contact technical support accordingly.
5.3
Obtaining Technical Assistance
Contact information for obtaining technical assistance is provided at the
beginning of this manual and on the Oxford Optronix web site.
When contacting technical support or your local distributor please provide
the serial number of your monitor (found at the rear of the unit), details of
probe type(s) used, the nature of the application, and details of the problem
or error message(s) encountered.