Probes that are available for your monitor are described on the product 'home page' for that monitor. In addition to this, we hope the following general notes on Probe Theory, Probe cleaning and Durability are useful.
PROBE THEORY
For laser Doppler flow measurements, laser light is transmitted from the monitor to the tissue surface (e.g. the skin) via a flexible optic fibre, and laser light scattered from the small blood vessels and surrounding tissue is transmitted back to the monitor via a second optic fibre where it is photodetected. For some measurements more than one light collecting fibre is used.
The combination of optic connector, optic fibres and probe head make up the optic probe.
In comparing probes designed for a particular laser Doppler flow monitor the main distinguishing features are the size, shape and material of the probe head together with the fibre types and their positioning in the probe head. For a given tissue type and probe position the tissue volume sampled depends mainly on the separating distance of the emitting and collecting fibres in the probe head. In comparing laser Doppler flow measurements probes with the same fibres and fibre separations should be used.
Different applications in general require different probe end designs, though in some cases one design may be suitable for more than one application.
Optic Fibres
A length of optic fibre delivers light from a source, such as a laser, to a probe head or detector with very little loss of light. The attenuation, i.e. the decrease in light power, can be as low as a few percent over kilometre distances though this is dependent on the fibre type and the wavelength of the light. There are several fibre types suitable for the transmission of visible and near infra-red light in the wavelength ranges 400nm to 1500nm. (The typical wavelength used in the Moor Instruments laser Doppler monitors is 785nm near infra-red).
Types of Fibre
There are two basic fibre types, single mode and multi-mode. Multi-mode fibres are sub divided into graded index and step index. Single mode and graded index multi-mode fibres are used mainly for wide bandwidth communication systems and step index mainly for light power delivery. Most of Moor instruments optic probes use step index optic fibre. These have a silica glass core, diameter typically 100mm or 200mm, coated with a hard polymer cladding which gives the fibre a high tensile strength. The coated fibre is further protected by a plastic buffer which can be stripped off near the fibre ends to allow connectors or probe heads to be attached.
CLEANING OPTIC PROBES
The following procedures describe how a probe should be handled and cleaned according to how it has been used.
1. New Probe. e.g. as supplied by the manufacturer. The probe head, sleeving and connectors will be wiped with an alcohol impregnated cloth prior to packing in its probe box and despatch to the customer.
It is recommended that the probe head and probe holder (if being used) is wiped with an alcohol impregnated cloth prior to use, e.g. using a Medi-Wipe (manufacturer Smith & Nephew).
2. Non Invasive Use. After use and before using on a new patient. Visually inspect the probe head, sleeving and connectors. If it is free of particles and has no obvious soiling the probe head and sleeving should be wiped using an alcohol impregnated cloth, e.g. Medi-Wipe.
If the probe is soiled or has particles attached, the particles should be removed by rubbing with an alcohol impregnated cloth. If necessary the probe should be washed in running water to remove dirt and grime.
After washing, excess water should be gently shaken off the probe connectors and probe end and the probe dried with a clean paper towel. When dry, the probe end should be wiped with a clean alcohol impregnated cloth.
3. Low Risk - invasive use. e.g. after use in the mouth with no visible lesions and no infection suspected.
Medical establishments such as hospitals will have approved cleaning/washing protocols to be followed. Where these are not in place the following is recommended:-
Probes should be cleaned in warm clean water with a neutral or enzymatic detergent, e.g. Neutracon (manufacturer Decon).
Cleaning should be sufficiently thorough to leave the probe external surfaces visually clean and free of particles. Carefully rubbing with a clean cloth and/or clean brush may be necessary.
Probes should be rinsed in cold or warm running water. Note: under some circumstances the user or the infection control officer will treat the introduction of a probe into the mouth as an intermediate risk.
4. Intermediate Risk - invasive use. e.g. application of probes to broken/infected areas of skin or broken/infected areas in the mouth, insertion of probes into the nasal cavity or the ear canal, insertion of probes via endoscopes into stomach, duodenum, colon, rectum, bronchitrachea.
Medical establishments such as hospitals will have approved cleaning/washing protocols to be followed. Where these are not in place the following is recommended:-
a. Probes should be cleaned in warm clean water with a neutral or enzymatic detergent e.g. Neutracon (manufacturer Decon).
b. Cleaning should be sufficiently thorough to leave the probe external surfaces visually clean and free of particles. Carefully rubbing with a clean cloth and/or clean brush may be necessary.
c. Probes should be rinsed in cold or warm running water.
d. Disinfection of Probes - All probe types (after washing and cleaning ) can be disinfected, including tuberculoidal, by immersion in 2% Cidex Gluteraldehyde for 20 minutes or 5 minutes in Cidex OPA or 5 minutes in NU-Cidex (manufacturer Johnson and Johnson). Alternatively probes may be disinfected by using low temperature steam (LTS) at 73°C to 80°C for 10 minutes. Note: the LTS cycle typically takes up to 50 minutes as the air has to be evacuated from the steam chamber prior to the introduction of steam and returned to atmospheric pressure after the steam cycle. A high level of disinfection including sporicidal can be achieved by immersion for 10 hours in either Cidex or Cidex OPA, or 5 minutes in NU-Cidex. It is advised that Johnson and Johnson, the manufacturers of Cidex, be consulted.
5. High Risk - invasive use. e.g. Insertion of probes into normally sterile sites such as a joint, application of probe to an internal organ during an operative procedure, e.g. liver.
Cleaning, washing and rinsing cycles will be performed by a customer approved organisation prior to the sterilisation. Sterilisation by the approved organisation is required.
The validated method of sterilisation of Moor Instruments optic and temperature probes is the STERRAD METHOD (manufacturer Johnson and Johnson). This uses hydrogen peroxide gas plasma technology at a temperature of approximately 50ºC.
DURABILITY OF OPTIC PROBES
The sterilisation process recommended will not significantly affect the optic properties of the probes; however the frequent washing and handling will increase the likelihood of damage. With care probes can be expected to survive between 10 to 20 washing/sterilisation cycles.
After washing or sterilisation, the probe should be visually inspected for damage to sleeving, connector and the probe end. The optical transmission of the fibres can be checked by illuminating one end with light from a lamp, e.g. the probe end and checking that light is transmitted to the connector ends. Where the probe end has more than 2 fibres the check should be repeated illuminating the connector end and viewing the probe end for transmitted light. Damaged probes must not be used.
After sterilisation a probe will normally be stored in a double sealed pack as for a surgical instrument. It will generally not be possible to check the light transmission; however it has been established in trials that the STERRAD sterilisation process does not significantly affect the probe function.