| Assemblies at special
risk Blockage
is very much more likely to occur with lumina that have a
diameter less than 0.6mm.
Causes of blockage
Lumina block because material aggregates or solidifies
in manometric channels, either because it has been passed
down a channel, or has refluxed up it.
Be critical about the materials that you pass down assembly
lumina. Always bear in mind the size of the channel, and the
nature of the material that you want to pass down this.
Solids contained in body fluids can aggregrate within manometric
channels if they are allowed to reflux into assemblies via
side holes. If all channels are perfused, there is no risk
of this. If some recording channels are not used in a measurement
session, they should be filled with water, and then the luer
connector plugged with the plugs that we supply with each
assembly. These plugs are autoclavable, but must not be left
inserted in the luer connector during autoclaving.
Thorough cleaning is essential after each use to prevent any
internal build-up of solids from body fluids. See Dentsleeve
Technical Note 3, Version 2 - 'Cleaning and sterilisation
of Dentsleeve assemblies'.
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First steps to
correct blockage
Gentle flushing with a 20 ml syringe should be tried first,
but excessive pressure must be avoided. Smaller syringes have
considerably more hydraulic leverage than a 20 ml syringe and
can easily cause rupture of manometric channels by generation
of very high pressure.
Next steps to rectify
blockage
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Soak the shaft of the manometric assembly
in isopropyl alcohol for one hour. Do not immerse
the junction between the extrusion and the connector tubes
in isopropyl alcohol, as this may disrupt the connections
between the extrusion and connector tubes.
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Observe all normal safety
precautions appropriate for highly inflammable organic
solvents.
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Isopropyl alcohol causes a 5-10%
increase of luminal diameter after a period of soaking,
and also lubricates the silicone rubber surfaces of the
extrusion.
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After soaking of the extrusion,
gently flush the blocked lumen with isopropyl alcohol.
Ensure that full eye protection is worn to avoid
eye injury from the isopropyl alcohol should the luer
connector be forced off the syringe during flushing.
The isopropyl alcohol makes the silicone rubber connector
slippery, so this is a real risk. Also, cover
the manometric assembly with a towel so that any jet of
isopropyl alcohol that is forced out of a side hole is
contained.
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Use a 20 ml syringe, with only gentle
pressure. Isopropyl alcohol weakens silicone rubber,
so considerable care needs to be taken. |
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If all else fails
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Immerse the extrusion section of the
assembly in toluene within a fume cupboard.
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Observe all normal safety precautions
appropriate for highly inflammable organic solvents.
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Do not immerse the junction between
the extrusion and the connector tubes in the toluene.
Soaking of the junction in toluene will almost
certainly destroy this.
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Soaking in toluene produces an approximate
20% increase of the inner diameter of the manometric extrusion
and lubricates its internal surfaces. Toluene
also makes the silicone rubber extremely fragile.
The blocked channel must then be flushed very
gently with water.
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Remove the manometric assembly from
the toluene and leave in the fume cupboard to air for
24 hours. The assembly will return to its normal dimensions.
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Autoclave the unblocked assembly.
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Assemblies soaked in isopropyl
alcohol or toluene must be completely free of these solvents
before autoclaving is undertaken in order to avoid any
risk of explosion. |
If you don't want to attempt to
unblock your assembly -
Please send it to us with details.
We will do our best, but cannot be held responsible for damage
resulting from our own attempts at unblocking assemblies. |
