INNER CANNULA FOR TRACHEOSTOMY TUBE

CANULE INTERNE POUR TUBE DE TRACHEOTOMIE

English Abstract

The present invention relates to a new, superior inner cannula (10) for insertion into a tracheostomy tube. The inner cannu-
la according to the present invention is formed of a material that allows the inner cannula to have a smooth lumen, while avoid-
ing kinking or collapse when inserted into the tracheostomy tube.

Claims

What is claimed is:
1 An inner cannula for insertion into a tracheostomy
tube, said inner cannula comprises a flexible tube
having a smooth lumen.
2 An inner cannula according to claim 1, wherein said
flexible tube is formed of a flexible material
having sufficient strength to avoid kinking and
collapse when inserted into a tracheostomy tube.
3 An inner cannula according to claim 2, wherein said
flexible material is a expanded polytetrafluoro-
ethylene material or other material having a similar
polymer matrix.
4 An inner cannula for inserting into a tracheostomy
tube, wherein said inner cannula comprises a
flexible tube having a wall thickness of 0.3mm to
0.5mm.
An inner cannula according to claim 4, wherein said
wall thickness is about 0.4mm.

Description

WO94/011~6 213 81~ ~ PCT/US93/06~6
Inner Cannula For TracheostomY Tube
Backqround
Tracheostomy tubes are normally inserted into the
trachea of a patient through an opening cut in the front of
the throat. The tracheostomy tube is generally designed to
include a relatively straight proximal and distal end
portion connected by a curved central portion.
Alternatively, the tracheostomy tube may be formed entirely
in an arced configuration.
The distal end portion of the tracheostomy tube
extends down into the trachea, while the proximal end
portion extends through the cut in the throat. An
inflatable cuff may be included around the distal end
portion and may be used to seal the space between the tube
and the surrounding wall of the trachea, so that all
ventilation cccurs through the tracheostomy tube.
During use, mucous and other secretions collect and
dry within the tracheostomy tube causing obstruction of the
ventilation path. Therefore, it is necessary to
periodically remove the tracheostomy tube for cleaning,
followed by reinsertion into the patient's trachea. This
removal and reinsertion is traumatic to the patient, and
increases the risk of injury to the trachea and surrounding
membranes. In addition, a skilled practitioner is required
to administer the procedure.
To overcome the disadvantages of removal and
reinsertion, it has been proposed to include a second,
removable, tube or cannula which can be inserted into the
tracheostomy tube. This inner cannula may easily be
removed from the tracheostomy tube and cleaned or replaced
by a new inner cannula, without disturbing the tracheostomy
tube. The inner cannula must be flexible enough to be

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2~381 ~ 2
inserted into the proximal end of the tracheostomy tube and
then pushed around the curved central portion into the
distal end. However, the inner cannula must also be rigid
enough to avoid collapse or kinking in the curved portion,
which would restrict or close off the ventilation pathway.
One type of inner cannula is described in US Patent
3,443,564 to Oehmig, and includes a spirally wound wire
along a portion of its length which will correspond to the
curved portion of a tracheostomy tube when inserted. This
inner cannula has several disadvantages including the lack
of a solid wall where the wound wire exists. This is
disadvantageous because gaps will be present between
convolutions of the wire, which will gather mucous and
other secretions. Also, such an inner cannula is
relatively expensive, so as not to be suitable as a
disposable unit. Therefore, this inner cannula must be
cleaned every time it is removed, which is a difficult task
because of the wire and grooves formed there between.
Another known inner cannula is shown in US Patent
3,948,274 to Zeldman et al, such inner cannula comprising
a normally straight one-piece flexible tube of plastic
having circumfirentially formed corrugations along a
portion of its length. The corrugations enable the inner
cannula to have enough flexibility to be pushed through the
curved portion of a tracheostomy tube while maintaining
structural integrity and preventing collapse of the inner
cannula when inserted. However this inner cannula also has
disadvantages associated with the corrugations. In
particular, the corrugations will allow relatively rapid
buildup of mucous and other secretions. This buildup
creates a need for relatively frequent removal of the inner
cannula for cleaning or replacement. While this inner
cannula is low in cost, cleaning may still be preferred to

WO94/011~6 2 1 3 8 1 4 2 PCT/US93/06046
replacement, by some patients. Cleaning is made difficult
because the mucous and other secretions may become embedded
- in the corrugations. This in turn may lead to excessive
build up and possible infection.
Therefore, there remains a need in the art for an
inner cannula which overcomes all of the above problems.
Obiects Of The Invention
It is one object of the present invention to provide
a superior inner cannula for use in tracheostomy tubes.
It is another object of the present invention to
provide a flexible inner cannula having a smooth lumen and
which possesses sufficient strength to avoid kinking and
-collapse.
SummarY Of The Invention
The objects above and others are accomplished
according to the present invention, by providing an inner
cannula made from a material which allows for a minimum
outside diameter (OD) to inside diameter (ID) ratio, while
maintaining structural integrity. In particular, the
objects of the present invention are accomplished by
providing an inner cannula formed from a expanded
polytetrafluoroethylene (EPTFE) material or other compound
of similar polymer matrix.
Brief DescriPtion Of The Drawinqs
Fig. l is a plan view of an inner cannula for a

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2l38l42
tracheostomy tube according to the present invention.
Detailed Description Of The Invention
Fig. l shows an inner cannula, generally designated by
reference numeral l0, according to the present invention.
The inner cannula l0, comprises a flexible tube 20, having
a distal end 30, and a proximal end 40. The flexible tube
20, has a single lumen extending the entire length thereof.
An end piece 50, is attached to the proximal end 40. The
end piece 50, is formed so as to fit securely into the
distal end of a tracheostomy tube when inserted.
The flexible tube 20, is formed of a material which
has sufficient flexibility to allow for insertion into the
lumen of a tracheostomy tube while maintaining structural
integrity and avoiding kinking and collapse. In
particular, the flexible tube 20, is formed of a material
as described above which also allows the flexible tube 20,
to have a smooth lumen. In a preferred embodiment, the
flexible tube 20, is formed of a EPTFE material or
another compound of similar polymer matrix.
The end piece 50, may be attached to the proximal end
40, by any suitable means, such as adhesive bonding,
compression fitting or an insert molding process.
An inner cannula according to the present invention
provides several advantages over those known in the prior
art. In particular, the use of a material as described
above for the flexible tube of the inner cannula provides
a low ratio of OD to ID. In other words, the walls of the
inner cannula can be very thin, e.g. about 0.4mm thick. In
a particular example, the wall thickness of an inner
cannula for a 9mm tracheostomy tube is from about 0.3mm to

WO94/011~6 2 1~ 8 1 4 2 PCT/US93/06046
0.5mm.
The inner cannula according to the present invention
may have any suitable OD, so as to fit snugly and securely
within any standard tracheostomy tube. In addition, the
inner cannula can be of any suitable length to correspond
with the length of the tracheostomy tube in which it is to
be inserted.
The use of the material described above for the inner
cannula according to the present invention provides several
other advantages. In particular, less drag is exerted on
the tracheostomy tube during insertion of the inner lumen.
Also, there may be less drag exerted on instruments which
may be inserted through the inner cannula and used for
suctioning of the airway of the patient by an attending
practitioner. In addition, there is less resistance to
airflow when the inner cannula is inserted. This is
attributable both the relatively low friction coefficient
of the material used, and because the OD to ID ratio can be
minimized making the ID as large as possible.
Because the inner cannula according to the present
invention can be formed with a smooth lumen, other
advantages are realized over prior art devices. In
particular, it is believed that less build-up of mucous and
other secretions may occur. Therefore, it may not be
necessary to remove and clean or replace the inner cannula
as frequently as needed by prior art devices. The
relatively low cost of the inner cannula according to the
present invention makes replacement highly feasible and
affordable. However, cleaning of the inner cannula
according to the present invention is also possible. The
smooth lumen and low friction coefficient make cleaning
easier and more efficient. There are no corrugations or

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2 i38 i 42 6
wires for mucous and secretions to become embedded in.
Therefore, cleaning is more thorough and creates less risk
of subsequent contamination and infection.
The foregoing has been a description of certain
preferred embodiments of the present invention, but is not
intended to limit the invention in any way. Rather, many
modifications, variations and changes in details may be
made within the scope of the present invention.

Representative Drawing