U.S. patent application number 11/915556 was filed with the patent office on 2009-06-11 for laryngeal mask airway device.
This patent application is currently assigned to THE LARYNGEAL MASK COMPANY LTD.. Invention is credited to Archibald I. J. Brain.
Application Number | 20090145438 11/915556 |
Document ID | / |
Family ID | 34834809 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090145438 |
Kind Code |
A1 |
Brain; Archibald I. J. |
June 11, 2009 |
LARYNGEAL MASK AIRWAY DEVICE
Abstract
The invention relates to a laryngeal mask airway device (1) for
insertion into a patient to provide an airway passage to the
patient's glottic opening, the device (1) comprising an airway tube
(2) a mask (3) attached to the airway tube (2), the mask (3)
comprising a body (4) having a distal end (5) and a proximal end
(6), a peripheral inflatable cuff (7), and defining an outlet (8)
for gas, the mask (3) being attached to the airway tube (2) for
gaseous communication between the tube (2) and the outlet (8), the
device (1) further comprising an oesophageal drain (10), the drain
(10) comprising a conduit extending from an inlet (12) at the
distal end (5) to an outlet (13) disposed to the outside of the
patient when the device (1) is in place, the conduit including a
mask section (11) and an airway tube section (41), wherein the
conduit mask section (11) is formed integrally in the material of
the body (4).
Inventors: |
Brain; Archibald I. J.;
(Mahe, SC) |
Correspondence
Address: |
WILMERHALE/BOSTON
60 STATE STREET
BOSTON
MA
02109
US
|
Assignee: |
THE LARYNGEAL MASK COMPANY
LTD.
London
GB
|
Family ID: |
34834809 |
Appl. No.: |
11/915556 |
Filed: |
May 24, 2006 |
PCT Filed: |
May 24, 2006 |
PCT NO: |
PCT/GB06/01913 |
371 Date: |
December 5, 2008 |
Current U.S.
Class: |
128/207.15 |
Current CPC
Class: |
A61M 16/04 20130101;
A61M 16/0463 20130101; A61M 16/0409 20140204; A61M 16/0875
20130101; A61M 16/0415 20140204; A61M 16/0816 20130101; A61M
16/0447 20140204; A61M 16/0443 20140204; A61M 16/0493 20140204;
A61M 16/045 20140204 |
Class at
Publication: |
128/207.15 |
International
Class: |
A61M 16/04 20060101
A61M016/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2005 |
GB |
0510951.7 |
Claims
1. A laryngeal mask airway device for insertion into a patient to
provide an airway passage to the patient's glottic opening, the
device comprising an airway tube, a mask attached to the airway
tube, the mask comprising a body having a distal end and a proximal
end, a peripheral inflatable cuff, and defining an outlet for gas,
the mask being connected to the airway tube for gaseous
communication between the tube and the mask, the device further
comprising an oesophageal drain, the drain comprising a conduit
extending from an inlet at the distal end to an outlet disposed to
be outside of the patient when the device is in place in the
patient, the conduit including a mask section and an airway tube
section, wherein the conduit mask section is formed integrally in
the material of the body.
2. A device according to claim 1, wherein the conduit extends
substantially centrally from the distal end to the proximal end of
the mask body.
3. A device according to claim 1, the mask body comprising a plate,
the plate having a dorsal side and a ventral side, the dorsal side
being substantially smooth and having a convex curvature across its
width, the conduit being formed on and extending from the ventral
side of the plate.
4. A device according to claim 1, the conduit including an
extension part which extends past the distal extent of the mask
body.
5. A device according to claim 4, wherein the extension part is
enclosed by, and opens out of an integrally formed pocket.
6. A device according to claim 5, wherein the pocket extends from
the material of the inlet.
7. A device according to claim 4, wherein the pocket is
inflatable.
8. A device according to claim 7, wherein the pocket is inflated by
gas from the cuff.
9. A device according to claim 8, wherein the pocket and cuff are
sealed together, there being an access point for gas from the cuff
to the pocket.
10. A device according to claim 9, wherein the access way is
provided by a pinch-off of the cuff.
11. A device according to claim 4, wherein the extension part
includes means to prevent it collapsing under increased air
pressure in the pocket.
12. A device according to claim 11, wherein the prevention means
comprises one or more support web formed integrally with the
extension part.
13. A device according to claim 12, wherein the or each support web
extends from the extension part, substantially perpendicular
thereto.
14. A device according to claim 1, wherein the mask comprises a
plastics material.
15. A device according to claim 1, wherein the material is a shore
50A material.
16. A device according to claim 12, wherein the airway tube
comprises a shore 90A material.
Description
[0001] The present invention relates to a laryngeal mask airway
device.
[0002] The laryngeal mask airway device is a well known device that
is useful for establishing airways in unconscious patients. U.S.
Pat. No. 4,509,514 is one of the many publications that describe
laryngeal mask airway devices. Such devices have been in use for
many years and offer an alternative to the older, even better known
endotracheal tube. For at least seventy years, endotracheal tubes
comprising a long slender tube with an inflatable balloon disposed
at the tube's distal end have been used for establishing airways in
unconscious patients. In operation, the endotracheal tube's distal
end is inserted through the mouth of the patient, past the
patient's trachea. Once so positioned, the balloon is inflated so
as to form a seal with the interior lining of the trachea. After
this seal is established, positive pressure may be applied to the
tube's proximal end to ventilate the patient's lungs. Also, the
seal between the balloon and the inner lining of the trachea
protects the lungs from aspiration (e.g., the seal prevents
material regurgitated from the stomach from being aspirated into
the patient's lungs).
[0003] Although they have been enormously successful, endotracheal
tubes suffer from several major disadvantages. The principal
disadvantage of the endotracheal tube relates to the difficulty of
properly inserting the tube. Inserting an endotracheal tube into a
patient is a procedure that requires a high degree of skill. Also,
even for skilled practitioners, insertion of an endotracheal tube
is sometimes difficult or not possible. In many instances, the
difficulty of inserting endotracheal tubes has tragically led to
the death of a patient because it was not possible to establish an
airway in the patient with sufficient rapidity. Also, inserting an
endotracheal tube normally requires manipulation of the patient's
head and neck and further requires the patient's jaw to be forcibly
opened widely. These necessary manipulations make it difficult, or
undesirable, to insert an endotracheal tube into a patient who may
be suffering from a neck injury.
[0004] In contrast to the endotracheal tube, it is relatively easy
to insert a laryngeal mask airway device into a patient and thereby
establish an airway. Also, the laryngeal mask airway device is a
"forgiving" device in that even if it is inserted improperly, it
still tends to establish an airway. Accordingly, the laryngeal mask
airway device is often thought of as a "life saving" device. Also,
the laryngeal mask airway device may be inserted with only
relatively minor manipulation of the patient's head, neck and jaw.
Further, the laryngeal mask airway device provides ventilation of
the patient's lungs without requiring contact with the sensitive
inner lining of the trachea and the size of the airway established
is typically significantly larger than the size of the airway
established with an endotracheal tube. Also, the laryngeal mask
airway device does not interfere with coughing to the same extent
as endotracheal tubes. Largely due to these advantages, the
laryngeal mask airway device has enjoyed increasing popularity in
recent years.
[0005] U.S. Pat. Nos. 5,303,697 and 6,079,409 describe examples of
prior art devices that may be referred to as "intubating laryngeal
mask airway devices." The intubating device has the added advantage
that it is useful for facilitating insertion of an endotracheal
tube. After an intubating laryngeal mask airway device has been
located in the patient, the device can act as a guide for a
subsequently inserted endotracheal tube. Use of the laryngeal mask
airway device in this fashion facilitates what is commonly known as
"blind insertion" of the endotracheal tube. Only minor movements of
the patient's head, neck and jaw are required to insert the
intubating laryngeal mask airway device, and once the device has
been located in the patient, the endotracheal tube may be inserted
with virtually no additional movements of the patient. This stands
in contrast to the relatively large motions of the patient's head,
neck and jaw that would be required if the endotracheal tube were
inserted without the assistance of the intubating laryngeal mask
airway device. Furthermore, these devices permit single-handed
insertion from any user position without moving the head and neck
of the patient from a neutral position, and can also be put in
place without inserting fingers in the patient's mouth. Finally, it
is believed that they are unique in being devices which are airway
devices in their own right, enabling ventilatory control and
patient oxygenation to be continuous during intubation attempts,
thereby lessening the likelihood of desaturation.
[0006] Artificial airway devices of the character indicated, are
exemplified by the disclosures of U.S. Pat. No. 4,509,514; U.S.
Pat. No. 5,249,571; U.S. Pat. No. 5,282,464; U.S. Pat. No.
5,297,547; U.S. Pat. No. 5,303,697; and by the disclosure of the UK
Patent 2,205,499. Such devices with additional provision for
gastric-discharge drainage are exemplified by U.S. Pat. No.
4,995,388 (FIGS. 7 to 10); U.S. Pat. No. 5,241,956; and U.S. Pat.
No. 5,355,879.
[0007] In general, laryngeal mask airway devices aim to provide an
airway tube of such cross-section as to assure more than ample
ventilation of the lungs, and the designs with provision for
gastric drainage have been characterized by relatively complex
internal connections and cross-sections calculated to serve in
difficult situations where substantial solids could be present in a
gastric discharge. As a result, the provision of a gastric
discharge opening at the distal end of the mask applicable for
direct service of the hypopharynx has resulted in a tendency for
such masks to become bulky and unduly stiff, thus making for
difficulty in properly inserting the mask. Moreover, undue bulk and
stiffness run contrary to the requirement for distal flexibility
for tracking the posterior curvature of the patient's throat on
insertion, in such manner as to reliably avoid traumatic encounter
with the epiglottis and other natural structures of the
pharynx.
[0008] A number of problems have been experienced with all of these
prior types of device. For example, some prior devices seek to
prevent occlusion of the airway outlet by parts of the patient's
anatomy, such as the epiglottis, by the provision of bars and the
like across the outlet. Although such devices function well in most
cases, they can make manufacturing more complex, and can affect the
performance of devices in use. This is especially so in devices
formed from relatively rigid materials, like PVC, as opposed to the
more traditional Liquid Silicon Rubber (LSR).
[0009] In general, devices formed from materials such as PVC are
attractive because they are cheaper to make, and can be offered
economically as "single-use" devices. However, there are material
differences in PVC and PVC adhesives, such as increased durometer
hardness as compared to LSR, which affect how the devices perform
in use. For example, it has been observed that for a given volume
of air, an LSR cuff will expand to a larger size than a comparable
PVC cuff. This superior elasticity allows the LSR cuff to provide
an anatomically superior seal with reduced mucosal pressure. To
close the performance gap, the PVC cuff must be of reduced wall
thickness. However, a PVC cuff of reduced wall thickness, deflated
and prepared for insertion, will suffer from poor flexural response
as the transfer of insertion force through the airway tube to cuff
distal tip cannot be adequately absorbed. The cuff assembly must
deflate to a thickness that preserves flexural performance i.e.
resists epiglottic downfolding, but inflate so that a cuff wall
thickness of less than or equal to 0.4 mm creates a satisfactory
seal. And where mask backplates are formed from PVC, as well as
cuffs, the fact that the increased durometer hardness of PVC is
inversely proportional to flexural performance (hysterisis) means
that the flexural performance of the device in terms of reaction,
response and recovery on deformation is inferior to a comparable
LSR device.
[0010] The above described problems are particularly acute in
devices which incorporate an oesophageal drain. As mentioned above,
in any such device regardless of the material from which it is
formed, adding an oesophageal drain in itself adds greatly to
complexity of manufacture and can also affect the performance of
devices, in terms of ease of insertion, seal formation and
prevention of insufflation. These problems can be exacerbated still
further if PVC or similarly performing materials are used. For
example, the skilled worker will appreciate that in terms of
manufacture, the need to provide a drain tube which is sealed from
the airway, and which must pass through the inflatable cuff poses a
particularly difficult problem. In terms of effects on
functionality, the provision of a drain tube can cause unacceptable
stiffening of the mask tip area and occlusion/restriction of the
airway passage.
[0011] According to the invention there is provided a laryngeal
mask airway device for insertion into a patient to provide an
airway passage to the patient's glottic opening, the device
comprising an airway tube, a mask attached to the airway tube, the
mask comprising a body having a distal end and a proximal end, a
peripheral inflatable cuff, and defining an outlet for gas, the
mask being connected to the airway tube for gaseous communication
between the tube and the mask, the device further comprising an
oesophageal drain, the drain comprising a conduit extending from an
inlet at the distal end to an outlet disposed to be outside of the
patient when the device is in place in the patient, the conduit
including a mask section and an airway tube section, wherein the
conduit mask section is formed integrally in the material of the
body. Thus it can be seen that the invention addresses the problems
which result from the need to incorporate an oesophageal drain, in
terms of the performance of the device and also its
manufacture.
[0012] It is preferred that the conduit extends substantially
centrally from the distal end to the proximal end of the mask body,
so that a straight and short flow path for liquids and solids is
provided.
[0013] The mask body may comprise a plate, the plate having a
dorsal side and a ventral side, the dorsal side being substantially
smooth and having a convex curvature across its width, the conduit
being formed on and extending from the ventral side of the plate.
This maintains a smooth dorsal profile which aids insertion and
patient comfort and keeps the device's dorsal to ventral dimension
to a minimum, which further aids insertion.
[0014] In a preferred embodiment, the conduit includes an extension
part which extends past the distal extent of the mask body. The
extension part may be enclosed by, and open out of an integrally
formed pocket, and the pocket preferably extends from the material
of the inlet. The pocket is preferably inflatable, and most
preferably is inflated by gas from the cuff. The pocket and cuff
can be sealed together, there being an access way for gas from the
cuff to the pocket, and the access way can conveniently be provided
by a pinch-off of the cuff.
[0015] The extension part may include means to prevent it
collapsing under increased air pressure in the pocket. The
prevention means may comprise one or more support web formed
integrally with the extension part, and the or each support web may
extend from the extension part, substantially perpendicular
thereto.
[0016] The mask preferably comprises a plastics material, such as a
shore 50A material, and the airway tube preferably comprises a
shore 90A material.
[0017] The invention will further be described by way of example
and with reference to the following drawings, in which,
[0018] FIG. 1 is a dorsal three quarter perspective view of a
device according to the invention;
[0019] FIG. 2 is a right side view of the device of FIG. 1;
[0020] FIG. 3 is a dorsal view of the device of FIG. 1;
[0021] FIG. 4 is a ventral view of the device of FIG. 1;
[0022] FIG. 4a is a ventral view of a further embodiment of device
according to the invention;
[0023] FIG. 5 is an end view, looking from the proximal towards the
distal end of the device of FIG. 1;
[0024] FIG. 6 is an end view, looking from the distal towards the
proximal end of the mask of the device of FIG. 1;
[0025] FIG. 7 is an enlarged view of the mask of the device of FIG.
1;
[0026] FIG. 8 is a dorsal view of the device of FIG. 4a;
[0027] FIG. 9 is a longitudinal sectional view along line Y-Y in
FIG. 8;
[0028] FIG. 10 is a side view, enlarged, of the device of FIG.
4a;
[0029] FIGS. 11A to 11K are transverse sectional views along lines
A-A to K-K in FIG. 10;
[0030] FIG. 12 is an exploded dorsal perspective view of a device
according to the invention;
[0031] FIG. 13 is an exploded ventral perspective view of a device
according to the invention;
[0032] FIG. 14 is a dorsal three quarter perspective view of a
device according to the invention;
[0033] FIG. 15 is a right side view of the device of FIG. 14;
[0034] FIG. 16 is a dorsal view of the device of FIG. 14;
[0035] FIG. 17 is a ventral view of the device of FIG. 14;
[0036] FIG. 18 is an end view, looking from the proximal towards
the distal end of the mask of the device of FIG. 14;
[0037] FIG. 19 is an end view, looking from the distal towards the
proximal end of the mask of the device of FIG. 14;
[0038] FIG. 20 is a dorsal three quarter perspective view of the
device of FIG. 14;
[0039] FIG. 21 is a view of section CC-CC in FIG. 20;
[0040] FIG. 22 is a view of section VC-VC in FIG. 17;
[0041] FIG. 23 is a proximal end view of a part of the device of
FIG. 14; and
[0042] FIG. 24 is a distal end view of a part of the device of FIG.
14.
[0043] Referring now to the drawings, there is illustrated a
laryngeal mask airway device 1 for insertion into a patient to
provide an airway passage to the patient's glottic opening, the
device 1 comprising an airway tube 2 a mask 3 attached to the
airway tube 2, the mask 3 comprising a body 4 having a distal end 5
and a proximal end 6, a peripheral inflatable cuff 7, and defining
an outlet 8 for gas, the mask 3 being attached to the airway tube 2
for gaseous communication between the tube 2 and the outlet 8, the
device 1 further comprising an oesophageal drain 10, the drain 10
comprising a conduit extending from an inlet 12 at the distal end 5
to an outlet 13 disposed to the outside of the patient when the
device 1 is in place, the conduit including a mask section 11 and
an airway tube section 41, wherein the conduit mask section 11 is
formed integrally in the material of the body 4.
[0044] As can be seen from the drawings, the device 1, in terms of
overall appearance is somewhat similar to prior art devices, in
that it consists of the basic parts which make up most if not all
laryngeal mask airway devices, i.e. an airway tube 2 and mask 3
which includes a body part 4, and a cuff 7.
[0045] For the purposes of description it is appropriate to assign
reference names to areas of the device 1 and accordingly with
reference to FIGS. 2 to 6, the device 1 has a dorsal side 14, a
ventral side 15, a proximal end 16 (in a sense that this is the end
nearest the user rather than the patient) a distal end 17 and right
and left sides 18 and 19.
[0046] Referring firstly to the airway tube 2, in the illustrated
embodiments the tube comprises a relatively rigid PVC material such
as a shore 90A Colorite PVC moulded into an appropriately
anatomically curved shape. The tube 2 has some flexibility such
that if it is bent it will return to its original shape. Although
it is resiliently deformable in this way, it is sufficiently rigid
to enable it to assist in insertion of the device 1 into a patient,
acting as a handle and guide. In this embodiment the airway tube 2
does not have a circular cross-section as in many prior devices,
but instead is compressed in the dorsal/ventral direction which
assists in correct insertion of the device 1, helps prevent
kinking, and assists in comfortable positioning for the patient as
the shape generally mimics the shape of the natural airway. In this
embodiment each side 18, 19 of the airway tube 2 includes a groove
or channel 20 extending for most of the tube's length from the
proximal to distal ends. These grooves 20 further assist in
preventing crushing or kinking of the airway tube 2. Internally the
grooves 20 form ridges along the inner surfaces of the sides 18 and
19.
[0047] Referring now to FIG. 13, which shows an exploded view of
the device 1, it can be seen that the airway tube 2 includes a
flared distal end 22 with surfaces 22a disposed to allow for
attachment of the tube 2 to the mask 3, conveniently by over
moulding of the mask 3 onto the airway tube 2. Thus, the airway
tube 2 itself can form a pre-mould used in formation of the device
1, which substantially simplifies manufacturing. Of particular note
is the airway tube's dorsal mould surface 23 (FIG. 13). This
surface 23 is located at the flared distal end 22, and takes the
form of a flat land extending between the outer dorsal surface 2a
and the inner dorsal surface 2b (FIG. 24) of the dorsal wall 2c. It
includes optional through holes 2d to allow the over moulded back
plate 4 to lock onto the tube 2, as will be described later on.
This feature helps ensure a secure connection between the different
materials making up the airway tube 2 and mask 3.
[0048] A further feature of the airway 2 is the oesophageal drain
tube 41. This drain tube 41 is located within airway tube 2,
extending centrally through it from one end to the other, and in
this embodiment it is disposed in contact with the inner surface 2a
of the dorsal wall 2b of the airway tube 2, and bounded on each
side by raised, smooth walls (not shown) which form a shallow
channel through which it runs.
[0049] The proximal end of the airway tube 2 is provided with a
connector 42, for connection of the device 1 to a gas supply and
drain (not shown) as shown for example in FIGS. 12 and 13 and in
section in FIG. 9. The connector 42 comprises a connector body 43,
an optional bite block 44 and a connector plug 45. The connector
body 43 and bite block 44 correspond in shape and dimension with
the internal shape of the proximal end of the airway tube 2 such
that they fit inside it. The connector body 43 has a
perpendicularly extending peripheral flange 46 which extends at one
point on its circumference into a tab 47. Connector plug 45
attaches to connector body 43 by adhesive or other suitable means
applied to flange 46. The connector plug 45 comprises major and
minor bores 48, 49 which both lead into a common atrium 50 at the
distal end of the connector plug 45 where it attaches to the
connector body 43. Drain tube 41 extends into and through minor
bore 49, such that the bore of the airway tube 2 and the bore of
the drain tube 41 are separated from one another.
[0050] Turning now to the mask 3, the mask 3 consists of two parts,
a body part 4 often referred to as a back plate, and a peripheral
cuff 7.
[0051] The back plate 4 is formed in these embodiments by moulding
from a shore 50A Vythene PVC+PU. This material is substantially
softer and more deformable than the material of airway tube 2.
[0052] Referring now to FIG. 23, the back plate 4 comprises a
generally oval moulding when viewed from the dorsal or ventral
directions, having a smooth dorsal surface 24, a formed ventral
surface 24a (FIG. 17), a proximal joining portion 24b, and a distal
tip 61.
[0053] The dorsal surface 24 has a convex curvature from one side
to the other, corresponding to the curvature of the dorsal surface
of the airway tube 2, and longitudinally, the dorsal surface 24 is
also curved, having a curvature beginning at the joining portion
24b and extending with constant rate of curvature toward the distal
tip 61. As a result the tip 61 is ventrally biased relative to the
distal end of the airway tube, in the assembled device 1, the
extent of displacement of the distal tip 61 being approximately 20
mm or 10 degrees, in order to produce a curvature in the mask that
is suited to the anatomy of the patient. This is shown
schematically at X in FIG. 2. On insertion, this displacement of
the tip 61 assists the mask in "turning the corner" in the
insertion path.
[0054] When viewed from the ventral side, the integrally moulded
structures of the back plate 4 can best be seen (FIGS. 4,7,12,17).
The precise shape of the ventral side 24a of the back plate is
illustrated particularly in the sectional views shown in FIGS. 11A
to 11K and in the enlarged perspective view in FIG. 7. Referring to
the exploded view shown in FIG. 12, the convex curvature of the
dorsal surface 24 of the back plate 4 is mirrored in a
corresponding concave-curvature on the ventral side. Thus, the
ventral surface 24a forms a shallow, elongate channel tapering
towards the distal tip 61. The channel is bounded by walls 26. The
walls 26 have correspondingly shaped, longitudinally extending
convex outer surfaces 25. Each wall 26 extends longitudinally
substantially the entire length of the back plate 4 from the
proximal joining portion 24b towards the distal tip 61. Each wall
26 also has a convex inner surface 28, but rather than terminating
at an angle normal to the channel floor, the curve of each wall 26
is continued, the walls curving back over the channel and
terminating in inwardly extending webs 27 (FIGS. 7 and 11). The
inner surfaces 28 of the side walls 26 curve down to form the floor
of the channel but do not meet, because the base or floor of the
channel is bisected by a longitudinally extending, integrally
moulded conduit which is an oesophageal drain tube 11 extending
along it for its entire length from joining portion 24b to distal
tip 61. Thus, it can be seen that the channel has three
longitudinally extending conduits on its inner surface, the two
open outer conduits 28a which are minor gas conduits in the
assembled device 1, and the central drain tube 11, which forms a
septum there between.
[0055] Referring now in greater detail to the drain tube 11, it
will be seen that the tube 11 has a sufficient diameter such that
its upper wall section 11a, i.e. the wall section furthest from the
floor of the channel, is on a similar level with the inwardly
extending webs 27 of the side walls 26. Furthermore, the upper wall
section 11a itself also has outwardly extending webs 30, which
taper toward, but do not meet, the correspondingly tapered edges of
the webs 27. Thus, the upper surface 11b of the upper wall section
11a of the drain tube 11, and the webs 27, 30, together define a
surface 11c shown schematically by a dotted line in FIG. 11), below
the level of which run all three conduits 11, 28a.
[0056] Referring now particularly to FIG. 7, it can be seen that
although the drain tube 11 extends the full length of the back
plate 4 from its proximal joining portion 24b to distal tip 61, the
conduits 28a do not extend the full length of the back plate 4, but
instead terminate about half way along its length. The floors 31 of
the conduits 28a curve gently upwards as they extend towards the
distal tip 61 of the back plate 4 until they terminate at a level
approximately equal to the level of the webs 27 and 30. In the
embodiment shown in FIG. 4a, these areas are hollowed out to form
depressions 31b.
[0057] As illustrated in FIG. 12 and FIGS. 21 to 23, drain tube 11
extends to distal tip 61, terminating in an opening 12. Thus, an
end section 11e of the drain tube 11 protrudes past the end of back
plate 4. This end section 11e is provided with dorsal webbing 11a
which extends to either side of it, and around it to form a hood or
pocket 36a which encloses the end section 11e around its
circumference. The hood or pocket 36a is attached to the distal end
of the drain tube 11 around the circumference 12a of opening 12
(FIG. 22). This hood or pocket 36a is integrally formed in the
material of the back plate 4 at distal tip 61. It completely
surrounds and extends from the circumference of the drain tube
opening 12 and the joint therebetween is smooth. As illustrated,
the ventral extent of the hood is more limited than the dorsal
extent, the dorsal extent being to about midway back towards the
proximal end of the back plate 4. Referring to sectional views A-A
and B-B in FIG. 11, it can be seen that the drain tube 11 is
supported on its right and left sides, and on its dorsal surface,
by perpendicularly extending webs 62. These webs 62 are integrally
formed, and extend back from the opening 12 to the point where the
end section 11e meets the extent of the back plate 4. In the
illustrated embodiment the dorsal webs 62 extend substantially
perpendicularly from the drain tube, but in a preferred embodiment,
they may extend to one side or the other, at an angle of less than
90 degrees.
[0058] The second part of the mask 3 is the peripheral cuff 7. The
cuff 7 is in this embodiment blow moulded PVC and takes the form of
a generally elliptical inflatable ring having a central aperture
7a, a relatively deeper proximal end 37 with an inflation port 38
and a relatively shallower distal end 7b tapering to a "wedge"
profile 39. As will be appreciated, particularly from the exploded
views shown in FIGS. 12 and 13, the cuff 7 is integrally formed in
one piece. The wedge profile is provided such that the ratio of
dorsal to ventral side surface areas favours the dorsal side. Thus,
when deflated the distal end 7b of the cuff 7 will curl with bias
from dorsal to ventral side.
[0059] In the assembled device 1, drain tube 41 is inserted into
airway tube 2, such that it protrudes from proximal end 16. The
connector 42 is attached to the airway tube 2 by inserting the
connector body 43 and bite block 44 into proximal end 16. The parts
are an interference fit and can be secured by adhesive. Plug 45 is
attached to connector body 43 via flange 46, such that drain tube
41 passes into minor bore 49, terminating at or adjacent its mouth.
Thus it will be seen that the minor bore 49 is solely in fluid
communication with drain tube 41, and the major bore 48 is solely
in fluid communication with the interior of airway tube 2.
[0060] Airway tube 2 is attached to the back plate 4 conveniently
by overmoulding the back plate 4 onto the already formed tube 2.
Thus, the joining portion 24b of the back plate 4 is moulded onto
the dorsal arc of the airway tube 2 (FIG. 13). Secure attachment is
facilitated by the surfaces 22a, 23 which provide an increased
surface area onto which the moulding occurs, and through-holes 2d,
into which back plate material can flow. Drain tube 41 is connected
in fluid tight manner to integrally moulded drain 11, as
demonstrated by arrow Z (FIG. 13).
[0061] The cuff 7 is bonded to the back plate 4 as illustrated in
FIGS. 12 and 13 by inserting the wedge shaped distal end 7b of the
cuff 7 into the hood or pocket 36a at the distal tip 61 of the back
plate 4 such that the wedge surface 39 mates with the inner surface
36b of the hood 36a, and sections of the inner periphery of the
cuff 7 mate with convex outer surfaces 25 of back plate walls 26.
The cuff 7 is bonded into the hood such that the space between the
hood and the cuff is airtight and in this embodiment the cuff is
provided with a "pinch off" 40 (FIGS. 21 and 22) putting the cuff 7
and hood 36a into fluid communication so that the air space in the
hood can also be inflated, in addition to the cuff 7 itself.
However the cuff 7 pinch off does not extend the entire distance
towards the distal tip of the cuff to prevent the pressure of
inflation occluding the opening 12. The proximal dorsal surface of
the cuff is bonded to the ventral arc of the distal end 22 of the
airway tube 2. Thus, it will be appreciated that unlike in previous
devices incorporating oesophageal drains, in the invention the
drain 11 does not pierce the cuff 7, making manufacturing simpler.
Furthermore, in prior devices in which the drain pierces the cuff,
the cuff must be securely attached around the circumference of the
drain tube at the distal tip. Such a secure attachment, for example
with adhesive, can make the tip hard, and prevent the drain tube
collapsing in the deflated, flattened device, which is highly
desirable to enable the mask to pass easily around the curvature of
the anatomy. In addition, the acute curvature of a drain tube to
cuff joint would be highly susceptible to cracking. In the
invention, these problems are avoided because the drain tube 11 is
integrally moulded with the hood 36a, which in effect forms a
second or minor cuff at the distal tip.
[0062] As will be appreciated, the airway of the device 1, which is
the conduit through which gas is passed to the patient, is provided
by the bore of airway tube 2, which terminates at flared distal end
22. Flared distal end 22 defines, along with back plate 4 and cuff
7, outlet 8 for gas passing from tube 2 into mask 3. Outlet 8
includes three routes by which gas may pass into the mask, namely a
main gas conduit 8a (FIG. 6), and two minor gas conduits 28a.
[0063] In use, the deflated device 1 is inserted into a patient in
the usual manner with devices of this type. As noted above, the
relative rigidity of the airway tube 2 allows a user to grip it and
use it to guide the device 1 into the patient, whilst the
relatively softer, more compliant material of the back plate means
that the mask will more readily deform to negotiate the insertion
path without causing damage to the anatomy, and will return to its
optimum shape to ensure that a good seal is achieved at the
furthest extent of insertion. The ventral displacement of the
distal tip 61 relative to the join between the back plate 4 and
airway tube 2 further enhances ease of insertion, because the
distal tip 61 is thereby presented at the optimum angle to
negotiate the "bend" in the insertion path. In devices formed from
relatively rigid materials such as PVC, as opposed to the often
used LSR these features are particularly important in easing
insertion and providing for an enhanced seal.
[0064] Referring now to the features of the moulded back plate 4,
it will be seen that by providing drain tube 11 integrally moulded
in the material of the back plate 4, problems of mask stiffness and
difficulty of manufacture in prior designs caused by the presence
of a separate drain tube bonded in place with adhesive can be
mitigated.
[0065] Moreover, with the back plate 4 of the invention, the
combination of the centrally located drain tube 11 and minor gas
conduits 28a assist in solving the problem of occlusion of the
airway by parts of the patient's anatomy. The minor gas conduits
28a can be thought of as "nostrils" through which gas may continue
to pass into the patient even if the main outlet 8a becomes
occluded by, for example the patient's epiglottis, as the
epiglottis will rest upon the septum provided by the drain tube 11.
As illustrated particularly in FIGS. 11I and 11J the webs 27, 30
form a partial closure over the conduits 28a, to assist in
preventing structures such as the epiglottis from falling into and
blocking the conduits 28a, and also to make the back plate 4 more
resistant to lateral compression. It will be appreciated that in
this embodiment, the drain 11 forms a convenient septum between the
conduits 28a, however, in devices with no oesophageal drain, a
solid septum could simply be formed in the material of the back
plate by moulding. In addition, a larger number of conduits 28a
could be provided.
[0066] Thus, it can be seen that the above described embodiments
address the problems of prior art devices in novel and inventive
ways.
* * * * *