U.S. patent application number 11/710032 was filed with the patent office on 2007-06-28 for breathing device.
This patent application is currently assigned to E.M.E. Limited. Invention is credited to Stuart Corner, Stephen Foster, Stephen Harrison.
Application Number | 20070144517 11/710032 |
Document ID | / |
Family ID | 9931519 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070144517 |
Kind Code |
A1 |
Foster; Stephen ; et
al. |
June 28, 2007 |
Breathing device
Abstract
A breathing device for assisting patients to breathe by
maintaining positive airway pressure during the breathing cycle
comprises, in fluid communication, a breathing channel (2) and an
exhaust channel (4) extending from a junction therebetween. A gas
inlet channel (8) is arranged, so as in use, to introduce gas into
said breathing channel (2). A positive pressure may be maintained
in the breathing channel (2), wherein the axis of said gas inlet
channel (8) is laterally offset (10) at the point at which the gas
inlet channel (8) introduces the gas into the breathing channel (2)
from the axis of the narrowest part of the breathing channel
(2).
Inventors: |
Foster; Stephen; (Uckfield,
GB) ; Corner; Stuart; (Pevensey, GB) ;
Harrison; Stephen; (Bristol, GB) |
Correspondence
Address: |
STETINA BRUNDA GARRED & BRUCKER
75 ENTERPRISE, SUITE 250
ALISO VIEJO
CA
92656
US
|
Assignee: |
E.M.E. Limited
|
Family ID: |
9931519 |
Appl. No.: |
11/710032 |
Filed: |
February 23, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10505466 |
Mar 14, 2005 |
|
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|
PCT/GB03/00758 |
Feb 21, 2003 |
|
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11710032 |
Feb 23, 2007 |
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Current U.S.
Class: |
128/204.18 ;
128/200.24 |
Current CPC
Class: |
A61M 16/127 20140204;
A61M 16/08 20130101 |
Class at
Publication: |
128/204.18 ;
128/200.24 |
International
Class: |
A62B 7/00 20060101
A62B007/00; A61M 16/00 20060101 A61M016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2002 |
GB |
0204117.6 |
Claims
1-17. (canceled)
18. A breathing device comprising, in fluid communication, a
breathing channel and an exhaust channel extending from a junction
therebetween; and a gas inlet channel arranged so as in use to
introduce gas into the breathing channel such that in use a
positive pressure may be maintained in the breathing channel,
wherein an axis of the gas inlet channel is directed towards an
inner edge of the junction between the breathing and exhaust
channels.
Description
[0001] This invention relates to breathing devices for assisting
patients, particularly human patients, to breathe by maintaining a
positive airway pressure during the breathing cycle.
[0002] It is well recognised that the application of continuous
positive airways pressure (CPAP) is a successful clinical technique
for assisting patients with breathing difficulties. Recently a
particularly successful non-invasive CPAP device has been described
in EP-A-0447 443 and marketed by the Applicant as the INFANT FLOW
(registered trade mark) generator. This device has been shown to
deliver reliable CPAP whilst at the same time resulting in a lower
work of breathing when treating respiratory distress syndrome. This
lower work of breathing is important as it leads to faster patient
recovery times which is of course beneficial to the patient, but
which also helps to keep down running costs of intensive care
departments.
[0003] It has been recognised that the phenomenon of jet bypass,
whereby a proportion of fresh gas supplied to the patient passes
directly out of the exhaust tube is crucial in giving the low added
work of breathing.
[0004] The Applicant has realised that, at least for some
applications, such devices may be further improved. When viewed
from a first aspect therefore the invention provides a breathing
device comprising, in fluid communication, a breathing channel and
an exhaust channel extending from a junction therebetween; and a
gas inlet channel arranged so as in use to introduce gas into said
breathing channel such that in use a positive pressure may be
maintained in the breathing channel, wherein the axis of said gas
inlet channel is laterally offset from the axis of the breathing
channel at the point at which the gas inlet channel introduces the
gas into the breathing channel.
[0005] Thus it will be seen that in accordance with the present
invention, a CPAP-type breathing assistance device is provided in
which the gas inlet channel is offset from the axis of the
breathing channel. It has been found that providing such an offset
can reduce the fluctuations in pressure in the breathing channel
over the breathing cycle. This is recognised to be beneficial in
reducing the work of breathing and thus in aiding patient
recovery.
[0006] Furthermore, it has been recognised that the amount of
lateral offset can be set to give a determinable degree of jet
bypass. In particular, the Applicant has recognised that whilst in
many cases a constant positive airway pressure is the most
appropriate breathing assistance to provide, in some cases it may
be desirable to provide an increased pressure during the inhalation
phase. This might be appropriate, for example, in particularly
serious cases where the patient is unable properly to expand
his/her lungs. The increased pressure can assist in the recruitment
of alveoli. The increased inhalation pressure may be achieved by
setting the degree of bypass appropriately.
[0007] Whilst, as set out above, the required bypass effect may be
achieved by offsetting the gas inlet from the axis of the breathing
tube, it been further recognised that in fact the same effect is
achievable by simulating such an offset. Thus, the gas inlet need
not be offset from the main axis of the breathing tube if the
breathing tube undergoes a change in cross-sectional area and the
gas inlet is offset from the central axis of the narrower portion.
The narrower portion could be a relatively small proportion of the
length of the breathing channel--for example a partial baffle.
[0008] When viewed from a more general aspect therefore the present
invention provides a breathing device comprising, in fluid
communication, a breathing channel and an exhaust channel extending
from a junction therebetween; and a gas inlet channel arranged so
as in use to introduce gas into said breathing channel such that in
use a positive pressure may be maintained in the breathing channel,
wherein the axis of said gas inlet channel is laterally offset at
the point at which the gas inlet channel introduces the gas into
the breathing channel from the axis of the narrowest part of the
breathing channel.
[0009] Thus it will be appreciated that a preferred embodiment of
the aspect of the invention set out above has the breathing channel
being of substantially constant cross-sectional area, such that the
gas inlet channel is laterally offset from the main axis of the
breathing channel.
[0010] The breathing channel may have any convenient
cross-sectional shape, for example it could be triangular or oval
in cross-section. Alternatively it may have a substantially
circular cross-section. Similarly the exhaust channel could also
have any convenient cross-sectional shape e.g. circular, triangular
or oval, and need not be the same shape as the breathing
channel.
[0011] The gas inlet channel may comprise a discrete tube extending
at least partially into the breathing channel. It is preferred
however that the gas inlet channel opens into the breathing
channel--i.e. that the mouth of the gas inlet is at a wall of the
device. Most preferably the gas inlet channel is arranged to open
into the junction between the breathing channel and the exhaust
channel, on the outer side of said junction
[0012] Preferably the gas inlet channel is laterally offset from
the axis of the breathing channel, or the central axis of its
narrowest point, in the direction towards the exhaust channel. This
means that the jet of fresh gas emerging from the gas inlet channel
will be directed at least partially towards the elbow at the inner
edge of the junction between the exhaust and breathing channel or
to the lower edge of a narrower portion. The elbow or other flow
restrictor effectively serves to split the jet of gas between the
breathing and exhaust channels, thereby giving the required
bypass.
[0013] The gas inlet channel could be parallel to the breathing
channel. Preferably however it is inclined at a small angle e.g.
approximately 5.degree., to the breathing channel axis in the
direction away from the exhaust channel. This has been found to
give marginally better performance.
[0014] In fact it has been appreciated that the inclination of the
gas inlet channel can also have an effect on the degree of bypass,
albeit lesser, in general, than the effect of lateral bypass and
that a suitably chosen inclination can give a useful degree of
bypass, even if the gas inlet channel is not laterally offset.
Thus, when viewed from a further aspect the invention provides a
breathing device comprising, in fluid communication, a breathing
channel and an exhaust channel extending from a junction
therebetween; and a gas inlet channel arranged so as in use to
introduce gas into said breathing channel such that in use a
positive pressure may be maintained in the breathing channel;
wherein the axis of said gas inlet channel is inclined relative to
the axis of said breathing channel.
[0015] As in accordance with the earlier aspects of the invention,
the gas inlet channel axis is preferably laterally offset at the
point at which it joins the exhaust channel or laterally offset
from an axis through the centre of a narrowed section of the
breathing channel.
[0016] Clearly the degree of lateral offset will affect the
relative proportions of the split flows and thus the degree of
bypass. Possible embodiments are envisaged in which the offset is
in the direction away from the exhaust channel. However such
embodiments require a relatively large inclination of the gas inlet
channel which is undesirable for other reasons.
[0017] As has been explained above, both the offset and the
inclination of the gas inlet channel relative to the breathing
channel, or narrowest part thereof, influence the degree of bypass
achieved during use. This, in turn, has varying beneficial effects
on the pressure profile in the breathing channel. In general a
particular pressure profile will be suitable for a large number of
patients. However the Applicant has recognised that in some
circumstances it may be desirable to be able to change the pressure
profile by changing the degree of bypass. In some preferred
embodiments therefore the breathing device comprises two or more
gas inlet channels at different offsets and/or inclinations. A
physician may then decide which gas inlet to use for the desired
mode of operation.
[0018] Additionally or alternatively, in some embodiments a movable
gas inlet channel is provided. It is envisaged that the inlet
channel may be moved so either the inclination of the offset may be
varied, or indeed it may be possible to vary both. In one example
the gas inlet channel could be pivotably mounted to the rest of the
device with a flexible gaiter or the like being provided to ensure
a gas-tight seal. In another example the gas inlet could be
slidably mounted to the rest of the device. Again a suitable seal
or gasket may be provided.
[0019] In accordance with all aspects of the invention, it is
preferred that the gas inlet channel has a smaller cross-sectional
area than either the exhaust or breathing channels, preferably less
than a quarter of either. In one particular embodiment in which the
channels are circular, the ratio of their diameters is 1.4 mm to 5
mm.
[0020] Preferably the breathing and exhaust channels are
substantially linear and most preferably meet substantially at a
right angle or greater.
[0021] The breathing device of the invention may be adapted to be
attached directly to the face of a patient. For example it may
comprise a pair of nasal prongs for insertion into the patient's
nose. Indeed where the breathing device is adapted for use by
infants, the infant's nostrils will effectively form part of the
breathing tube. Alternatively, the device may comprise or be
adapted to be connected to a mask for fitting over a patient's
face--e.g over the nose and mouth, the mask being in communication
with the breathing channel.
[0022] In some preferred embodiments an elongate tube is provided
in fluid communication with the exhaust channel. This is not
essential to the operation of the device but it has been found to
reduce the noise generated.
[0023] Certain preferred embodiments of the present invention will
now be described, by way of example only, with reference to the
accompanying drawings in which:
[0024] FIG. 1 is a schematic cross-sectional view of a breathing
device in accordance with the invention;
[0025] FIGS. 2a to 2c are respective schematic flow diagrams
showing air flow in the device during the breathing cycle;
[0026] FIG. 3 is a schematic diagram of a test set-up used to test
an embodiment of the invention;
[0027] FIG. 4 is a graph of pressure v time for an embodiment of
the invention and for a prior art device tested under the same
conditions for the purposes of comparison only;
[0028] FIG. 5 is a graph of pressure v time for three different gas
inlet pressures; and
[0029] FIGS. 6 to 8 are respective schematic perspective views of
further embodiments of the invention.
[0030] FIGS. 9a to 9e are various elevations of another embodiment
of the breathing device in accordance with the invention.
[0031] FIGS. 10a to 10e are various elevations of a further
embodiment of the breathing device in accordance with the
invention.
[0032] The breathing device of FIG. 1 generally comprises a
breathing channel 2 and an exhaust channel 4 in fluid communication
with one another. The breathing channel 2 is provided at its distal
end with a face mask, nasal prongs or other suitable device (not
shown) as the patient interface.
[0033] The exhaust channel 4 is continued by a tube (not shown)
which is open to the atmosphere. It joins the breathing channel 2
at an oblique angle to form a corner 6 on the inside of the
junction.
[0034] A gas inlet channel 8 joins the device so as to introduce
gas into the breathing channel 2 in the region of its junction with
the exhaust channel 4. It will be seen that at the point 8a at
which the gas inlet channel 8 introduces the gas, there is an
offset 10 between the axis 12 of the gas inlet channel 8 and the
axis 14 of the breathing channel 2.
[0035] The respective axes 12, 14 of the gas inlet channel 8 and
the breathing channel 2 are not quite parallel since the former
axis 12 is inclined at an angle A. Furthermore, it may be seen that
the diameter and therefore cross-sectional area of the gas inlet
channel 8 is substantially smaller than that of the breathing or
exhaust channels 2, 4.
[0036] FIGS. 2a to 2c show, schematically, operation of the device
shown in FIG. 1. Firstly FIG. 2a shows the pattern of fresh gas
flow during patient exhalation. As a result of the offset 10
between the axes 12, 14 of the gas inlet and breathing channels
(see FIG. 1) the jet 16 of fresh gas from the gas inlet channel 8
impinges upon the corner 6 at the junction of the breathing and
exhaust channels 2, 4. This causes part of the jet 18 to "bypass"
the breathing channel 2 to flow straight down the exhaust channel
4. The degree of bypass is enhanced by the remainder of the jet 20
which loops back on itself in the breathing channel 2 and also
passes down the exhaust channel 4. This flow 20 combines with the
gas being exhaled by the patient to deflect the jet 16 downwardly
and so causes more high momentum gas to impinge upon the corner
6.
[0037] The effect of the bypass is to reduce pressure in the
breathing channel 2 and so the work required by the patient to
exhale, as compared to what it would have been otherwise without
bypass.
[0038] FIG. 2b shows the pattern of fresh gas flow at zero breath
(the transition between patient exhalation and inhalation). It will
be seen that the bypass portion of the jet 18 is significantly
reduced since the jet 16 is no longer being deflected by the
exhaled air. However the offset 10 and the looped-back fresh gas
flow 20 mean that there is still some bypass. It may further be
observed that the loop 20 of fresh gas is larger than during the
exhalation phase shown in FIG. 2a since the fresh gas is no longer
working against the pressure of the air being exhaled and because
less of it is being bypassed.
[0039] Finally, FIG. 2c shows the pattern of fresh gas flow during
patient inhalation. In this phase the degree of bypass is similarly
low, but still not completely absent, as the low pressure created
inside the patient's lungs draws in the majority 22 of the fresh
gas flow. As shown there is still a portion 20 of the fresh gas
which loops back on itself and passes down the exhaust channel 4.
Depending upon the needs of the patient, the looped flow may in
fact be reversed to supplement the fresh gas with ambient air.
[0040] FIG. 3 shows schematically an experimental set-up used to
test a breathing generator 22 in accordance with the invention. The
breathing generator 22 had a breathing channel 2 and an exhaust
channel 4 at right angles to one another. Both channels had an
internal diameter of 5 mm. A gas inlet channel 8 with a 1.4 mm
internal diameter was provided at the end of the breathing channel
such that its central axis is offset by 1.5 mm relative to the axis
of the breathing channel.
[0041] The breathing channel 2 was connected by means of a tube 24
to a lung simulator 26 comprising a piston driven by an actuator
(not shown). The actuator is controlled by a computer in order to
simulate a representative patient breathing profile. At the inlet
to the lung simulator 26 a pressure feed 28 was taken to a pressure
transducer connected to a personal computer (not shown) to allow
the pressure to be measured and recorded. This pressure feed was
taken 7 cm downstream of the end of the gas inlet channel 8.
[0042] The artificial lung was set to a tidal volume of 30
millilitres and an inhale to exhale ratio of 3:7, which are
reasonably typical figures for an infant. The gas inlet channel 8
was then connected to a source of fresh gas at 37.degree. C. (so
called "medical air") For the first experiment, the rate of fresh
gas flow was set to eight litres per minute. The pressure recorded
by the pressure transducer is shown by line A on the graph in FIG.
4.
[0043] The experiment was then repeated with a known breathing
device--the Applicant's INFANT FLOW (registered trade mark)
generator under the same conditions (except that pressure was
measured at the generator pressure connection, which accounts for
only approximately 0.25 cm H.sub.2O pressure difference) with a
fresh gas flow rate of eight litres per minute. The results may be
seen from the line B in FIG. 4. It is clear from this not only that
a higher airway pressure is achievable for a given flow rate, but
also that the pressure fluctuation over the breathing cycle has
been even further reduced in accordance with the present
invention.
[0044] The experiment was repeated with fresh gas flows of six and
fourteen litres per minute and results are shown by lines C and D
respectively in FIG. 5. FIG. 5 also shows the results obtained with
a flow rate of eight litres per minute (line A). As may be seen, at
six and eight litres per minute (lines C and A respectively) there
is negligible pressure fluctuation. At fourteen litres per minute
(line D), there is in fact negative fluctuation--in other words
there is an increase in pressure on inhale and a decrease on
exhale. This gives a degree of breathing assistance and is
potentially extremely beneficial for those patients having
difficulty breathing.
[0045] Thus it will be seen that at least an embodiment of the
invention provides a breathing device with very low fluctuations in
pressure which is therefore able to assist in breathing with
minimal added work of breathing as compared to already beneficial
prior art devices.
[0046] A further potential embodiment of the invention is shown
schematically in FIG. 6. In this embodiment, two separate gas inlet
channels 8b and 8c are provided. The first inlet 8b is provided
offset below the axis of the breathing channel 2 to provide a
predetermined degree of offset. The second inlet 8c has the same
amount of offset but is also inclined with respect to the axis of
the breathing channel 2. This will give a higher degree of bypass
which may be required in certain situations--e.g. if a higher fresh
gas flow is required. In use a physician or medical attendant may
select which inlet channel 8b, 8c to use as needed. This could
simply be by placing a gas supply tube over the desired inlet
channel or it could be by means of a two-way valve.
[0047] Another potential embodiment is shown in FIG. 7. In this
embodiment the gas inlet channel 8 is shown extending through a
rubber gaiter 30. Inside the breathing device (not shown) the gas
inlet channel 8 is pivotally attached to the main body. This allows
it to be inclined up and down to provide the desired degree of
bypass. A screw or the like could be provided to hold the inlet 8
in the desired inclination.
[0048] FIG. 8 shows another possible embodiment. In this embodiment
the gas inlet channel 8 is connected to a block 32 received in a
recess 34 in the corner of the device. The gas inlet channel is in
gaseous communication with an internal passage in the block which
opens into the interior of the device to provide fresh gas into the
breathing channel. The block 32 is a reasonably gas-tight fit into
the side walls of the recess 34. Stops may be provided to limit the
movement of the block 34. It will be seen that the block 34 is
provided on its upper face with a protrusion 36 to facilitate
movement thereof.
[0049] A further embodiment of the breathing device is shown in
FIGS. 9a to 9e. In this embodiment the breathing channel 2 is of a
substantially triangular cross-section as shown by the end
elevations 9c and 9d. The breathing channel 2 and an exhaust
channel 4 are in fluid communication with one another. As before, a
gas inlet channel 8 joins the device so as to introduce gas into
the breathing channel 2 in the region of its junction with the
exhaust channel 4. As in previous embodiments, it will be seen that
at the point 8a at which the gas inlet channel 8 introduces the
gas, there is an offset 10 between the axis 12 of the gas inlet
channel 8 and the axis 14 of the breathing channel 2.
[0050] Unlike previously however, the side elevation, FIG. 9a,
shows that the breathing channel 4 is at a right angle to the
exhaust channel 4. The exhaust channel 4 is of substantially
circular cross section, as shown in the bottom view of the device
given in FIG. 9e, and is therefore not the same cross section shape
as that of the breathing channel 2.
[0051] Finally, FIGS. 10a to 10e show another embodiment of the
breathing device. In this embodiment the breathing channel 2 is of
a substantially oval cross-section as shown by the end elevations
10c and 10d. Again, the side elevation, FIG. 10a, shows that the
breathing channel 4 is at a right angle to the exhaust channel 4.
The exhaust channel 4 has substantially oval cross-section and
therefore has the same cross-sectional shape as the breathing
channel 2, as shown in the bottom elevation of the device given in
FIG. 10e.
[0052] It will be appreciated by those skilled in the art that many
variations and modifications of the described embodiments are
possible within the scope of the present invention. For example,
the breathing device may be configured deliberately to increase the
airway pressure during the inhalation phase by increasing the
offset between the axes of the gas inlet channel and the breathing
channel in order to give a corresponding smaller degree of bypass.
Such a device could be useful for treating acute respiratory
distress syndrome in which the increased pressure on inhalation can
help in the recruitment of alveoli.
[0053] Furthermore, the breathing channel need not be of constant
bore as depicted. It may comprise a local reduction in the
cross-sectional area--e.g. by virtue of a baffle, step or other
protrusion. In this case the gas inlet channel may not be offset
from the main axis of the breathing channel but will be offset from
the effective central fluid axis thereof which is determined by the
reduction in cross-section or bore.
* * * * *