"BREATHING ASSISTANCE APPARATUS FOR NEONATAL INFANTS"
FIELD OF INVENTION
This invention relates to Nasal Cannulae particularly though not solely to nasal
cannulae for delivering Continuous Positive Airway Pressure (CPAP) to neonates.
BACKGROUND
Certain individuals require a respiratory supplement such as air, oxygen, or other
gases. Such gases are freely supplied and/or supplied at controlled pressures. Such
gases are also supplied through the patient's mouth and/or through the patient's nose.
Nasal supply systems provide an advantage in that they are generally more convenient
and less intrusive than mouth based or mouth covering devices. Despite their
convenience, nasal based devices are deemed uncomfortable in light of securement
straps placed across the face and/or around the head and used to secure the device to
an individuals breathing cavity. Moreover, conventional cannulas do not provide a
proper seal around the nares to inhibit apnoea and to provide a high flow system to
stimulate the patient's breathing. Hence, even with such securement straps, these nasal
devices often dislodge from the breathing cavity. This is of particular concern with
children, infants, or the elderly who do not understand the importance of keeping the
nasal breathing device in place, whether it be a nasal CPAP or nasal cannula.
It is known to be beneficial and therapeutic to supply an individual with a
sufficient amount of respiratory airway pressure in order to maintain a minimum level
of air volume in the lungs. If the air volume falls below this minimum level, then the
lungs may collapse, which can be extremely dangerous or even deadly to the individual.
Moreover, the back pressure can increase oxygen levels in the lungs and decrease
carbon dioxide levels. This will also improve PH by removal of carbon dioxide, which
is an acid, from the blood. Hence, the application of such sufficient pressure, called
continuous positive airway pressure (CPAP), has been found to be advantageous in
maintaining a minimum air volume or lung pressure when an individual is
spontaneously breathing. CPAP can be supplied through nasal attachment devices such
as a nasal cannulae, or through mouth based or endotracheal devices.
A number of CPAP devices are known including endotracheal tubes, head
chambers, face chambers, face masks, nasal prongs, and nasal cannula.. While each type
of device has advantages and disadvantages, the nasal cannula provides a comfortable
alternative for providing CPAP and/or airflow assistance. Prior art nasal cannulae have
been disclosed in many forms with various methods of securing the device to the nasal
passageway. One such cannula assembly is disclosed in United States Patent No.
3,513,844 which uses an adjustable strap that encircles an individual's head. A similar
device is disclosed in United States Patent No. 4,106,505 wherein the supply tubes to
the cannula are hooked over an individual's ears and around the head. Even more
cumbersome, United. States Patent No. -5,477,852 discloses a device with a headboad -
for holding and positioning the nasal inserts and associated supply tubes. Yet another
system in United States Patent No. 5,271,391 discloses a cannula, which is secured by
applying strips of pressure sensitive adhesive tape to the supply tubes leading from each
side of the cannula, thereby attaching the supply tubes to the cheeks of an individual
with the cannula positioned in between.
"Bonnet" type devices are also used to hold the CPAP nasal cannulae in place-
However, this method generally puts pressure on an individual's nose and upper lip
thereby causing pressure necrosis in the centre of the nose. A particularly sensitive
individual is a young child, infant or baby. The bonnet also fails to adequately keep the
nasal prongs in position, particularly with infants who move or roll around in their crib.
In a hospital or care facility setting, it is not uncommon for an attendant to discover that
the CPAP device has been disconnected from a patient's nose, which can, lead to
apnoea, desaturations, bradycardia, or hypoxia which is dangerously low oxygen levels
in the blood. In practice, the tubing for these bonnet type CPAP's is draped around both
sides of the patient's cheek which means that the most comfortable lying down position
is on the patient's back. Pressure on the patient's cheeks caused by the securement
device can make other positions uncomfortable.
Other prior art anchoring systems include adhesive devices which attach directly
to the nose. United States Patent No. 4,823,789 discloses a nose tube anchoring strip
which has an adhesive coated sheet shaped to fit over an individual's nose and an
appendage for holding a nasal-gastric tube. A similar system is found in United States
Patent No. 5,156,641 which has an anchoring cord adhesively attached to an
individual's nose at one end and attached to hold a naso-gastric catheter at the other
end. United States Patent No. 5,513,635 provides a securement device with a body
engagement portion which adheres across the nose of an individual with cannula
engaging portions extending down therefrom. Similarly, United States Patent No.
5,682,881 discloses the use of an adhesive foam pad secured to the upper lip for
positioning of the cannula.
In United States Patent No. 3643660 a unified nasal cannula comprises a hollow
tubular body having an upper flat or plane surface and a pair of spaced and curved
elongated tubular extensions, having exterior orifices for directing a gas flow which
extensions project upwardly at an angle from the surface. Referring to Figures 2 and
3 we see that because the inlet 400 is from one side the prongs 402,404 may see slightly
different pressures. There is also the potential for downstream prong 404 to rebreathe
the expired CO2 from upstream prong 402.
In United States Patent No. 5975077 a cannula is disclosed including an airway
injecting gaa in fluid communication with nootrib of a patient and acrodynamically
designed passageways for both the ambient air and the injected gas to optimize the liquid
flow characteristics during inhalation and exhalation of the patient.
In United States Patent No. 4774946 a cannula is described attached to an
elongated flexible tube. The nasal prongs include bulbous portions that seat and seal
the nasal tubes in the nares.
In United States Pat. No. 5193 532 a device is disclosed for generating by ejector
action a continuous positive airway pressure (CPAP), comprising a breathing-channel
which at one end opens into the atmosphere and at another end is adapted to be
provided with an attachment device to the nose and/or mouth of the patient as seen in
Figure 1. The inlet is situated between a channel open to the atmosphere and open to
the prongs in such a manner that the stream of fresh gas is directed mainly co-axially
into the channel, producing an ejector action.
However, while these prior art systems do provide nasal CPAP they suffer from
a number of disadvantages including: insufficiently securement to the patients head,
potential for unbalanced pressure in each prong, and potential for rebreathing of
expired CO2.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a nasal cannula which goes
someway to overcoming the above mentioned disadvantages or which will at least give
the public a useful choice.
Accordingly in a first aspect the present invention maybe broadly said to consist
in nasal cannula for delivering respiratory gases to a neonatal infant comprising:
a manifold including a chamber, a gases inlet configured to engage an
inspiratory conduit, a gases outlet configured to engage an expiratory conduit and a low
resistance path for said gases through said chamber from said inlet to said outlet
a pair of nasal prongs in fluid communication with said chamber substantial
equidistant said inlet, said prongs juxtaposed directly in said path.
Preferably said cannula includes securement means to hold said prongs in place
in the nares of said neonate.
Preferably said securement means including a strap adapted to pass around the
back of the neck of said neonate and engage with said cannula and thereby hold said
prongs in place in the nares of said neonate.
Preferably said strap includes a low resistance portion, said low resistance
portion adapted to engage with said cannula in a sliding fashion to allow said strap
substantial lateral (iguanian axial) movement relative to said cannula.
Preferably said low resistance portion comprises a thin plastic strand or strip.
Preferably the remainder of said strap includes an adjustable attachment to said
low resistance portion to in use adjust the tension of said strap.
Preferably said securement means including an infant bonnet comprising head
cover means adapted to at least partially cover the head of an infant and including at
least a cuff of elastic property to securely locate said cover means on said infant head,
and medical tube securing means connected with said cover means on the outer surface
thereof, said medical tubes adapted to in use connect to said cannula said securing
means operable to hold medical tubes passing over said cover means against at least
lateral (iguanian axial) movement.
Preferably said head cover means is formed of a knit fabric in a tubular
configuration and open at both ends, said securing means is connected with said outer
surface adjacent one said open end and end closing means are connected with said outer
surface adjacent the other said open end, said end closing means being operable to hold
the said knit fabric of its respective said end in a closed, bunched together, condition.
Preferably either or both of said tube securing means and said end closing means
are or include a lace or tie stitched to said head cover means.
Preferably said lace or tieing is secured at its centre to said head cover means to
provide two arms, said arms passing through a tightening toggle slidable on said arms.
Preferably said tightening toggle is operable between at least two conditions,
being biased to a pinch off condition in which said arms of said lace or tie are clamped
within their passage through said toggle and manipulable to a free configuration in
which said toggle may slide a long said arms of said lace or tie.
In a second aspect the present invention may be broadly said to consist in a
system for delivering respiratory gases in a neonatal infant comprising
a source of pressurised gases,
an inhalatory conduit in fluid communication with said source of gases and
adapted to convey gases,
a nasal cannula in fluid communication with said inhalatory conduit and adapted
to deliver gases to the nasal passages of said infant,
an exhalatory conduit in fluid communication with said delivery means and
adapted to convey gases from said delivery means, and
a pressure regulating device disposed within or in fluid communication with said
exhalatory gases transport means and adapted to achieve a predetermined mean
pressure of gases delivered to the nasal passages of said infant by regulating the flow
of gases through said pressure regulating device.
Preferably pressure regulating device comprising:
a container adapted to house a body of liquid,
terminal conduit means including proximate and distal ends, said proximate end
adapted for connection to said exhalatory conduit, and said distal end adapted for
submergence in said body of liquid,
such that in use the mean pressure of gases delivered to the nasal passages of
said infant is determined by the level to which said distal end is submerged in said body
of liquid.
To those skilled in the art to which the invention relates, many changes in
construction and widely differing embodiments and applications of the invention will
suggest themselves without departing from the scope of the invention as defined in the
appended claims. The disclosures and the descriptions herein are purely illustrative and
are not intended to be in any sense limiting.
The invention consists in the forgoing and also envisages constructions of which
the following gives examples.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
One preferred form of the present invention will now be described with
reference to the accompanying drawings in which:
Figure 1 is a side view of a prior art cannula on an infant,
Figure 2 is a perspective view of a prior art cannula on an infant,
Figure 3 is a cross section of a prior art cannula,
Figure 4 is a closeup perspective view from above of the present invention,
Figure 5 is a section view of the present invention,
Figure 6 is a closeup perspective view of the present invention,
Figure 7 is a side view of the present invention,
Figure 8 is a closeup-view of the present invention from below,
Figure 9 is a closeup view of the present invention from above,
Figure 10 is an illustration of the present invention is use on an neonate,
Figure 11 is a block diagram of the CPAP system,
Figure 12 is a side view of the bonnet, and
Figure 13 is an illustration of the bonnet is use on an neonate
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figure 11 in which a typical application is depicted. A
humidified Continuous Positive Airway Pressure,(CPAP),system is shown in which a
patient 19 is receiving humidified and pressurised gases through a nasal cannula 28
connected to a inhalatory conduit 21. It should be understood that the present
invention, however, is not limited to the delivery of CPAP gases but is also applicable
to other types of gases delivery systems. Inhalatory conduit 21 is connected to the
outlet 12 of a humidification chamber 10 which contains a volume of water 15.
Inspiratory conduit 21 may contain heating means or heater wires 20 which heat the
walls of the conduit to ensure a constant humidity profile along the conduit and
therefore reduce condensation of humidified gases within the conduit. As the volume
of water 15 within humidification chamber 10 is heated, water vapour begins to fill the
volume of the chamber above the water's surface and is passed out of the
humidification chamber 10 outlet 12 with the flow of gases (for exzmple air) provided
from a gases supply means or blower 18 which enters the chamber 10 through inlet 16.
The humidified gases pass through the inhalatory conduit 21 to the cannula 100
connected to the patient's 19 nose through prongs 116,118. The expired gases pass
through the prongs 116,118 to the output manifold 130. The excess gases then flow
through the exhalatory conduit 230 to a pressure regulator 234.
In the preferred embodiment of the present invention the pressure regulator 234,
takes the form of discharging the flow of exhalatory gases into a chamber 204
containing a column of water 238 as seen in Figure 11. The gases flowing through the
exhalatory conduit 230 are discharged into the body of water 238 from a short conduit
236 which extends from the expiratory conduit into the chamber 204. This results in
a bubbling effect, whereby the gases eventually exit the chamber 204 via the outlet port
252, which can also be used to initially fill the chamber 204 with water. The outlet port
252 includes shielding to prevents liquid aerosols created by the vigorous bubbling on
the surface of the water from being expelled. It will be appreciated that the short
conduit 236, could equally be integrated into the end of the expiratory conduit 230. It
will also be appreciated that by adjusting the level of which the short conduit 236 is
submerged in the body of water 238 the mean pressure of supplied gases through the
cannula 100 can be controlled.
Nasal Cannula
Referring now to Figure 4 to 10 the nasal cannula 100 is seen in more detail.
The inlet manifold 110, includes an inlet port 112. This accepts the gas flow from the
humidifier and air/oxygen blender or any other flow source apparatus as would be
appropriate. The diameter of the inlet manifold 110 is as large as possible to ensure
minimal pressure drop in the gases before delivery to the patient. In fluid
communication with the inlet manifold are two nasal prongs 116, 118. The gases are
then able to flow from the inlet manifold 110 up through the nasal prongs into the
corresponding nares of the patient. The prongs 116, 118 themselves are cylindrical with
a slight taper narrowing at the top. The diameter is carefully chosen such that it will
substantially seal against the interior of the nare, without imparting any substantial
pressure thereon. As well as sealing this also provides some level of securement and
keeps the cannula 100 in place.
An important feature of the present invention is shown in Figure 2 and in more
detail in Figure 3. The two nasal prongs 116, 118 are spaced apart at a distance
optimised for the nare spacing for a neonatal infant. However the present invention
would be equally applicable for patients of all sizes and the design is easily scalable.
It will be appreciated that while the nasal structure of each infant will be somewhat
different, almost inevitably the septum will be lower than the fleshy parts on the side
of the nose. As mentioned in the discussion of the prior art this may result in irritation
and pressure necrosis on the septum. It can be seen that the inlet manifold 110 has a
notch 126 or indentation in its uppermost portion between the two nasal prongs 116,
118. The indentation 126 is designed such that there will be no contact with the septum.
Referring now particularly to Figure 5 showing a sectional view of the cannula
100. The inlet manifold 110 is separated from the outlet manifold 130 by a partition
132 running horizontally the length of both manifolds. The partition 132 terminates
approximate to the base 134 of the prongs 116, 118. In this fashion there will always
be at least some flow flowing directly from the inlet manifold 110 to the outlet
manifold 130. This ensures that the deadspace or tidal volume is limited to the volume
of the prongs 116,118. This configuration results in the minimum build up of expired
CO2 and also reduces any opportunity for condensation in the cannula 100.
The prongs 116, 118 are made from a moulded rubber or silicon insert 136
which has an interference or compression fit seal to the hard plastic body 138 of the
cannula 100. The prongs are able to be used as a disposable component or alternatively
easily interchangeable for different sizes, a nasal mask, mouthpiece or other interface
as desired. The inlet port 112 connects directly to inlet manifold 110 and may be
provided with any typical connection configuration for commercially available
conduits. Similarly the outlet port 142 is in fluid communication with the outlet
manifold 130. A further sensor port 144 is provided to measure any parameters of the
delivered gases for example pressure, temperature, humidity. An integral 10mm inlet
10mm outlet conduit 154 formed from extruded PVC or silicon was found to be
suitable for this purpose. The sensor port 144 is connected to a measurement tube 156
which may also form part of the integral inlet outlet tube 154 connected to the cannula
100.
Head Securement
As can be seen in Figures 10 to 12 the cannula 100 is secured to the neonates
head by a bonnet overs its head. The infant bonnet of the present invention includes
a head covering portion 330 which is preferably formed of a stretchable or elastic
material having thermal insulation property. An example of appropriate material is a
synthetic or cotton knit fabric. The head covering 330 is provided in the form of a open
ended tube. Where the material of the covering 330 provides more stretch along one
principal axis then that principal axis as preferably aligned across the axis of the tube.
The head covering 330 preferably includes a zone adjacent one open end 332
which is stiffer than the surrounding region. The zone 331 may comprise for example
a region of modified knit form, a cuff formed from an alternate material or material
configuration or a multi layer hem of the tube.
A securing device is provided on the outer surface of the covering 330 for
supporting a breathing tube or other medical conduits or wiring.
The securing means is a strap 333 with which is sewn onto the bonnet. The
strap has Velcro attached at one end. The nasal tubing is fitted with a foam block 334
with a triangular outside shape. The foam block 334 is positioned on the strap 333.
The strap 333 is then closed around the foam block and secured with the Velcro. The
foam block 334 is used to firmly hold the nasal tubing 321 in place on the bonnet 330
to prevent displacement of the nasal prongs from the nares.
The second open end 347 of the head covering 330 is preferably formed with a
simple hem. The open end 347 is preferably closeable or retainable in a closed position
by a closing means 340. The closing means 340 may comprise a further lace or tie of
similar configuration to the securing means 333. The lace or tie 340 has two arms 342,
344. The arms 342, 344 preferably tie together or pass through a toggle.
In use the end 347 of head covering 330 is bunched together as an end bunch
341 The loop of lace or tie 340 is passed over the bunch 341. The bunch 341 is firmly
secured in a closed configuration within the tightened loop of the lace or tie 340.
The closing means 340 thus provides for easy and efficient closing or opening
of the infant bonnet should there be a need for access to the top of the head of the
infant. Access may for example be required for placement of electrodes or for cranial
ultrasounds. Where access is required the closing means 340 may be released and the
bunched portion of end 347 opened to provide necessary access. This access is
available without disturbing the other end 332 of the head covering 330 or the securing
means 333 supporting medical tubes or wires in place.
Cannula Securement
Ideally the neonate should not be breathing out of it's mouth. Both inhalation and
exhalation should be done through the cannula. In the preferred embodiment the
neonates jaw is strapped shut to eliminate mouth leak. Mouth leak is undesirable
because it causes a lower pressure thus reducing the level of CPAP.
Referring now particularly to Figures 8 to 10 we see that the cannula 100 is
secured at its base to the back of the neonates head using strap 150. The strap connects
at the base of the neonates skull on the back of the neck. It connects to the cannula 100
by way of a sliding strap 152. This strap is secured by way of clips to the hard plastic
body 138 allowing the securing strap 150 substantial relative movement with respect
to the cannula 100 as the neonate twists its head while providing adequate restraining
force directly on the cannula 100 without any twisting of the cannula 100. In one
embodiment this is accomplished by a plastic e.g. acetal sliding strap which engages
into sliding clips on the outer face of the cannula. The teflon strap is adjustably
attached to the neck strap 150 to allow the tension to be adjusted to a comfortable level.
What has been described is an improved nasal cannula for use with a CPAP
respirator. The improvement reduces the likelihood of pressure necrosis or irritation
that might normally be associated with the use of such a device. The improvement
ensures a balanced feed to both prongs, low deadspace high flow through the manifold
so rebreathing of expired CO2 is minimised.
CLAIMS:
1. A nasal cannula (100) for delivering respiratory gases to a neonatal infant
comprising:
a manifold (110, 130) including a chamber, a gases inlet (112) configured to
engage an inspiratory conduit (21), a gases outlet (142) configured to engage an
expiratory conduit (230) and a low resistance path for said gases through said chamber
from said inlet to said outlet,
a pair of nasal prongs (116, 118) in fluid communication with said chamber
substantial equidistant said inlet, said prongs j uxtaposed directly in said path.
2. A nasal cannula (100) for delivering respiratory gases to a neonatal infant as
claimed in claim 1, wherein said cannula includes securement means (152) to hold said
prongs in place in the nares of said neonate.
3. A nasal cannula (100) for delivering respiratory gases to a neonatal infant as
claimed in claim 2, wherein said securement means (152) including a strap (150) adapted
to pass around the back of the neck of said neonate and engage with said cannula (100)
and thereby hold said prongs in place in the nares of said neonate.
4. A nasal cannula for delivering respiratory gases to a neonatal infant as claimed in
claim 3, wherein said strap (150) includes a low resistance portion (152), said low
resistance portion adapted to engage with said cannula in a sliding fashion to allow said
strap substantial lateral movement relative to said cannula.
5. A nasal cannula for delivering respiratory gases to a neonatal infant as claimed in
claim 4, wherein said low resistance portion comprises a thin plastic strand or strip (152).
6. A nasal cannula for delivering respiratory gases to a neonatal infant as claimed in
claim 5, wherein the remainder of said strap includes an adjustable attachment to said low
resistance portion to in use adjust the tension of said strap.
7. A nasal cannula for delivering respiratory gases to a neonatal infant as claimed in
anyone of claims 2 to 6, wherein said securement means including an infant bonnet
comprising head cover means (330) adapted to at least partially cover the head of an
infant and including at least a cuff of elastic property to securely locate said cover means
on said infant head, and medical tube securing means (330) connected with said cover
means on the outer surface thereof, said medical tubes adapted to in use connect to said
cannula, said securing means operable to hold medical tubes passing over said cover
means against at least lateral movement.
8. A nasal cannula for delivering respiratory gases to a neonatal infant as claimed in
claim 7, wherein said head cover means (330) is formed of a knit fabric in a tubular
configuration and open at both ends, said securing means (330) is connected with said
outer surface adjacent one said open end and end closing means (340) are connected with
said outer surface adjacent the other said open end, said end closing means (340) being
operable to hold the said knit fabric of its respective said end in a closed, bunched
together, condition.
9. A nasal cannula for delivering respiratory gases to a neonatal infant as claimed in
claim 8, wherein either or both of said tube securing means (333) and said end closing
means are or include a lace or tie (340) stitched to said head cover means.
10. A nasal cannula for delivering respiratory gases to a neonatal infant as claimed in
claim 9, wherein said lace or tieing (340) is secured at its centre to said head cover means
to provide two arms (342, 344), said arms passing through a tightening toggle slidable on
said arms.
11. A nasal cannula for delivering respiratory gases to a neonatal infant as claimed in
claim 10, wherein said tightening toggle is operable between at least two conditions,
being biased to a pinch off condition in which said arms of said lace or tie are clamped
within their passage through said toggle and manipulable to a free configuration in which
said toggle may slide a long said arms of said lace or tie.
12. A system for delivering respiratory gases in a neonatal infant comprising:
a source of pressurised gases (18),
an inhalatory conduit (21) in fluid communication with said source of gases (18)
and adapted to convey gases,
a nasal cannula (100) in fluid communication with said inhalatory conduit and
adapted to deliver gases to the nasal passages of said infant,
an exhalatory conduit (230) in fluid communication with said nasal cannula (100)
and adapted to convey gases from nasal cannula (100), and
a pressure regulating device (234) disposed within or in fluid communication with
said exhalatory conduit (230) and adapted to achieve a predetermined mean pressure of
gases delivered to the nasal passages of said infant by regulating the flow of gases
through said pressure regulating device (234).
13. A system as claimed in claim 12, wherein pressure regulating device comprising:
a container (204) adapted to house a body of liquid (238),
terminal conduit means (236) including proximate and distal ends, said proximate
end adapted for connection to said exhalatory conduit (230), and said distal end adapted
for submergence in said body of liquid (238),
such that in use the mean pressure of gases delivered to the nasal passages of said
infant is determined by the level to which said distal end is submerged in said body of
liquid.
14. A system in as claimed in claim 13, wherein said nasal cannula (100) is
constructed according to any one of claims 1 to 11.

A nasal cannula
(100) for delivering respiratory
gases to a neonatal infant
comprising a manifold including
a chamber (10), a gases inlet (16)
to the chamber and a gases outlet
(12), a low resistance path for
gases through the chamber from
its inlet to its outlet and a pair of
nasal prongs (116, 118) in fluid
communication with the chamber
with each prong substantial
equidistant the inlet, and directly in
the low resistance path to eliminate
deadspace.