U.S. patent number RE42,843 [Application Number 11/334,822] was granted by the patent office on 2011-10-18 for nasal cannula.
This patent grant is currently assigned to Innomed Technologies, Inc.. Invention is credited to Jonathan Lee, Roger Strickland, Thomas J. Wood.
United States Patent |
RE42,843 |
Strickland , et al. |
October 18, 2011 |
**Please see images for:
( Certificate of Correction ) ** |
Nasal cannula
Abstract
A nasal cannula for delivering air to a patient's nares. Two
delivery tubes are provided to supply air to a pair of nasal
inserts each of which conform to the shape of the nare. Properly
placed bleed ports reduce noise and reduce carbon dioxide retained
in the system. The cannula is positioned on the face with the aid
of a strap system.
Inventors: |
Strickland; Roger (Blackshear,
GA), Lee; Jonathan (St. Augustine, FL), Wood; Thomas
J. (Coconut Creek, FL) |
Assignee: |
Innomed Technologies, Inc.
(Coconut Creek, FL)
|
Family
ID: |
21919741 |
Appl.
No.: |
11/334,822 |
Filed: |
January 19, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
10042042 |
Oct 25, 2001 |
6679265 |
Jan 20, 2004 |
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Current U.S.
Class: |
128/207.18;
128/207.11; 128/207.13 |
Current CPC
Class: |
A61M
16/0833 (20140204); A61M 16/0666 (20130101); A61M
16/0683 (20130101) |
Current International
Class: |
A61M
15/08 (20060101); A62B 18/08 (20060101); A62B
7/00 (20060101); A62B 18/02 (20060101) |
Field of
Search: |
;128/200.24,202.18,203.22,203.29,204.12,205.25,206.11,206.12,206.18,206.27,206.28,207.11,207.13,207.14,207.18
;600/529,532,538 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
US. Appl. No. 12/842,271, filed Jul. 23, 2010, for Nasal Cannula.
cited by other.
|
Primary Examiner: Yu; Justine
Assistant Examiner: Matter; Kristen C
Attorney, Agent or Firm: Bacon & Thomas, PLLC
Claims
What is claimed is:
1. A nasal cannula for use with a constant positive pressure air
supply, comprising: first and second nasal inserts for insertion
into a patient's nares; said inserts adapted for a sealing
relationship with the patient's nares; a left and a right delivery
tube, each coupled to both of said nasal inserts, each of said
delivery tubes is sufficient to provide all of the air required by
the patient; a coupler located remote from said nasal inserts for
coupling said cannula to a source of respiration gas; two tubular
bleed ports having an internal lumen directly opening into said
delivery tubes connecting an interior of the cannula with an
exterior of the cannula; each of said bleed ports having a
characteristic area expressed as a bleed port diameter called BPD,
and separated by a distance called L; each of said tubular bleed
ports located beneath each of said nasal inserts such that a first
bleed port is located beneath a first insert and a second bleed
port is located beneath a second insert, for preferentially
intercepting expired gas during exhalation; the sum total of said
bleed port diameters, called the Total Bleed Port Diameter (TBPD),
have a T BPD/L ratio of between 0.1 and 0.5 such that for the two
bleed ports: 0.5>2*BPD/L>0.1
2. A nasal cannula for use with a constant positive pressure air
supply, supplying air (F) at between about 10 to 50 liters/minutes,
said cannula comprising: first and second nasal inserts for
insertion into a patient's nares; said inserts adapted for a
sealing relationship with the patients nares; a left and right
delivery tube coupled to both of said nasal inserts, each of said
delivery tubes is sufficient to provide all of the air (F) required
by the user; each nasal insert communicates with both the left
delivery tube and right delivery tube; a coupler located remote
from said nasal inserts for coupling said cannula to a source of
respiration air; at least two bleed ports having an internal lumen
directly opening into said delivery tubes connecting the interior
of the cannula with the exterior of the cannula; said bleed port
active during exhalation to remove respired air from the cannula;
each of said bleed ports located beneath each of said nasal inserts
for preferentially intercepting expired gas during exhalation; each
of said bleed ports has an individual diameter size (BPD) which is
approximated by
.times..times..times..times..times..times..times..pi. ##EQU00003##
where IDS is the immediate dead space volume of the delivery tubes
proximate the nares, and `X` is the cross section area of the
cylinder volume of the delivery tubes between said bleed ports.
3. A nasal cannula for use with a constant positive pressure air
supply for supplying air (F) between about 10 to 50 liters/minutes,
said cannula comprising: first and second nasal inserts for
insertion into a patient's nares; said inserts adapted for a
sealing relationship with the patients nares; a left and right
delivery tube coupled to both of said nasal inserts, each of said
delivery tubes is sufficient to provide all of the air (F) required
by the user, each nasal insert communicates with both the left
delivery tube and right delivery tube; a coupler located remote
from said nasal inserts for coupling said cannula to a source of
respiration gas; at least two bleed ports having an internal lumen
directly opening into said delivery tubes connecting the interior
of the cannula with the exterior of the cannula; said bleed port
active during exhalation to remove respired air from the cannula;
each of said bleed ports located beneath each of said nasal inserts
for preferentially intercepting expired gas during exhalation; said
bleed ports when two in number and they have a separation distance
(L) which is approximated by;
.times..times..times..times..times..times..times..times..times..times..ti-
mes..times..apprxeq. ##EQU00004## where `A` is a constant of
proportionality an `X` is the cross sectional area of the delivery
tubes.
.Iadd.4. A nasal cannula for use with a constant positive pressure
air supply, comprising: left and right delivery tubes, each tube
having a size sufficient to provide all the air required by a
patient; first and second nasal inserts for insertion into a
patient's nares, said inserts connected to and extending at an
angle relative to respective portions of said tubes; said nasal
inserts each being elongated and comprising a soft, compliant
material configured to conform to the cross-section of a nare of a
patient when inserted into a nare up to a location where the inner
cross-section of the nare equals the outer cross-section of the
insert to effect said sealing relationship with the patient's
nares; and two tubular bleed ports, each bleed port having an open
internal lumen directly opening into a respective delivery tube and
connecting an interior of the delivery tube with an exterior of the
delivery tube; and wherein each bleed port is located directly
opposite and aligned with a respective nasal insert, said bleed
ports comprising together one of three air exit paths leading away
from the nasal inserts..Iaddend.
.Iadd.5. The nasal cannula as claimed in claim 4, including a soft
flange located at a distal terminal end of each nasal insert, each
flange readily conformable with a patient's nare and enabling a
sealing with the interior of a nare in which the insert is placed
when the insert is inserted up to a location where the
cross-section of the flange equals the cross-section of the
nare..Iaddend.
.Iadd.6. The nasal cannula as claimed in claim 5, wherein said left
and right delivery tubes include portions adjacent to the nasal
inserts, wherein said delivery tube portions adjacent to the nasal
inserts, the nasal inserts and the flanges are made in one integral
piece..Iaddend.
.Iadd.7. The nasal cannula as claimed in claim 6, wherein said
delivery tube portions adjacent the nasal inserts, the nasal
inserts and the flanges are made of silicone rubber..Iaddend.
.Iadd.8. The nasal cannula as claimed in claim 4, further
comprising a coupler located remote from said nasal inserts for
enabling coupling said delivery tubes to a source of respiration
gas..Iaddend.
.Iadd.9. The nasal cannula as claimed in claim 4, wherein each
bleed port extends inwardly of an inner wall of a respective
delivery tube, and comprises a bleed tube that extends toward a
respective nasal insert..Iaddend.
.Iadd.10. The nasal cannula as claimed in claim 4, wherein said
delivery tubes include portions generally aligned adjacent to the
nasal inserts so as to feed pressurized air towards a central area
between the delivery tubes beneath the nasal inserts, and wherein
each bleed port comprises a bleed tube extending into the interior
of a respective delivery tube from an inner wall thereof in a
direction generally normal to the direction of motion of the air
supply flowing in the respective delivery tube, each bleed tube
further extending toward and parallel with a respective nasal
insert..Iaddend.
.Iadd.11. The nasal cannula as claimed in claim 10, each bleed tube
terminating at a location spaced inwardly from an inner wall of a
respective delivery tube and directly opposite an inner end of a
respective nasal insert at its juncture with a delivery
tube..Iaddend.
.Iadd.12. The nasal cannula as claimed in claim 11, wherein each
delivery tube has a wall thickness, and each bleed tube has a
characteristic height that is at least twice and less than 10 times
the wall thickness of a respective delivery tube at the location of
the bleed tube..Iaddend.
.Iadd.13. The nasal cannula as claimed in claim 10, wherein the
bleed tube has a tapered outer shape, tapering inwardly from the
respective delivery tube inner wall towards each nasal
insert..Iaddend.
.Iadd.14. The nasal cannula as claimed in claim 10, wherein the
cannula, including nasal inserts, bleed tubes, and at least part of
the delivery tubes adjacent to the nasal inserts, are made in a
single unitary and integral piece..Iaddend.
.Iadd.15. The nasal cannula as claimed in claim 14, wherein the
cannula, including said nasal inserts, bleed tubes and said at
least part of the delivery tubes adjacent to the nasal inserts, are
made of silicone rubber..Iaddend.
Description
FIELD OF THE INVENTION
The present invention relates generally to a nasal mask or cannula
and more particularly to a nasal cannula for treating a patient
with a positive ventilation pressure machine for assisted
ventilation.
BACKGROUND OF THE INVENTION
Positive air pressure (PAP) assisted ventilation systems have been
adopted for the treatment of various disorders. PAP systems are
commonly used to treatment sleep apnea. Variations of PAP systems
have been used to administer drugs and the like.
In operation the patient's respiration is assisted by an external
pump which supplies air to the patient under a slight positive
pressure. In the conventional system, air is delivered in response
to preset conditions selected for each individual patient. In
normal operation the patient's inspiratory phase is assisted by a
pump which delivers an adequate supply of air at a slight positive
pressure to a mask or cannula that is placed on the face of the
patient. Full face mask systems which cover both the mouth and the
nose are used. Systems which cover the mouth or nose alone are also
common.
In use, when the patient exhales, the higher pressure in the mask
or cannula system is used to open an exhaust valve. Thus the
patient respiration is assisted on the inhalation phase by positive
pressure while the expiration phase takes place at approximately
atmospheric pressure.
In instances where the patient compliance is affected by the
comfort of the mask it is now widely accepted that "nose only"
cannula devices are preferred. Examples of current devices can be
seen in U.S. Pat. No. 5,477,852 to Landis; U.S. Pat. No. 5,533,506
to Wood; U.S. Pat. No. 5,269,296 to Landis; U.S. Pat. No. 5,687,715
to Landis; U.S. Pat. No. 5,724,965 to Handke.
SUMMARY OF THE INVENTION
In contrast to prior air nasal masks, the present system includes a
pair of nasal inserts which are fed bilaterally from a pair of
delivery tubes which includes both a left and a right leg. If the
patient occludes one leg on one side of the mask, the complimentary
side is sufficient to provide all of the air required by the
patient.
Air is introduced into the system through a Y-shaped adapter or
coupler. The shape of the coupler cooperates with other elements to
minimize noise.
A pair of bleed ports are placed in the cannula body near the
patient's nose. These bleed ports reduce the amount of carbon
dioxide retained by the system. The two complex ports are placed in
the cannula body to reduce noise and to reduce carbon dioxide build
up in the system. Example calculations show how the size, shape and
location of each of these ports cooperate to reduce the inhaled
carbon dioxide concentration.
An additional feature relates directly to the shape of the nasal
inserts. The nasal inserts are sufficiently long and compliant that
they may be inserted into the nose until they adopt a location
where the cross-section of the nare and the cross-section of the
insert are essentially equal. The compliance of the material used
to manufacturer the device is sufficient to provide an extremely
comfortable fit in the nares.
BRIEF DESCRIPTION OF THE DRAWING
Throughout the figures of the drawing like reference numerals
indicate identical structure wherein:
FIG. 1 is a schematic representation of the nasal cannula on the
head of a user;
FIG. 2 is a projection of the nasal cannula in isolation;
FIG. 3 is cross section of a portion of the nasal cannula showing
the bleed ports;
FIG. 4 is cross section of a portion of the nasal cannula showing
the bleed ports;
FIG. 5 is cross section of a portion of the nasal cannula showing
the bleed ports;
FIG. 6 is cross section of a portion of the nasal cannula showing
the bleed ports; and,
FIG. 7 is diagram of volumes and dimensions related to the
calculation of the size and location of the bleed ports.
DETAILED DESCRIPTION
Turning to FIG. 1 there is shown a nasal cannula 10 which shows a
nasal insert 12 placed into a patient's nare 14. Directly beneath
each nasal insert is a bleed port as seen at reference numeral 16.
The complete nasal cannula is held on the patient's face with a
strap system 18 which may be of any convenient and conventional
construction. The left and right delivery tubes typified by
delivery tube 20 terminate in a coupler 22. This Y-shaped coupler
22 is connected to a conventional positive pressure ventilation
machine 24.
In operation, the positive pressure ventilation machine 24 supplies
air under pressure to the nasal cannula 10 and releases exhaled air
to the atmosphere. Conventional machines have a valve that is
overpressure during exhalation to exhaust air. In some instances
the system may also warm and humidify the delivered air. In some
instances the machines are used to deliver medications.
The left delivery tube and the right delivery tube 20 should lie
close to the face of the patient and the coupler 22 should be
positioned in the vicinity of the neck as seen in the figure.
FIG. 2 shows the nasal cannula 10 in perspective view. The entire
cannula 10 may be molded out of a polymeric material such as
silicone rubber or urethane. Portions of the nasal cannula may be
locally reinforced to increase rigidity. For example it may be
useful to reinforce the structure at the location where the strap
18 system meets the cannula device 10 In the figure a portion of
the strap system 18 is shown coupled to delivery tube 20. The
various changes in section depicted in the figure add stiffness or
rigidity to the device. The optimal shape and cross section is not
known and some experimentation may be required to optimize the
device. However the softness and compliance of the elastomer is an
important factor in patient comfort. The Y-shaped connector 22 is
adapted for connection to the PAP system 24.
Nasal insert 12 and nasal insert 13 are tubes connected to and
extending from the delivery tube 20 and delivery tube 21
respectively. The most distal portion of the insert 12 terminates
in a flange 26. It is expected that each flange 26 will be quite
soft. The flange 26 is designed to readily conform to the patient's
nare. In use the patient will direct the inserts into the nose and
the inserts 12 and 13 will move in the nare until the .Iadd.inner
.Iaddend.cross section of the nare matches the .Iadd.outer
.Iaddend.cross section of the flange. The anatomy of the nose will
deform the shape of the insert and its flange to achieve a
comfortable seal. It is expected that only one or two sizes will be
required to fit a large population as most patients have similarly
sized nares.
The bleed port typified by port 16 is a tube extending from the
delivery tube 20 into the insert 12. Each tube has a characteristic
height or length. These bleed ports serve several functions. If the
bleed ports 16 and 17 are appropriately placed and sized they can
reduce the accumulation of carbon dioxide. If they are properly
configured, sized and located they can also be used to decrease
"whistling" or other acoustic effects. One objective of the bleed
ports is to decreases the amount of carbon dioxide in the cannula
during inhalation to a targeted value between 0.2 to 0.7 percent. A
preferred value is below approximately 0.5 percent. Applicant
believes that low carbon dioxide concentrations in the system will
prevent build up of carbon dioxide in the patient.
FIG. 3 is a composite and schematic view that shows the air flow in
the nasal cannula 10 during normal inhalation. Inspired air seen as
arrows 30 and 32 depict flow under pressure from the air source 24.
A small flow depicted by vortex 34 enters the space between insert
12 and insert 13. In normal operation each side of the system
carries one half of the required flow.
FIG. 4 is a composite and schematic view that depicts an occlusion
23 or pinch off in the delivery tube 20. In use, when one of the
delivery tubes such as delivery tube 20 is closed off by patient
movement or the like, there is still sufficient air supplied
through the alternate delivery tube 21 as indicated by the airflow
31 depicted in the figure. In this instance the full amount of air
enters the patient through inserts 12 and 13 of the system. In the
figure the height or length of the bleed port is shown as "h2" and
this represents a minimum height bleed port 16. It is expected that
the minimum height is twice the delivery tube thickness at the
location of the bleed port.
FIG. 5 is a composite and schematic view that shows the idealized
airflow in the nasal cannula 10. There are three distinct exit
paths. Path 50 and path 51 depict flow back to the exhaust valve of
the ventilator 24. This flow overpowers the exhaust valve and most
of this flow leaves the system. Path 52 and 53 show exhaust
directly through the bleed ports 16 and 17 respectively. The paths
identified by path arrows 54 and 55 reflect complex scavenging of
the volume between the inserts. This flow dilutes the air in the
volume and helps to reduce carbon dioxide.
Throughout the figures and specification the following definitions
obtain: BPD is the diameter of the bleed port corresponding to port
16 or port 17; h1 or h2 are the height for the bleed port extending
into he cannula. This height is the length of the tubular portion
of the bleed port; IDS is the immediate dead space volume
corresponding to the sum of the volumes 40 42 and 44 and 48 and 46;
X is the cross section area in mm squared of the volume 40 that
corresponds to a portion of the plenum fed by the inducted flow
from the positive air pressure supply 24; L is the distance between
the two bleed ports shown in the preferred embodiment seen in FIG.
7 inter alia; F is the flow rate in ml per sec of the inducted flow
into the cannula, in general one half the flow enters the right
delivery tube 20 and one half enters the left delivery tube 21.
FIG. 6 is a composite and schematic view that shows airflow during
the respiratory pause. In this phase the patient is neither
inhaling or exhaling. During this portion of operation the air from
the PAP ventilator 24 exits though bleed ports 16 and 17 as
indicated by path arrows 60 and 61. In this figure "tall" bleed
ports are depicted. The height value h1 is less than about 10 times
the wall thickness at the location of the bleed port. The diameter
of the bleed ports (BPD) is established to reduce the accumulation
of carbon dioxide. The height of the bleed ports "h1 or h2" is
established to reduce the incidence of parasitic acoustic effects.
The relationship between the bleed port diameter (BPD) and the
height (h1) is optimized between a value of 0.1 and 0.5. that is
when 0.1=<(BPD/h1)=<0.5. It is preferred to use two bleed
ports located near the inserts but other numbers and locations of
bleed port are within the scope of the invention.
Example
It is now recognized that simple ventilation systems which retain a
large volume of exhaled gas within the air inlet track result in
increased carbon dioxide concentration in the patient's blood. An
increase in dissolved carbon dioxide results in the acidification
of the blood and increases respiration drive and usually increases
respiration rate. In the system the dead space of the device is
balanced with both the size and location of the bleed port
structures to prevent build-up of the concentration of carbon
dioxide in the inhaled air. When the size and location of the ports
is optimized, a significant reduction in carbon dioxide gas
concentration is achieved.
Generally speaking if the bleed ports are to be small, they need to
be located near the nasal inserts. This effect is more important if
the dead space within the cannula is large. For this reason, it
should be recognized that there is a relationship between dead
space, bleed port location and size which can cooperate together to
provide a nasal cannula with superior performance. Although it
appears that the optimized ports are restrictive due to their
length and size, it has also been determined that they can be
shaped to minimize parasitic acoustic effects such as "whistling"
which is exhibited by current generations of current nasal
cannula.
Turning to FIG. 7 the immediate dead space is the sum of all the
cylinders shown in the figure as cylinders 40; 42;44; 46; and 48.
The dead space is used in calculations to determine a suitable
bleed port size (BPD). The immediate dead space volume is defined
as the volume of the nasal inserts and the delivery tube between
the inserts Simple geometry can be used to estimate the volume of
the space through the cylinders depicted in FIG. 7. As the bleed
ports 16 and 17 move laterally along the delivery tubes the volume
of cylinder 40 increases by the distance between the inserts. Thus
for the bleed port to pass the volume of the immediate dead space
into the atmosphere within one second requires a computed area
(BPD) related to the square root of the sum of the distance between
the bleed ports. Thus for a given expiration time taken as one
second and a desired concentration of carbon dioxide taken at 0.5
percent one can compute the size of the bleed port or any given
distance or for any given bleed port the optimal distance between
them. Based on these criteria the bleed port's diameter is related
to the square root of the cross sectional area (X), the Immediate
Deadspace (IDS) and the maximum system flow rate (F) as
follows:
.times..times..times..times..times..times..times..pi. ##EQU00001##
A first level approximation identifies that for a given bleed port
of area (BPD), the separation distance of the bleed ports is
inversely related to the square of the cannula cross sectional area
(X)(see FIG. 7) and directly related to the maximum system flow
rate (F) as follows:
.times..times..times..times..times..times..apprxeq. ##EQU00002##
where "A" is the constant of proportionality for the expression and
may be solved with reference to the given and established
relationships.
It should be noted that if the ports are very far apart they need
to be large to reach the carbon dioxide reduction goal, but such
large bleed ports reduce the pressure in the system by such a large
margin that it no longer effectively provides the positive pressure
assistance.
Representative prototype devices have been fabricated with a
diameter (to match cross sectional area X) of between 3/8 and 5/8
inches and other dimensions may be approximately scaled from FIG.
2.
Various modification and additions to the invention may be made
without departing from the scope of the invention.
* * * * *