(12) United States Patent
`Bordewick
`
`(10) Patent N0.:
`
`(45) Date of Patent:
`
`Us 6,431,172 B1
`Aug. 13, 2002
`
`US006431172B1
`
`128/206.11
`
`5/1992 Dickerman el al.
`5,113,857 A *
`9/1993 Sullivan et 211.
`5,243,971 A
`12/1993 Landis
`5,269,296 A
`........ .. 128/204.18
`5,477,852 A * 12/1995 Landis et al.
`5,682,881 A
`11/1997 Winthrop et al.
`5,687,715 A
`11/1997 Landis et 211.
`5,752,510 A
`5/1998 Goldstein ............ .. 128/200.24
`5,794,619 A *
`8/1998 Edelman et al.
`..... .. 128/200.24
`6,354,293 B1 *
`3/2002 Madison .............. .. 128/204. 13
`
`FOREIGN PATENT DOCUMENTS
`
`W0
`
`WO 90/01963
`
`3/1990
`
`* cited by examiner
`
`Primary Examiner—Aaron J. Lewis
`Assistant Examiner—Teena Mitchell
`
`(74) Attorney, Agent, or Firm—RothWell, Figg, Ernst &
`Manbeck
`
`(57)
`
`ABSTRACT
`
`A nasal cannula for delivering a breathing gas includes a
`rigid support adapted for placement at least partly beneath
`the nose of a user, an inflatable plenum chamber mounted on
`the rigid support, and a pair of nares elements mounted on
`the inflatable plenum chamber for insertion into the nostrils
`of the user. The inflatable plenum chamber includes a
`flexible membrane mounted on the rigid support. The flex-
`ible membrane can be preformed to define laterally spaced
`humps for mounting individual nares element and can
`further be pleated. Alternatively, a pair of inflatable plenum
`chambers can be separately mounted on the rigid support.
`
`19 Claims, 3 Drawing Sheets
`
`(54) NASAL CANNULA WITH INFLATABLE
`PLENUM CHAMBER
`
`(75)
`
`Inventor:
`
`Steve Bordewick, Shoreview, MN (US)
`
`(73) Assignee: Mallinckrodt Inc., St. Louis, MO (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/692,172
`
`(22) Filed:
`
`Oct. 20, 2000
`
`Int. Cl.7 ............................................. .. A61M 15/08
`(51)
`(52) U.S. Cl.
`............................ .. 128/207.18; 128/206.11
`(58) Field of Search ..................... .. 128/200.24, 200.26,
`128/204.11, 204.12, 206.11, 206.18, 206.21,
`207.13, 207.18, 912, 203.22, 203.18, DIG. 26;
`604/9401; 606/199, 204.45
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`9/1956 Ellman ..................... .. 128/198
`5/1970 Smith
`.. 128/207.18
`4/1975 Baum
`128/200.14
`9/1975 Guichard
`128/203.22
`1/1983 Dali
`.................... .. 128/203.22
`8/1984 Koch et 211.
`11/1988 Trimble et 211.
`4/1990 Lee
`4/1990 Kopala et al.
`8/1991 Kopala et 211.
`
`
`
`2,763,263 A *
`3,513,844 A *
`3,874,380 A *
`3,902,486 A *
`4,367,735 A *
`4,465,067 A
`4,782,832 A
`4,915,105 A
`4,919,128 A
`5,042,478 A
`
`RMD 1020
`
`1
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`RMD 1020
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`U.S. Patent
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`0...UA
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`20023:1
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`Sheet 1 of3
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`US 6,431,172 B1
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`U.S. Patent
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`0...UA
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`20023:1
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`Sheet 2 of3
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`US 6,431,172 B1
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`3
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`

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`U.S. Patent
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`Aug. 13, 2002
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`Sheet 3 of3
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`Us 6,431,172 B1
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`16
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`10
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`36 K
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`V
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`1
`NASAL CANNULA WITH INFLATABLE
`PLENUM CHAMBER
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention relates generally to the field of
`respiratory therapy and, more particularly, to an apparatus
`and method for delivering a breathing gas to a patient.
`2. Description of the Background Art
`Continuous positive airway pressure (CPAP) therapy has
`been shown to be an effective treatment for obstructive sleep
`apnea, a condition in which the patient’s airway passage is
`repeatedly blocked during a period of sleep resulting in
`interruption of the flow of air to the patient’s lungs and
`causing the patient
`to awaken. CPAP therapy involves
`delivering a breathing gas at a constant gas pressure through
`the nasal passages to prevent negative pressure conditions
`within the upper air passageway which can lead to
`obstruction, thereby allowing continuous air flow through
`the upper air passageway. The gas is typically administered
`by placing a mask over the nose of the patient by means of
`a strap or harness or other headgear and providing a source
`of positive low pressure air connected to the mask.
`Conventional nasal masks, exemplified by US. Pat. No.
`4,655,213 to Rapoport et al., include a shell that contacts the
`face of the patient around the nose to form a seal. This type '
`of mask is sometimes considered uncomfortable because of
`the contact pressure needed to obtain an adequate seal, and
`are often noisy due to air leaks. In many cases, use of a
`conventional mask represents a formidable obstacle to
`patient acceptance of CPAP therapy.
`An alternative approach which has gained widespread
`acceptance, exemplified by U.S. Pat. No. 4,782,832 to
`Trimble et al., involves use of a nasal cannula having a pair
`of nares elements or inserts configured for insertion into the
`respective nostrils of a patient. The nares elements are
`mounted on a rigid plenum chamber extending from a gas
`inlet
`tube connected with a source of breathing gas and
`include passages formed therethrough in communication
`with openings in the plenum chamber. The outer wall of each
`nares element is generally frustoconically shaped so as to
`sealingly engage the nares—defining surface of the nose.
`Adjustability of the r1ares elements is provided by rotatably
`mounting the elements to the plenum chamber and mounting
`the elements in slots permitting selective lateral positioning
`of the elements with respect
`to each other. The nares
`elements can be provided with flexible corrugated sections
`to achieve greater degrees of flexibility and adjustability.
`The nares elements are also formed of a relatively soft,
`deformable, shape-retaining synthetic resin material permit-
`ting manual deformation and alteration of the effective shape ,
`and position of the elements.
`A variation of the aforementioned nasal cannula, dis-
`closed in US. Pat. No. 5,269,296 to Landis, includes nares
`elements with inflatable cuffs that engage the interior walls
`of the nose defining the nares in order to hold the cannula in
`place within the nares. The cuffs can be inflated by means of
`apertures formed in the side walls of the nares elements or,
`alternatively, by tubes delivering gas from a separate source
`of gas. The nasal cannula is held in place by an inflatable
`harness composed of hoses made of soft inflatable plastic
`which inflate upon application of air pressure to the hoses.
`While such an inflatable harness is potentially softer than a
`conventional harness,
`the increased bulk associated there-
`with can contribute to patient discomfort and the lack of
`rigidity can make it diflicult to properly position and main-
`tain the device in a desired position without frequent read-
`justment.
`
`2
`While the aforementioned nasal cannulae are an improve-
`r11er1t over prior nasal masks, there continues to be a need for
`an improved nasal cannula that offers greater adjustability
`and comfort for the patient without added complexity.
`SUMMARY OF THE INVENTION
`
`Accordingly, it is a primary object of the present invention
`to provide a nasal cannula which overcomes the disadvan-
`tages of prior nasal masks and cannulae.
`A first aspect of the present invention is generally char-
`acterized in a nasal cannula for delivering a breathing gas
`including a rigid support adapted for placement at least
`partly beneath the nose of a user, an inflatable plenum
`chamber mounted on the rigid support, and a pair of nares
`elements mounted on the inflatable plenum chamber for
`insertion into the nostrils of the user. The inflatable plenum
`chamber preferably includes at least one flexible membrane
`mounted on the rigid support. The flexible membrane can be
`preformed to define laterally spaced humps for mounting
`individual nares element and can further be pleated.
`The nares elements can be mounted on a single inflatable
`plenum chamber or on separate inflatable plenum chambers.
`The nares elements can further be provided separately and
`attached to the inflatable plenum chamber or formed inte-
`grally as part of the plenum chamber. The inflatable plenum
`chamber can be fixed to the rigid support or detachably
`connected to the rigid support.
`invention is generally
`Another aspect of the present
`characterized in a method of delivering a breathing gas using
`a nasal cannula including at least one inflatable plenum
`chamber mounted on a rigid support and a pair of nares
`elements mounted on the at
`least one inflatable plenum
`chamber. The method includes the steps of securing the
`nasal cannula to the head of the user, positioning the nasal
`cannula such that the nares elements are disposed within the
`nostrils of the user and the at least one inflatable plenum
`chamber is disposed between the nares elements and the
`rigid support, and delivering a breathing gas to the user via
`the inflatable plenum chamber and the nares elements.
`The above and other features and advantages of the
`present invention will be further understood from the fol-
`lowing description of the preferred embodiments thereof,
`taken in conjunction with the accompanying drawings in
`which like reference numerals are used to denote like parts.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows a front view of a nasal cannula according to
`the present invention.
`FIG. 2 shows a side view of the nasal cannula of FIG. 1,
`partly in section, with its plenum chamber deflated.
`FIG. 3 shows a side view of the nasal cannula of FIG. 1,
`partly in section, with its plenum chamber inflated.
`FIG. 4 shows how a nares element mounted on an
`inflatable plenum chamber can move with several degrees of
`freedom.
`
`FIG. 5 shows a fragmentary front view, partly in section,
`of another embodiment of a nasal cannula according to the
`present invention.
`FIG. 6 shows an enlarged fragmentary view, in section, of
`the interface between inflatable and rigid plenum portions of
`the nasal cannula of FIG. 5.
`
`FIG. 7 shows a fragmentary front view, partly in section,
`of yet another embodiment of a nasal cannula according to
`the present invention.
`
`5
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`US 6,431,172 B1
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`3
`FIG. 8 shows a fragmentary front view, in section, of still
`another embodiment of a nasal cannula according to the
`present invention.
`FIG. 9 shows an exploded view of a further embodiment
`of a nasal cannula according to the present invention.
`FIG. 10 shows an exploded View of an additional embodi-
`ment of a nasal cannula according to the present invention.
`DETAILED DESCRll"l‘l()N OF Tl-IE
`PREFERRED EMBODIMENTS
`
`Anasal cannula 10 according to a first embodiment of the
`present invention is shown in FIGS. 1 and 2. FIG. 1 shows
`the nasal cannula looking distally, and FIG. 2 shows a side
`view of the nasal cannula with a partial section taken
`through line 2—2 in FIG. 1. Nasal cannula 10 includes a
`rigid support 12 for placement at least partly beneath the
`nose of a user, an inflatable plenum chamber 14 mounted on
`the support, and a pair of nares elements 16 mounted on the
`inflatable plenum chamber. Support 12 is shown as a gen-
`erally diamond-shaped frame with a central opening. The ,
`support extends downwardly at an oblique angle from the
`proximal end 18 of an optional gas inlet tube 20. Inflatable
`plenum chamber 14 includes upper and lower flexible mem-
`branes 22A and 22B mounted on opposite sides of support
`frame to define a chamber therebetween in communication V
`with a gas outlet at the proximal end of gas inlet tube 20.
`Upper membrane 22A is shown with a pair of laterally
`spaced gas outlets 24 formed therein for receiving nares
`elements 16.
`The nares elements shown in FIGS. 1 and 2 are similar to
`those described in U.S. Pat. No. 4,782,832, the disclosure of
`which is incorporated herein by reference. These nares
`elements or inserts are generally frustoconical and mounted
`on a bellows 20 type corrugated section, with a central air
`passageway formed therethrough to permit gas flow from
`plenum chamber 14 into the nose. Elements 16 are prefer-
`ably formed of a soft synthetic resin material, such as
`silicone, so as to allow axial and radial adjustment of the
`inserts to accommodate variations in the nasal passages of
`different wearers. While a particular type of nares element is
`shown and described, it will be appreciated that any type of
`soft, semi-soft, or hard nares element capable of forming a
`seal with a nasal passage can be used.
`The optional gas inlet tube 20 is shown in FIGS. 1 and 2
`with a fitting 26 at a distal end for receiving a gas hose 28
`of the type commonly used to convey a breathing gas from
`a ventilator or respirator. Gas inlet tube 20 and support 12
`can be formed of any medically acceptable rigid material but
`are preferably formed of rigid polycarbonate or PVC. The
`term “rigid” is used in a broad sense to mean subtantially .
`non—deformable and non—inflatable under normal operating
`loads and pressures. If the gas inlet tube and the support are
`formed of the same material, it is possible to form them as
`an integral one—piece unit. The inflatable plenum chamber in
`general, and flexible membranes i11 particular, can be formed
`of any medically acceptable flexible material capable of
`being inflated by normal breathing gas pressures (e.g., about
`3 to 35 cm H20) but are preferably formed of an elastomeric
`material such as silicone. In the case of the embodiment
`shown in FIGS. 1 and 2, marginal portions of the inflatable
`plenum chamber membranes 22A and 22B can be aflixed to
`support 12 and inlet tube 20 using adhesives, co-molding,
`thermal welding, mechanical attachment or any other suit-
`able techniques. Alternatively, a single membrane having a
`socl<—like configuration can be slipped over the support and
`can be permanently or detachably affixed to the support
`and/or the tube instead of using two membranes.
`
`4
`In use, nasal cannula 10 is secured to the head of a patient
`such that nares elements 16 are inserted into the patient’s
`nostrils and inflatable plenum 14 is disposed underneath the
`patient’s nose between the nares elements and support 12.
`Support 12 extends distally from beneath the patient’s nose
`to gas inlet tube 20 which extends upwardly to receive a gas
`supply hose 28 draped over the top of the patient’s head.
`Standard straps and harnesses that extend around the head of
`the patient from the rigid portions of the nasal cannula are
`preferably used in securing the nasal cannula and hose to the
`patient; however, the mask can be attached to the wearer
`using any suitable headgear including, by way of example,
`anchors biased against the wearer’s head as described in
`U.S. patent application Ser. No. 09/276,799, filed on Mar.
`26, 1999, the disclosure of which is incorporated herein by
`reference.
`Hose 28 connects the nasal cannula to a ventilator or
`respirator that generates a flow ofbre athing gas. Gas flowing
`from the generator is conveyed by hose 28 into gas inlet tube
`20 which directs the gas into inflatable plenum chamber 14.
`As shown in FIG. 2, inflatable plenum chamber 14 is
`flaccid when not pressurized by a breathing gas. In the
`uninflated or flaccid state, flexible membranes 22A and 22B
`are slack and are not effective in transmitting forces between
`nares elements 16 and rigid support 12. Nares elements 16
`are thus loosely positioned in the user’s nostrils without
`much force. Nevertheless, rigid support 12 provides suffi-
`cient structural support to maintain the nominal position of
`nares elements 16 relative to other parts of the nasal cannula
`so that initial alignment of the nares elements with the
`patient’s nostrils can be accomplished.
`When pressurized by a breathing gas, plenum chamber 14
`is inflated as shown in FIG. 3. In the inflated state, internal
`gas pressure within chamber 14 takes up the slack in
`membranes 22Aand 22B, which expand outwardly to gently
`apply an inward retention force to nares elements 16. The
`use of internal gas pressure to regulate the amount of force
`applied to the nares elements is a major departure from prior
`art cannulae which rely on relatively non—compliant mem-
`bers such as straps to retain the nares elements ir1 place
`within the nose.
`
`From plenum chamber 14, the breathing gas flows into the
`nares elements 16 via outlets 24 in the chamber. The nares
`elements then direct the breathing gas into the patient’s
`nostrils. To ensure a leak-free fit, the nares elements are
`preferably snugly positioned within the patient’s nostrils. In
`the past, patients have experienced some discomfort from
`snugly fitted nares elements because of their tendency to
`transmit physical shocks and jolts to the sensitive nasal
`passages of the patient when fully compressed.
`In the
`present invention, however, the inflated plenum Chamber
`o ers additional compliance so that most shocks and jolts
`which would otherwise be transmitted to the patient are
`absorbed. It will also be appreciated that the added compli-
`ance of the inflatable plenum chamber provides additional
`degrees of freedom for movement of the nares elements
`while at the same time increasing the range of movement in
`all directions. This results in improved adjustability of the
`nares elements, a owing the nasal cannula to accommodate
`large physical di erences between patients. FIG. 4 shows
`how a nares element 16 mounted on an inflatable plenum
`chamber 14 can move with five or more degrees of freedom.
`For example, the nares element can move axially along its
`long axis as indicated at “A", or translate laterally in
`orthogonal directions perpendicular to its long axis as indi-
`cated at “D”, or tilt relative to its long axis as indicated at
`“G”, or rotate about its long axis as indicated at “w”, or some
`combination of the movements in the foregoing directions.
`
`6
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`

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`US 6,431,172 Bl
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`5
`Another embodiment of a nasal cannula 10 according to
`the present invention is shown partly in section in FIGS. 5
`and 6. The nasal cannula in this embodiment is similar to the
`nasal cannula described in conjunction with FIGS. 1 and 2,
`but with a solid support 12 defining a lower portion of the
`inflatable plenum chamber 14 and a flexible membrane 22
`preformed to increase isolation of the nares elements from
`one another in the inflated state. Support 12 includes side-
`walls 32 that extend upwardly from a bottom wall 34 to
`define a compartment with an open top. Aflexible membrane
`22 extends across the open top of the compartment to define
`an inflatable plenum chamber 14 in conjunction therewith.
`As best seen in FIG. 6, flexible membrane 22 is molded into
`grooves formed in sidewalls 32 of the support to present a
`substantially [lush outer surface without protruding edges
`that could irritate a user. It will be appreciated, however, that
`edges of the flexible membrane could be connected to the
`sidewalls using an interior or exterior lap joint. As best seen
`in FIG. 5, flexible membrane 22 is preformed to define
`laterally spaced humps 36 separated by a recess 38 in the
`inflated state. Nares elements 16 are mounted on the ,
`elevated regions or humps 36 to permit a greater degree of
`independent movement. Alternatively,
`the flexible mem-
`brane can form a single hump as shown in FIG. 1. As a
`further alternative, the solid support can be replaced by a
`support in the form of a frame with the inflatable plenum ,
`being formed by a pair of membranes on opposite sides of
`the frame, at least one of the membranes being preformed to
`define plural humps in an inflated state.
`FIG. 7 shows a fragmentary View of still another embodi-
`ment of a nasal cannula 10 according to the present inven-
`tion having a modified flexible membrane 22. Nasal cannula
`10 in FIG. 7 is similar to the nasal cannula described in
`conjunction with FIG. 5, however, flexible membrane 22 is
`formed with pleats or folds 40 about the circumference of
`each hump 36 allowing a greater range of movement of the
`nares elements 16 in the lateral direction.
`FIG. 8 shows a fragmentary view of an additional
`embodiment of a nasal cannula 10 according to the present
`invention having a modified flexible membrane 22. Flexible
`membrane 22 is similar to the flexible membrane described
`in conjunction with FIG. 5 but defines integral nares ele-
`ments l6 on each hump 36. The nares elements 16 have
`smoothly sloping walls but could be formed with pleats or
`folds if desired.
`A further embodiment of a nasal cannula 10 according to
`the present
`invention is shown in FIG. 9.
`In this
`embodiment, support 12 is a rigid hollow member defining
`a rigid plenum chamber in fluid communication with gas
`inlet
`tube 20 and the inflatable plenum chamber 14 is
`mounted on the rigid plenum chamber. Inflatable plenum ,
`chamber 14 is a bag formed of a flexible membrane with a
`pair of laterally spaced gas outlets 24 on a top surface
`thereof for receiving nares elements 16 and a tubular gas
`inlet 44 on a bottom surface thereof for communicating with
`an opening 46 in the support.
`Still another embodiment of a nasal cannula 10 according
`to the present invention is shown in FIG. 10. Nasal cannula
`10 is similar to the nasal cannula described ir1 conjunction
`with FIG. 9 but includes a pair of inflatable plenum cham-
`bers 14 mounted in lateral relation to one another on a rigid
`plenum chamber defined by a hollow rigid support 12.
`Support 12 includes a pair of gas outlet openings 46, and
`each of the inflatable plenum chambers 14 includes a tubular
`gas inlet 44 configured to eommruiicate with a gas outlet 46
`in the support. Inflatable plenum chambers 14 each have a
`gas outlet 24 configured to receive one of the nares elements
`16.
`
`6
`The nasal cannulae 10 shown in FIGS. 9 and 10 are
`advantageous in that they facilitate easy removal of the
`inflatable plenum chambers from the supports to permit
`sterilization and reuse of the supports, and/or replacement of
`one type of inflatable plenum chamber with another type of
`inflatable plenum chamber. While separate nares elements
`are shown, it will be appreciated that the nares elements can
`be formed as integral parts of the plenum chamber as shown
`in FIG. 8.
`
`The nasal cannula of the present invention can be used to
`deliver one or more gases to a patient in connection with any
`type of respiratory therapy, but
`is particularly useful
`in
`administering CPAP and BiPAP therapy to patients suffering
`from obstructive sleep apnea.
`While the invention has been described ir1 detail above,
`the invention is not intended to be limited to the specific
`embodiments as described. It is evident that those skilled in
`the art may now make numerous uses and modifications of
`and departures from the specific embodiments described
`herein without departing from the inventive concepts. For
`example, a vent aperture can be formed in any portion of the
`nasal cannula to expel
`the carbon-dioxide laden gases
`exhaled by the patient between breaths. Any conventional
`vent aperture can be used including, by way of example, the
`vent configuration described in the U.S. Pat. No. 5,065,756
`to Rapoport, the disclosure of which is incorporated herein
`by reference. By way of further example, the vertical gas
`inlet tube can be replaced by a horizontal tube that extends
`laterally across the face, or a tube oriented perpendicular to
`the face. When a single inflatable plenum chamber
`is
`provided, independent movement of the nares elements can
`be enhanced by structures, such as walls or baffles, disposed
`within the inflatable plenum chamber. When a pair of
`inflatable plenum chambers are provided,
`the inflatable
`chambers can be mounted on a single support or individually
`mounted on a pair of supports.
`What is claimed is:
`1. Anasal cannula for delivering a breathing gas to a user,
`said nasal cannula comprising
`a rigid support adapted for placement at
`beneath the nose of the user,
`an inflatable plenum chamber mounted on said rigid
`support, said inflatable plenum chamber having at least
`one gas inlet and at least one gas outlet; and
`at least one nares element mounted on said inllatable
`plenum chamber, said nares element having a gas flow
`passage therethrough in communication with said gas
`outlet.
`2. A nasal cannula as set forth in claim 1, further Com-
`prising a rigid gas inlet tube having a gas outlet in commu-
`nication witli said at least one gas inlet of said inflatable
`plenum chamber.
`3. Anasal cannula as set forth in claim 2, wherein said gas
`inlet tube has proximal and distal ends, and wherein said
`rigid support extends from said proximal end of said gas
`inlet tube.
`4. Anasal cannula as set forth in claim 2, wherein said gas
`inlet tube and said support are formed as an integral one-
`piece unit.
`5. A nasal cannula as set forth in claim 1, wherein said
`rigid support is a frame having at least one opening formed
`therein.
`6. A nasal cannula as set forth in claim 5, wherein said
`inflatable plenum chamber includes a pair of flexible mem-
`branes mounted on opposite sides of said frame to define a
`plenum chamber therebetween.
`
`least partly
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`US 6,431,172 B1
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`7
`7. A nasal cannula as set forth in claim 1, wherein said
`inflatable plenum chamber includes a flexible membrane,
`and wherein said rigid support and said flexible membrane
`cooperate to define said inflatable plenum chamber.
`8. A nasal cannula as set forth in claim 1, wherein said
`rigid support is solid and said inflatable plenum chamber
`includes a membrane mounted on said rigid support to
`define a plenum chamber therebetween.
`9. A nasal cannula as set forth in claim 1, wherein said at
`least one nares element is formed by said membrane.
`10. A nasal cannula as set forth in claim 1, wherein said
`inflatable plenum chamber includes a pleated membrane.
`11. A nasal cannula as set forth in claim 1, wherein said
`inflatable plenum chamber is removably mounted on said
`rigid support for disassembly from said cannula.
`12. A nasal cannula as set forth in claim 1, wherein said
`inflatable plenum chamber includes a flexible membrane
`preformed to define a pair of humps in an inflated state.
`13. A nasal cannula as set forth in claim 12, wherein a pair
`of nares elements are mounted on said humps.
`14. A nasal cannula as set forth in claim 12, wherein said
`flexible member is pleated circumferentially around said
`humps.
`15. A nasal cannula as set forth in claim 1, wherein said
`inflatable plenum chamber is a first inflatable plenum cham-
`ber with an inlet and an outlet, and further comprising a
`second inflatable plenum chamber with an inlet and an outlet
`mounted on said rigid support, wherein one of said nares
`elements is mounted on said first inflatable plenum chamber
`
`8
`and the other of said nares elements is mounted on said
`second inflatable plenum chamber.
`16. A nasal cannula as set forth in claim 1, wherein said
`at least one nares element
`includes a corrugated portion
`providing compliancy.
`17. A method of delivering a breathing gas to a user, said
`method comprising the steps of
`securing a nasal cannula to the head of the user, the nasal
`cannula including at least one inflatable plenum cham-
`ber mounted on a rigid support and a pair of nares
`elements mounted on the at least one inflatable plenum
`chamber;
`positioning the nasal cannula such that the nares elements
`are disposed within the nostrils of the user and the at
`least one inflatable plenum chamber is disposed
`between the nares elements and the rigid support; and
`delivering a breathing gas to the user Via the inflatable
`plenum chamber and the nares elements.
`18. A method as set forth in claim 17, wherein the rigid
`support is attached to a gas inlet tube, and further comprising
`the steps of attaching the at
`least one inflatable plenum
`chamber to one end of the gas inlet tube and attaching the
`opposite end of the gas inlet tube to a source of breathing
`gas.
`19. A method as set forth in claim 17, and further
`comprising the step of detaching the at least one inflatable
`plenum chamber from the rigid support.
`*
`*
`*
`*
`$
`
`10
`
`15
`
`20
`
`25
`
`8