Patent ID: 12226580

DETAILED DESCRIPTION

To provide an overall understanding of the systems, methods, and devices described herein, certain illustrative implementations will be described. Although the implementations and features described herein are specifically described for use in connection with a high flow therapy system, it will be understood that all the components and other features outlined below may be combined with one another in any suitable manner and may be adapted and applied to other types of respiratory therapy and respiratory therapy devices, including low flow oxygen therapy, continuous positive airway pressure therapy (CPAP), mechanical ventilation, oxygen masks, Venturi masks, and Tracheostomy masks. Furthermore, it should be noted that while certain implementations are discussed herein within regards to manufacturing nosepieces and systems for respiratory therapy, these various implementations may be used in various combinations to increase both the efficacy of treatment and the patient's overall level of comfort during the treatment.

Disclosed herein are systems, methods, and devices providing a bifurcated nasal cannula with low flow resistance and increased patient comfort. A nosepiece for respiratory therapy is described below that provides a custom bridge between nasal prongs of a nasal cannula with a smooth bore gas path. The nosepiece may be manufactured by dip molding at least three mandrels fixedly arranged relative to each other. The three mandrel method allows for design freedom and an open geometry of the nasal bridge. Sacrificial material may be molded completely around the third mandrel and then trimmed. The relatively low monetary cost of the dip molding material allows for discarding the excess material without significantly affecting the production cost.

The methods described for creating a dip molded bifurcated cannula that has low gas flow resistance also create nasal bridges that are flexible and can conform to irregular facial geometries. The systems, methods, and devices described herein provide a smooth gas path with a gentler bend than devices in the current state of the art, resulting in low flow resistance, quiet operation, and patient comfort. The low flow resistance of the disclosed devices is especially important for devices that provide the flow of gas through nasal cannulas by means other than compressed gas provided by a hospital. For example, the low flow resistance of the disclosed devices may be beneficial in home use respiratory therapy systems. The smooth bore design of the systems, method, and devices described herein eliminates places for moisture to coalesce and therefore reduces rainout.

FIG.1shows an illustrative prior art nasal cannula nosepiece mandrel arrangement. A first mandrel110is placed in close proximity to a second mandrel112. A small gap114is left between the two mandrels110and112. Mandrels110and112may be dipped in liquid material to create a dip mold. Liquid plastic may flow into gap114that connects mandrels110and112, sealing off the gas path between the two halves of the nosepiece and forming a ridge (as shown inFIG.2and described below).

FIG.2shows an illustrative prior art nasal cannula nosepiece200. Nosepiece200may be made using the mandrel arrangement ofFIG.1. A first section210and a second section212of the nosepiece are separated by ridge214. Outputs216,218may output breathing gas to a patient. Breathing gas may be input to parts220and222. Sections212and210are configured to have relatively wide diameters (compared to the diameters of input parts222and220) where they join at ridge214. This provides a surface for the nosepiece to rest beneath the patient's nose. However, the orientation of connecting ridge214creates a hard feeling piece of plastic where it contacts the skin on the upper lip, which can cause patient discomfort. Furthermore, the geometry of nosepiece200and, in particular, placement of ridge214, creates an inflexible surface where the nosepiece rests on the patient's face, which can cause the nosepiece to roll outward, away from the patient's face, and additionally increases the amount of discomfort the patient feels.

The wide diameter of sections210and212, combined with the sharp change in direction of breathing flow at ridge214, causes a high flow resistance gas path and disruptions in the flow of breathing gas. Consequences of the disruptions can be loss of heat from the breathing gas, liquid formation and excess water dripping (rainout), and pressure drop, which can decrease the efficacy of respiratory therapy. The shape of the sections210and212also can create a high level of noise during operation, which can further increase patient discomfort.

Systems, methods, and devices providing a bifurcated nasal cannula with low flow resistance and increased patient comfort are disclosed herein to remedy the deficiencies of the prior art shown inFIGS.1and2and described above. For example, a nosepiece for respiratory therapy is described below that provides a custom bridge between nasal prongs of a nasal cannula with a smooth bore gas path. The nosepiece may be manufactured by dip molding three mandrels fixedly arranged around each other. The three mandrel method allows for design freedom and an open geometry of the nasal bridge.

FIG.3shows an illustrative nosepiece300of a nasal cannula for respiratory therapy. Nosepiece300comprises a first lumen330, a second lumen332, and a bridge314. Nosepiece300may desirably be shaped to prevent sharp changes in direction of the flow of breathing gas within lumens330and332. Lumens330and332may be, for example, nasal prongs used to deliver breathing gas to nares of a patient. First lumen330has an outer surface310,312. Outer surface310,312may form a tube. First lumen330has a first inlet end326to receive a first flow of breathing gas, a first outlet end322to deliver the first flow, and a first bend between first inlet end326and first outlet end322. Second lumen332has an outer surface334,336. Outer surface334,336may also form a tube. Second lumen332has a second inlet end328to receive a second flow of breathing gas, a second outlet end324to deliver the second flow, and a second bend between second inlet end328and second outlet end324.

In certain implementations, nosepiece300is formed from a flexible material (e.g., polyvinyl chloride (PVC) plastic, plastisol, vinyl, silicone, non-latex rubber, an elastomer, ethylene vinyl acetate (EVA), styrene-butadiene copolymer (SBC), polyether ether ketone (PEEK), a polyether block amide (such as PEBAX), a polyethylene material, a high-density polyethylene (HDPE) material, a medium-density polyethylene (MDPE) material, a low-density polyethylene (LDPE) material, a crack-resistant material, a material with a low coefficient of friction, a material less than 70 Durometer Shore A, or any other flexible plastic).

Bridge314spatially separates first lumen330and second lumen332. Bridge314attaches to the outer surface310,312of first lumen330at the first bend and attaches to the outer surface334,336of second lumen332at the second bend. Bridge314has at least one opening316and is hollow. Bridge314may fluidically seal the two lumens330and332from each other, and maintain the first flow of breathing gas in the first lumen330separate from the second flow of breathing gas in the second lumen332. For example, the bend in sections334and the bend in section312may attach to bridge314, while maintaining a solid barrier between lumens330and332and bridge314. Preventing the first and second flows of breathing gas from mingling helps to prevent disruptions to the breathing gas flow delivered to a patient, which in turn reduces rainout and the coalescence of large droplets of rainout. Rainout may be uncomfortable and potentially dangerous to patients. The separation of lumens330and332also allows for a smooth bore gas path, providing a steady flow of breathing gas to a patient.

Bridge314may act as a “pillow” to provide a comfortable fit for patients using the nosepiece and prevent nosepiece300from rolling outward from a patient's nose. Bridge314may be customized to provide different levels of flexibility and greater comfort to patients, especially those with unique facial features. For example, bridge314may be three-sided, cylindrical, four-sided, etc., depending on patient needs. Bridge314may be hollow to allow greater flexibility and lighter weight. Opening316is along a base of bridge314. Opening316may be a variety of shapes, allowing for the bridge to collapse more easily and conform to patients' unique facial geometry.

First lumen330comprises a first section310and a second section312. The internal diameter of sections310and312may be different. Second lumen332comprises a first section334and a second section336. The internal diameter of sections334and336may be different. The difference in internal diameter between sections310and312, and334and336allows for different diameters for inlet ends326,328and outlet ends322,324. For example, as shown inFIG.3, an internal diameter of the first inlet end326is greater than an internal diameter of the first outlet end322, and an internal diameter of the second inlet end328is greater than an internal diameter of the second outlet end324. In certain implementations, the nosepiece shown inFIG.3may be part of nasal cannula comprising third and fourth elongated lumens (shown inFIG.8). The change in internal diameter between sections310and312, sections334and336may allow the third and fourth elongated lumens to be fitted within sections310,336respectively, as shown inFIG.10and described below. By fitting a lumen, for example through a solvent bonded connection, the same constant internal diameter may be maintained through the third and fourth lumens into sections312and334, respectively.

The diameter of sections312and334may taper to outlet ends322and324, respectively. A taper may begin where section310meets section312or before or after the bend in section312. A taper may begin where section334meets section336or before or after the bend in section334. The diameter of ends322and324will affect output gas flow velocity from nosepiece300. For example, the diameter of section312may decrease as section312approaches outlet end322. Such a decrease in diameter increases output gas flow velocity at outlet end322. Output gas flow velocity may therefore be adjusted to suit patient needs by adjusting the diameter at outlet ends322and324. However, as gas flow approaches outlet end322or324, a narrowing taper may increase flow resistance. Increasing the abruptness of the taper increases the flow resistance for gas flows through sections330and332. To decrease flow resistance, the taper may be gradual.

Nosepiece300is not limited to the above components, but may include alternative or additional components, as would be understood by one of ordinary skill in the art from the description herein. For example, nosepiece300may be connected to additional lumens as shown inFIG.8and described below. Nosepiece300may be part of system for respiratory therapy, such as HFT, and may be connected to a gas source, nebulizer, and/or nasal cannula for delivery of heated and humidified air with or without aerosolized medicament.

In some implementations, opening316may be configured to allow a medical device to be coupled to nosepiece300. For example, opening316may be used to connect a medical device tube to nosepiece300. In some implementations, bridge314may have more than one opening. For example, bridge314may have an opening along its base and its top, allowing a tube to be threaded through bridge314and held in place by an attachment or friction fitting. In some implementations, a device to measure a patient's breathing rate may be coupled to nosepiece300.

Such couplings between medical devices and nosepiece300may be accomplished through fittings wherein the medical device “snaps” into opening316. For example, a ball-like connector of the medical device or nebulizer may sit in the cavity of bridge314, forming a lock-type fit between the device and nosepiece300, or forming a ball and socket joint.

In some implementations, a nebulizer may be coupled to nosepiece300at opening316. Nebulizers allow aerosolized respiratory medications, such as bronchodilators (e.g., Albuterol (Ventolin), Salbutamol (Proventil), Levosalbutamol/Levalbuterol (Xopenex)) for treating asthma or Chronic Obstructive Pulmonary Disease (COPD) to be administered through inhalation directly to a patient's lungs. Such a coupling between nosepiece300and a nebulizer would allow nebulized medication to be delivered to a patient together with supplemental breathing gas (as provided via lumens330,332), allowing a patient to receive the medication without stopping use of a respiratory assist device. For example, the aerosolized medication may be delivered through a separate third outlet end of the nebulizer. During respiratory therapy, the breathing gas and aerosolized medicament may merge through the slipstream effect. A combination of nebulized medication and HFT can be used to assist patients experiencing respiratory distress and provide a comfortable and effective management of cardiopulmonary conditions.

Nosepiece300allows for delivery of both breathing gas and aerosolized medicament by separate flow paths and separate cannula outlets that are not in fluid communication with each other. The delivery of the aerosolized medicament (attached at bridge314) and breathing gas (delivered by lumens330and332) by separate tubes allows a source of the aerosolized medicament (e.g., a nebulizer) to be disconnected without interrupting the delivery of the breathing gas. Unlike systems that use a ‘T’ or ‘Y’ adaptor to connect a nebulizer to a respiratory therapy circuit, the nosepiece300involves no junction point between the flow of aerosolized medicament and the flow of breathing gas. Thus, removal of the source of aerosolized medicament does not introduce another opening in the breathing gas circuit, and the source of aerosolized medicament can be simply removed without having to place a plug or cap in its place. Similarly, a device to measure the breathing rate of a patient may be attached or detached to nosepiece300with minimal disruption to the patient.

In some instances, bridge314may be configured to allow the first flow of breathing gas through lumen330and the second flow of breathing gas through lumen332to be in fluid communication with each other. For instance, bridge314may be configured with small flow channels or membranes that permit flow, osmosis, or any other suitable fluid communication between lumens330,332and bridge314. Specifically, bridge314may comprise a plurality of openings, in addition to opening316, configured to allow medicament to flow from an attached medicament delivery device, such as a nebulizer, to lumens330and332. These openings may allow aerosolized medicament from the attached medicament delivery device to join the first and second breathing gas flows through a slipstream effect, as described in U.S. Pat. No. 9,333,317, the contents of which is hereby incorporated by reference in its entirety.

Nosepiece300may be part of a system for respiratory therapy with a source of heated and humidified breathing gas. Heating and humidifying breathing gas may increase patient comfort. For example, providing heated and humidified breathing gas to the patient along with aerosol from a nebulizer can increase patient comfort by counterbalancing the cooling and drying sensations associated with the delivery of aerosol to the nostril.

Nosepiece300may be used in a method for respiratory therapy. Such a method may comprise receiving two separate flows of breathing gas through the two inlet ends328,326of nosepiece300and delivering the two flows through two respective outlet ends322,324. The first flow of breathing gas through section312and the second flow of breathing gas through section334may be heated and humidified.

FIG.4shows an illustrative mandrel arrangement400for manufacturing a nosepiece of a nasal cannula for respiratory therapy. For example, mandrel arrangement400may be used to manufacture nosepiece300, as shown inFIG.3. Arrangement400comprises a first mandrel418, a second mandrel420, and a third mandrel422. Third mandrel422is placed in close proximity between first mandrel418and second mandrel420.

The first mandrel418has a circular cross section and comprises two diameters: a first diameter through section410and a second diameter through section412. The diameter of section412is less than the diameter of section410. The second mandrel420has a circular cross section and comprises two diameters: a first diameter through section426and a second diameter through section424. The diameter of section424is less than the diameter of section426. In certain implementations, the diameter of section410may be the same as the diameter of section426. In certain implementations, the diameter of section412may be the same as the diameter of section424. In certain implementations, the first mandrel418may further comprise a third diameter through section430. The third diameter through section430may be the same as or different than the first diameter through section410. In certain implementations, the second mandrel420may further comprise a third diameter through section428. The third diameter through section428may be the same as or different than the first diameter through section426.

The diameter of sections412and424may taper to ends432and434, respectively. A taper may begin where section410meets section412or before or after the bend in section412. A taper may begin where section426meets section424or before or after the bend in section424. The diameter of ends432and434will affect output gas flow velocity from the nosepiece formed by mandrels418,420, and422. For example, the diameter of section412may decrease as section412approaches end432. Such a decrease in diameter increases output gas flow velocity at the output of a nosepiece formed on mandrel418(such as the output from outlet end322ofFIG.1). The diameter at outlet ends322and324may be adjusted to suit patient needs.

The third mandrel422comprises an upper portion414and a lower portion416. The distal end of portion414is attached to the proximal end of portion416. The distal end of portion414is larger than the proximal end of portion416so as to create an undercut. Portion414is placed between section412and section424of first mandrel418and second mandrel420, respectively.

Mandrels418,420,422are in a fixed arrangement with respect to each other. Third mandrel422is arranged between first mandrel418and second mandrel420. Section414of third mandrel422is placed between a bend in section412and a bend in section424. A small distance is left between section414and sections412and424, respectively. For example, the distance may be 3 mm, 2 mm, 1 mm, or any other suitable distance.

In some implementations, the arrangement is coated with a material. For example, the material may be, polyvinyl chloride (PVC) plastic, plastisol, vinyl, silicone, non-latex rubber, an elastomer, a material less than 70 Durometer Shore A, ethylene vinyl acetate (EVA), styrene-butadiene copolymer (SBC), polyether ether ketone (PEEK), a polyether block amide (such as PEBAX), a polyethylene material, a high-density polyethylene (HDPE) material, a medium-density polyethylene (MDPE) material, a low-density polyethylene (LDPE) material, a crack-resistant material, a material with a low coefficient of friction, flexible plastic, or any other suitable material.

The distance between mandrels418,420, and422allows material to flow around the mandrels and form two lumens and a hollow bridge, while sealing off the gas path between the two lumens. The arrangement may be coated by, for example, fixedly holding mandrels418,420, and422on a substrate and dipping arrangement400in liquid material, spraying material onto arrangement400, dipping arrangement400arranged on a rack into material, or any other suitable means.

After arrangement400is coated in material, it may be cured. For example, the coated arrangement may be cured at room temperature, or at a temperature or set of temperature (such as those determined by the material's curing temperature profile) determined to accelerate the curing time. For example, the coating may be cured using a heat lamp, oven, UV radiation or any other suitable means. After curing, at least one coated mandrel may be trimmed to create an opening in the coating of the trimmed mandrel. For example, mandrel422may be a “sacrificial” mandrel. Coated mandrel422may be trimmed to allow the pertinent cured coating to be removed from mandrel422. The cured coating on mandrel422may correspond to bridge314ofFIG.3. Trimming the coating allows for the different openings of bridge314, as described above. The cured coating may then be removed from arrangement400to leave a single intact structure. For example, the cured coating may be a flexible plastic that is in the shape of the nosepiece shownFIG.3. For example, mandrels418and420may form lumens330and332, respectively, while mandrel422may form hollow bridge314. The material coating is joined where there was distance left between mandrels418,420, and420. By leaving a small distance between the mandrels, the material that flows around the mandrels will separate the structures formed by the mandrels with a thin layer of material.

Mandrel422geometry may be of any shape such that it comes within close proximity of mandrels418and420that form the gas path of the nosepiece. The bridge created by mandrel422and connecting the coatings on mandrels418and422can be three-sided or hollow, allowing for the bridge to collapse more or less easily and, therefore, better conform to patients' unique facial geometry. The inherent opening of the coating of mandrel422can also be any shape, so long as mandrel422can be forcibly pulled through the flexible opening of material coating it. Varying the opening of the bridge formed by mandrel422can be done to perform different functions, such as adding intentional undercuts or to aid in the collapsibility of the bridge. Mandrel422may include raised patterns or ribbing to alter the inner surface of the coating on mandrel422. These alterations to the inner surface of the coating may add strength and/or alter the flexibility of bridge314ofFIG.3.

This method allows for the design of nearly any bridge geometry to provide customized comfort and ergonomics to patients. The form of the bridge is no longer tied to the round or rectangular geometries required by manufacture. Dip molding, for example, allows for smaller production runs, more effective cost, less time, and more customizable geometries than traditional manufacturing means.

FIG.5shows an illustrative cross-sectional view500of a bridge of a nosepiece before trimming excess material away. For example,FIG.5may represent a portion of a structure similar to that ofFIG.3, wherein section510corresponds to section310and section312corresponds to section312of lumen330. After the mandrel arrangement ofFIG.4is coated with material and cured, the coated, cured material must be removed from the arrangement. The mandrel forming the bridge (such as mandrel422ofFIG.4) may be entirely coated in cured material. The bridge mandrel itself is a “sacrificial” mandrel and may be trimmed to provide an opening for the bridge mandrel to be removed through. The sacrificial material is molded completely around the third mandrel that must be cut off. The relatively low cost of the material allows for discarding the excess.

After the sacrificial mandrel is removed, opening514remains. Opening514may then be trimmed to suit the needs of a patient. For example, the opening may be trimmed close to the connection with lumen512(as shown inFIG.3at opening316). In another instance, the opening may not be trimmed as closely, and may instead leave the majority of opening514to provide an input “tube” to attach a medical device. Other openings may further be trimmed in the structure of opening514, such as creating a second opening to allow a medical device to be threaded through the nasal bridge. The trimming may depend on the patient's facial structure, the amount of flexibility needed, the configuration of devices to attach to the bridge, or other suitable factors.

FIG.6shows an illustrative cross-sectional view600of a nosepiece formed by three mandrels located in close proximity to form connecting ribs, after the sacrificial mandrel has been trimmed. For example,FIG.6may represent a structure similar to that ofFIG.3, wherein section612corresponds to section312, section622corresponds to section334, and section614corresponds to section314. As shown by cross section616, section612forms a lumen with a smooth inner surface. As shown by cross section618, section622forms a lumen with a smooth inner surface similar to that of section612. As shown by cross section620, section614is a hollow bridge between sections612and622. The hollow space surrounded by section614is isolated from the lumens formed by sections612and622. As such, breathing gas flowing through the lumen formed by section612is separated from breathing gas flowing through the lumen formed by section622. No breathing gas enters section614. The separation between sections612and622may help to decrease disruptions to gas flow during delivery to patients.

FIG.7shows an illustrative cross-sectional view of a bridge of a nosepiece. Section710corresponds to section310ofFIG.3, and section712corresponds to section312ofFIG.3. Section714illustrates a cross section of bridge314ofFIG.3after excess material is trimmed away and the mandrels have been removed. Section712is a nasal prong used to deliver breathing gas to the nostril of a patient. Inlet section710may connect to a separate lumen to, for instance, form a nasal cannula. Breathing gas may flow in through inlet section710through section712to the patient. While section714is connected to section712, breathing gas does not flow through section714, because there is a thin barrier of flexible material between the two sections. This barrier prevents breathing gas from escaping section712before reaching its outlet end and the nostril of the patient and is a result of the dip molding process with the three mandrels discussed above in relation toFIG.4.

FIG.8shows an illustrative nasal cannula in use by a patient. Nasal cannula800comprises a nosepiece portion802, a third lumen806, and a fourth lumen808. Nosepiece portion802corresponds to nosepiece300as shown inFIG.3and described above. The third elongated lumen806has an inlet end and an outlet end. Fourth elongated lumen808has an inlet end and an outlet end. Nosepiece portion802is connected to the outlet end of third lumen806at connection810and the outlet end of fourth lumen808at connection812. Nasal cannula800may include, for example, padding814and816around the patient's ears for added comfort.

The third lumen806and nosepiece portion802define a constant diameter flow path for the first flow of breathing gas from the inlet end of the third lumen to the outlet end804of the first lumen (lumen330ofFIG.3). Fourth lumen808and the nosepiece portion802define a constant diameter flow path for the second flow of breathing gas from the inlet end of fourth lumen808to the outlet end818of the second lumen (lumen332ofFIG.3). The constant internal diameter of the flow paths decreases noise creation during breathing gas delivery by preventing disruptions (e.g. eddies) in breathing gas flow. Minimizing noise during cannula use may increase a patient's comfort level.

In certain implementations, the first inlet end of the first lumen is adapted to be connected to the outlet end of third lumen806without constricting the internal diameter of third lumen806. The second inlet end of the second lumen is adapted to be connected to the outlet end of fourth lumen808without constricting the internal diameter of fourth lumen808. For example, the connections between third lumen806, fourth lumen808, and nosepiece802may be similar to the connection shown inFIG.9and described below.

Nasal cannula800is not limited to the above components, but may include alternative or additional components, as would be understood by one of ordinary skill in the art from the description herein. For example, nasal cannula800may be part of a system for respiratory therapy. The system may comprise the nosepiece described above and a source of breathing gas. In an exemplary implementation, the source generates heated and humidified breathing gas for delivery to the patient. The source may be configured to provide, for example, breathing gas at flow rates between 1 and 8 liters per minute (lpm) for infants, between 5 and 20 lpm for pediatric patients, or up to 40 lpm for adults. Suitable sources of heated and humidified gas will be known to one of ordinary skill in the art. For example, the source may be the Vapotherm Flowrest System, Vapotherm Careflow System, Precision Flow unit, or the Vapotherm2000i, all of which are provided by Vapotherm, Inc. of Exeter, New Hampshire, USA. Other suitable sources of breathing gas will be known to one of ordinary skill in the art from the description herein.

FIG.9shows a non-desirable but typical to prior art connection between two lumens. A first lumen is defined by tube902. A second lumen is defined by tube904. Tube904has a smaller internal diameter than tube902. Tube904fits into902, creating an airtight seal through, for example, a friction fitting. Breathing gas flow906flows through tube904to tube902. The sharp change in internal diameter between tubes904and902creates eddies and disruptions in gas flow906. Such disruptions cause, for example, noise and resistance in the gas flow path, making the connection less efficient and any system using such connection for a nasal cannula less comfortable for a patient. In some implementations, there may be a coupling to connect tubes904and902.

FIG.10shows an illustrative connection to maintain a constant inner diameter between two lumens. A first lumen is defined by tube1002. A second lumen is defined by tube1004. Tube1002is connected to tube1004without constricting the internal diameter of tube1004. Tube1002has an enlarged portion1008. Enlarged portion1008has an internal diameter equal to the outer diameter of tube1004. Tube1002transitions to the internal diameter of tube1004, thereby maintaining a substantially constant diameter between tubes1002and1004. Breathing gas flow1006flows through tube1004to tube1002. By maintaining a constant inner diameter, gas flow1006may be relatively undisturbed resulting in lower flow resistance and less noise than the typical connection shown inFIG.9. Such a connection may be used, for example, to connect the nosepiece ofFIG.3to elongated lumens to form a nasal cannula or system for respiratory therapy, as described above. This connection may be a solvent bonded connection.

FIG.11shows a flowchart of an illustrative manufacturing process for a nosepiece of a nasal cannula. Process1100begins at step1102where a first mandrel, a second mandrel, and a third mandrel are maintained in a fixed arrangement. The third mandrel is positioned between the first and second mandrels in close proximity. The third mandrel is held at a distance from the first and second mandrels. The mandrels may be made of, for example, steel, aluminum-bronze alloys, stainless steel, or any other suitable material, such as those resistance to curing methods and which will not permanently adhere to the flexible material used in forming the nosepiece. The process continues from step1102to step1104where the arrangement is coated with a material. For example, the material may be, polyvinyl chloride (PVC) plastic, plastisol, vinyl, silicone, non-latex rubber, an elastomer, ethylene vinyl acetate (EVA), styrene-butadiene copolymer (SBC), polyether ether ketone (PEEK), a polyether block amide (such as PEBAX), a polyethylene material, a high-density polyethylene (HDPE) material, a medium-density polyethylene (MDPE) material, a low-density polyethylene (LDPE) material, a crack-resistant material, a material with a low coefficient of friction, a material less than 70 Durometer Shore A, or any other suitable material). The process continues from step1104to step1106, where the coated arrangement is cured. For example, the coated arrangement may be cured at room temperature or at a temperature or set of temperatures determined to accelerate the curing time. For example, the coating may be cured using a heat lamp, oven, UV radiation, or any other suitable means. The process continues from step1106to step1108where at least one coated mandrel is trimmed to create an opening in the coating of the trimmed mandrel. For example, the third mandrel may be a “sacrificial” mandrel, as described above. The coated third mandrel may be trimmed to allow the cured coating to be removed from the arrangement. The process continues from step1108to step1110where the cured coating is removed from the arrangement. For example, the cured coating may be a flexible plastic that is in the shape of the nosepiece shown inFIG.1. The remaining excess material formed on the remaining untrimmed mandrels or all mandrels may then be trimmed.

In a bifurcated cannula, such as that described above in relation toFIG.3, gas flow cannot split across a bridge between the two lumens. Because the two lumens split the total gas flow and are completely separate (e.g., not in fluid communication with one another), occluding one lumen will divert all flow through the other, non-occluded lumen. Occlusions may occur due to an obstruction, momentary kinking of the lumen, crushing the lumen by rolling over onto the tubing during sleep, or any other suitable occlusion. If the total gas flow through the system is maintained as a constant, when one lumen is occluded, the entire gas flow is directed to the other, non-occluded lumen, effectively doubling the flow rate delivered to the patient from that prong of the cannula. In many cases, the flow rate through a system is set to the maximum that is comfortable for the patient. The limiting factor for this is often the sensation of high velocity flow in the patient's nares. For this reason, doubling the flow is likely to be unpleasant for the patient.

FIGS.12A-12Bshow an illustrative non-bifurcated nosepiece during operation of a respiratory therapy system.FIG.12Ashows “normal” flow during operation.FIG.12Bshows flow during operation when a portion of the nosepiece is occluded. During normal operation as shown inFIG.12A, air flow1214flows through first lumen1202and exits outlet end1210. Air flow1216flows through second lumen1204and exits outlet end1212. Little to now air flow travels through bridge1206. If however, one of the first and second lumens is occluded, as shown inFIG.12B, a large portion of air flow will flow through bridge1206. InFIG.12Bfirst lumen1202is effectively blocked at occlusion1208such that little to no gas flow can pass through first lumen1202from one side of occlusion1208to the other side of occlusion1208. Occlusions may include, but are not limited to, a bend in the tubing forming a lumen (e.g., if the tubing is bent at a sharp angle), pressure applied to the lumen externally (e.g., if the tubing is pinched), debris or other elements blocking the lumen internally, or any other occlusion that obstructs the flow of gas through a lumen1202,1204in the nosepiece1200. Due to occlusion1208, gas flow1218flowing through second lumen1204splits off—a portion of gas flow1218exits second lumen1204through outlet end1212, while a portion of gas flow1218flows through bridge1206, into first lumen1202, and exits via outlet end1210. Thus, in non-bifurcated nosepieces such as nosepiece1200, the nosepiece effectively self corrects if one of the two lumens is occluded—i.e., even if gas flow cannot pass through the entirety of one lumen (e.g., first lumen1202), gas flow will still exit the outlet ends (e.g., outlet ends1210,1212) of both lumens (e.g., lumens1202,1204) because gas flow can pass through a bridge (e.g., bridge1206) between the two lumens. A patient will therefore still receive gas from both outlet ends (that, in many cases, are placed within the patient's nares during operation of the system) even if one of the lumens is occluded.

In a bifurcated cannula, such as that described above in relation toFIG.3, however, gas flow cannot split across a bridge (e.g., bridge314) between the two lumens (e.g., first lumen330and second lumen332), unlike in the nosepiece ofFIGS.12A-Bdescribed above.FIG.13shows a graph depicting how pressure varies with flow between normal and occluded operation in a bifurcated cannula nosepiece. Pressure in pounds per square inch (Psi) is shown along the y-axis and flow in liters per minute (L/min) is shown along the x-axis. Curve1310shows pressure and flow through the cannula when one of two lumens is occluded. Curve1320shows pressure and flow through the cannula when both lumens are operating under normal conditions (i.e., non-occluded). Blower flow characteristic line1350shows a constant pressure of 1.5 Psi. Occluded curve1310intersections blower flow characteristic line1350at occluded operating point1330. Normal operation curve1320intersects blower flow characteristic line1350at normal operating point1340. As evidenced inFIG.13, when a single lumen is occluded (e.g., as shown by curve1310) the flow at a given pressure (e.g., 1.5 Psi shown by blower flow characteristic line1350) is significantly less the flow at that pressure under normal operating conditions (e.g., as shown by curve1320). In some implementations, a system may be configured to provide a constant flow. To maintain a constant flow, when one lumen is occluded, the pressure of the system would have to significantly increase. For example, if the system is set to maintain a flow rate of 40 L/min, when one lumen becomes occluded, the pressure necessary to maintain that flow rate would increase from 1.5 Psi to approximately 3 Psi.

There are multiple solutions to resolve this problem of reduced patient comfort resulting from occlusions in bifurcated cannulas. Such solutions include a flow feedback loop, an inherent flow limitation, a pressure feedback loop, a balancing shunt, or any suitable system or modification.

To prevent occlusions from inhibiting a patient's comfort, a flow feedback loop may be used. In the flow feedback loop, a desired flow rate is selected and set. In some implementations, the flow rate may be set by a clinician, a patient, an automated process, or any other suitable means. The respiratory therapy system monitors the back pressure required to deliver the set flow rate for a period of time. For example, the respiratory therapy system may include a sensor and processor configured to monitor back pressure and adjust the delivered flow rate. By monitoring the back pressure, the system establishes a benchmark for a non-occluded cannula—i.e., a cannula with two lumens where gas can flow through both lumens. The system maintains the current flow rate to the extent possible within a range of acceptable pressures around the benchmark. If the system requires more pressure than that acceptable pressure range allows to maintain the set flow rate, the system may trigger an alarm indicating the possibility of a partial occlusion. The system may also limit the flow rate to avoid causing discomfort to the patient.

To prevent occlusions from inhibiting a patient's comfort, an inherent flow limitation may be implemented. In this implementation, no feedback is required. A flow generator delivers a constant pressure at a particular input (operating rotations per minute) would be used. For example, the flow generator may be a standard blower system, and the speed of the blower may be the input. If the speed is maintained at a constant value, the pressure will also remain substantially constant at low flow rates (i.e., flow rates that require the blower to operate very close to the maximum pressure the blower can deliver when fully occluded). A desired flow rate is selected and set (e.g., by a clinician). The system then delivers a constant pressure output. An occlusion in a lumen would result in a decreased flow rate. The system monitors and detects the reduced flow rate and triggers an alarm (e.g., to notify a clinician of the reduced flow rate).

To prevent occlusions from inhibiting a patient's comfort, a pressure feedback loop may be implemented. A desired flow rate is selected and set (e.g., by a clinician). The system monitors the back pressure required to deliver this set flow rate for a period of time to establish a target pressure for a non-occluded cannula. The system maintains the pressure as a constant. If the flow rate deviates from the targeted flow set point, the system triggers an alarm indicating the possibility of a partial occlusion.

To prevent occlusions from inhibiting a patient's comfort, a balancing shunt may be implemented. A modification to the bifurcated cannula approach is to use a balancing shunt in the nosepiece. The shunt may comprise a flow path that connects the separate lumens in an area adjacent to the cannula prongs. The flow passage is configured so that in normal, non-occluded conditions, the pressure at both ends of the shunt (i.e., at the connection between the shunt and the lumens) are equal and net flow will pass through the shunt. If one of the lumens is occluded, however, the resulting pressure differential between the two lumens would cause flow through the shunt to balance the flow between the two prongs. In some implementations, the shunt is disposed in a location where the openings from the two lumens into the shunt do not disturb the flow in the lumens. For example, the shut may be located on a point tangent to the flow in the lumen and away from bends in the lumen.

The foregoing is merely illustrative of the principles of the disclosure, and the apparatuses can be practiced by other than the described implementations, which are presented for purposes of illustration and not of limitation. It is to be understood that the apparatuses disclosed herein, while shown for use in high flow therapy systems, may be applied to systems to be used in other ventilation circuits.

Variations and modifications will occur to those of skill in the art after reviewing this disclosure. The disclosed features may be implemented, in any combination and subcombination (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented.

Examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and made part of this application.