GB2493520A - Nasal cannula with spherical foam sleeve - Google Patents

Abstract

A prong for use in nasal ventilation therapies featuring a dome-shaped resilient flexible foam member that locates in the nostril socket, more effectively distributing sealing contact pressure for a range of nose morphologies, akin to a ball and socket. A nasal cannula 20 extending from base 22 through spherical foam sleeve 23 provides a stiffened lumen for ventilation gas transport. Foam member 23 may have a compressible flange 24, which elastically engages with a nostril's internal sill feature. The foam member may have a second compressible flange 26 at its base, which shields the patient's skin from direct contact by the stiffer structure of the combination gas delivery device. Dissimilarly sized or shaped or rotationally oriented left-right prong halves may be combined. The foam member may be divided at the midline, along a thinned section 27. A plurality of foam prongs may be packed on to a common carrier (42, see figures 12, 13) and have a detachable selection gauge (36, see figure 13) or information instrument.

Description

Nasal prong interface This invention relates to the mechanical construction of a prong for insertion into a nostril pair for the purpose of a gas interface for use in nasal ventilation therapiea.

The challenge in nasal interface design is to optimise the sealing at the nostril, for minimal lcsa of ventilation gas and pressure, and patient comfort from the sealing member contact with the nostril and its surrounding tissue. The challenge is more difficult to manage in the non-participating' patient group, such as those patients who are unable to signal or self-intervene on the occurrence of gas leak or discomfort.

This patient group includes infants, children and adults that are either sleeping or in a reduced state of consciousness or have otherwise reduced mental or physical ability.

With regards to gas sealing, an occurring small loss in ventilation pressure may adversely affect efficiency in blood carbon dioxide elimination. A larger loss in ventilation pressure may, in addition, result in alveolar dc-recruitment, or collapse, with loss of lung functional residual capacity (FEC) . Under sustained conditions, associated lung tissue stress may lead to chronic lung disease (OLD) With regards to patient comfort, nasal trauma and injuries resulting from nasal continuous positive airway pressure (NCFAP) devices has been reported to occur in 20% of infant treatment sessions (Robertson N.J. et ai "Nasal deformities resulting from flow driver continuous positive airway pressure". Arch Dis Child Ed 1996;75:F209-212) Variability in nose anatomy, both person-to-person and by asymmetry in an individual person's nose shape, presents a particular design problem.

The degree of nose variability is described, for example, by Parkas L.G.

et 51 "Objective assessment of standard nostril types: a morphometric study". Ann Plast Surg. 1983;ii:38l. A range of nose shape factors are illustrated in figures 1 to 3. Nose shape factors can, in some respect, be generalised into ethnic groupings. ft is a common problem in the nasal prong markets that a design optimised for a nose shape that is common in one world region, is sub-optimal for another nose shape that is common in a second world region. This adds to complexity, by solutions multiplicity, in the nasal prong manufacturing and supply channels. Solutions that are flexible in use across a wide range of nose shapes are preferred.

Prior art nasal prong solutions for maintaining airway pressure make use of one, or a combination, of the three mechanisms illustrated in figure 4. In sub-figure 4-A a substantially planar member 16 abuts the nasal base. Often such planar member 16 is a deformable material, with purpose to conform to the 3-dimensional nasal base shape. For nasal bases that are irregular in shape or if the planar member 16 is inadvertently misaligned to or tilted on the nasal base plane, the abutment can exert an uneven force over the various areas of the nasal base and result in discomfort from concentrated skin pressure points. In sub-figure 4-B a conical seal 17 is axially inserted into the nostril, until its circumference matches that of the nostril rim and a seal is formed.

Often, the conical member 17 is a deformable material, with purpose to conform to the nostril rim shape. A frequent problem is that the conical member 17, under load from its associated securing feature, works its way deeper into the nostril, and causes the nostril rim to excessively expand and deform. To advert this, clinical staff tend to select an under-sized conical member 17 and rely on more abutment effect for minimising leak (as for figure 4-A) . The conical member 17 may be somewhat tolerant to nasal base angle variability (as in figure 1) and to axial misalignment, with regards to its leak profile, but not without causing discomfort from associated prolonged deformation of the nostril wall. In sub-figure 4-c a smaller bore cannula 18, forming a tolerated leak path 19, is inserted into the nasal cavity 7; and the therapeutic gas is delivered at a relatively higher flow rate and velocity. This mechanism, firstly, can be used to entrain ambient pressure gas, into the lower pressure gas stream, thereby partially countering the reverse flow out of the nostril. Secondly, the kinetic energy in the gas flow counters flow from the upper airway into the nasal cavity 7. Thirdly, it uses the property that escapement flow rate at the leak path 19 increases with the pressure inside the nasal cavity 7. Any desired airway pressure can therefore be achieved, by adjusting the therapeutic gas flow rate to balance that of the nostril, and mouth, leak rate.

High-flow devices that enter deeper into the nasal cavity 7 interfere with a larger portion of the oensitivc mucous membranc, which results in irritation, mucus secretion and/or inflammation. All three mechanisms require the prong base angle 15 be optimally adjusted to the nasal base angle. The gas delivery device therefore requires a movable or flexible linkage member.

Resilient flexible foam has been used for its cushioning property. In order to distribute the load evenly and prevent densification of parts of the foam structure, the foam member conventionally requires mounting on a positioning adjustable base member, such as a swivelling joint or shape retaining flexible tubing, to orientate the prong best possible parallel to the nasal base and/or axial to each the individual nostrils.

Densification' is the point where the flexible foam structure does not compress any further (bottoms out) and behaves as a firm structure -i.e. conforms no further to the nose shape, and thereby deforms the nose instead and potentially concentrates load onto pressure points.

Present invention is a nasal prong interface providing effective sealing and patient comfort over an improved range of nose shapes. The said prong has a resilient flexible polymeric foam member, which is axially stiffened with a cannula extending through the said foam member. In particular, the foam member has a dome shaped feature that locates the nostril rim, in what resembles a ball-and-socket' joint, which more evenly distributes contact pressure for a wide range of nose angles and shapes. This assures an even degree of foam surface compression across the full circumference of the nostril rim. The resilient flexible foam further has a first compressible flange feature, which elastically engages with a nostril's internal silt feature. The first flange adds a further sealing element, and it eases the fitting by one person by helping to retain the prong in the nostril. The resilient flexible foam further has a second compressible flange feature at its base, which shields the patient skin from direct contact by the stiffer structure of the combination gas delivery device. The nasal prong interface is scaled for infant, child and adult use. Dissimilarly sized or shaped or rotationally orientated left-right prong halves may be combined for patients with substantially asymmetrical and irregular nose shapes. The foam prong may have a detachable size gauge or information instrument.

The present invention will now be described byway of example and with reference to the accompanying drawings in which: Figure 1 demonstrates anatomical variances in the nasal base angle.

Figure 2 shows five sub-figures A to F demonstrating example anatomical variances in the nostril rim shape and nasal base shape, in a first plane.

Figure 3 shows five sub-figures A to E demonstrating example anatomical variances in the nasal base shape, in a second plane.

Figure 4 shows three sub-figures A to C demonstrating prior art nasal prong interfaces.

Figure 5 shows three sub-figures A to C illustrating present invention basic shape feature and its coupling ability at different nasal base angles.

Figure 6 is a section view of an embodiment of present invention.

Figure 7 is a section view of a further embodiment of present invention.

Figure 8 is a section view of a further embodiment of present invention.

Figure 9 shows example size embodinents of present invention.

Figure 10 shows an example shape enbodiment of present invention and illustrates a method for modifying the shape's rotational orientation.

Figure 11 demonstrates the present invention attached to a combination gas delivery device.

Fgure 12 shows a packing arrangement and a method for combining two size variants.

Figure 13 shows four sub-figures A to D of further packing arrangements.

Figures 1 to 3 are intended as background information demonstrating the variety of nose shapes, with which the nasal prong is required to effectively interface with. Figure 1 illustrates variability in the nasal base angle, by example of an infant head in side section view. The nasal base is the external skin surface viewed when looking axially into the nostrils. The nasal base angle lines 1,2,3 are relative to a fixed reference line 4. The reference line 4 represents the position of gas delivery device body (as shown in figure 11) . The nominal angle line 2 is 45 degree to the reference line 4. For a sharper nasal base angle (nose sticking down) the high angle line 1 is 60 degree to the reference line 4. For a shallower nasal base angle (nose sticking up) the low angle line 3 is 30 degree to the reference line 4. Variance in the nasal base angle lines 1,2,3 also vary relative to the philtrum 6; and also relative to the nasal sill 9 formed immediately inside the nostril opening, on the nasal wail 5 and on the nasal floor 8 and inside/behind the columella 12 on the septum partitioning the two nostrils.

Figure 2, sub-figures A to B, illustrate a selection of nostril rims and nasal base shapes, viewed axially to the nostrils. The individual nostril rim 10 can vary in shape, size and angle to that of other noses.

The nose tip 11 can vary in its degree of projection. The oolumella 12 partitioning the two nostrils can vary in its shape and angie.

Approximately I in 8 humans have a noticeable degree of asymmetry in their nose shapes 14.

Figure 3, sub-figures A to F, illustrate a selection of nasal base topographical shapes. When observing the nose face-on, the nasal base may appear generally convex 3-A and 3-B, flat 3-0, or concave 3-P in shape. The shape of the alar wall 13 can affect the net amount of sill 9 formed inside the nostril. The nasal base may also be topographically asymmetrical, as illustrated by sub-figure 3-B.

Figure 4 illustrates three prior art mechanisms, as described in the

background to the present invention.

Figure 5 illustrates how the present invention approximates a ball-and-socket' joint between the prong member 23 and the nostril,where a prong member's spherical surface feature 25 provides the ball function, and where the nostril rim 10 provides the socket function. The ball-and-socket principle is tolerant of variability in mating angles, shown here on a side section view. At any nasal base angle, within the required 45 degree +/-15 degree range, as described for figure 1, the ball' locates in the socket' in a manner where the mating force is comparably evenly distributed around the circumference of the said socket' . The ball-and-socket principle provides a basis for a nasal prong interface where the pirong base angle line 15 and gas delivery device reference line 4 can remain fixed over the range of required nasal base angles 1,2,3, while simultaneously establishing improved potential for patient comfort. The gas sealing and patient comfort is further assured by constructing the prong member 23 in a resilient flexible polymeric foam material. The ball' shape now assures an equivalent degree of foam compression, and thereby a more even distribution of skin contact pressure and skin deformation around the circumference of the nostril rim 10.

Figure 6 is a section view of an embodiment of the present nasal prong invention. The prong is constructed in two parts, shown here in their assembled state. The first prong part is a base 22 with twin cannulae 20 and lumens 21 for transporting gas. The base 22 attaches to or otherwise interfaces with a combination gas delivery device, as the example device described for figure 11. The cannulae 20 stiffen the combined prong structure, to prevent a gas flow resistive or obstructive collapse of the lumens 21. For ease of manufacturing, the cannulae part 20 is preferably formed as two parallel lumens 21. However, the cannulae 20 and lumens 21 nay be inclined or otherwise angled non-parallel. The base 22 snd cannulae 20 material is preferably a thermoplastic rubber or silicone, with durometer hardness between 60 and 70 on the shore A scale. The second prong part is a twin resilient flexible polymeric foam sleeve 23, which when in use is positioned, by sliding, over the cannula part. The foam part 23 is a cushioned abutment member for providing gas sealing and patient comfort. The spherical surface feature 25 described for figure 5 is represented by the construction line 28. To further demonstrate the tolerance to variability in nasal base shape, the two straight construction lines 29,30 represent example nostril rim mating angles, here shown on the face plane view (as opposed to figure 5 lines 1,2,3 being shown on the side plane). The spherical surface feature 25 is in fact a segment of a sphere, or a spherical dome, and is provided only within the zone of contact with the nostril rim 10. In another embodiment, the spherical dome surface feature 25 may be that of a proiate spheroid (elongated in its projected height) or an oblate spheroid (flattened in its projected height) or an ellipsoid (narrowed on one axial side, to form an ellipse or oval on its planar cross-section) . It is important that the dome shaped member body has sufficient thickness to prevent foam densification (bottoming out) over the angular mating rangc and that it remains comfortable to the patient.

Care should be taken not to make a prolate spheroid domed surface feature 25 too tall', to a degree where its mating surface, in relation to the nostril rim 10 axial tangent, resembles that of a conical or cylindrical prong, because changing the angle of the prong relative to the nostril axis, then, would result in the nasal wall deforming with the prong part and becoming stressed. This could be expressed as the ball' being too elongated to effectively slide in the socket' The resilient flexible polymeric foam part 23 may further have a flange 24 near its insertion leading circumference edge. The resilient flexible flange 24 engages elastically with the available sill 9 on the nasal floor 8 and nasal wall 5 and inside/behind the columella 12, which adds an element of gas sealing and also helps retain the prong in the nostrils while fitting the device to the patient. The flange 24 deforms by the foam material compressing and re-distributing within itself, which is relatively softer and more conforming than an equivalent flange constructed in a flexible solid structure, such as silicone or rubber.

The resilient flexible polymeric foam part 23 may further have a base flange 26, which provides a cushion that shields the patient skin from possible contact with the solid stiffer parts of the gas delivery device (as shown in figure 11) . The polymeric foam part 23 further has a pre-formed thin section 27 located reflectively symmetrical between the twin foam sleeves. The thin section 27 makes it easy to tear, by hand, the prong part into two mirrored halves. Alternatively, the clinician may elect to divide the prong using a cutting tool; and in such case the thin section 27 serves to visually indicate a cutting line.

The resilient flexible polymeric foam member 23 with its done shape 25 ax-id flange features 24,26 is preferably constructed in visco-elastic polyurethane foam. Visco-elastic' refers to appreciable and conjoint viscous and elastic properties, with a degree of ability to redistribute own material within own deformed structure and, thereby, conform to the variety of nostrils shapes with a comparably even distribution of contact load. The visco-elastic foam has a slow recovery time, after a deformation load is removed. The slow recovery property enables the clinician to initially compress or otherwise deform the prong, prior to insertion into the nostril. Subsequent to said insertion, the prong slowly recovers and attempts to regain its original shape. By doing so, the recovering prong conforms to the nostrils shapes and establishes a seal. In a preferred embodiment, the time is between 10 seconds and about 45 seconds, for the foam to recover from 80% compression to 20% compression when at 30 degree Celsius and 95U Relative Humidity. The foam has an open cell structure, with an average cell diameter of about to 250um (micron) . Preferably the foam material has an outer skin that is impermeable to gas flow, and which makes the prong significantly lass prone to harbouring germs and moisture. Preferably, the said skin is a self-skinning feature of the polyurethane foaming process; or, alternatively, the skin may be applied separately, in a similar or dissimilar material, during or after the foaming process. The preferred polyurethane foam density is 80 kg/m3 to 120 kg/m3 (or about 6 pound per cubic foot) ; although another foam compound or process resulting in a density between 30 kg/m3 and 300 kg/m3 may be workable. The skinned visco-ciastic polyurcthanc foam has a durometer hardncss of between 35 and 70 on the shore 00 scale (approximately equivalent to 3 to 20 shore A). For infants, with particularly fine and sensitive skin, a low hardness below 55 shore 00 (10 shore A) is preferable. The foam hardness can also be expressed as indentation force deflection (IDE), which preferably is between 4kg and 8kg, for 25% block deflection under a 323 cm2 (50 square inch) pressure plate, and is conventionally classed as super-soft' foam. The foam compression modulus (TOP 65%/IDE 25%) is preferably between 1.8 and 2.5, unless the alternative arrangements described for figures 7 and B are being applied. The prong materials are oxidation resistant and have a biocompatibility profile appropriate for msdical use. The polyurethane foam compression set, or fatigue, profile should be reflected in the parts storage and shelf-life.

In another embodiment, an open-or closed-cell plasticized polyvinyl chloride (PVC) foam or any other resilient flexible material with equivalent functional properties may be used, with particular attention paid to identifying a biocompatible plasticiser.

Figure 7 is an alternative embodiment, which may be preferable if using resilient flexible foam thst has a compression modulus (IDE 65%/loP 25%) less than 1.8. Tn this alternative embodiment, the semi-rigid cannuls 20 exhibits a partial spherical support structure 31, which underpins the foam dcme surface feature 25. The spherical support structure 31 is represented by the construction line 32. The spherical support structure may be somewhat spheroidal or ellipsoidal in shape. The support structure 31 assures that the ball' shape and its associated benefits (as described for figure 5) is maintained if the flexible foam structure has a low compression modulus and too easily densifies (bottoms-out) Figure B is a further alternative embodiment, which is constructed using two or more dissimilar polymeric foam materials for separate functional zones of the foam sleeves 23. The naterial properties of interest may include differences in surface texture and coefficient of friction, softness or compression modulus, or visco-elastic recovery rates. Figure B illustrates an example arrangement, where a first material 33 is used for a nasal sill engaging flange; and a second material 34 is used for a nostril rim sealing feature; and a third material 35 is used for a cushioning base. The illustrated part may be manufactured by injecting or pouring a first material into a mould, and then subsequently injecting or pouring an additional second material into the same mould, during or after the first material foam rising phase. The plurality of materials will combine into a conjoint part that has layered properties.

The conjoint part may also be constructed in an over-moulding process that positions the adjacent dissimilar foams in other patterns than a layered one, such as, for example, a soft outer skin layer moulded over a stiffer central core.

Figure 9 shows how the cannulae 20 may receive a range of foam sleeves 23a,23b,23c in different sizes. This increases the flexibility in configuring the single gas delivery system, at the point of care, for a wider range of patient sizes. In another variant of the method, the different foam sleeves 23a,23b,23c variants may each have a permanently fixed cannula 20.

Figure 10-A shows a foam sleeve 23e variant that has an ellipsoidal dome shaped surface feature 25e. Sub-figures 10-B to l0-D shows a sequence for dividing a foam sleeve 23e into two halves, and where the individual halves are received on to and rotated about the cannula 20 axis, and thereby establishing a modified foam sleeve 41a that can have a more accurate rotational orientation to a particular or irregular nostril rim shape. In a further variant, the individual prong halves may be marketed in a divided form, for the user to combine two halves in pneparation for use.

Figure 11 shows an example embodiment of a gas delivery device 47 making use of the nasal prong invention. The gas delivery device 47 is coupled to a wider ventilation system, which controls the supply and exhaust of gas. The gas delivery device 47 conprises an elongated body section, aligned to the reference line 4; and a gas outlet part 48 that is angled at a fixed 45 degree to the said body reference line 4. The gas delivery device 47 further comprise a pair of textile straps 49, for securing the device to the patient's head and, thereby, help create a positive abutment force and prevent the prong interface from becoming dislodged.

Gas is in communication with the nasal cavity 7 via the cannulae lumens 21. Gas sealing is provided by the compressible spherical surface feature 25 and the insertion leading flange 24. The compressible base flange 26 shields the patient skin against direct contact by the stiffer gas outlet part 48. The base 22 and cannulse 20 and/or the polymeric foam sleeve 23 may be manufactured as separate detachable parts or may be integral and/or permanently fixed members of the gas delivery device 47, 48. The polymeric foam sleeve 23 may be marketed separately as a generic part, for use with a selection of different cannulae and gas delivery devices.

Figure 12 shows a packing arrangement, whioh may be preferred in certain segments of markets, where a selection counting two or more of different foam sleeves 23a,23b,23c are conveniently manufactured as a single part.

The single part incorporates nostril size gauges 36a,36b,36c which aids tho ciinioian in solocting the appropristo prong sizE. Upon identifying the best prong size, the clinician can tear the corresponding foam sleeve off the common runner 38. The common runner 38 may carry additional user information in text and/or symbolic format. Figure 12 also illustrates how the halves from two different size prongs 39,40 can be torn off 37 along the thin section 27, away from their original configuration, and the two dissimilar halves being combined into making a new asymmetrical prong size 4th. This feature may be particularly useful for patients ith substantially asymmetrical and/or deformed nose shapes.

Figure 13, sub-figures A to D, shows further packing arrangements, which may be preferred in certain particular segments of markets. A selection of different polymeric foam sleeve members 23 are attached to a common rigid or semi-rigid carrier 42a,42b,42c,42d. The foam sleeves mix may count two or more and be selected for their differences in dimensions, shapes and/or material properties. Figure 11-A shows a size collection, which is likely suitable for a hospital infant care unit, covering patient sizes from a small pre-term newborn to a 1-year old. The foam sleeves are retained on tongues 43 projected from the carrier 42a main body. Figure 11-P shows a shape collection where two of three foam members 23d,23e,23f have differently angled ellipsoidal dome shaped surfaces 25d,25e, which is likely suitable for adult care use in a multi-ethnical market. The first foam member 23d correlates to the nostril shape shown in figure 2-B. The second foam member 23e correlates to the nostril shape shown in figure 2-c, or figure 2-D if rotated 180 degree. The third foam member 23f has a generic spherical dome shape 2Sf for use in any other eventuality. The carrier 42b features shapes gauges 36d,36e,36f that represents the corresponding foam sleeves 23d,23e,23f.

In figure fl-s the foam members are retained in cut-outs 44. In figure 11-0 the foam members are retained on an adhesive surface 45 and may be manually peeled-off. Two foam members 23g,23h represent variants as those described for figure 8 and their functional properties are described on the carrier 42d in text format 46, as opposed to being a size or shape gauge. For all figures 11-A to 11-0, the common carrier 42a,42b,42c,42d may contain additional user information in text format or symbolic format or by any other information instrument.

Claims (1)

1. <claim-text>Claims 1. A nasal prong interface for use in ventilation therapy comprising: a base defining a first face for coupling to a combination gas delivery device, and defining a second face for coupling to a human or animal nose receiving said gas; and a cannulae pair projecting from said base second face; said cannulae furthest projected distance from said base second face defining a distal end; said base and cannulae defining a lumens pair for conveying a gas; said lumen defining a first opening at said base first face, and defining a second opening at said cannulae distal end; said cannulae defining a stiffening member within said nasal prong interface preventing a gas-obstructive collapse of said lumens when coupled to a nose; and a resilient flexible polymeric foam member defining a sleeves pair for receiving said cannulae; said resilient flexible polymeric foam sleeve defining a spherical or spheroidal or ellipsoidal dome shaped surface byway of an increasing outer circumference and thickening of said sleeve wall, where said dome shaped surface locates and abuts a nostril rim anatomical socket.</claim-text> <claim-text>2. A nasal prong interface according to claim 1 wherein said base and cannulae can be selectively received into and removed from said polymeric foam sleeves.</claim-text> <claim-text>3. A nasal prong interface according to claim 2 wherein said cannulae can be selectively received into one of a plurality of variants of said polymeric foam sleeves, where said polymeric foam sleeves variants differ in dimension or shape or material property.</claim-text> <claim-text>4. A nasal prong interface according to claim 1 wherein said base and cannulae is permanently fastened to said polymeric foam sleeves in said received position.</claim-text> <claim-text>5. A nasal prong interface according to claim 1 wherein said base and cannulae member is defined as a separate part adapted for attaching to a combination gas delivery device.</claim-text> <claim-text>6. A nasal prong interface according to claim 1 wherein said base and cannulae is defined as a permanent integral member of a gas delivery device or wider ventilation system.</claim-text> <claim-text>7. A nasal prong interface according to claim 1 wherein said base and cannulae member further defines a spherical or spheroidal or ellipsoidal dome shaped outer wall surface feaTure proximal to said base second face, where said cannula dome shape structurally underpins and supports said polymeric foam sleeve dome shape when said nasal prong interface is coupled to a nose.</claim-text> <claim-text>8. A nasal prong interface according to claim 1 wherein said resilient flexible polymeric foam member further defines at least one first flange proximal to said distal end, where said first flange defines a substantially lateral and circular or elliptical or oval projection exhibiting an increasing outer circumference relative to an underlying body circumference.</claim-text> <claim-text>9. A nasel prong interface according to claim 1 or claim B wherein said resilient flexible polymeric foam member further defines a aecond flange proximal to said base second face, where said second flange defines a substantially lateral projection exhibiting an increasing cuter circumference relative to an underlying body circumference.</claim-text> <claim-text>10. A nasal prong interface according to claim 1 or claim 8 or claim 9 wherein at least one material in said resilient flexible polymeric foam member is a visco-elastic material exhibiting a slow recovery time.</claim-text> <claim-text>11. A nasal prong interface according to claim 1 or claim B or claim 9 wherein said polymeric foam sleeve member is constructed from at least two conjointly and adj acently arranged materials with dissimilar properties.</claim-text> <claim-text>12. A nasai prong interface according to claim 1 or claim 8 or ciaim 9 wherein said polymeric foam member is substantially covered or coated with a substantially gas-impermeable skin.</claim-text> <claim-text>13. A nasal prong interface according to claim 1 wherein said polymeric foam member exhibits a division line on its base centrally between two prong projections, where said division line defines a thinned material section for manually tearing or to indicate a line of cutting of said polymerio foam member into two mirrored halves, where each said half exhibits one projected feature for interfacing with a single nostril.</claim-text> <claim-text>14. A nasal prong interface according to claim 13 wherein said two halves from a first divided polymeric foam member are individually defined to combine with an individual half from a second divided polymeric foam member of different dimension or shape or rotational orientation or material property.</claim-text> <claim-text>15. A nasal prong interface according to claim 1 wherein said polymeric foam member is defined by way of two separated halves, where each said half exhibits one projected feature for interfacing with a single nostril.</claim-text> <claim-text>16. A nasal prong interface according to claim I wherein said polymeric foam member defines a detachable size or shape gauge or other information instrument for comparing to a nostril size or nostril ii shape or otherwise assist or guide in a selection of a polymeric foam member.</claim-text> <claim-text>17. A nasal prong interface according to claim 1 wherein a selection counting two or more of said polymeric foam members sharing a common carrier member are defined as a single part for packing purpose, where said carrier member incorporates a gauge or other information instrument for comparing to a nostril size or nostril shape or otherwise assist or guide in a selection of a pofymerio foam member.</claim-text> <claim-text>18. A nasal prong interface according to claim 1 wherein said conveyed gas is air or oxygen enriched air or any other therapeutic gas mixture or vaporised material.</claim-text>