WO2003068301A1

WO2003068301A1 - Dual function nasal cannula

Info

Publication number: WO2003068301A1
Application number: PCT/IL2003/000117
Authority: WO
Inventors: Ron Porat; Joshua Coleman; Leonard F. Czuba; Jason Billig; Steven R. Remy
Original assignee: Oridion Medical 1987 Ltd.
Priority date: 2002-02-15
Filing date: 2003-02-13
Publication date: 2003-08-21
Also published as: AU2003207984A1

Abstract

A compact nasal or nasal/oral cannula comprising separate gas supply (164) and gas collection lumens (166) having a common wall. The cannula provides dual functionality of gas collection and supply, applied equally to both nostrils of a subject. The lumens for the collection and supply functions of the cannula have different dimensions and may be embedded, one partially within the other.

Description

DUAL FUNCTIONNASAL CANNULA

FIELD OF THE INVENTION

The present invention relates to nasal and oral/nasal cannulae, especially those having the dual function of collecting exhaled breath for analysis and supplying oxygen to a subject.

BACKGROUND OF THE INVENTION

One commonly used type of nasal and oral/nasal cannula provides exhaled breath collection, generally to enable the subject's breath to be analyzed for carbon dioxide content, and also simultaneously supplies oxygen to the subject. The breath collection can be performed at the nose or at the nose and the mouth. Such cannulae are known as dual function cannulae, and are characterized in that they are of dual lumen design, one lumen for collection and the other for supply. A number of prior art examples are described in US Patent No. 6,422,240 for "Oral/Nasal Cannula" to G. Levitsky et al., hereby incorporated by reference in its entirety. In that application, there is also described a novel cannula in which nasal prongs, the sample collection tube, and, where provided, an oral prong, are all joined at a single junction. Furthermore, in that cannula, the oxygen can be supplied through a series of holes in an oxygen tube, configured to be located near the nostrils of the subject. In this connection, it is noted that in dual function cannulae, both functions should be provided in close proximity or even at the same point since the exhalation (for collection) and inhalation (for supply) functions operate through the same organ and are separated only temporally and not spatially.

The morphologies of the collection and supply lumens in such dual parameter cannulae, because of their different functional requirements, are generally very dissimilar. Thus, for example, the oxygen supply lumen should be capable of providing flow rates of 5 liters per minute, or even more, with typically used levels being 2-3 1/min, while breath collection flow rates as low as 50 ml/min are required. Furthermore, the breath collection lines should have small diameters in order to provide small dead space in the line and fast response times, as further described in the above mentioned U.S. Patent No. 6,422,240. This difference is one of the constraints that influence the way in which such cannulae may be constructed.

Prior art dual parameter cannulae are generally manufactured by one of three methods, as follows:

1. Two separate dip molded bodies, each the full width of the cannula, are produced, one for each lumen function. Each separate lumen has its own shape and attached prongs as appropriate for its function, and the two are glued together to produce a single dual parameter cannula. Cannulae produced by this method are available from Salter Laboratories, Inc., of Arvin, CA, and are called the Salter Sampling Cannula with Simultaneous O₂ Delivery, model 4002 being a nasal cannula, and 4003 being an oral nasal cannula. Such cannulae are comparatively large and cumbersome, since it is difficult to fit separate lumens with different morphology together in a small, compact package, without compromising their individual structural requirements based on their respective functional needs. Furthermore, the gluing process adds an additional manufacturing step, thereby probably increasing the manufacturing costs of the device which, like medical disposables in general, is very cost sensitive.

2. An injection molding process is used. Such a process is generally limited by the capabilities of injection molding, such as the need to have almost straight geometric designs, and the difficulty of manufacturing reentrant parts, namely, those parts having a section distant from the opening with a diameter larger than the diameter at the neck of the opening itself. This is generally a requirement of cannula lumens, whose neck connections are generally significantly smaller than the dimensions at the inner sections. Furthermore, it is very difficult with generally used injection molding processes and mold design, to embed one lumen within the external contours of another. In addition, the body of the cannula should preferably have a profile which curves to match the profile of the face of a user, and the nasal prongs should also be curved to match the angle of entry of a user's nostrils. This combination is not easy to execute by injection molding. Examples of cannulae produced, to the best of the applicant's understanding, by this method, are available from Hudson Respiratory Care Incorporated of Temecula, CA, under the trade name "Softech Bi-Flo (TM) Cannula", models 1843, 1844 and 1845. These cannulae, however, have generally simple geometric forms, possibly because of the above- mentioned difficulties. 3. The cannula is divided laterally and symmetrically down the center, and each side fulfils a separate one of the dual functions. Thus, one nostril prong is used for breath collection, while the second nostril prong is used for oxygen supply. Such a cannula, because of its simple and open design, can be made in a single unit by dip molding with all of the advantages of this process, namely smooth outer contours of the part, and soft pliable materials, as is discussed hereinbelow. Such cannulae are available from the Salter Laboratories, Inc., of Arvin, CA, and are called the "Salter Divided Cannula" 4700 series. However, such a split function cannula suffers from disadvantages in use. Firstly, since supply and collection are accomplished in different nostrils, if one nostril is obstructed, then the function being performed in that nostril is disabled. In addition, the whole indicated quantity of oxygen is delivered through one nostril, which has been found to be less comfortable for the patient.

A further method, known as rotational molding, is simpler than conventional injection molding, in that there are no internal cores, but is limited to use on the outer features only of the product. This technology would thus be limited to a single lumen or chamber design, a dual lumen product being virtually impossible to produce in one step by this method.

Currently available dual function cannulae generally have one or another disadvantage, either with respect to functional aspects of their use, or to patient comfort, or both. There therefore exists a need for a dual function cannula, wherein both functions are integrated into a small sized body, while maintaining ergonomic features to fit comfortably on the face, and to minimize patient irritation, while providing superior performance characteristics relative to those prior art products. At the same time, the manufacturing method must be capable of volume production at affordable cost to maintain the competitiveness of the cannula. SUMMARY OF THE INVENTION

The present invention seeks to provide a new dual function cannula, which provides compactness, a low internal volume, ergonomic comfort and low production cost without detracting from the functional efficiency of the cannula by compromising the individual morphological requirements of each functional component. The cannula of the present invention can be provided in nasal or nasal/oral preferred embodiments, and includes collection and supply functions, integrated into one cannula without compromising their operational functionality. In accordance with a preferred embodiment, the cannula preferably incorporates the single junction construction as disclosed in the above-mentioned U.S. Patent No. 6,422,240, whereby all component parts of the breath collection lumen meet at a single junction. However, it is to be understood that the present invention is not limited to cannulae constructed with single junction construction, but is equally applicable to other dual function cannula designs.

There is thus provided in accordance with a preferred embodiment of the present invention, a cannula which provides dual functionality of gas collection and supply, and wherein each of the two functionalities are applied essentially symmetrically to the user relative to the facial center line, such that gas is supplied and collected essentially equally to and from both nostrils. The dual functions of the cannula are integrated into a single body shape while maintaining minimum possible external dimensions. At the same time, the cannula construction is such that the efficiency of each of the collection and supply functions is not compromised.

These properties are achieved by providing, according to a preferred embodiment of the present invention, a rounded cross section, bi-lumen body, the first lumen, preferably having a larger diameter, being preferably utilized for oxygen supply and essentially comprising the major part of the entire cannula body, and the second lumen, having a smaller diameter and preferably serving as the breath collection lumen, being embedded into one side of the first lumen in a manner that retains the external generally rounded shape of the cannula. It is to be understood that although the most common use of the gas supply lumen is in the provision of oxygen for the subject, and is so generally described in this specification, the gas delivered could equally well be an anaesthetic gas such as nitrous oxide, or any other gas which is to be supplied to the subject. The dual function cannula of the present invention can be provided as a nasal cannula, in which case a pair of symmetrically located nasal prongs are preferably added to the collection lumen, or as an oral/nasal cannula, in which case, an oral prong is also preferably added to the collection lumen.

According to the generally desired shape of a nasal or oral/nasal cannula, the oxygen supply and breath collection tubes are preferably connected to the cannula at its sides, and constitute the anchoring points for tying the cannula to the subject's face. These requirements essentially mean that the lateral asymmetry of the supply and collection lines can be incorporated into the above-mentioned compact design by providing separate lumens that overlap in space. This means that no plane can be defined in the cannula morphology in which the supply lumen is entirely on one side of it and the collection lumen is on the other side

In accordance with a further preferred embodiment of the present invention, all of the above requirements of the cannula of the present invention can be provided by means of a dip-molding process, preferably performed in one dipping step. The morphological asymmetry of the lumens is realized by using dipping mandrels that overlap relative to any axis chosen. The use of such a dip molding process also easily enables the provision of lumens that are significantly larger at their inner sections, at the center of the cannula, than at the lumen ends, where the gas supply or collection tubes are attached. This requires the use of mandrels having dimensions at the inner parts of the cannula larger than those of the exit port dimension through which the mandrel is to be removed. Such a dip molding process, allows the cannula to be made of a soft and pliable plastic material, such as plastisol, thus enabling such mandrels to be withdrawn from the dipped part without damaging or deforming the part. Hence the internal dimensions of the dipped part retain the exact shape of the mandrel used to form it. Such a soft pliable material has the added required properties of wearing comfort for the patient, both to the facial skin and to the nasal septum.

In contrast to injection or rotational molding, dip molding, because of the nature of the material application method by dipping, is able to provide rounded and smooth external features without any sharp protrusions or corners. This is because tooling mandrels utilized in dip molding are of the positive form, forming only the internal features of the part, whereas in injection and rotational molding, a negative form is used, resulting in every imperfection of the tool being reproduced on the outside of the cannula or molded part. Thus, dip molding results in accurate intemal dimensions combined with the soft external features required in a cannula, as discussed above.

Where suitable injection molding techniques are available, however, the cannulae of the present invention can also preferably be constructed by such injection molding techniques.

There is further provided in accordance with yet another preferred embodiment of the present invention a nasal cannula comprising a first lumen adapted for supply of gas to the nostrils of a subject, and a second lumen adapted for collection of gas from the nostrils of the subject, the first and the second lumens having a common wall along at least part of their lengths, one of the lumens being contained at least partially within the cross section of the other, the first lumen having outlets disposed such that it supplies gas essentially equally to both nostrils of the subject, and the second lumen having inlets disposed such that it collects gas essentially equally from both nostrils of the subject.

In accordance with still another preferred embodiment of the present invention, there is provided an oral/nasal cannula comprising a first lumen adapted for supply of gas to a subject, and a second lumen adapted for collection of gas from the nostrils and mouth of the subject, the first and second lumens having a common wall along at least part of their lengths, one of the lumens being contained at least partially within the cross section of the other, the first lumen having outlets disposed such that it supplies gas essentially equally to both nostrils of the subject, and the second lumen having inlets disposed such that it collects gas essentially equally from both nostrils of the subject.

In either of the above-mentioned cannulae, whether a nasal or an oral/nasal cannula, one of the lumens may preferably be of cross section generally smaller than that of the other. Furthermore, either or both of the lumens may have a cross section which is smaller at its outer end than at its center. The lumens may preferably be shaped such that the cannula conforms to the facial profile of the subject. In addition, either of the above mentioned cannulae may preferably be dip molded.

There is further provided in accordance with still another preferred embodiment of the present invention, a nasal cannula comprising a gas supply lumen having outlets for supply of gas to both nostrils of a subject, the supply lumen having its input on one lateral side of the cannula, and a gas collection lumen having inlets for collection of gas from both nostrils of the subject, the collection lumen having its output on the lateral side of the cannula opposite to that of the supply lumen, the lumens having a common wall, and the supply lumen having a cross section generally larger than that of the collection lumen.

In accordance with a further preferred embodiment of the present invention, there is also provided an oral/nasal cannula comprising a gas supply lumen having outlets for supply of gas to a subject, the supply lumen having its input on one lateral side of the cannula, and a gas collection lumen having inlets for collection of gas from both nostrils and mouth of the subject, the collection lumen having its output on the lateral side of the cannula opposite to that of the supply lumen, the lumens having a common wall, and the supply lumen having a cross section generally larger than that of the collection lumen.

In either of the two last-mentioned cannulae, the lumens may preferably be such that the supply of gas is provided essentially equally to both nostrils of the subject and the collection of gas is performed essentially equally from both nostrils of the subject.

Furthermore, in either of the two last-mentioned cannulae, whether a nasal or an oral/nasal cannula, one of the lumens may preferably be contained at least partially within the cross section of the other. Furthermore, either or both of the lumens may have a cross section which is smaller at its outer end than at its center. The lumens may preferably be shaped such that the cannula conforms to the facial profile of the subject. In addition, in either of the two last-mentioned cannulae, that part of the cannula comprising at least the gas supply lumen and the gas collection lumen may preferably be dip molded as one piece.

In any of the above mentioned cannulae, the outlets for supply of gas to both nostrils of a subject are preferably in the form of an array of holes uniformly disposed beneath the subject's nostrils. However, it is to be understood that the outlets, as described throughout this specification, and as claimed, may be of any other form or shape that provides supply of gas essentially equally to both nostrils. Likewise, in any of the above mentioned cannulae, the inlets for collection of gas from both nostrils of the subject are preferably in the form of a pair of nasal prongs. However, it is to be understood that the inlets, as described throughout this specification, and as claimed, may be of any other form or shape that provides collection of gas essentially equally from both nostrils. Thus for instance, according to another preferred embodiment of the present invention, the supply outlets could be nasal prongs and the collection inlets an array of holes, though such an arrangement is likely to be less efficient than the reverse arrangement. The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:

Fig. 1 is a simplified pictorial illustration of a portion of a cannula constructed and operative in accordance with a preferred embodiment of the present invention

Figs. 2A, 2B, 2C and 2D are sectional illustrations taken along the lines VA - VA, VB - VB, VC - VC and VD - VD in Fig. 1;

Fig. 3 is another simplified pictorial illustration of the portion of the cannula shown in Figs. 1 - 2D taken from a different angle;

Figs. 4A, 4B, and 4C are sectional illustrations taken along the lines VTLA - VHA, VUB - Vim and VTC - VπC in Fig. 3;

Figs. 5 A and 5B are pictorial illustrations of the portions of the cannula shown in Figs. 1 - 4D;

Figs. 6A and 6B are pictorial illustrations of portions of a cannula constructed and operative in accordance with another preferred embodiment of the present invention;

Fig. 7 is a simplified pictorial illustration of a portion of the cannula shown in Figs 6 A and 6B;

Figs. 8A and 8B are sectional illustrations taken along the lines XIA - XIA, and X 3 - XIB in Fig. 7; and

Figs. 9A, 9B and 9C are simplified illustrations of mandrel examples as used in dip molding of a cannula in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to Fig. 1 , which illustrates a nasal cannula, constructed and operative according to a preferred embodiment of the present invention. The cannula preferably includes nasal prongs 160 and 162, which communicate with a breath collection lumen 164. The cannula has a uni-junction construction, wherein nasal prongs 160 and 162 and breath collection lumen 164 all meet at a single junction, as will be shown in detail in Figs. 4B and 4C hereinbelow. The single junction and its associated lumen and prongs are embedded in the side of an oxygen supply lumen 166. The oxygen supply lumen 166 is suitable for providing a flow of oxygen to a subject preferably via a plurality of apertures 168, without unduly interfering with the waveform or concentration of the sampled breath. If the cannula is manufactured by a molding process, the apertures 168 may be generated as part of the molding process, but it may generally be simpler to drill them in an additional, post molding operation.

Reference is now made to Figs. 2A to 5B which schematically illustrate different isometric views and cut away cross-sectional views of nasal cannulae according to preferred embodiments of the present invention, the figures illustrating the internal and external structure and features of the cannulae of the present invention.

Figs. 2A, 2B, 2C and 2D are cross-sectional views of the cannula shown in Fig. 1, taken along the lines VA - VA, VB - VB, VC - VC and VD - VD.

Fig. 3 is another isometric view of the cannula shown in Fig. 1, viewed from above to show the array of apertures 168 supplying gas as uniformly as possible to both nostrils of a subject wearing the cannula.

Figs. 4A, 4B, and 4C are sectional views taken along the lines VHA - VILA, VTJB - Vim and VπC - VIIC of the cannula shown in Fig. 3.

Figs. 5 A and 5B are more isometric views of the cannula shown in Figs. 1 and 3, taken from different angles in order to more clearly illustrate the structure of the cannula.

The previous figures clearly illustrate the asymmetric morphology of the cannula around its lateral centerline, in addition to the symmetric nature of the operation of each functionality. The functional symmetry of the oxygen supply, providing essentially equal supply to both nostrils is maintained even though the shape of the lumen is asymmetric relative to the cannula, the supply being from one side. Similarly, the functional symmetry of the breath collection system, collecting essentially equally from both nostrils, is maintained even though the shape of the lumen is asymmetric relative to the cannula, the collection being from one side. Furthermore, the input oxygen supply line to the cannula, and the output breath collection line from the cannula, are symmetrically disposed relative to the lateral center line of the cannula, and both are suitably angled to match the profile of the user's facial features.

As seen in Figs. 1 to 5B, oxygen supply lumen 166 is a generally larger diameter lumen, making up the major part of the diameter of the cannula body, while breath collection lumen 164 is generally smaller in diameter than oxygen supply lumen 166. In another preferred embodiment of the present invention, the breath collection lumen 164 does not have to be connected with both nasal prongs 160 and 162 at a single junction. It is evident from Figs. 1 to 5B that although the cannula is not symmetrical, the functionality of the collection system is symmetric, in that there are identical prongs in each nostril, and the collection point is symmetric to the two nasal prongs. Likewise, as is clearly seen in Fig. 3, the oxygen delivery to the nostrils takes place through holes 168, which are symmetrically drilled relative to the nostril positions of the subject, such that each nostril is provided with essentially equal quantities of gas.

The structure of the cannula, according to the preferred embodiments of the present invention, has the advantage of providing added mechanical stability to the cannula, as compared to prior art cannulae for nasal collection only, wherein the small diameter collection lumen has little support.

Reference is now made to Figs. 6A to 8B, which illustrate another cannula, constructed according to another preferred embodiment of the present invention, which includes nasal prongs 260 and 262 and oral prong 263 which communicate with a breath collection lumen 264. The cannula preferably has a uni-junction construction, wherein nasal prongs 260 and 262 and oral prong 263 and breath collection lumen 264 all meet at a single junction, as shown in Fig. 8B. The single junction and its associated lumen and prongs are embedded in the side of an oxygen supply lumen 266. The oxygen supply lumen 266 is suitable for providing a flow of oxygen to a subject via a plurality of apertures 268, without unduly interfering with the waveform or concentration of the sampled breath. Apertures 268 may be generated as part of the molding process, but are preferably drilled in an additional, post molding operation.

Figs. 6A to 8B illustrate the asymmetric morphology of the cannula around its lateral center line, in addition to the symmetric nature of the operation of each functionality. The functional symmetry of the oxygen supply relative to the nostrils is maintained even though the shape of the lumen is asymmetric relative to the cannula, the supply being from one side. Furthermore, the input oxygen supply line to the cannula, and the output breath collection line from the cannula, are symmetrically disposed relative to the lateral center line of the cannula, and both are suitably angled to match the profile of the user's facial features.

As seen in Figs. 6A to 8B, oxygen supply lumen 266 is a large diameter lumen, making up the major part of the diameter of the cannula body, while breath collection lumen 264 is smaller in diameter than oxygen supply lumen 266. In another preferred embodiment of the present invention, the breath collection lumen 264 does not have to be connected with nasal prongs 260 and 262 and oral prong 263 at a single junction. It is evident from Figs. 6A to 8B that although the cannula is not symmetrical, the functionality of the collection system is symmetric, in that there are identical prongs in each nostril, and the collection point is symmetric to the two nasal prongs.

Reference is now made to Figs. 9A, 9B and 9C, which are simplified illustrations of typical mandrels as used in dip molding of a cannula in accordance with a preferred embodiment of the present invention. As seen in Fig. 9A, a first lumen defining mandrel 300 is preferably formed as a generally elongate element having an irregularly shaped recess 302 formed therein. A second lumen forming mandrel 304 is preferably formed as a generally elongate element having a curved nasal prong joining lumen defining portion 306 attached thereto.

As seen in Fig. 9B, in accordance with a preferred embodiment of the invention, mandrels 300 and 304 are mutually positioned such that the mandrel 304 and, specifically, the curved nasal prong joining lumen defining portion 306 is located at least partially within recess 302, in non-touching relationship with mandrel 300. Additionally, in accordance with a preferred embodiment of the present invention, a pair of nasal prong defining mandrels 308 and 310 are arranged in touching relationship with ends of the curved nasal prong joining lumen portion 306, as seen in both Figs. 9B and 9C. If an oral/nasal cannula is to be formed, an additional mandrel for the oral prong (not shown) is required.

Mandrels curved in all three axes are required in order to provide the appropriate shapes for the various lumens and prongs of the cannula, so that they function correctly and ergonomically match their intended sampling regions. The mandrels preferably have small outer diameters, corresponding to the small dimensions of the cannulae, and also preferably have flared shapes, as required by the ergonomic feature design, since the end opening dimensions of the lumens are generally smaller than the inner dimensions thereof.

It is a particular feature of the present invention, as observed for instance by referring back to Figs. 8A and 8B, that the nasal prongs 260 and 262 and oral prong 263 and the breath collection lumen 264 are not in fluid communication with the oxygen supply lumen 266, being separated by walls including an internal common wall. Such a common wall is possibly realized, when the cannula is produced using dip molding technology, by non-touching relative spatial positioning of mandrels during the dip molding of the cannula, as depicted in Figs. 9A-9C hereinabove. The wall structure is produced favorably by the dip molding method, as the material flows readily into the area between the mandrels which were located in the channels of the cannula. As seen by comparing the finished cannula depicted in Fig. 1, with the mandrel placement shown in Figs. 9A-9C, oxygen supply lumen 166 and breath collection lumen 164 are formed by mandrels 300 and 304, respectively.

It is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.

Claims

1. A nasal cannula comprising: a first lumen adapted for supply of gas to the nostrils of a subject; and a second lumen adapted for collection of gas from the nostrils of the subject; said first and said second lumens having a common wall along at least part of their lengths, one of said first and said second lumens being contained at least partially within the cross section of the other, said first lumen having outlets disposed such that it supplies gas essentially equally to both nostrils of the subject, and said second lumen having inlets disposed such that it collects gas essentially equally from both nostrils of the subject.

2. A nasal cannula according to claim 1 and wherein one of said lumens is of cross section generally smaller than that of the other.

3. A nasal cannula according to claim 1 and wherein at least one of said lumens has a cross section which is smaller at its outer end than at its center.

4. A nasal cannula according to claim 1 and wherein said lumens are shaped such that said cannula conforms to the facial profile of the subject.

5. A nasal cannula according to claim 1 and wherein said cannula is dip molded.

6. A nasal cannula according to claim 5 and wherein said cannula is dip molded as one piece.

7. An oral/nasal cannula comprising: a first lumen adapted for supply of gas to a subject; and a second lumen adapted for collection of gas from the nostrils and mouth of said subject; said first and second lumens having a common wall along at least part of their lengths, one of said lumens being contained at least partially within the cross section of the other, said first lumen having outlets disposed such that it supplies gas essentially equally to both nostrils of the subject, and said second lumen having inlets disposed such that it collects gas essentially equally from both nostrils of the subject.

8. An oral/nasal cannula according to claim 7 and wherein one of said lumens is of generally smaller cross section than the other.

9. An oral/nasal cannula according to claim 7 and wherein at least one of said lumens has a cross section which is smaller at its outer end than at its center.

10. An oral/nasal cannula according to claim 7 and wherein said lumens are shaped such that said cannula conforms to the facial profile of the subject.

11. An oral/nasal cannula according to claim 7 and wherein said cannula is dip molded.

12. An oral/nasal cannula according to claim 11 and wherein said cannula is dip molded as one piece.

13. A nasal cannula comprising: a gas supply lumen having outlets for supply of gas to both nostrils of a subject, said supply lumen having its input on one lateral side of said cannula; and a gas collection lumen having inlets for collection of gas from both nostrils of the subject, said collection lumen having its output on the lateral side of said cannula opposite to that of said supply lumen; said lumens having a common wall, and said supply lumen having a cross section generally larger than that of said collection lumen.

14. A nasal cannula according to claim 13 and wherein said lumens are arranged such that said supply of gas is provided essentially equally to both nostrils of said subject and said collection of gas is performed essentially equally from both nostrils of the subject.

15. A nasal cannula according to claim 13 and wherein one of said lumens is contained at least partially within the cross section of the other.

16. A nasal cannula according to claim 13 and wherein at least one of said lumens has a cross section which is smaller at its outer end than at its center.

17. A nasal cannula according to claim 13 and wherein said lumens are shaped such that said cannula conforms to the facial profile of the subject.

18. A nasal cannula according to claim 13 and wherein said cannula is dip molded.

19. A nasal cannula according to claim 18 and wherein said cannula is dip molded as one piece.

20. An oral/nasal cannula comprising: a gas supply lumen having outlets for supply of gas to a subject, said supply lumen having its input on one lateral side of said cannula; and a gas collection lumen having inlets for collection of gas from both nostrils and mouth of the subject, said collection lumen having its output on the lateral side of said cannula opposite to that of said supply lumen; said lumens having a common wall, and said supply lumen having a cross section generally larger than that of said collection lumen.

21. An oral/nasal cannula according to claim 20 and wherein said lumens are arranged such that said supply of gas is provided essentially equally to both nostrils of the subject, and said collection of gas is performed essentially equally from both nostrils of said subject.

22. An oral/nasal cannula according to claim 20 and wherein one of said lumens is contained at least partially within the cross section of the other.

23. An oral/nasal cannula according to claim 20 and wherein at least one of said lumens has a cross section which is smaller at its outer end than at its center.

24. An oral/nasal cannula according to claim 20 and wherein said lumens are shaped such that said cannula conforms to the facial profile of the subject.

25. An oral/nasal cannula according to claim 20 and wherein that part of said cannula comprising at least said gas supply lumen and said gas collection lumen is dip molded.

26. An oral/nasal cannula according to claim 25 and wherein said part of said cannula comprising at least said gas supply lumen and said gas collection lumen is dip molded as one piece.