GB2106396A - Anaesthesia mask - Google Patents

Abstract

A mask for relative analgesia and anaesthesia is moulded from polymeric foam and fits over the nose of the patient, with lateral ports (30) for inlet and outlet of gases and a rigid reinforcement (52) in the front of the mask. The periphery of the mask has a lower region (20) which bears upon the base of the upper lip, an upper region (16) which contacts the nasal bones, and lateral regions (18) which contact the nasal processes of the maxilla and the maxilla itself and meet the lower region (16) at the points (25) where the base of the upper lip meets the naso-labial grooves. Certain parts of the face-contacting surfaces are inwardly chamfered. <IMAGE>

Description

SPECIFICATION Anaesthesia mask This invention relates to masks for administering anaesthetic gases to a patient.

The invention is especially applicable to the field of relative analgesia, which is a form of conscious sedation produced by the administration of anaesthetic gas at a level insufficient to produce complete anaesthesia but sufficient to suppress the gag reflex. By this means a throat pack can be inserted into the patient's mouth so as to obstruct the oro-pharyngeal region during surgical or dentral work in the patient's mouth. The anaesthetic gases normally used are a mixture of nitrous oxide and oxygen, but other anaesthetic gases could be used in other situations. In any event, the escape of anaesthetic gases into the surrounding atmosphere of the surgery or theatre is a considerable problem, as it can have noticeable effects on the skilled personnel in attendance, and the possible long term effects to such people of continual exposure to such gases is giving rise to some concern.

Conventional relative analgesia masks are of two main types. In one type the mask is provided around its face-contacting periphery with a pneumatic cuff. This is intended to be deformable so as to adapt to the facial contours of different patients. However, in practice the cuff has rather limited deformability, and moreover tends to be uniformly deformable as a result of its being a continuous inflated envelope, and hence it does not take account of the fact that there is much more variation in shape and dimensions of some facial areas, as compared with others. As a result, there is usually a very imperfect seal against the patient's face, and a considerable escape of gas results.The other form of conventional mask does not have a pneumatic cuff, but is simply a resilient moulded rubber or plastics shape which is intended to fit closely around the nose of the patient, and whose periphery is intended to be sufficiently flexible so as to accommodate different facial shapes and dimensions in the area contacted. In practice, however, it is found that insufficient regard is paid to the greater variation of facial shapes and dimensions in some parts of the face as compared with others, and again leakage is commonly experienced. Moreover, the mask has to be held firmly against the face to minimise leakage, and is easily displaced by pressure applied to the gas inlet and outlet conduits which are located one on each side of the mask.

The present invention provides an anaesthesia mask moulded from polymeric foam material having an opening to receive the nose of the patient, lateral ports for the inlet and outlet of gases, and substantially rigid reinforcement in the region of the mask remote from said opening, the periphery of the mask around the opening being shaped so as to have a lower region adapted to bear upon the base of the upper lip, an upper region adapted to contact the nasal bones, and lateral regions joining the upper and lower regions, the lateral regions being shaped so as to contact the nasal processes of the maxilla and the maxilla itself, and to meet the lower region over the points where the base of the upper lip meet the nasolabial grooves, the face-contacting surfaces which contact the inferior and lateral surfaces of the nasal bones and the maxilla on either side of the nose being chamfered inwardly with respect to the interior of the mask. The distance over the outside surface of the mask between the said gas inlet and outlet ports and the nearest point thereto of lateral face-contacting regions is preferably at least 24 mm, and most preferably at least 27 mm. The gas inlet and outlet ports preferably take the form of apertures in the sides of the mask into which respective inlet and outlet connectors can be fitted.

In order that the invention may be more clearly understood, one embodiment will now be described with reference to the accompanying drawings, wherein: Fig. 1 shows a plan view from below of the mask, Fig. 2 shows a rear view of the mask on the facial opening thereof, Fig. 3 shows a plan view from above of the mask, Figs. 4 and 5 show cross-sectional side views of the mask on the lines lV-lV and V-V, Fig. 6 shows the areas of the face which are contacted by the mask in use, and Fig. 7 shows plan, rear and side views of the mask marked for the purpose of indicating some of the dimensions thereof.

Referring to the drawings, the mask is moulded from resiliently flexible polyurethane foam or similar polymeric foamed material, and has a cavity 10 to receive the nose of the patient, the cavity having an opening 12 bounded by a facecontacting edge surface 14. The shape of this surface, as shown in Figs. 1 to 5, can be defined in relation to the areas of the face which are to be contacted by it, as shown in Fig. 6. At the top of the mask the surface 14 is formed as a tapering recess 16 which seats around the nasal bones 17.

This upper region 16 merges into lateral regions 1 8 which seat upon the nasal processes 19 of the maxilla and on the maxilla 21 itself. A lower region 20 of the surface 14 seats upon the base of the upper lip 23, and merges with the lateral regions 18 over the points 25 where the base of the upper lip meets the naso-labial grooves 27. Thus, the mask does not obstruct the eyes 28 nor the mouth 29, but encloses the nose 31 and the alar base 33 on each side of the nose. As can be seen best in Figs. 4 and 5, the apex of the upper region 1 6 of the surface 14, and also the lateral surfaces 18 are chambered inwardly, as indicated at 22 and 24 respectively.This not only conforms more readily to the shape of the face in those regions, but also allows a greater degree of deformability of the mask in these regions, where it has been found that the greater variations in facial dimensions between patients occur. Moreover, it allows this deformation to be produced without applying undue pressure to the mask, and hence undue discomfort to the patient or undue risk of leakage if the pressure changes.

The mask is provided with two lateral ports 30 into which are fitted gas inlet and outlet connectors 32. Each connector comprises an adaptor portion 34 and an elbow portion 36. The adaptor portion 34 is a straight sleeve with axially spaced apart flanges between which is received and compressed somewhat the region of the mask around the port 30, as shown in Fig. 3. Fig. 3 only shows one connector fitted, but another similar connector is fitted to the other port 30. The elbow part 36 projecting from the mask can be push fitted into a flexible hose for gas supply or removal. With the connectors 32 thus fitted to the mask, either of the elbow portions can be rotated without disturbing the mask. This enables the hoses to be readily moved by the surgeon with little risk of displacing the mask and allowing leakage of gas.

The front portion 50 of the mask is provided with a substantially rigid insert 52, which is conveniently moulded from polypropylene sheet material. As can be seen from Figs. 3 and 4, the insert extends across the front portion of the mask and around the side portions until it terminates just short of the ports 30. This insert enables pressure to be applied to the mask towards the face to ensure that a satisfactory seal is provided between the mask and the face. The ends of the insert bear upon the gas inlet and outlet connectors 32, so that essentially the front portion of the mask is not distorted by this pressure, and the distortion only occurs in the region of the face contacting surface 14.

As well as the shape of the mask, its dimensions are of some importance in achieving applicability to a wide range of patients. The principal dimensions are indicated in Fig. 7 as follows.

A. The shortest distance on the outside surface of the mask from the port 30 to the nearest point on the face contacting edge 14 is about 27 mm.

This is quite important in providing sufficient compressibility at this point, since there can be considerable variation in the facial dimensions of different patients in this region. This dimension should be at least 24 mm, and 27 mm gives a reasonable margin to allow for the more unusual facial shapes.

B and C. The overall external and internal widths respectively of the mask at the facial opening, are about 93 mm and 58 mm respectively.

D. The horizontal distance from the points on the outside surface of the mask where the lateral regions 18 meet the lower region 20 to the apex of the upper region 1 6 is about 26 mm.

E. The horizontal distance from the points on the outside surface of the mask where the lateral regions 18 meet the lower region 20 and the centre of the lower region 20 is about 19 mm.

F. The distance on the outside surface of the mask from the apex of the upper region 16 and a projected point 60 representing an extension of the outside surface of the lateral regions 1 8 is about 17 mm. This gives an indication of the forward extension of the upper region 1 6 as compared with the lateral regions 18.

G. The overall height of the mask is about 48 mm.

The foregoing dimensions B to F are the preferred dimensions for the embodiment shown, and represent about a 10% margin of safety over the ranges of dimensions which have been found from extensive measurements carried out on people of different ages, sexes and races. Thus, this embodiment of mask should fit the vast majority of patients.

In the foregoing description the expressions "top", "front", "rear" etc., relating to features of the mask refer for convenience to the mask when worn by a patient in the upright posture. It will be appreciated however that in practice the patient will normally be in a supine or near supine position.

Claims (6)

1. An anaesthesia mask moulded from polymeric foam material having an opening to receive the nose of the patient, lateral ports for the inlet and outlet of gases, and substantially rigid reinforcement in the region of the mask remote from said opening, the periphery of the mask around the opening being shaped so as to have a lower region adapted to bear upon the base of the upper lip, an upper region adapted to contact the nasal bones, and lateral regions joining the upper and lower regions, the lateral regions being shaped so as to contact the nasal processes of the maxilla and the maxilla itself, and to meet the lower region over the points where the base of the upper lip meet the naso-labial grooves, the facecontacting surfaces which contact the inferior and lateral surfaces of the nasal bones and the maxilla on either side of the nose being chamfered inwardly with respect to the interior of the mask.

2. Anaesthesia mask according to claim 1 wherein the distance over the outside surface of the mask between the said gas inlet and outlet ports and the neatest point thereto of lateral face contacting regions is at least 24 mm.

3. Anaesthesia mask according to claim 2 wherein said distance is at least 27 mm.

4. Anaesthesia mask according to any one of claims 1,2 and 3 wherein the gas inlet and outlet ports take the form of apertures in the sides of the mask into which respective inlet and outlet connectors can be fitted.

5. Anaesthesia mask according to claim 4 further including said inlet and outlet connectors, each connector comprising a short adaptor sleeve portion which fits into a said aperture and has axially spaced apart flanges to receive and compress somewhat the material of the mask around the aperture, and an elbow shaped portion projecting from the mask and rotatable relative to the mask, the end of the elbow portion remote from the adaptor sleeve portion being arranged for fitting to a gas transfer hose.

6. Anaesthesia mask substantially as described herein with reference to the drawings.