GB2367009A

GB2367009A - Airway bite protector

Info

Publication number: GB2367009A
Application number: GB0115670A
Authority: GB
Inventors: Timothy Michael Craft; John James Hughes
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-06-30
Filing date: 2001-06-27
Publication date: 2002-03-27
Also published as: GB0016058D0; GB0115670D0

Abstract

A bite block protector 17 for an airway comprising an elongate body 18 possessing a longitudinal passage extending through it, a discontinuity extending though the wall down one side of the body and a hinge extending along the other side, a flange 20 at one end to limit the distance it may be inserted into the mouth and having flat, unreinforced tooth engagement surfaces 31 adjacent to the flange which is formed in two parts one on either side of the hinge. The hinge allows the body to open laterally to admit a tracheal tube and has locking means 35, 40 to secure it shut. The body may have parallel walls in the proximal region which are bevelled and taper 22 to a distal end 21 of circular cross-section. The bite protector may be used with an inflatable laryngeal mask and an elongate flexible tube which it is intended to prevent patients recovering from anaesthetic from biting though.

Description

AN IMPROVED AIRWAY BITE PROTECTOR

The present invention relates generally to oral airways for medical practices, and particularly to an improved oral airway having means for protecting associated reusable parts of equipment from damage which may be inflicted by the patient.

The introduction of oral airways, often referred to as intubation, may be required for various reasons although most frequently it is required to enable a medical practitioner to administer air or oxygen (or other gas) when a patient is under sedation or anaesthetic. When a general anaesthetic is being administered to a patient who is breathing spontaneously there is always a risk of upper airway obstruction. Such obstruction is dangerous and potentially fatal. It may be caused by the tongue falling into the hypopharynx or by the structures of the pharynx collapsing as a result of the loss of normal muscle tone.

One widely used device to prevent such obstruction from occurring and allow the continued smooth administration of oxygen with or without anaesthetic gases is the reusable laryngeal mask airway. One type of laryngeal

mask airway is the reinforced laryngeal mask. An advantage of this particular device is that the patient may be allowed to regain consciousness with the device in situ. This helps ensure that the upper airway remains open and permits the continued administration of oxygen in the recovery room. One of the problems of the use of such a device, however, is that during emergence from anaesthesia, but before consciousness has been regained, the patient almost invariably bites on the reinforced flexible tube component of the laryngeal mask airway at the point where it passes between his or her incisors due to the (unconscious) physiological bite reaction. There are two serious consequences of this. First, the flow of oxygen to the patient is obstructed, frequently resulting in the saturation of haemoglobin with oxygen in the patient's blood falling to undesirable or even dangerous levels. Secondly, the reinforced laryngeal mask airway becomes damaged and is not thereafter available for further use as intended.

The problems associated with the patient's unconscious bite reaction on regaining consciousness have been recognised, and various bite protector devices have been devised. One prior art bite protector device is described

in US patent 4425911 which describes a bite-block for tracheal tubes which comprises a substantially rectangular body having a central channel which is upwardly open and a pair of side members shaped to match the curve of the mouth and having surfaces shaped to engage the teeth other than the incisors. In use the bite block is inserted into the patient's mouth with the lateral wing portions engaged between the patient's molars such that the patient's incisors are held spaced apart.

Airway tubes, such as endotracheal tubes, suction catheters and the like are then introduced longitudinally through the channels in the bite protector and are protected from damage inflicted by the patients bite reaction due to the presence of the lateral wings which effectively prevent the molars from approaching one another and, therefore, hold the incisors spaced by a sufficient distance to prevent them from contacting the tubes. This bite protector works effectively for certain medical practices, but has a number of disadvantages in others. In particular, because it has to be fitted in position before the airways are introduced, it limits the available range of the medical practices to those in which the distal ends of the airway tubes are not

equipped with anything larger than the cross-sectional dimension of the channel in the bite protector. In particular, therefore, such a bite protector cannot be used with a laryngeal mask airway as the laryngeal mask, which is permanently connected, as discussed above, to the distal end of the airway tube, is of sufficient dimensions to occupy the entirety of the patient's larynx lumen. This is considerably larger than the crosssectional dimension of the airway passage.

Moreover, when utilising a laryngeal mask airway this may frequently be left in place whilst the patient regains consciousness in order to allow administration of oxygen.

For access to the patient's mouth, and for the patient's comfort, it is necessary to be able to remove the bite protector from the patient's mouth whilst leaving the laryngeal mask in place. Such manipulation would be entirely impossible with the bite block described in US 4425911.

Another prior art endotracheal tube bite block is described in US 4896667. This has a simple design comprising a body with an elongate C-shape cross-section and comprises a core of a hard material surrounded by a material which is less hard than the core, the softer

material being secured to a portion of the exterior of the hard core, and a portion of the hard core being exposed. This bite block has no face flange like the bite block of US 4425911 and it is described that such bite block may be secured to an endotracheal tube by taping the exposed portion of the hard core to the tube.

A longitudinal slot extends the length of the body, and radial apertures are provided for receiving locating straps to secure the bite block in position at a determined point along an endotracheal tube. Although the longitudinal slot would allow the introduction longitudinally of a narrow member it will not allow lateral introduction of a flexible airway such as to permit positioning of the bite block after the airway has been positioned within the patient's throat, nor to allow subsequent removal of the bite block whilst leaving the airway tube in position.

Existing bite protectors resist the bite reaction using a reinforced region such as a solid bite block, or use more resistant material in the region likely to come into contact with the patient's teeth and be crushed. These solutions add to the complexity of production and/or to the amount of material used.

The present invention seeks to provide a bite protector which is simple and cheap to produce and which does not require specific and additional reinforcement to resist a bite reaction, but has its strength as a consequence of the shape of the element, and which is therefore smaller than prior art such services and more easily manipulated in the oral region.

According to one aspect of the present invention, therefore, there is provided a bite protector for an airway, comprising an elongate body having a longitudinally extending passage therethrough, a discontinuity extending along the wall at one side of the body and a hinge extending along the other side, a flange at one end to limit the distance the bite protector can be introduced into the mouth of a patient, and surfaces for engagement by the teeth of a patient when the body is introduced into the mouth, at least adjacent the flange, for resisting the bite reaction of a patient upon recovery from anaesthesia, the said engagement surfaces being substantially unreinforced, and being substantially flat whereby to be engaged by the teeth of the patient over substantially the entire width thereof.

In this respect the discontinuity is preferably an elongate slot and the closed position of the elongate body occurs when the opposite edges of the slot are in contact with one another. In this position the body is relaxed (that is unstressed) and in preferred embodiments of the invention there are provided locking means to ensure a secure relative location. The locking means may be a snap fit engagement provided by co-operating members on either side of the discontinuity. In some embodiments co-operating interengaging shapes may be used such as a V groove in the edge along one side of the slot with an appropriately shaped ridge along the other edge of the slot which ridge engages in the groove by form engagement when the slot is closed. Other shapes, including labyrinthine shapes, may be provided to ensure secure interengagement of the edges of the slot.

It is noted that because the surfaces are flat, and in use the teeth of the patient will be substantially parallel thereto, they will be engaged over substantially their entire width; the force of the bite reaction is therefore not concentrated as it would be were such surfaces to be curved. The structure of embodiments of the present invention is such that no additional thickening or strengthening of the walls is required in

the region anticipated to bear the load. The ability to resist crushing, attributable to the even distribution of the force, allows the engagement surfaces to be substantially unreinforced.

The hinge may be such as to allow the body to be opened laterally to an extent such that the opposite peripheral edges of the discontinuity are spaced from one another by a distance at least as great as the maximum diameter of the passage through the body when closed. The protector can then be introduced laterally and closed around a tube, and also opened and removed laterally from the tube. In each case the tube can already be in position and introduction or removal of the protector can be performed with little or no disturbance of the tube.

In one embodiment of the invention the end of the slot remote from the flange (hereinafter referred to as the distal end, whereas the end provided with the flange will be referred to as the proximal end) has an atraumatic curvature of the end portion of the wall whereby to avoid damage to a patient's palate upon introduction and/or removal.

Preferably the said face flange is formed into parts, one

on each side of the hinge of the body, the two parts being shaped such as to limit the introduction of the body into the patient's mouth without restricting the opening movement of the body about the hinge thereof.

The external, teeth-contacting surfaces of the wall are substantially flat; the internal surface of the wall of the body which defines the passage may also be flat, in which case the wall is laminar, or may be curved to define a tubular passage.

The surfaces may be at least partly shaped and conformed to the anticipated biting components.

The wall defining the surface may be a laminar structure, for example the surfaces may include a cushioning portion such as a thin layer of deformable material for absorbing part of the biting force and to avoid damage to the teeth or gums. Additionally the lining of the passage may be formed from deformable material to absorb distortion of the wall against an included tube.

The present invention also comprehends an assembly comprising a laryngeal mask airway having an elongate flexible airway tube, an inflatable laryngeal mask at a

distal end thereof, an inflation tube, and a bite protector as defined hereinabove, the internal diameter of the body of the bite protector being substantially the same as, or slightly greater than, the outer diameter of the flexible airway tube.

Embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a laryngeal mask airway provided with a bite protector as defined herein; Figure 2 is a schematic perspective view of the bite protector shown separated from the laryngeal mask airway and in an open position; Figure 3 is a schematic perspective view of the bite protector of Figure 2 shown in a closed, relaxed position; and Figure 4 shows the bite protector of Figures 2 and 3 in use on a patient.

Referring now to the drawings, Figure 1 illustrates a laryngeal mask airway of known form comprising a flexible tube 12 having a connector 13 at a proximal end thereof, and a laryngeal mask generally indicated 14 at the distal end. The tube 12 is relatively soft and flexible in

order to allow it to be introduced through a patient's mouth and into the pharynx where the mask 14 may be inflated via a separate inflation line 15 connected at its distal end to the mask 14 and having at its proximal end a bulb inflator 16 of known type. Injection of air through the bulb 16 causes the mask 14 to inflate and fill the pharynx thereby preventing air from escaping from the lungs around the outside of the tube 12, and correspondingly acting to prevent saliva and other liquids from draining into the lungs during medical operations. The bulb 16 includes valves (not shown) for controlling delivery of air to the line 15, and also for allowing deflation of the mask 14 when it is desired to remove it.

Around the flexible tube 12 is fitted a bite protector generally indicated 17, shown in more detail in Figures 2 and 3, and comprising an elongate body 18 having a longitudinally extending central passage through which the tube passes, and a face flange 20 at a proximal end thereof. The body 18 is straight but in other embodiments (not shown) may have a slight curve at the distal end. In the embodiment shown the distal end 21 of the body 18 has a tapered portion 22 defining rounded atraumatic shoulders which ensure that the bite protector

can be introduced into the mouth of a patient and, in particular, approach the throat without causing damage.

As can be seen in Figures 2 and 3, the body 18 is longitudinally split along a discontinuity or separation line 23 which may be considered as a slot extending the full length of the body, and diametrically opposite the separation line 23 the body has a ligament hinge 24 extending part of the way along the body parallel to the slot 23 and, with the slot 23, separating the body 18 into upper and lower halves 18a, 18b and, likewise, separating the face flange 20 into upper and lower halves 20a, 20b.

The main part of the body 18 has a rectangular, box-shape form with flat parallel opposite engagement faces 30,31 and a rectangular passage of corresponding form. At the junction lines between adjacent faces the body has bevelled edges 31 which merge at the distal end 21 into the tapered portion 22. These bevelled edges serve to increase the strength of the body by effectively smoothing what would otherwise be sharp edges at the junction between adjacent flat faces.

The upper half 18a of the protector has a tab 35 having

a slightly hooked end 40, the lower half 18b has a loop 45 correspondingly positioned. When the halves are closed together the tab 35 snap engages the loop 45, but can easily be released because the end 40 of the tab 35 is only slightly hooked, and is operable using one hand if necessary.

Figure 4 shows the bite protector 17 of Figures 2 and 3 in place on a patient with a tube 12 installed. The protector 17 is introduced so that the hinge and discontinuity are horizontal and will not be contacted by teeth in the bite reaction, because the protector 17 is better able to resist crushing forces in this orientation.

There is no necessity for the body 18 to extend further than is required to engage the teeth in the bite reaction. However, some applications may require an extended body in which case the box-shape structure may be confined to be immediately adjacent the flange the tapered end 22 may extend as a tubular body away from the engagement surfaces.

In use of the equipment shown in Figure 1 the laryngeal mask 14 at the distal end of the flexible tube 12 is

introduced into the patient's mouth and positioned in the region of the larynx and then inflated by use of the bulb 16. The bite protector 17 is opened as shown in Figure 2 and fitted over the flexible tube 12, following which it can be displaced longitudinally of the tube 12 into the patient's mouth with the engagement surfaces 30,31 in contact with the patient's incisors and the face flange 20 in contact with the patient's lips thereby defining a maximum insertion of the bite protector 17 into the patient's mouth.

The bite protector does not, in fact, have to be fitted until shortly before the patient is expected to arouse from the anaesthetic, and therefore does not have to be in place during initial administration of anaesthetic or during the operation where it may obstruct any manipulations of the flexible tube 12 or laryngeal mask 14. Once positioned, however, the bite protector offers a strong and robust protection against the jaw spasmic bite reaction which occurs unconsciously during the time a patient is recovering from anaesthesia. After recovery, however, the bite protector can be removed readily by displacing it longitudinally of the flexible tube 12, opening it to the position shown in Figure 2 and removing it laterally from the tube 12 without disturbing

it or applying any force which could cause disturbance to the location of the laryngeal mask 14.

If the entire bite protector is made from an appropriate plastics material, for example polypropylene or polyethylene, even a relatively small thickness will provide sufficient strength to resist the unconscious bite reaction. This is enhanced by the fact that the surfaces engaging the incisors are substantially flat so that contact across the entire width is made therefore spreading the load and releasing the force at any one point. The strength to resist crushing also comes from the fact that the side walls separating the faces contacted by the patient's teeth are substantially perpendicular to these walls, that is parallel to the direction of force transmission. They thus act as "columns"and have the strength of columns, only buckling when subject to Euler's crippling load, which is known to be very high. Additional strength may be provided by fitting an external sleeve of stronger material over the body, or by co-moulding an insert into it. Such insert may, for example, be of metal or other more resistant plastics.

After use the bite protector can be discarded. Although it would be possible to make reusable bite protectors the necessity for sterilisation would involve a more complex structure than the simple moulded structure described, particularly since the hinge 24 which, in the embodiment described, is a simple polypropylene ligament hinge, would need to be of more complex structure. Disposable bite protectors are expected to be more hygienic and safer than reusable ones.

Claims

1. A bite protector for an airway, comprising an elongate body having a longitudinally extending passage therethrough, a discontinuity extending along the wall at one side of the body and a hinge extending along the other side, a flange at one end to limit the distance the bite protector can be introduced into the mouth of a patient, and surfaces for engagement by the teeth of a patient when the body is introduced into the mouth, at least adjacent the flange, for resisting the bite reaction of a patient upon recovery from anaesthesia, the said engagement surfaces being substantially unreinforced, and being substantially flat whereby to be engaged by the teeth of the patient over substantially the entire width thereof.

2. A bite protector as claimed in Claim 1, further comprising locking means for joining the opposite peripheral edges of the discontinuity.

3. A bite protector as claimed in Claim 1 or Claim 2 in which the hinge is such as to allow the body to be opened laterally to an extent such that the opposite peripheral edges of the discontinuity are spaced from one

another by a distance at least as great as the maximum diameter of the passage through the body when closed.

4. A bite protector as claimed in any of the Claims 1 to 3, in which the end of the body remote from the flange has a tapered end portion of the wall terminating in a substantially circular cross section whereby to avoid damage to a patient's palate upon introduction and/or removal.

5. A bite protector as claimed in any preceding claim, in which the said flange is formed in two parts, one on each side of the hinge, the two parts being shaped such as to limit introduction into the patient's mouth without restricting the opening movement of the body about the hinge thereof.

6. A bite protector as claimed in any preceding claim, in which the said body has opposite substantially parallel wall portions in the region of the said engagement surfaces to be engaged by the incisors of a patient during recovery from anaesthesia.

7. A bite protector as claimed in Claim 6, in which the body has bevelled edges between adjacent wall portions.

8. In combination a laryngeal mask airway having an elongate flexible airway tube, an inflatable laryngeal mask at a distal end thereof, an inflation tube, and a bite protector as claimed in any preceding claim, the internal diameter of the body of which is substantially the same as or slightly greater than the outer diameter of the flexible airway tube.

9. bite protector for any airway, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.