FIELD OF THE INVENTION

The present invention relates to patient interface arrangements for transporting a gas to and/or from an airway of a user.

BACKGROUND OF THE INVENTION

There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e. without inserting a tube into the airway of the patient or surgically inserting a tracheal tube in their oesophagus. For example, it is known to ventilate a patient using a technique known as non- invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle, to treat a medical disorder, such as sleep apnoea syndrome, in particular, obstructive sleep apnoea (OSA).

Non- invasive ventilation and pressure support therapies involve the placement of a patient interface device including a mask component on the face of a patient. The mask component may be, without limitation, a nasal mask that covers the patient's nose, a nasal pillow/cushion having nasal prongs that are received within the patient's nostrils, a nasal/oral mask that covers the nose and mouth, or a full face mask that covers the patient's face. The patient interface device interfaces between the ventilator or pressure support device and the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient.

Such devices are typically maintained on the face of a patient by headgear having one or more straps adapted to fit over/around the patient's head.

Fig. 1 shows a typical system to provide respiratory therapy to a patient. In this description and claims, the overall system is referred to as a "patient interface

arrangement".

The system 2 includes a pressure generating device 4, a delivery conduit 16 coupled to an elbow connector 18, and a patient interface device 10. The pressure generating device 4 is structured to generate a flow of breathing gas and may include, without limitation, ventilators, constant pressure support devices (such as a continuous positive airway pressure device, or CPAP device), variable pressure devices, and auto-titration pressure support devices.

Delivery conduit 16 communicates the flow of breathing gas from pressure generating device 4 to patient interface device 10 through the elbow connector 18. The delivery conduit 16, elbow connector 18 and patient interface device 10 are often collectively referred to as a patient circuit.

The patient interface device 10 includes a mask 12, which in the exemplary embodiment is nasal mask. However, any type of mask, such as a nasal oral mask, a nasal pillow/cushion or a full face mask, which facilitates the delivery of the flow of breathing gas to the airway of a patient, may be used as mask 12. The mask 12 includes a cushion 14 coupled to a shell 15. The cushion 14 is made of a soft, flexible material, such as, without limitation, silicone, an appropriately soft thermoplastic elastomer, a closed cell foam, or any combination of such materials. An opening in shell 15, to which elbow connector 18 is coupled, allows the flow of breathing gas from pressure generating device 4 to be

communicated to an interior space defined by the shell 15 and cushion 14, and then to the airway of a patient.

The patient interface device 10 also includes a headgear component 18, which in the illustrated embodiment is a two-point headgear. Headgear component 18 includes a first and a second strap 20, each of which is structured to be positioned on the side of the face of the patient above the patient's ear.

Headgear component 18 further includes a first and a second mask attachment element 22 to couple the end of one of the straps 20 to the respective side of mask 12.

A problem with this type of "low profile" mask is that the headgear force vectors necessary to achieve a robust and stable seal against the face of the patient can cut a straight line near the corners of a patient's eyes, which can be uncomfortable and distracting.

In order to avoid this, it is well known to include a forehead support to spread the required forces over a larger area. In this way, an additional cushion support on the forehead balances the forces put by the mask around the nose or nose and mouth.

In order to allow the mask to be a comfortable fit for a variety of users, the forehead support needs to be adjustable with respect to the nasal/oral mask part. In one known design, this is achieved by providing the forehead support on the end of an arm which is pivotally connected to the main nasal/oral mask part. This enables the forehead support to be pivoted towards and away from the forehead, to allow different relative positioning for different users. An example is disclosed in US 2007/0215161. Typically, an adjustment of around 3 cm is needed between the facial plane and the forehead plane.

US 2007/0215161 also recognises that the relative linear position between the mask part and the forehead support part should be adjustable so that different cushion sizes can be accommodated, as well as the relative angular position as allowed by the pivoting of the arm. In US 2007/0215161, this adjustment is possible by providing two pivot axes between the forehead support arm and the main body of the mask. Depending which axis is engaged, a positioning of the forehead support can be varied.

The prior art fails to provide an adjustment mechanism which can simply and quickly be adapted to a particular user, with adjustment of the angular and also the linear relative positioning between the mask part and the forehead support part.

SUMMARY OF THE INVENTION

According to the invention, there is provided a patient interface arrangement as defined in claim 1.

This arrangement provides two joints in the path between the patient interface device (i.e. the mask part of the overall arrangement) and the rigid forehead support part. This defines a three arm linkage which can be used to adjust the position in the direction towards/away from the face as well as the position up/down the face. However, this can be achieved with a single movement, in that the forehead support can simply be moved to the desired position, and the two joints will naturally adopt the required settings. These settings can then be fixed manually or else the friction in the joints can be relied upon.

A first rotary joint can be provided between the patient interface device and one location of the forehead support arm, and a second rotary joint can be provided between another location of the forehead support arm and the forehead support.

The forehead support can comprise a forehead support cushion coupled to a rigid support part.

The second rotary joint axis is preferably at a distance (dl) from the face of the support cushion which is in the range 2cm to 7.5cm. This means there is sufficient movement to provide a desired range of adjustment to the position of the forehead support cushion up and down the user's face, to accommodate size differences between different users.

The distance (dl) can be in the range 2cm to 4cm. This provides a lower profile mask. In this case, when the support comprises a support cushion which is mounted to a rigid forehead support part, this mounting can be by means of a third rotary joint. This means the cushion angle can be adjusted to keep the cushion comfortable.

The first rotary joint can comprise a cylinder joint or a ball joint. Similarly, the second rotary joint can comprise a cylinder joint or a ball joint. This gives four possible combinations of joint design.

The first connecting arm can comprise a single connection or else it can comprise a parallelogram arrangement. A parallelogram arrangement enables the angle of the cushion support to be constant even when the adjustment (about the first joint) is made. BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1 shows a known patient interface arrangement;

Fig. 2 shows a known patient interface arrangement as disclosed in US 2007/0215161;

Fig. 3 shows schematically the concept underlying the invention;

Fig. 4 shows a first example of patient interface arrangement of the invention;

Fig. 5 shows a second example of patient interface arrangement of the invention;

Fig. 6 shows a third example of patient interface arrangement of the invention;

Fig. 7 shows a fourth example of patient interface arrangement of the invention; and

Fig. 8 shows a fifth example of patient interface arrangement of the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention provides a patient interface arrangement which has a forehead support which is adjustable by means of at least two rotary joints between a patient interface device (such as a mask) and the rigid forehead support, thereby defining a three-arm linkage. This means that linear and rotational positioning of the forehead support with respect to the patient interface device is made possible.

Fig. 2 is taken from US 2007/0215161 and shows a patient interface device in the form of a respiratory mask assembly 12 that includes a rigid shell 15 and a cushion 14 that may be permanently or removably connected to the shell 15. A forehead support 30 is movably mounted to an upper portion 15' of the shell 15. In Fig. 2, the mask assembly is a nasal mask structured to deliver breathable gas to a patient's nose. However, the mask assembly 12 may be a mouth mask, a nasal pillow mask or a full- face mask.

The forehead cushion 40 is fixed to the top of a rigid forehead support 30, and the forehead support 30 is pivoted to the region 15 Of the mask shell 15. A pivot shaft 32 is provided on each side of the forehead support 30, and is positioned in one 34 of two possible slots. The choice of slot changes the positioning (dimensions el and HI) to allow different size forehead cushions to be used.

The invention is based on the recognition that different users require different alignments of the forehead support, both in distance from the pateint interface device (the mask) and angular positioning in the direction towards and away from the face.

To provide this functionality, at least two rotary joints are provided between the patient interface device, in particular the rigid mask shell 15, and the forehead support 30 thereby defining a three-arm linkage.

Each of the two rotary joints can be either a single axis joint, namely a hinge, or else a joint allowing pivoting in 3D, namely a ball joint.

The user can position the forehead support in the right position relative to the patient interface device by using the adjustment mechanism. The joints make it easy to adjust the offset between the forehead plane and the mask in one move.

Fig. 3 shows schematically the concept underlying the invention. The mask

12 has a first rotary joint 50 connecting to a first arm 51, for example to one end as shown. This first arm 51 has a length such that a remote location (such as the other end) away from the mask is located at the distance corresponding to a default location for the forehead support cushion 40. With the mask in place, the remote location (the other end) of the arm 51 is offset from the tip of the nose by about 10cm. At this remote location (the other end) of the arm 51, there is a second rotary joint 52 which connects to the forehead support 30.

The joints 50,52 need not be at the ends of the arm 51 , for example one of them may be at an adjustable position along the arm 51 to enable a coarse adjustment to be made, and the joints can then be used for a fine adjustment.

The forehead support 30 is designed such that when the forehead support cushion 40 is against the user's forehead, the second rotary joint 52 is at a distance dl from the user. Thus, dl is the distance from the rotation axis to the face of the forehead support which will be against the user's head. If there is a cushion, this face will be the face of the cushion. However, the forehead support can comprise a single component with sufficient rigidity to be held by the joint but some pliability for comfort. When a cushion is used, the distance dl is the combined length of the support 30 and the thickness of the cushion 40.

This effectively defines a three arm linkage - the arms being the mask 12 between the user's mouth/nose and the first joint 50, the arm 51 between the first and second joints 50,52, and the forehead support 30 between the second joint 52 and the user's forehead.

The first joint 50 enables adjustment to take account of different depths of the forehead with respect to the nose and mouth (i.e. how raked back is the top of the user's head). The first joint 50 allows the first arm 51 to pivot towards and away from the user's face.

The second joint 52 enables adjustment to take account of the different height of the forehead, i.e. the distance from the nose/mouth to the forehead, which varies depending how tall the user's face is. The second joint 52 allows the forehead support 30 to pivot up and down the user's face. This will be termed "height adjustment" in the following description.

The distance dl dictates how much height adjustment is possible. If the distance dl is large, a height adjustment d2 can be made with a small angle change a. As can be seen from the enlarged part of Fig. 3: d2=dl .sin a

The amount of adjustment needed is of the order of 3cm to take account of different user's head shapes. The mask does not want to be too large around the user's face, and an example of acceptable distance dl is 5cm. Setting d2=1.5cm (since adjustment can be above or below the default position) gives a=17.4 degrees.

If the forehead support cushion is rigidly fixed to the forehead support 30, it will also rotate by the same amount, and thus not remain flat against the head. If enough cushioning is provided, this does not matter for small angles.

If the cushion is designed with a circular contact surface, large angles can be tolerated. Alternatively, the cushion 40 can also be pivotally mounted to the support 30.

These two alternative measures enable the outward dimension of the support 30 to be reduced.

For example, if the support 30 is expected to be adjusted between +45 degrees and -45 degrees, with the same desired position change of d2=1.5cm each way, this gives dl=2.12cm. Thus, it can be seen that a low profile hinge point 52 is sufficient to enable a reasonable range of adjustments.

A larger range of adjustments may be desired, for example 5 cm. For a 45 degree adjustment range, this requires the joint 52 to be dl=3.53cm from the face of the forehead cushion.

If a flat cushion 40 with no pivot connection is desired, a maximum angle of adjustment may be considered, for which the cushion remains comfortable and effective, and for which the mismatch between the profile of the user's forehead and the angle of the cushion is taken up by the cushion compression. This angle may for example be 20 degrees. For a 3cm adjustment range (d2=l .5cm), this requires dl=4.38cm. For a 5cm adjustment range (d2=2.5cm), this requires dl=7.31cm.

It can be seen that there is a range of options. Generally, the distance from the surface of the cushion to the rotation axis of the second joint 52 is in the range 2cm to 7.5cm. With a pivoted cushion, the range is more preferably 2cm to 4cm. This enables a lower profile mask to be formed.

The length of the arm 51 depends on where it is connected to the mask shell 15. Because there is a large available distance of around 10cm from the centre of the mask to the forehead area, the joint 50 can be at the middle of the mask, or it can be higher up as in the example of Fig. 2. The amount of adjustment needed is around 3cm, and this is easily obtained when the length of the support arm 51 is 3cm or more.

The arm 51 and joints 50,52 at each end can be defined by:

a parallelogram comprising a two-bar mechanism with rigid rods and rotational joints at each end;

two (or more) ball joints, one on the mask shell and one on the forehead support, with a connecting arm between;

two (or multiple) cylindrical joints, one on the mask shell and one on the forehead support with a connecting arm between;

a cylindrical joint on the mask shell and a ball joint on the forehead support; or a ball joint on the mask shell and a cylindrical joint on the forehead support.

These various possibilities are outlined in schematic form further below.

In all cases, locking of the position at the desired setting can be achieved by friction in the mechanism, or else a locking system can be provided, for example a spring biased locking system. The adjustment can be made by manually moving the forehead support into position against the friction or spring biasing in the joints, or else mechanisms such as turning knobs may be employed to move the arm into a preferred position. Visible indexation can be provided to enable the arm to be positioned in a previous position.

Figs. 4 to 8 show various embodiments of the invention. The forehead support 30 and cushion 40 are shown in simplified form as single component. As outlined above, the cushion part 40 may be pivotally mounted to the rigid support part 30, and it is the rigid support part 30 that is coupled to the second joint 52. In all examples, the discussion above relating to the positions of the joints 50 and 52 applies.

Fig. 4 shows a first embodiment of the invention. The mask shell 15 is connected to the forehead support 30 using a parallelogram arm configuration 51 that is fixed to the mask shell 15 using cylinder hinges on a first end of the arm, which together define the first joint 50. The cylinder hinges at the first end of the arm 51 allow for a movement of the arm in a substantially circular fashion orthogonal to the face plane of the user and thus ensure that the main movement of the arm relative to the face stays substantially in the centre of the face of a user.

The position of the arm 51 on the mask shell 15 and the length of the arm are chosen in such a fashion that the second end of the arm 51 opposite the cylindrical hinge is substantially in the vicinity of the forehead of the user. The second joint 52 comprises a ball joint that holds the forehead support 30. The ball joint 52 holds the forehead support loosely, which ensures that the forehead support has an even pressure distribution on the forehead. The movement possibilities of the forehead support 30 on the ball joint 52 may be restricted to ensure that the forehead support is always pointing roughly in the direction of the forehead, and may be spring loaded to be inclined in a preferred position.

The parallelogram design of the arm 51 allows the forehead support 30 to be substantially parallel to the forehead independent of the angular movement of the arm around the cylinder hinges 50. The arm 51 may be spring loaded to move in a direction towards the user's face.

The use of a parallelogram arm 51 means that the second joint 52 has multiple components - the cylindrical joints 60 forming the end of the parallelogram connecting arm 51 and the ball joint for enabling adjustment of the angle of the forehead support 30, and which functions as the second joint 52. The second joint can be implemented as a cylindrical joint instead of the ball joint shown.

Fig. 5 shows a second example, which differs from Fig. 4 in that a single connecting arm 51 is used, and both joints 50,52 are ball joints. Fig. 6 shows a third example, which differs from Fig. 5 in that both joints 50,52 are cylindrical joints.

Fig. 7 shows a fourth example, which differs from Fig. 5 in that the first joint 50 is a cylindrical joint and the second joint 52 is a ball joint.

Fig. 8 shows a fifth example, which differs from Fig. 5 in that the first joint 50 is a ball joint and the second joint 52 is a cylindrical joint.

The concepts of the invention can be applied to many different designs, and the more detailed design shown in Fig. 2 is purely by way of example.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" or "including" does not exclude the presence of elements or steps other than those listed in a claim. In a device claim

enumerating several means, several of these means may be embodied by one and the same item of hardware. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination. Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.