This invention relates to face masks of the kind arranged to fit around at least the mouth of a patient for use in delivering breathing gas to and from the patient.

Face masks are often used to deliver supplemental oxygen to patients having a poor lung function or to those recovering from a medical procedure. They are also used to deliver air at elevated pressure such as to patients requiring PEEP therapy or to those suffering from sleep apnoea. Face masks can be relatively easy to use and of low cost. One problem with facemasks, however, is that they obscure the mouth, making it difficult for others to hear speech made by the patient. To overcome this problem patients often resort to holding the face mask away from their mouth. This, however, can be tiring and uncomfortable and reduces the amount of oxygen delivered. It can also pull on the retaining strap and alter the fit of the face mask around the mouth.

It is an object of the present invention to provide an alternative face mask.

According to one aspect of the present invention there is provided a face mask of the above-specified kind, characterised in that the face mask includes a sound sensor responsive to speech sounds made by the patient, and a sound generator connected to receive an output of the sensor and arranged to generate externally of the face mask sounds derived from patient speech.

The sound sensor is preferably mounted inside the face mask or in an opening through the wall of the face mask. The sound generator is preferably mounted externally on the mask. The sound sensor and sound generator may be parts of the same unitary assembly. The face mask preferably includes a gas coupling by which gas is supplied to and from the mask, and the sound sensor is preferably spaced from the gas coupling to one side. The sound sensor is preferably a directional microphone. The sound sensor may be connected with the sound generator by an electrical conductor. Alternatively, the sound sensor may be connected with the sound generator by a wireless connection, such as by radio frequency transmission, inductive coupling, or infra-red transmission. The sound generator preferably includes speech signal processing such as including filtering, pitch shifting or noise cancellation. The mask is preferably arranged to cover both the nose and mouth.

According to another aspect of the present invention there is provided a sound sensor with a sound generator for use in a face mask according to the above one aspect of the present invention.

Face masks according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a front elevation view of a first form of face mask;

Figure 2 is an enlarged cross-sectional side elevation through a part of the wall of the face mask along the line II-II; and

Figure 3 is an enlarged cross-sectional side elevation through a part of the wall of an alternative face mask.

With reference first to Figures 1 and 2, the face mask 1 comprises a mask body 10 and speech sound assembly indicated generally by the numeral 20. The mask body 10 is substantially conventional, being moulded from a soft, transparent plastics and of generally triangular shape having an upper portion 11 shaped to extend over the bridge of the nose and down either side, and a wider mouth portion 12 shaped to extend down either side and under the mouth. Opposite sides of the mouth portion 12 are formed with two slots 13 that receive opposite ends of a head strap 14 by which the face mask 1 is retained about the head. The mask body 10 also includes a gas coupling 15 positioned in the mouth portion 12 directly opposite the mouth of the patient. The gas coupling 15 is adapted to be connected with a cooperating coupling at the patient end of a breathing tube (not shown) by which breathing gas (typically air or an air and oxygen mixture) can be supplied to and from the patient. In alternative embodiments the mask need not enclose the nose as well as the mouth. The speech sound assembly 20 is shown as being mounted on the mask body 10 level with and spaced to one side of the gas coupling 15. In the example shown in Figures 1 and 2 the speech sound assembly 20 is a single, unitary assembly having a nose portion 21 on its patient side and a sound generator in the form of an enlarged disc-shape speaker unit 22 on its opposite side. The nose portion 21 is a close sliding fit in a circular opening 16 formed in the wall 17 of the mask body 10 with the speaker unit 22 extending radially outwardly in abutment with the front, external surface of the mask body. The friction between the nose portion 21 in the opening 16 may be sufficient to retain the assembly 20 securely on the mask body 10. Alternatively, adhesive may be used to bond the assembly 20 in position, or the inner end of the nose portion 21 could be formed with a mechanical formation engaging the internal side of the mask body 10. The nose portion 21 includes a sound sensor in the form of a microphone 23 receptive to speech sound made by the patient. Preferably the microphone 23 has a directional sensitivity to minimise feedback from sound generated by the speaker unit 22. An electrical conductor 24 connects the output of the microphone 23 to the speaker unit 22. The speaker unit 22 includes an electronics unit 25 arranged to receive the output of the microphone 23 and drive a speaker 26 or other sound generator exposed on the outside of the face mask 1. The electronics unit 25 is arranged to amplify the microphone signal sufficiently to drive the speaker 26 so that speech sounds made by the patient wearing the mask 1 are amplified to a more audible condition for people in the vicinity of the patient. The electronics unit 25 is preferably arranged to process the output of the microphone 23. In its simplest form this processing may include filtering so that extraneous noise, such as caused by gas flow through the mask, is reduced. The filtering may be arranged so that tones muted by the presence of the face mask are amplified in preference to other tones so that the sound produced by the speaker is more representative of normal speech and easier to understand. A similar effect could be achieved by conventional pitch correction software incorporated into the electronics unit 25. Extraneous noise could also be reduced by means of conventional noise cancelling techniques, which could use a separate microphone more exposed to the noise source to generate a signal in antiphase to the noise.

The arrangement described above enables the same mask body 10 to be used in a conventional face mask, without any speech sound assembly 20, simply by capping the opening 16, or by only forming the hole in mask bodies intended to receive a sound generator.

There are various ways in which the face mask could be modified.

For example, the sound sensor and sound generator or speaker need not be parts of a single unitary assembly, as described above, but could be separate components linked by a signal connection such as via a wire or wireless link. The wireless link could include a radio frequency transmission such as using Bluetooth protocol. Alternatively, the wireless link could include some form of inductive coupling between the sound sensor and the sound generator, or an infra-red or other optical radiation link, which could be via the air or via a radiation guide, such as a fibre-optic cable, or by transmission through the transparent material of the mask body.

Figure 3 shows an example where the sound sensor unit 123 generates a wireless signal in response to sensed speech by the patient. The sensor unit 123 is attached to the inside surface of the mask body 110, such as with an adhesive. The sound generator unit 122 is arranged to receive the wireless signal from the sound sensor unit 123 and generate a sound output accordingly. The sound generator unit 122 is attached to the outside surface of the mask body, such as by means of an adhesive. The two units 122 and 123 could be attached to the mask body 110 directly on top of one another or, as shown in Figure 3, the two units could be spaced from one another. This would enable the sound sensor unit 123 to be mounted in the best place to receive speech sound made by the patient and to minimise sound made by gas flow through the mask, and would enable the sound generator to be mounted in the best place from which sound could be produced. Such arrangements also avoid the need to make any opening through the wall of the mask.

Where the sound sensor unit and sound generator unit are separate it might be possible for them to be attached to the mask body by means of magnets in the two units that interact with one another. This would enable the units to be removed and replaced on a different mask body when the mask body needs to be replaced, thereby reducing waste and cost. Units attached with the mask body using a peel-off adhesive or mechanically engaged with the mask body could similarly be removed and reused.

It is not essential that the sound sensor unit be mounted inside the mask body providing the sound sensor was responsive to speech sounds made by the patient. A microphone could be mounted externally in line with an opening through the wall of the mask body. Alternatively, an external microphone acoustically coupled to the wall of the mask body (such as by direct contact or by means of an acoustically-transmitting gel for example) might be capable of picking up patient speech sounds with sufficient clarity. In such an arrangement it might be best to mount the microphone where the wall of the mask body was relatively thin. Contact microphones, such as those including a piezo element, might be most suitable for such an application.