Patent Description:
Respiratory masks are used to supply inhalation gases, and possibly also atomised liquids, such as drugs in solution, to the airways of a patient. In general, a gas is supplied to a respiratory cavity that is defined by the respiratory mask urged against the face of the patient, and the patient inhales the inhalation gas from this respiratory cavity. Conventional masks typically also have an inlet for the inhalation gas, and an outlet through which exhaled gas escapes the respiratory mask.

Conventional respiratory masks for breathing assistance and/or patient therapy typically comprise a mask body defining a cavity and a sealing member at the periphery of the mask body that is urged against the wearer's face, about their nose and/or mouth.

During operation, ie whilst providing breathing assistance and/or therapy to a patient, it is desirable to be able to monitor one or more characteristics of the patient's expiratory gases, such as the CO<NUM> concentration, in order to provide an indication of the patient's wellbeing during operation.

Conventionally, this is done by sensing the patient's expiratory gases in an exhalation tube connected to the respiratory mask, either via a respiratory monitoring unit that the exhalation tube delivers the expiratory gases to, or by placing a sensor, such as a CO<NUM> cuvette, in the exhalation tube.

Alternatively, in masks which vent the patient's expiratory gases to atmosphere, ie where no exhalation tube is present, such as oxygen masks, a dedicated sample tube may be connected to a spigot on the mask, to collect some of the expiratory gases before they escape, and deliver the gases to a sensor, such as a respiratory monitoring unit.

<CIT> discloses a nasal ventilation mask having one or more attachment ports located adjacent to and overlying an upper lip of a patient when worn. <CIT> discloses a gas sensor kit that includes a gas sensor that measures a gas concentration of an exhalation gas of a subject and a gas supply unit that supplies a therapeutic gas, supplied through a tube, to the subject.

It is an aim of the present invention to provide a respiratory mask, typically for patient therapy, which can offer an improved expiratory gas monitoring arrangement.

According to a first aspect of the invention, there is provided respiratory apparatus comprising a sensor and a respiratory mask, the respiratory mask comprising a mask body having an enclosing wall that defines an interior cavity, and the sensor having a transmitter of electromagnetic radiation and a receiver of electromagnetic radiation, wherein the enclosing wall has a sensor portion including first and second sensor windows, a portion of the interior cavity being defined between the first and second sensor windows, and the sensor being mounted relative to the sensor portion of the respiratory mask, such that electromagnetic radiation from the transmitter is transmitted, in use, through the first sensor window of the sensor portion of the enclosing wall, through the portion of the interior cavity defined between the first and second sensor windows, through the second sensor window, to the receiver, wherein the respiratory mask further comprises an inspiratory gas inlet port for delivering inspiratory gas to the wearer, and the sensor portion is spaced from the inspiratory gas inlet port.

According to a further aspect of the invention, there is provided a kit of parts comprising a sensor and a respiratory mask, the respiratory mask comprising a mask body having an enclosing wall that defines an interior cavity, and the sensor having a transmitter of electromagnetic radiation and a receiver of electromagnetic radiation, wherein the enclosing wall has a sensor portion including first and second sensor windows, a portion of the interior cavity being defined between the first and second sensor windows, and the sensor being mountable relative to the sensor portion of the respiratory mask, such that electromagnetic radiation from the transmitter is transmitted, in use, through the first sensor window of the sensor portion of the enclosing wall, through the portion of the interior cavity defined between the first and second sensor windows, through the second sensor window, to the receiver, wherein the respiratory mask further comprises an inspiratory gas inlet port for delivering inspiratory gas to the wearer, and the sensor portion is spaced from the inspiratory gas inlet port.

According to a further aspect of the invention, there is provided a respiratory mask for use with a sensor having a transmitter of electromagnetic radiation and a receiver of electromagnetic radiation, the respiratory mask comprising a mask body having an enclosing wall that defines an interior cavity, the enclosing wall having a sensor portion including first and second sensor windows, a portion of the interior cavity being defined between the first and second sensor windows, wherein the respiratory mask further comprises an inspiratory gas inlet port for delivering inspiratory gas to the wearer, and the sensor portion is spaced from the inspiratory gas inlet port.

The arrangement of the respiratory mask provides that, in use, the sensor may be mounted relative to the sensor portion of the respiratory mask, and electromagnetic radiation from the transmitter may be transmitted through the first window of the sensor portion of the enclosing wall, through the portion of the interior cavity defined between the first and second windows, through the second window, to the receiver.

The respiratory apparatus and respiratory mask according to the invention may be advantageous in that the sensor portion being formed in the enclosing wall of the mask body allows the sensor to monitor the patient's expiratory gases before they leave the mask body, reducing the delay between the gases being exhaled and the measurements being taken. In contrast, using conventional respiratory masks that are connected to a sensor via an exhalation tube or a sampling tube, expiratory gases exhaled by the wearer have to travel from the respiratory mask to the sensor, eg a respiratory monitoring unit, before they can be monitored.

Furthermore, in respiratory masks used with an exhalation tube in a breathing circuit including a gas delivery unit, such as a ventilator or anaesthesia delivery machine, the expiratory gases often cross flow paths with incoming inspiratory gases, at least briefly, before reaching the sensor, meaning that the expiratory gases can be diluted, leading to less accurate measurements. The sensor portion being formed in the enclosing wall of the mask body may therefore be further advantageous in that, in use, it allows the sensor to monitor the patient's expiratory gases almost immediately after expiration, before significant mixing with incoming inspiratory gases. This also ensures that each time the patient breathes, the expiratory gases of that breath flush the expiratory gases of the previous breath out of the sensor portion, ensuring that the sensor is monitoring expiratory gases breathed out in the most recent breath, and thus providing more accurate readings.

The sensor may be a gas sensor. In use, the wearer of the respiratory mask may inhale inspiratory gases from the interior cavity and/or exhale expiratory gases into the interior cavity. Each of the first and second sensor windows may have an interior surface and an exterior surface. The sensor may be mounted relative to the sensor portion of the respiratory mask with the transmitter disposed adjacent to the exterior surface of the first sensor window and the receiver disposed adjacent to the exterior surface of the second sensor window.

The sensor may monitor the composition of expiratory gases exhaled by the wearer in use. The sensor may be a gas composition sensor. In particular, the sensor may monitor the carbon dioxide concentration of expiratory gases exhaled by the wearer in use. The sensor may be, for example, a carbon dioxide sensor, such as an end-tidal CO<NUM> (EtCO<NUM>) sensor.

The sensor may comprise a housing. The housing may accommodate the transmitter and the receiver, ie the transmitter and receiver may be disposed in the housing. The portion of the housing that accommodates the transmitter and/or the portion of the housing that accommodates the receiver may project outwardly of the remainder of the housing, such that the transmitter and the receiver are disposed adjacent to the exterior surface of the first and second sensor windows respectively, when mounted relative to the sensor portion of the respiratory mask. The transmitter and the receiver may be substantially aligned, for example such that a beam of electromagnetic radiation emitted from the transmitter will be received at the receiver. Some misalignment may be necessary to account for refraction of the electromagnetic radiation when passing through the first and second sensor windows and the at least a portion of the cavity, although this can generally be avoided by transmitting the electromagnetic radiation at a wide beam angle.

The respiratory apparatus according to the invention may be without connecting tubes and a gas delivery unit. However, in use, the respiratory apparatus according to the invention may be connected to a gas delivery unit, for example via at least one gas delivery tube arranged to deliver inspiratory gas from the gas delivery unit to the respiratory mask.

The respiratory mask may be arranged to receive the nose and/or mouth of a wearer, eg within the interior cavity of the mask body. In particular, the respiratory mask may be shaped and/or dimensioned to receive the nose and/or mouth of a wearer, eg within the interior cavity of the mask body.

The respiratory mask may be arranged to seal about the nose and/or mouth of a wearer. The respiratory mask may comprise a sealing member. The sealing member may be positioned at or around the periphery of the mask body. The sealing member may be urged against the wearer's face in use, about their nose and/or mouth, ie to provide a seal around the wearer's nose and/or mouth. The sealing member may comprise a resiliently deformable member, such as a membrane.

The respiratory mask may be a patient therapy mask, such as a continuous positive airway pressure (CPAP) mask, a non-invasive ventilation (NIV) mask, an aerosol mask, an oxygen mask, or any other respiratory mask for delivering respiratory gases to a wearer. Alternatively, the respiratory mask may be for protective purposes. For example, the respiratory mask may be a filter mask having a filter through which ambient air passes before being inhaled by the wearer. The respiratory mask may therefore be any face mask in which monitoring of the expiratory gases exhaled by the wearer may be beneficial or desirable.

The wearer of the mask may be a patient. The inspiratory gas inlet port may be arranged to connect to a gas inlet, or have a gas inlet integrally or detachably connected thereto. The respiratory mask may comprise an expiratory gas outlet port for delivering expiratory gas from the wearer. Escape of expiratory gases via the expiratory gas outlet port may be controlled by one or more exhalation valve. The expiratory gas outlet port may be arranged to connect to a gas outlet, or have a gas outlet integrally or detachably connected thereto.

The inspiratory gas inlet port and the expiratory gas outlet port may be separate ports, ie the inspiratory gas inlet port may comprise a first aperture in the enclosing wall of the mask body and the expiratory gas outlet port may comprise a second aperture in the enclosing wall of the mask body. Alternatively, the inspiratory gas inlet port and the expiratory gas outlet port may be the same port, and the port may be operated using a Y-piece connector and/or a suitable valve arrangement, ie the inspiratory gas inlet port and the expiratory gas outlet port may comprise a single aperture in the enclosing wall of the mask body. In a further alternative, the expiratory gas outlet may comprise at least one opening in the mask body, eg a plurality of openings in the mask body. In this embodiment, escape of expiratory gases via the plurality of openings may also be controlled by exhalation valves.

The respiratory mask itself will also differ in structure relative to conventional respiratory masks.

The sensor portion may be formed separately from the expiratory gas outlet. For example, the sensor portion may be spaced from the expiratory gas outlet. This may be further advantageous in that, in use, it further reduces the chance of the patient's expiratory gases mixing with incoming inspiratory gases before measurements are taken by the sensor.

In contrast to the inspiratory gas inlet port and/or the expiratory gas outlet, the sensor portion may not be a port or an aperture. The sensor portion may be a discontinuity in the enclosing wall of the mask body. For example, the sensing portion may project, either inwardly or outwardly, relative to the enclosing wall of the mask body. The sensing portion projecting relative to the enclosing wall of the mask body and including the first and second sensor windows may be advantageous in that it makes the first and second sensor windows more accessible to the transmitter and the receiver of the sensor in use.

The electromagnetic radiation transmitted by the transmitter and received by the receiver may be infrared radiation. Infrared radiation may refer to radiation having a wavelength between approximately <NUM> and approximately <NUM>.

The first and second sensor windows may be transmissive of the electromagnetic radiation transmitted by the transmitter. For example, the first and second sensor windows may be transmissive of infrared radiation, ie radiation having a wavelength between approximately <NUM> and approximately <NUM>. The first and second sensor windows may also be transmissive to other wavelengths of light, such as visible light. The first and second sensor windows may be more transmissive of the electromagnetic radiation transmitted by the transmitter than the remainder of any of, or any combination of, the mask body, the enclosing wall of the mask body, and the sensor portion.

The first and second sensor windows may be transmissive to at least <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% of the electromagnetic radiation transmitted by the transmitter. To obtain an accurate and/or viable reading, the sensor may require that a minimum amount of electromagnetic radiation, or a minimum proportion of the electromagnetic radiation transmitted by the transmitter, is received by the receiver. Hence, the first and second sensor windows may be transmissive of the electromagnetic radiation transmitted by the transmitter such that at least <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% of the electromagnetic radiation is received at the receiver after passing through the portion of the interior cavity defined between the first and second sensor windows.

The first and second sensor windows may be of a reduced thickness relative to the remainder of any of, or any combination of, the mask body, the enclosing wall of the mask body, and the sensor portion. The first and second sensor windows may have a thickness of up to <NUM>, up to <NUM>, up to <NUM>, up to <NUM>, up to <NUM>, or up to <NUM>. The thickness of the first and second sensor windows may refer to the distance between the interior surface and the exterior surface of each sensor window.

The first and second sensor windows, eg the interior surface of the first and second sensor windows, may be spaced apart by a distance of between <NUM> and <NUM>, or between <NUM> and <NUM>, ie the portion of the interior cavity defined between the first and second sensor windows may have a thickness of between <NUM> and <NUM>, or between <NUM> and <NUM>.

The mask body may comprise a nose cavity portion. The nose cavity portion may comprise the inspiratory gas inlet port for delivering inspiratory gas to the wearer. The mask body may comprise a mouth cavity portion. The mouth cavity portion may comprise the sensor portion.

The enclosing wall of the mask body may have an external surface that forms the exterior of the mask body in use, ie the external surface of the mask body may face away from the wearer in use. The sensor portion may be formed integrally with any of, or any combination of, the mask body, the enclosing wall of the mask body and the external surface of the enclosing wall. The sensor portion may be formed of the same material as any of, or any combination of, the mask body, the enclosing wall of the mask body and the external surface of the enclosing wall.

The sensor portion may project or protrude outwardly from the mask body, eg from the mouth cavity portion of the mask body. The sensor portion may be substantially cuboidal, for example having the form of a cuboid or a rectangular cuboid. The sensor portion may comprise a pair of side walls that extend outwardly from the external surface of the mask body, ie away from the wearer of the mask in use, and a front wall that extends between the pair of side walls.

The pair of side walls may be angled relative to the external surface of the mask body. The pair of side walls may extend from the external surface of the mask body substantially perpendicularly to a tangential plane of the external surface of the mask body. The side walls may extend substantially perpendicularly to a frontal plane of a wearer of the respiratory mask, in use. The side walls may extend from the external surface of the mask body substantially parallel to each other.

Substantially perpendicular may comprise, for example, at an angle of between <NUM> and <NUM> degrees, or at angle of between <NUM> and <NUM> degrees. Substantially parallel may comprise, for example, at an angle of up to <NUM> degrees, or at angle of up to <NUM> degrees.

Alternatively, the sensor portion may project or protrude inwardly from the mask body, eg from the mouth cavity portion of the mask body. In this embodiment, the sensor portion may comprise a pair of side walls that extend inwardly from the external surface of the mask body, ie towards a wearer of the mask in use. In this embodiment, the sensor portion may also comprise a recess positioned either side of the pair of side walls, in which the transmitter and receiver of the sensor are positioned in use. The pair of side walls may extend inwardly from the external surface of the mask body substantially perpendicularly to a tangential plane of the external surface of the mask body. The side walls may extend inwardly substantially perpendicularly to a frontal plane of a wearer of the respiratory mask, in use. The side walls may extend inwardly from the external surface of the mask body substantially parallel to each other.

The first and second sensor windows may be formed in the pair of side walls of the sensor portion. The first sensor window may be formed in the first side wall of the sensor portion and the second sensor window may be formed in the second side wall of the sensor portion. Thus, the first and second sensor windows may extend inwardly or outwardly from the external surface of the mask body substantially perpendicularly to a tangential plane of the external surface of the mask body, and/or the first and second sensor windows may extend inwardly or outwardly from the external surface of the mask body substantially perpendicularly to a frontal plane of a wearer of the respiratory mask, in use, and/or the first and second sensor windows may extend inwardly or outwardly from the external surface of the mask body substantially parallel to each other.

The sensor portion may face the mouth of the wearer in use. The mouth cavity portion of the mask body may be arranged generally opposite the mouth of a wearer in use. The sensor portion may be formed in the mask body in a region of intersection between an expiratory flow from a wearer's nose and an expiratory flow from a wearer's mouth. The sensor portion may be formed in the mouth cavity portion. The mouth cavity portion may be substantially linear in a transverse plane of the wearer of the respiratory mask, in use. The mouth cavity portion may be curved in a longitudinal plane of the wearer of the respiratory mask, in use.

The sensor portion may be arranged to receive and/or retain the sensor. The sensor portion may comprise at least one abutment surface arranged to receive and/or retain the sensor in use. The at least one abutment surface may be shaped and/or dimensioned to receive and/or retain the sensor in use. The at least one abutment surface may be shaped and/or dimensioned so as to correspond to at least one abutment surface of the sensor. In use, the sensor may detachably or releasably engage with the sensor portion, for example with a friction fit or a snap fit. In use, the at least one abutment surface of the sensor may detachably or releasably engage with the at least one abutment surface of the sensor portion, for example with a friction fit or a snap fit.

Alternatively, a different portion of the mask body, for example a portion adjacent to the mouth cavity portion, such as the nose cavity portion, may be arranged to receive and/or retain the sensor.

The mask body may be formed by injection moulding. The first and second sensing windows may be formed in the mask body prior to cooling of the mask body, for example using hot stamping or pressing of the material using pins. Alternatively, the first and second sensing windows may be formed by any conventional methods known in the art. For example, using two-shot injection moulding, the first and second sensing windows may be formed in a first shot using a first material, and the mask body may be overmoulded in a second shot using a second material, as described in <CIT>. The first and second materials may be the same material, or different materials. In another example, the mask body may be formed by injection moulding, and the first and second sensing windows may be formed separately of a thin film-like material, and fitted into the mask body, as described in <CIT>.

The inspiratory gas inlet port in the nose cavity portion may be arranged to direct inspiratory gas away from the mouth cavity portion. The nose cavity portion may be arranged towards a first end of the mask body and the mouth cavity portion may extend from the nose cavity portion towards an opposing end of the mask body. The first end of the mask body may be an upper end of the mask body, as viewed when worn by a wearer in use, and the opposing end of the mask body may be a lower end of the mask body, as viewed when worn by a wearer in use. The inspiratory gas inlet port may be arranged to direct inspiratory gas towards the first end.

The nose cavity portion may comprise an intervening wall depending outwardly from the mouth cavity portion, relative to a wearer in use, so as to define a nose cavity region of greater depth than that of the mouth cavity region. The inspiratory gas inlet port may be provided in the intervening wall.

The mask body may comprise a generally rigid polymer shell formed as a unitary piece and shaped to define the nose and mouth cavity portions. The inspiratory gas inlet port may extend through the rigid polymer shell between an interior and an exterior surface thereof. The mask body may be formed of a thermoplastic polymer such as polypropylene, polyethylene, polymethylmethacrylate (PMMA), or polycarbonate. Alternatively, the first and second sensor windows may be formed of a thermoplastic polymer such as polypropylene, polyethylene, polymethylmethacrylate (PMMA), or polycarbonate, and the remainder of any of, or any combination of, the mask body, the enclosing wall of the mask body, and the sensor portion may be formed of an alternative material. This may be advantageous in that thermoplastic polymers such as polypropylene and polyethylene are naturally transmissive to infrared light.

Practicable embodiments of the invention are described in further detail below by way of example only with reference to the accompanying drawings, of which:.

In each of the Figures there is shown a respiratory mask <NUM>, which is suitable for the delivery of respiratory gases, such as oxygen, to a wearer, such as a patient. The respiratory mask comprises a mask body <NUM>, often referred to as a mask shell, formed from a suitably strong and relatively rigid plastics material, in this example polypropylene, and a sealing formation <NUM> formed from a more flexible or compliant material, such as an elastomer. In particular, a Styrene-EthyleneButylene-Styrene (SEBS)-based thermoplastic elastomer may be used for the sealing formation. However, it will be appreciated that other conventional mask body and seal materials may be used.

The respiratory mask <NUM> is manufactured using a so-called two-shot injection moulding process. In particular, the mask body <NUM> is firstly injection moulded as a single component, the sealing formation <NUM> is then injection moulded onto the surface of the mask body <NUM>, and the mask body <NUM> and the sealing formation <NUM> are bonded together by this process. However, it will be appreciated that other conventional manufacturing processes may be used.

The mask body <NUM> is generally dome-shaped, so as to define a cavity via which an inhalation gas is delivered to a patient, and comprises a mouth portion <NUM> and a nose portion <NUM>. The mask body <NUM> is shaped such that the maximum depth of the cavity defined by the nose portion <NUM> is greater than the depth of the cavity defined by the mouth portion <NUM>. The nose portion <NUM> is generally tapered towards an apex <NUM> at a first end of the mask <NUM> that is shaped to fit around the bridge of the patient's nose in use.

The mouth portion <NUM> generally comprises a forward-facing, front wall 25A and laterally-extending side wall portions 25B, which are arranged to be located adjacent a wearer's cheeks or jowls, and particularly the lower portion thereof, in use.

An intermediate wall portion <NUM> (see <FIG> and <FIG>) is arranged between the mouth <NUM> and nose <NUM> portions of the mask body <NUM> and effectively defines an interface between those portions. The intermediate wall <NUM> is in the form of a shelf or shoulder, for example, which projects forwardly of the front wall 25A of the mouth portion <NUM>, relative to the wearer of the mask <NUM> in use. The intermediate wall <NUM> is angled relative to the front wall 25A, typically approximately perpendicularly. The intermediate wall <NUM> defines a lower wall of the nose portion <NUM> which projects beyond, or overhangs, the mouth portion <NUM>.

The sealing formation <NUM> is a unitary flange member that is bonded to, and extends from, the peripheral edge of the mask body <NUM>. The sealing formation <NUM> may pass substantially around the entire periphery of the mask body <NUM> and may comprise an inwardly depending lip portion, which extends into the opening defined by the edge of the mask body <NUM>. The sealing formation <NUM> may have discontinuities therein, in the form of slits which allow the seal to deform about the different contour portions of a wearer's face, in use. In this example the sealing formation <NUM> also comprises a chin cup formation <NUM>, which may provide a seal beneath the wearer's chin, in use, particularly for wearer's having a larger facial length.

The elastomeric nature of the sealing formation <NUM> enables an effective seal to be formed between the contact surface of the respiratory mask <NUM> and the face of the patient in use. However, it will be appreciated that the mask <NUM> may adopt different sealing formations about its peripheral edge in line with other conventional mask designs.

Furthermore, it is possible that the provision of a second, more-flexible sealing material <NUM> may be omitted altogether where the seal quality is of little consequence to the mask provider.

The mask body <NUM> further comprises an inlet port <NUM> for connection to a supply of an inhalation gas, such as oxygen. The inlet port <NUM> comprises an opening in the intermediate wall <NUM> (i.e. in a lower wall of the nose portion <NUM>), and a tubular connector <NUM> that extends outwardly/downwardly away from the mask body <NUM> into the space in front of the mouth portion <NUM>. The free end of the connector <NUM> is thus disposed outside of the mask body <NUM> in front of the mouth portion <NUM>, and the inlet port <NUM> and the connector <NUM> are spatially separated from the front face 25A of the mouth portion <NUM>. In use, a supply of an inhalation gas is connected to the tubular connector <NUM> of the inlet port <NUM> via a supply tube so as to supply the inhalation gas to the cavity of the respiratory mask <NUM> and hence the airways of the patient.

The mask body <NUM> has one or more exhalation openings <NUM>, which may be spaced from the inlet opening <NUM>. In this embodiment the exhalation openings are simple apertures in the wall of the mask body <NUM> that allow exhaled gases to exit the cavity of the respiratory mask <NUM>. The exhalation openings <NUM> are elongate in form. A pair of exhalation openings <NUM> is provided to either side of the nose portion <NUM>. A generally vertically aligned exhalation opening <NUM> is also provided on either side of the front face 25A of the mouth portion <NUM> (i.e. in side walls 25B). It will be appreciated that other shapes, configurations and orientations of exhalation openings <NUM> are possible. In some embodiments, the exhalation openings <NUM> may comprise a simple valve structure.

The mask body <NUM> has a pair of outwardly extending flange formations <NUM> on either side of the respiratory mask <NUM> which are arranged to receive an elastic strap in use. Each flange <NUM> is located adjacent the peripheral edge of the mask body <NUM> and has an aperture, to which an elastic strap (not shown in the Figures) is attached, in use.

The elastic strap extends between the flanges <NUM>, and fits around the patient's head when the respiratory mask <NUM> is fitted to the patient. In use, the strap is adjusted so that the respiratory mask <NUM> is urged against the face of the patient with an appropriate force to ensure that an effective seal is formed between the periphery of the respiratory mask <NUM> and the wearer's face, without causing excessive discomfort for the wearer.

In use, the mask <NUM> is urged against a wearer's face such that the first end (ie the apex <NUM>) is uppermost and rests against the bridge of the wearer's nose, typically at, or slightly below, the nasion, and the second end <NUM> is located towards or beneath the wearer's mouth, typically in the vicinity of the chin, such that generally the wearer's nose and mouth are located in the mask cavity, but in the case of patient's having a larger face, at least the wearer's nose is located in the mask cavity. The wearer's mouth is accommodated within the mouth portion <NUM> of the mask body <NUM> and the wearer's nose is accommodated within the nose portion <NUM> of the mask body <NUM>. The nose portion <NUM> is tapered towards the upper end <NUM> of the mask <NUM> and hence the bridge of the patient's nose.

The front face 25A of the mouth portion <NUM> comprises a generally cuboidal protrusion <NUM> that extends forwardly of the front wall 25A of the mouth portion <NUM>, relative to the wearer of the mask <NUM> in use. The protrusion <NUM> comprises two side walls and a front face, the two side walls extending forwardly of the front wall 25A of the mouth portion <NUM>, relative to the wearer of the mask <NUM> in use, and the front face extending between the two side walls.

Each of the side walls are substantially opposite one another, and comprise a window portion <NUM> (see <FIG>). Although only one window portion <NUM> can be seen in <FIG>, due to the angle of the illustration, the window portions <NUM> are positioned substantially opposite one another within the respective side walls, ie at substantially the same position in the side walls. Each of the window portions <NUM> is transmissive at least of infrared light, such that the space <NUM> formed between the window portions <NUM> may serve as an expiratory gas monitoring portion. The expiratory gas monitoring portion <NUM> is substantially in front of, and diametrically opposite, the wearer's mouth, in use.

The front face 25A of the mouth portion <NUM>, and the protrusion <NUM> in particular, is further arranged to function as a receiving port, such that a sensor <NUM>, eg an EtCO<NUM> sensor, may be releasably attached to the protrusion <NUM> of the mask <NUM>, to enable a measurement of the expiratory gas within the expiratory gas monitoring portion <NUM> to be taken. In particular, the protrusion <NUM> is shaped and dimensioned to correspond with the shape and dimensions of an engaging portion (not shown) of the sensor <NUM>, such that the sensor <NUM> may be clipped onto the mask <NUM> by engaging with the protrusion <NUM>, for example with a friction fit or a snap fit. It is foreseen that alternative conventional retention mechanisms may be employed for engaging the sensor with the front face 25A of the mouth portion <NUM>.

In use, gas is supplied to the mask interior via the inlet <NUM>, thereby generally flooding the nose portion <NUM> at least. During inspiration, gas within the interior of the mask is drawn in via the nose and/or mouth. In the event that the rate at which gas is drawn into the wearer's lungs is greater the gas supply rate via the inlet <NUM>, additional ambient air will be drawn into the mask via openings <NUM>.

Claim 1:
Respiratory apparatus comprising a sensor (<NUM>) and a respiratory mask (<NUM>), the respiratory mask (<NUM>) comprising a mask body (<NUM>) having an enclosing wall that defines an interior cavity, and the sensor (<NUM>) having a transmitter of electromagnetic radiation and a receiver of electromagnetic radiation, wherein the enclosing wall has a sensor portion including first and second sensor windows (<NUM>), a portion of the interior cavity (<NUM>) being defined between the first and second sensor windows (<NUM>), and the sensor (<NUM>) being mounted relative to the sensor portion of the respiratory mask (<NUM>), such that electromagnetic radiation from the transmitter is transmitted, in use, through the first window of the sensor portion of the enclosing wall, through the portion of the interior cavity (<NUM>) defined between the first and second windows (<NUM>), through the second window, to the receiver, wherein the respiratory mask (<NUM>) further comprises an inspiratory gas inlet port (<NUM>) for delivering inspiratory gas to the wearer, and the sensor portion is spaced from the inspiratory gas inlet port (<NUM>).