GB2581143A

GB2581143A - Breath flow indicator and method of use

Info

Publication number: GB2581143A
Application number: GB1901434.9A
Authority: GB
Inventors: Evans Chris; Ramsey Hugo
Original assignee: Little Sparks Hospital Ltd
Current assignee: Little Sparks Hospital Ltd
Priority date: 2019-02-01
Filing date: 2019-02-01
Publication date: 2020-08-12
Anticipated expiration: 2039-02-01
Also published as: GB201901434D0; GB2581143B

Abstract

A mechanical apparatus 302 comprising a first and second port for receiving and venting a flow of gas, a chamber connecting the first and second ports 202, 203 and a rotor located within the chamber 303 having a plurality of arms in which at least one arm of the rotor has a permanent magnet and a connecting portion 305 for connecting a sensor to the exterior of the chamber to detect the magnetic field of the magnet. An electronic apparatus 301 comprising a first sensor for detecting a magnetic field, an output for outputting signals from the first sensor and a connecting portion 304 for connecting the electronic apparatus to the mechanical apparatus. A breath flow detector unit for outputting an electronic signal indicative of the flow of breath of a user comprising the above mechanical and electronic apparatus. A breath monitor system comprising the breath flow detector unit and a computing device for receiving signals from the electronic apparatus. A kit of parts for an anaesthetic circuit including the mechanical apparatus and a kit of parts for an anaesthetic circuit including the mechanical and electronic apparatus. A method of operating the breath flow detector unit is also provided.

Description

BREATH FLOW INDICATOR AND METHOD OF USE

BACKGROUND

Field of the Invention

The invention relates to flow indicator devices, particularly for providing an indication of the breath flow of a patient in applications such as anaesthetic delivery, incentive spirometry and asthma management.

Description of Related Art

In many medical applications it is desirable to monitor the breathing patterns of a patient and if necessary to encourage the patient to improve this pattern.

For example, the effective delivery of an anaesthetic gas to a patient prior to a surgical procedure is heavily dependent on the patient breathing correctly. In paediatric applications this can pose a problem because children can become very disturbed by having a mask placed over their face and often resist this strongly; if this happens the facemask delivering the anaesthetic gas has to be held away from their face and the gas wafted towards them until they are sufficiently drowsy to correctly place the mask. This technique avoids direct connection between the breathing circuit and a patient's airway. Ventilation cannot be controlled with this technique, however, and the inspired gas contains unpredictable amounts of entrained atmospheric air. Furthermore, everyone in the vicinity becomes exposed to the gas too. A problem to be solved is therefore how to encourage paediatric patients to comply with wearing a facemask and also to breathe correctly when the facemask is in place.

In medical applications, particularly for use in surgical procedures, much of the equipment needs to be disposable for hygiene reasons; it is imperative that the surgical environment is sterile. The anaesthetic circuit used between an anaesthetic machine and the patient to deliver anaesthetic gas is disposable and, in general, designed for single-patient use for this reason.

Therefore any equipment used in such a procedure should be simple and low cost to manufacture.

It is therefore an object of the invention to provide a simple breathing monitor 5 that is low cost to produce and that can be used in a system to encourage children to comply with a facemask and breathe correctly during an anaesthetic delivery procedure.

Incentive spirometry, or sustained maximal inspiration, is designed to mimic natural sighing or yawning by encouraging the patient to take long slow deep breaths. The objective is to increase transpulmonary pressure and ensure maintenance of alveoli opening. This is accomplished by a device that provides patients with visual or other positive feedback when they inhale at a predetermined flow rate to achieve a target volume, therefore sustaining an inflation for a predetermined length of time. Compliance and correct use of incentive spirometry is often poor leading to negligible health benefits" especially when needed to be performed regularly over a period of days. It is therefore an object of the invention to provide a simple and inexpensive device for monitoring breath, provide positive feedback and gamifying the process to improve patient compliance and use.

Asthma management is another area where measurement and feedback of breath flow is required. Currently, asthma sufferers use inhalers to deliver medication, where medication is delivered into a breath stream as the patient inhales deeply. At present the measurement of a patient's inhalation to assess if it meets the required level for effective drug delivery is challenging. In addition, asthma sufferers use Peak Expiratory Flow Rate (PEFR): the maximum flow rate that can be generate by forceful exhalation which is used as an indicator of the effectiveness of their asthma management and the severity of an exacerbation. Inhalers are disposable, so the equipment for performing the measurement and providing the necessary feedback needs to be of simple construction to allow it to be disposable too.

A common theme in the above applications is the requirement to measure breath flow and feedback the data to positively affect the breathing patterns of a patient. It is therefore an object of the invention to provide a simple, low cost breath flow indicator in contact with breath that can be disposable for hygiene reasons.

SUMMARY OF THE INVENTION

In an embodiment of the present invention, mechanical apparatus suitable for use as a component of a breath flow detector unit is provided comprising a first port for receiving and venting a flow of gas, a second port for receiving and venting a flow of gas, a chamber connecting the first and second ports, a rotor located within the chamber and capable of rotating within the chamber, the rotor having a plurality of arms, wherein at least one arm of the rotor has a permanent magnet, the apparatus further comprising a connecting portion for connecting a sensor to the exterior of the chamber to detect the magnetic field of the magnet. This apparatus is of simple construction with only a single moving part and therefore low cost to produce.

The first port may have a restriction in the region where it connects to the chamber to accelerate the flow of gas tangentially onto the rotor. This ensures that the flow of gas activates the rotor. Alternatively there may not be a restriction to the flow.

The chamber may have a bypass duct for allowing a portion of gas to flow from the first pod to the second port without passing through the restriction, thereby reducing the resistance to the flow of gas and making the device easier to use.

The second port may be co-planar with the rotor or coaxial with the rotor. The second port may have a restriction in the region where it connects to the chamber to accelerate the flow of gas tangentially onto the rotor. The rotor therefore rotates to a flow of gas in both directions.

Two magnets may be provided in opposing arms of the rotor and arranged with poles perpendicular to the plane of the rotor. The poles of the magnets may be arranged in a direction opposite to each other. Either the first or second port may be provided with a restriction to restrict air flow. The restriction may allow air to flow freely in one direction but increase pressure resistance in the other direction. The restriction may comprise a sliding mechanism or a valve.

In another embodiment, electronic apparatus suitable for use with the mechanical apparatus described above as a component of a breath flow detector unit is provided, the electronic apparatus comprising: a first sensor for detecting a magnetic field, an output for outputting signals from the sensor, a connecting portion for connecting the electronic apparatus to a mechanical apparatus. The electronic apparatus may be provided separately to the mechanical apparatus, thereby allowing the cheaper mechanical apparatus to be disposable while the electronics part to be re-used. Alternatively, the mechanical apparatus and electronic apparatus may be permanently joined.

The electronic apparatus may have a transmitter for wirelessly communicating the signals from the sensor to a remote computational device. The apparatus may further include a second sensor for detecting a magnetic field located in proximity to the first sensor and an output for outputting signals from the second sensor.

In a further embodiment of the invention, a breath flow detector unit for outputting an electronic signal indicative of the flow of breath of a user is provided, comprising the mechanical apparatus described above and the electronic apparatus described above.

The mechanical apparatus may have a screw thread and the electronic apparatus may have a corresponding screw thread, enabling the mechanical apparatus and electronic apparatus to be releasably attached to each other. Alternatively, the electronic apparatus and the mechanical apparatus may be connectable with a bayonet fitting comprised of corresponding grooves and protrusions.

In a further embodiment, a breath monitor system is provided comprising the breath flow detector unit described above, and further comprising a computing device for receiving signals from the electronic apparatus.

The computing device may further include software that converts the signals from the sensor into a graphic representation on a screen. The graphic lo representation may be a game, where a user is rewarded for breathing in accordance with predefined parameters. The system may be for use in delivery of an anaesthetic gas, incentive spirometry, asthma management, peak breath flow measurement, positive expiratory pressure therapy, directed cough or peak cough flow.

Computer software is provided for converting the signals from a sensor in a breath flow detector unit of the type described above into a graphic representation on a screen.

A kit of parts for an anaesthetic circuit is provided including the mechanical apparatus and/ or the electronic apparatus described above.

A method of operating a breath flow detector unit of the type described above is provided, comprising installing the breath flow detector unit in a breathing circuit, allowing a user to breathe through the breath flow detector unit, detecting signals from the sensor representing breath flow rate, sending the signals to a remote computational device and converting the signals into a graphic representation on a screen of the computational device.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A is a schematic diagram showing an anaesthetic machine with an anaesthetic circuit connected.

Figure 1B is a detailed view of part of an anaesthetic breathing circuit including an embodiment of the present invention.

Figure 1C is a detailed view of part of an anaesthetic breathing circuit including an embodiment of the present invention in an alternative arrangement.

Figure 2 is a view of a breath flow detector unit in accordance with an embodiment of the present invention.

Figure 3 is a view of a breath flow detector unit of Figure 2 showing the electronics part and the mechanical part separated.

to Figure 4A is an exploded view of the mechanical part of the breath flow detector unit of Figure 2.

Figure 4B is a cross section of the mechanical part of the breath flow detector unit of Figure 2 showing the rotor in place.

Figure 4C is a view of the underside of the mechanical part of the breath flow detector unit of Figure 2.

Figure 4D is a cross sectional view of the mechanical part of the breath flow detector unit of Figure 2 showing the rotor within its rotor chamber.

Figure 5A is a view of the inside of the electronics part of the breath flow detector unit of Figure 2.

Figure 5B is a cross sectional view of the breath flow detector unit of Figure 2 showing the rotor within its rotor chamber and the electronics.

Figure 5C is a schematic view of the electronic components and their connections of the breath flow detector unit of Figure 2.

Figure 6 is a schematic view of the components of a computational device for use in an embodiment of the present invention Figure 7 is a schematic diagram showing the operational steps of the breath flow detector unit of Figure 2 in use.

Figure 8 is a schematic diagram showing the operational steps of the computational device of Figure 6 in use with the breath flow detector unit of Figure 2.

Figure 9A is a further embodiment of the present invention where the second port is in line with the first port and the second port has a restriction for directing gas tangentially onto the rotor.

Figure 9B is a further embodiment of the present invention where the second port is in line with the first port and the second port does not have a restriction.

Figure 10 is a further embodiment of the present invention where a by-pass channel is provided to allow gas to pass through the device without being directed through the restriction.

Figure 11 shows an embodiment of the present invention including two sensors for detecting the direction of breath flow.

to DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A typical set-up for delivery of anaesthetic is shown in Figure 1A. The anaesthetic is delivered from an anaesthetic machine 101, typically a Boyle's machine, used to generate a continuous flow of medical gases and inhalation anaesthetic agents for the purpose of producing and maintaining anaesthesia.

The machine 101 provides an accurate supply of medical gases mixed with an accurate concentration of anaesthetic vapour and delivers this to the patient at a safe pressure and flow. The machine 101 includes supplies of oxygen, medical air and nitrous oxide from either cylinders or a wall supply.

The machine 101 further includes pressure regulators, manifolds and valves for mixing the gases and pressure gauges and flow meters for achieving a desired gas mixture and pressure to the outlet 102. The gas mixture at the outlet is referred to below as the anaesthetic or anaesthetic gas.

Delivery of anaesthetic to the patient may be via an assembly of components referred to as an Ayers T-Piece 103, which allows controlled delivery of the anaesthetic to the patient.

The Ayers T-Piece includes an inlet tube 104 connected to the outlet of the anaesthetic machine 101. The inlet tube 104 joins a junction 105 that splits the flow into a reservoir branch tube 106 (expiratory limb) and delivery tube 107. At the end of the reservoir branch tube is an adjustable pressure limiting valve (APL) 108 and an inflatable rubber reservoir 109 that allows the anaesthetist to manually assist ventilation by compressing the reservoir 109.

At the end of the delivery tube 107 is a filter 110 to act as a barrier to bacteria in the patient's exhaled breath and/or reduce heat and moisture loss. A facemask 111 is connected to the filter 110 that is held over the patient's face and ideally forms a seal to prevent anaesthetic gas from escaping into the room. During inspiration the patient breathes fresh gas from the machine and gas is stored in the expiratory limb. During exhalation, a mixture of exhaled and fresh gas collects in the bag. On the next inspiration the patient inhales fresh gas from the machine and that stored in the expiratory limb. Fresh gas flow equal to two to three times the patient's minute ventilation is recommended to prevent rebreathing of exhaled gases.

Components at the patient side of the filter 110, including the filter itself, such as the facemask 111, are single use because they become contaminated with bacteria in the breath. Components on the machine side of the filter 110, excluding the filter, are multiple use, replaced for example weekly, because the filter prevents contamination. All components connected to the anaesthetic machine 101 need to be refreshed often and therefore have to be low cost.

It is important for the patient to breathe in a defined way during anaesthetisation, so that the anaesthetist can ensure that the patient loses consciousness in a predictable way. Correct breathing is considered to be regular tidal breaths. To determine whether the patient is breathing correctly a breath flow detector unit in accordance with an embodiment of the invention is provided within the anaesthetic circuit to give an indication of the breath flow rate.

An embodiment of the invention is a breath flow detector unit for use in a disposable or semi-disposable anaesthetic circuit for delivering anaesthetic to a patient. The breath flow detector unit is arranged to produce and transmit an electronic signal that indicates the rate of breath flow. The electronic signal can be used to produce an audible signal or for controlling a video game.

The breath flow detector unit 201 may be connected directly to the filter 110 either on the anaesthetic machine side as shown in Figure 1B, or on the patient side as shown in Figure 1C and connect wirelessly to a computing device 112.

An embodiment of a breath flow detector unit is shown in Figure 2. The detector unit 201 comprises a housing having a first port 202 to let gas in and out of the device and a second port 203 to let gas in and out of the device. Both ports are connected by a channel for ducting gas; the gas is a combination of anaesthetic gases and oxygen/air on inhalation or a mixture of anaesthetic gas and the patient's breath on exhalation.

The components of the breath flow detector unit 201 are shown in Figure 3. The unit has two major parts: i) an electronics part 301 and ii) a mechanical part 302. The mechanical part 302 ducts and responds to gas flow between the first port 202, a rotor chamber 303 and second port 203. The electronics part 301 detects the responses of the mechanical part to gas flow and transmits an electronic signal indicative of the gas flow. The mechanical part 302 and the electronics part 301 are joined by corresponding screw threads 304, 305 that allow them to be detached. The mechanical part 302 is a sealed unit, such that gas in the anaesthetic circuit is isolated from the electronics part 301. This allows the relatively low cost mechanical part 302 that is exposed to a lot of bacteria to be disposable while the more expensive electronics part 301 can be re-used.

The first port 202 of the mechanical part 302 is open at one end and tapers outward from chamber to opening to provide a female socket 306 for positively connecting to a male plug on other tubing in the anaesthetic circuit. The first port 202 narrows at the other end, where it joins the rotor chamber 303. The rotor chamber 303 is a hollow tubular structure having a radius at least 2 to 3 times greater than its height, so that it is effectively a hollow disk, orientated with its axis perpendicular to the axis of the first port 202. The first port 202 is arranged to direct gas flow tangentially into the rotor chamber 303. This arrangement has the effect that gas flowing into the rotor chamber through the first port will cause the rotor to rotate. The second pod 203 is open at one end and is tapered inwards from chamber to opening to provide a male plug 307 for positively connecting to a female socket on other tubing in the anaesthetic circuit. The second port 203 is aligned coaxially with the rotor chamber 303 and is arranged to direct gas flow axially into and out of the rotor chamber 303. This arrangement has the effect that gas flowing into the rotor chamber from the second port will not cause the rotor to rotate.

The construction of the mechanical part 302 is shown in Figure 4A. The mechanical part has three components; i) an upper shell 401, ii) a lower shell 402 and iii) a rotor 403. The upper shell 401 and lower shell 403 together form a housing that defines the gas flow path from the first port 202 to the second port 203 via the rotor chamber 303.

The upper shell 401 has a number of regions. An upper portion of the first port 202 is defined at one end of the upper shell 401 by a half tubular structure forming a trough 404. The radius of the half tubular trough 404 decreases away from the open end to define one half of the connecting neck 304, then decreases in radius and sweeps to one side to create a restricted tangential inlet into the rotor chamber 303. The upper shell 401 then broadens out to define a flat circular disk 405 having an upper wall 406 carrying the thread 305 for connecting to the electronics part 301 and a lower wall 408 defining one half of the rotor chamber 303. The flat circular disk 405 of the upper shell 401 provides the isolation of the mechanical part 302 of the breath flow detector unit 201 from the electronics part 301. The flat circular disk 405 has an underside, which forms the interior of the rotor chamber 303. In the centre of the underside of the flat circular disk is a raised axle 409 that provides a bearing surface.

The lower shell 402 also has a number of regions. A lower portion of the first port 202 is defined at one end of the lower shell 402 by a half tubular structure forming a trough 410. The radius of the half tubular trough 410 decreases away from the open end to define one half of the connecting neck 304, then decreases in radius and sweeps to one side to create a restricted tangential inlet 400 into the rotor chamber 303, shown in Figure 4B. The lower shell 402 then broadens out to define a flat circular disk 411 having a wall 412 that together define one half of the rotor chamber 303. The flat circular disk 411 of the lower shell 402 has an opening 413 of substantially the same diameter as the second port 203. A series of radial arms 414 as shown in Figure 4C span the opening 413 and support a raised axle 415 to provide a bearing surface corresponding to the axle 409 of the upper shell 401. The second port 203 extends away from the opening 413 coaxially with the rotor housing 303 The radius of the second port 203 decreases away from the opening 413.

The rotor 403 is a flat structure of thickness substantially equal to the distance between the bearing surfaces (409?) and (415?). and radius substantially equal to the radius of the rotor housing 303 so that it is a snug fit in the rotor housing 303 but able to freely rotate without coming into contact with chamber walls. The rotor 403 has a series of radially extending arms 416 arranged to catch in the flow of gas arriving tangentially from the first port 202. The rotor 403 is illustrated with eight arms, although an arrangement of four arms is preferable to reduce resistance to the flow of gas. This is important, particularly in paediatric applications, so that it is as easy as possible for the patient to breathe normally. A circular orifice 417 is provided in the centre of the rotor 403 of diameter slightly larger than the raised axles 409, 415 of the upper and lower shells 401, 402. Opposing arms 416A and 416B have recesses towards their ends. A neodymium magnet 418A, 418B is located in each recess. Alternatively, the magnets may be fully encased in the arms to reduce the risk of them coming loose. This may be through a two shot over-moulding process or by joining two symmetrical half fans. The magnets are arranged with their poles facing perpendicular to the flat plane of the rotor 403 and facing the flat circular disks 405, 411 of the upper and lower shells 401, 402. The magnets 418A, 418B are arranged with opposite poles, so that the south pole of the magnet in arm 416A and the north pole of the magnet in arm 416B points towards the flat circular disk of the upper shell, as shown in Figure 4D.

When assembled, the edge of the trough 404, the upper wall 406 and axle 409 of the upper shell 401 aligns with and is fixed to the edge of the trough 410, wall 412 and axle 415 of the lower shell 402. The rotor 403 is captured within the rotor housing 403 and able to freely rotate about the axles.

The electronics pad 301 is shown in more detail in Figure 5A. A base 501 is provided as a flat circular disk of the same diameter as the rotor housing 303 in the mechanical part 302. The base 501 has a wall 506 carrying an external thread 304 that can engage with the internal thread 305 on the wall of the upper housing of the mechanical part 302. The base 501 has an interior surface 501A and an exterior surface 501B, shown in Figure 5B. Mounted on the interior surface 501A of the base 501 is a magnetic field sensor 503 for detecting magnetic fields that produces a voltage output when exposed to a magnetic field or opposing magnetic fields. The sensor 503 is located in a position on the base 501 that corresponds to the circular path of the rotor magnets 418A,B, so that as the rotor rotates, the field of the magnets activates the sensor 503, causing it to produce a voltage signal each time a magnet passes it. Thus the sensor 503 provides an electrical signal corresponding to the movement of the rotor and hence the patient's breath flow.

Further included in the electronics part 301 are a printed circuit board carrying a processor 502, a power source 504 and a transmitter 505, that are arranged to convert the analogue signal from the sensor 503 to a digital transmission.

Figure 5B is a schematic diagram showing how the components are connected. The sensor 503 is connected to a processor 502 that is arranged to receive the signal from the sensor. The processor also has a register element capable of incrementing in response to an input. The processor 502 is powered by battery 504. A charging port 507 may be provided for charging the battery. The charging is controlled by the processor 502. Each time a magnet 418A,B passes the sensor 503, the magnitude of the voltage at its output changes. The passing of a north pole of a magnet creates a positive voltage spike while the passing of a south pole creates a negative voltage spike. Therefore a complete rotation of the rotor causes a transient voltage signature from positive to negative. This transient voltage is capable of being detected by the processor 502. Each time a transient voltage is detected, the value in the register of the processor is incremented; the register is polled periodically to extract the current value, and then the register is reset. A typical polling period is 0.25 seconds, although any suitable polling period may be selected. The value in the register represents the number of times the voltage changes from positive to negative in a given time period; the number of voltage changes per second is a measure of the rotation speed of the rotor, and the change in rotor speed corresponds to the inhalation rate of the patient's breath. The change in the value in the register provides an indication of the inhalation rate. The processor is arranged to periodically output a data signal representing the number of voltage transients per second corresponding to the current inhalation rate of the patient.

The processor is in communication with a transmitter module 505 and the periodic inhalation rate signal from the processor is arranged to be sent to the transmitter module 505. The transmitter module 505 includes a wireless transmitter microelectronics chip, with for example Bluetooth functionality.

An example chip is an RN4871-V/RM118 Bluetooth chip 4.2 available from RS Components. This chip is capable of encoding input data and transmitting it via radio frequency over a range of a few metres.

A protective cover is provided over the electronic components, attached to base 501, which may also include a status light. An on/off and pairing button 508 may also be provided for powering up the processor and initiating the pairing process for remote communication with other devices. Alternatively, detection of the rotor starting to rotate could initiate the start-up and pairing process.

The processor 502 runs firmware that operates in accordance with the steps set out in Figure 7: Step 701: Initiation step. Upon pressing the on/off pair button, the processor starts up. The transmitter 505 begins the pairing process and searches for a suitable computational device 112 within range. Upon successful pairing a communication channel between the transmitter 505 of the breath flow detector unit 201 and the receiver 601 of the computational device 112 is established.

S

Step 702: Polling step. The processor 502 polls its register to determine the current stored value of voltage transients from the sensor 503. This value is sent to the transmitter 505 and transmitted to the computational device 112 and the register reset.

Step 703: The polling step is repeated periodically, for example every second, until the breath flow detector unit 201 is turned off.

A computational device 112, such as a smartphone or tablet, is arranged to communicate with the detector unit and convert the transmitted data signals representing the current inhalation rate of the patient into signals that are human-perceivable.

The structure of the computational device 112 is shown in Figure 6. At the hardware level the computational device 112 has a data receiving module 601, supporting the same communication standard as the breath flow detector unit 201, in this instance Bluetooth 0, to allow a wireless private secure connection to be made between the computational device 112 and the breath flow detector unit 201. The computational device 112 further includes a processor 602 in communication with the data receiving module 601. The processor 602 is further in communication with memory modules, both permanent ROM 606 for storing software and volatile RAM 605 for use in executing software. The processor is further in communication with a graphics processor 603 and a screen 604, for rendering images generated by the software.

The computational device 112 is loaded with software arranged to convert the received data signal into a human-perceivable output. This may be an audible tone, where the pitch of the tone is proportional to the breath flow. This can be useful for the anaesthetist to be able to tell whether the patient is breathing correctly. Alternatively, the data signal may be used to control a character in a computer-generated scenario on a screen in the form of a game, which provides a feedback mechanism directly to the patient to encourage them to breathe correctly. The purpose of the game is to encourage a patient, particularly a child, to breathe correctly. Correct breathing can be difficult to achieve if the patient is not relaxed, as they will instead tend towards short shallow breaths. The clinical environment can be disturbing, particularly for children who can become agitated, if a mask is presented over their face. The use of a game can calm the patient and help switch focus from potential threat to familiarity, control and a sense of achievement.

The game includes a character under control of the patient, and the criteria for "winning" the game corresponds to compliance with firstly accepting a mask fitted to their face and to breathe deeply enough for the anaesthetic to work.

The character in this embodiment is riding a hot air balloon, where rewards are obtained for flying the balloon as high as possible. Correct breathing, i.e. deep long breaths, causes the balloon to fly higher.

The processing steps executed by the software are shown in Figure 8. The software is loaded into the ROM 606 and is capable of being executed by the processor 602 to convert an inhalation rate signal received by the data-receiving module 601 from the breath flow detector unit 201 into a moving image graphic on the screen of the computational device 112.

Step 801: Initiation step, where the initial scenario of a person in a balloon at ground level is rendered on the screen 604 Step 802: Interrogation step, where the data receiving module 601 is queried 30 to detect whether a data packet from the breath flow detector unit 201 has been received.

Step 803: Identification step, where, if a data packet has been received, then the inhalation rate data is extracted.

Step 804: Move step, where the character is moved on the screen by an amount proportional to the inhalation rate data, according to predefined rules: i) If this is the first Identification step and the inhalation rate data is greater than zero, this indicates that the patient is inhaling, which is desirable.

The character is then moved upwards in the scenario and the score increased.

ii) If this is a subsequent Identification step and the inhalation rate measured on this Identification step is greater than the previous lo measurement, this indicates that the patient is continuing to inhale, which is desirable. The character is then moved upwards in the scenario and the score increased.

Di) If this is a subsequent Identification step and the current inhalation rate measured on the Identification step is consistently less than previous inhalation rates, but within a predetermined time period, e.g. 5 seconds, this indicates that the patient has reached the end of the inhale phase or is exhaling, which is natural. The character is held stationary in the scenario and the score not increased.

iv) If this is a subsequent Identification step and the current inhalation rate measured on the Identification step is consistently less than previous inhalation rates for longer than the predetermined time of e.g. 5 seconds, this indicates that the patient is not inhaling as desired. The character is moved downwards and the score decreased.

The game therefore provides a positive feedback mechanism to train the patient to breathe correctly.

A trial may be arranged prior to the medical procedure where anaesthetisation is required, where the young patient can become familiar with the system, experience how it works and become enthusiastic about using it again to try to gain a higher score. If, in a potentially stressful medical environment, the patient is given the challenge of the game, they are much more inclined to accept the breathing mask and comply with the breathing requirements of the anaesthetic.

The breath flow sensor unit 201 may be provided in a sterile kit as part of an anaesthetic circuit. In preparation for use, an anaesthetist removes the components of the anaesthetic circuit from its protective packaging to connect the components of the kit together. An end of the inlet tube 104 is connected to the outlet of the anaesthetic machine 101. The other end of the inlet tube 104 is connected to the reservoir branch tube 106 having the adjustable pressure limiting valve (APU) 108 and inflatable rubber reservoir 109, and delivery tube 107. The delivery tube 107 is connected to the first port 202 of an embodiment of the present invention; in this instance it is just the mechanical part 302 of the breath flow detector unit 201, which is of simple construction and therefore low cost. The filter 110 is connected to the second port 203 of the mechanical part and the facemask 111 is connected to the filter 110.

An electronics part 301, separately provided and reusable, of the breath flow detector unit 201 is then attached to the mechanical part 302 by screwing it into place. On/off button 508 is activated and pair mode selected, which causes the processor to wake up the transmitter module 505 and broadcast a pairing signal (Step 701). A nearby computational device 112 loaded with the game software is turned on and paired with the breath flow detector unit 201, enabling data transmitted from the unit 201 to be received by the computational device 112.

Polling of the register by the processor 502 of the breath flow detector unit 201 and periodic transmission of the result begins (Step 702). As the unit 201 is not yet in use and there is no breath flow the value transmitted is zero.

The software in the computational device 112 is initiated (Step 801) and the data receive module 601 interrogated (Step 802). The value received is zero as there is no breath flow measured yet.

The supply of anaesthetic gas is then turned on and the face mask held over the face of the patient and the screen shown to the patient, with instructions to raise the image of the balloon on the screen by breathing deeply. As the patient inhales, gas flows through the inlet tube 104 of the Ayer's 1-Piece, in through the first port 202 of the breath flow detector unit 201, into the rotor chamber 303, causing the rotor 403 to rotate. Magnets 418A,B pass the sensor 503 which creates a voltage transient. The more forceful the breath of the patient, the higher the number of voltage transients measured over a given time period. The processor 502 increments the register each time a voltage transient is detected. Periodic polling, transmission and resetting of the contents of the register (Step 703) is established. The contents of the register represents inhalation rate. The inhalation rate data is received by the data receiving module 601 of the computational device 112. The data receiving module 601 is interrogated by the software (Step 802) and the inhalation rate data identified (Step 803). The image of the balloon is moved corresponding to the value of the inhalation rate data in accordance with the predetermined rules (Step 804).

As the patient exhales, gas flows in the reverse direction, i.e. into the second port 203 and then into the rotor chamber 303. The axial alignment of the second port 203 with the rotor 403 means that gas flowing inwards through this port does not have an effect on the rotor speed, so exhalation is not registered. The rotor will spin at a constant speed or slow down due to friction as the patient exhales; the balloon graphic on the screen of the computational device will either remain static or start to sink.

The upper shell 401, lower shell 402, rotor 403 of the mechanical part, the base 501 and protective cover of the electronics part are made from injection moulded plastic. The upper shell 401 and lower shell 402 are joined by ultrasonic welding.

The mechanical part 302 is a sealed unit, whereby gas can only enter and exit the unit via the first port 202 and second port 203; the gas and breath mixture in the anaesthetic circuit is thereby isolated from the electronics part 303. This allows the relatively low cost, potentially contaminated mechanical part 302 to be disposable while the more expensive electronics part 303 to be re-used.

Alternatively the electronics part 303 and the mechanical part 302 could be joined by a permanent connection such as adhesive or ultrasonic welding. This would remove the need for the anaesthetist to assemble the mechanical part and the electronics part prior to use; a complete breath flow detector unit 201 including both the mechanical part 302 and electronics part 301 could be included in the anaesthetic circuit kit.

An alternative arrangement for the mechanical part is shown in Figure 9A, where both the first port 901 and second port 902 are arranged with a restriction that directs gas flow tangentially into the rotor chamber 903. In this embodiment the restriction in the second port 902 causes the rotor to rotate on both the inhalation and exhalation breathing phases. This is useful in applications where measurement of both breathing phases is required. To measure breath flow direction, two sensors can be used in the electronics part 301, as shown in Figure 11. The sensors 1102, 1103 are mounted on the base 501 of the electronics part on the path of the magnets 418a, 418b in the rotor 403, with an angular separation that is less than the angular separation of the magnets. The signal from each sensor is sent to the processor 502, so that it receives a pair of signals, Si from a first sensor 1102 and S2 from a second sensor 1103. For each passage of a magnet over the sensors, the processor determines in which order Si and S2 are received and from this the direction of rotation of the rotor is established.

A further alternative as shown in Figure 9B is where the second port 902 does not have a restriction and therefore the apparatus measures a single breathing phase, either inhale or exhale, but the first port and second port are in-line. This is useful in applications where space is limited.

A further alternative arrangement is shown in Figure 10, where a bypass channel 1101 is provided around the rotor chamber. It is important, particularly in paediatric applications, to minimise the resistance to the flow of gas in the anaesthetic circuit, so that the patient can breathe as normally as possible. The purpose of the bypass channel is to reduce the resistance to gas flow. The restriction in the first port and rotation of the rotor cause a resistance to the flow of gas: not all of the gas flow is required to cause rotation of the rotor, therefore a portion of the flow is ducted around the restriction and the rotor to reduce flow resistance.

The breath flow detector unit 201 can be used in asthma management. In this application, the breath flow rate is calibrated, where the rpm (rotations per minute) and change in rpm of the rotor is converted into volume and velocity. These values are recorded and plotted over time against a target. The unit 201 can be part of an inhaler device during delivery of medication and used to ensure correct use of the inhaler, or, as a method of measuring Peak Expiratory Flow Rate to assess therapeutic management effectiveness.

An embodiment of the breath flow detector unit is also suitable for use in incentive spirometry, in a disposable unit for measuring breath flow and deriving lung capacity from this. A paired computational device is loaded with software that can plot actual lung capacity with a target lung capacity and the user encouraged to breathe in a way to meet the target lung capacity. If the direction of breath flow is required in this application or any other, it can be detected using the two-sensor arrangement of Figure 11.

An embodiment of the present invention is also suitable for use in breathing exercises, for example Positive Expiratory Pressure (PEP) therapy, where a greater resistance to airflow is required on the exhale. A patient breathes through the device which allows air to flow freely on the inhale and breathes out hard against a resistance. This helps air get behind any mucus on the lung and airway walls. A restriction can be placed in the second port 203, such as a slide mechanism or plug-in valve. A measure of the breath flow is then detected by the device 201 and breath flow signals sent to a computational device for analysis, helping to ensure that the patient is breathing optimally in this exercise.

Claims

CLAIMS1. Mechanical apparatus suitable for use as a component of a breath flow detector unit comprising: a first port for receiving and venting a flow of gas, a second port for receiving and venting a flow of gas, a chamber connecting the first and second ports, a rotor located within the chamber and capable of rotating within the chamber, the rotor having a plurality of arms, wherein at least one arm of the rotor has a 10 permanent magnet, the apparatus further comprising a connecting portion for connecting a sensor to the exterior of the chamber to detect the magnetic field of the magnet.
2. The apparatus of claim 1, wherein the first port has a restriction in the region where it connects to the chamber to accelerate the flow of gas tangentially onto the rotor.
3. The apparatus of claim 1 or 2, wherein the chamber has a bypass duct for allowing a portion of gas to flow from the first port to the second port without passing through the restriction.
4. The apparatus of any one of claims 1 to 3, wherein the second port is co-planar with the rotor.
5. The apparatus of any one of claims 1 to 3, wherein the second port is coaxial with the rotor.
6. The apparatus of any one of claims 1 to 4, wherein the second port has a restriction in the region where it connects to the chamber to accelerate the flow of gas tangentially onto the rotor.
7. The apparatus of any one of claims 1 to 6, wherein two magnets are provided in opposing arms of the rotor and arranged with poles perpendicular to the plane of the rotor.
8. The apparatus of claim 7, wherein the poles of the magnets are arranged in a direction opposite to each other.
9. The apparatus of any preceding claim, wherein either the first or second port is provided with a restriction to restrict air flow.
10. The apparatus of claim 9, wherein the restriction allows air to flow freely in one direction but restricts airflow in the other direction.
11. The apparatus of claim 10, wherein the restriction comprises a sliding mechanism or a valve.
12. Electronic apparatus suitable for use with the mechanical apparatus of the type as claimed in claims 1 to 11 as a component of a breath flow detector unit, the electronic apparatus comprising:a first sensor for detecting a magnetic field,an output for outputting signals from the first sensor, and a connecting portion for connecting the electronic apparatus to the mechanical apparatus.
13. The apparatus of claim 12, further including a transmitter for wirelessly communicating the signals from the sensor to a remote computational device.
14. The apparatus of claim 12 or 13, further including a second sensor for detecting a magnetic field located in proximity to the first sensor and an output for outputting signals from the second sensor.
15. A breath flow detector unit for outputting an electronic signal indicative of the flow of breath of a user, comprising: the mechanical apparatus of the type as claimed in claims 1 to 11, and the electronic apparatus of the type as claimed in claims 12 to 14.
16. The breath flow detector unit of claim 15, wherein the mechanical apparatus has a screw thread and the electronic apparatus has a corresponding screw thread, enabling the mechanical apparatus and electronic apparatus to be releasably attached to each other.
17. The breath flow detector unit of claim 15, wherein the mechanical apparatus and the electronic apparatus each have corresponding features of a bayonet fitting, enabling the mechanical apparatus and electronic apparatus to be releasably attached to each other.
18. A breath monitor system comprising the breath flow detector unit of the type as claimed in claims 15 to 17, further comprising a computing device for receiving signals from the electronic apparatus.
19. The breath monitor system of claim 18, wherein the computing device further includes software that converts the signals from the sensor into a graphic representation on a screen.
20. The breath monitor system of claims 18 or 19, where the graphic representation is a game, where a user is rewarded for breathing in accordance with predefined parameters.
21. The breath monitor system of claims 18 to 20, for use in delivery of an anaesthetic gas, incentive spirometry, asthma management, peak breath flow measurement, positive expiratory pressure therapy, directed cough or peak cough flow.
22. Computer software for converting the signals from a sensor in a breath flow detector unit of the type claimed in claims 15 to 17 into a graphic representation on a screen
23. A kit of parts for an anaesthetic circuit including the mechanical apparatus of the type as claimed in claims 1 to 14.
24. A kit of pads for an anaesthetic circuit including the mechanical apparatus of the type as claimed in claims 1 to 11 and the electronic apparatus of the type as claimed in claims 12 to 14.
25. A method of operating a breath flow detector unit of the type claimed in claims 15 to 17, comprising installing the breath flow detector unit in a breathing circuit, allowing a user to breathe through the breath flow detector unit, detecting signals from the sensor representing breath flow rate, sending the signals to a remote computational device and converting the signals into a graphic representation on a screen of the computational device.