This invention relates to respiratory therapy apparatus including a device having a flow path therethrough along which the user breathes.

Positive expiratory pressure (PEP) devices, that is, devices that present a resistance to expiration through the device, are now widely used to help treat patients suffering from a range of respiratory impairments, such as chronic obstructive pulmonary disease, bronchitis, cystic fibrosis and atelectasis. More recently, such devices that provide an alternating resistance to flow have been found to be particularly effective. One example of such a device is sold under the trade mark Acapella (a registered trade mark of Smiths Medical) by Smiths Medical and is described in US6581598, US6776159, US7059324 and US7699054.

US8534284 describes a device with an interrupter valve driven by pressurised gas delivered to the apparatus. The speed of the valve is dependent on the back pressure created by expired breaths from the patient. WO2016/902247 describes a respiratory therapy device including a compliance meter having a cylinder with a piston that moves progressively along the cylinder when air is released from the cylinder on each expiratory cycle. The piston drives a flag to indicate progress of a therapy session. Other vibratory respiratory therapy devices are available, such as "Quake" manufactured by Thayer, "AeroPEP" manufactured by

Monaghan, "TheraPEP" manufactured by Smiths Medical, "IPV Percussionator"

manufactured by Percussionaire Corp and Aerobika manufactured by Trudell. These devices generate vibratory positive pressures mechanically and fluctuating exhalation flows that help overcome the inertia and stiction of the sputum within the bronchi and lower passages of the lung. This enhances mucociliary clearance. Alternative apparatus such as "CoughAssist" manufactured by Philips is also available. Respiratory therapy devices can instead provide an alternating resistance to flow during inhalation.

Although respiratory therapy devices can be highly effective at treating respiratory impairments, the relief obtained is dependent on how closely the patient adheres to the prescribed treatment regime: how regularly he uses the device and the manner in which the device is used. Patients are trained to use the devices by a clinician in a hospital but it is essential that the devices are used regularly by the patient in the prescribed manner at home where there is no clinical supervision. The problem, however, is that the patient may not use the device as prescribed when unsupervised, outside a clinical environment. The clinician is unable to determine whether any lack of improvement in the patient's condition is due to his failure to adhere to the treatment regime or other factors so this makes control of the patient's condition very difficult. Existing devices do not provide any warning of worsening conditions.

It has been proposed to include sensors in therapy devices in order to be able to monitor use of the device. US2015/0335837 describes a piezo sensor mounted in a respiratory therapy device to monitor flow. WO14/140532 describes a respiratory therapy device including a pressure sensor. Use of sensors in therapy devices presents problems because of their cost and the need to ensure that the sensor does not obstruct flow or interfere with the pressure waveform produced in the device.

It is an object of the present invention to provide an alternative respiratory therapy device.

According to the present invention there is provided a respiratory therapy apparatus of the above-specified kind, characterised in that the flow path includes a flow sensor of the kind having a heated electrical resistive element exposed to breath flow through the device such that the rate of dissipation of heat from the resistive element is dependent on the user's breath flow rate, and that the device includes a processor connected with the resistive element and arranged to derive an output signal indicative of flow rate through the device from the response of the resistive element. The processor may be is arranged to supply power to the resistive element to maintain a substantially constant temperature of the element. The processor may be arranged to provide a flow rate signal dependent on the power necessary to maintain the constant temperature. The device is preferably a vibratory expiratory therapy device. The output signal may be supplied to a display mounted on the therapy device. Alternatively, the output signal may be supplied to a display in a remote unit by wireless transmission.

Respiratory therapy apparatus according to the present invention will now be described, by way of example, with reference to the accompanying drawing which is an exploded view of the device.

The respiratory therapy device 100 is in the form of a hand-held positive expiratory pressure (PEP) device, that is, a device that presents a resistance to expiration through the device. Such devices are now widely used to help treat patients suffering from a range of respiratory impairments, such as chronic obstructive pulmonary disease, bronchitis, cystic fibrosis and atelectasis. More recently, such devices that provide an alternating resistance to flow have been found to be particularly effective. One example of such a device is sold under the trade mark Acapella (a registered trade mark of Smiths Medical) by Smiths Medical and is described in US6581598, US6776159, US7059324 and US7699054.

The respiratory therapy device 100 comprises a rocker assembly 1 contained within an outer housing 2 provided by an upper part 3 and a lower part 4 of substantially semi- cylindrical shape. The device is completed by an adjustable dial 5 of circular section. The outer housing 2 contains an air flow tube 6 with a breathing inlet 7 at one end and an inspiratory inlet 8 at the opposite end including a one-way valve (not shown) that allows air to flow into the air flow tube but prevents air flowing out through the inspiratory inlet. The air flow tube 6 has an outlet opening 10 with a non-linear profile that is opened and closed by a conical valve element 11 mounted on a rocker arm 12 pivoted midway along its length about a transverse axis. The air flow tube 6 and housing 2 provide a structure with which the rocker arm 12 is mounted. At its far end, remote from the breathing inlet 7, the rocker arm 12 carries an iron pin 13, which interacts with the magnetic field produced by a permanent magnet (not visible) mounted on an adjustable support frame 14. The magnet arrangement is such that, when the patient is not breathing through the device, the far end of the rocker arm 12 is held down such that its valve element 11 is also held down in sealing engagement with the outlet opening 10. A cam follower projection 15 at one end of the support frame 14 locates in a cam slot 16 in the dial 5 such that, by rotating the dial, the support frame 14, with its magnet, can be moved up or down to alter the strength of the magnetic field interacting with the iron pin 13. The dial 5 enables the frequency of operation and the resistance to flow of air through the device to be adjusted for maximum therapeutic benefit to the user.

When the patient inhales through the breathing inlet 7 air is drawn through the inspiratory inlet 8 and along the air flow tube 6 to the breathing inlet. When the patient exhales, the one-way valve in the inspiratory inlet 8 closes, preventing any air flowing out along this path. Instead, the expiratory pressure is applied via the air flow tube 6 to the underside of the valve element 11 on the rocker arm 12 causing it to be lifted up out of the opening 10 against the magnetic attraction, thereby allowing air to flow out to atmosphere. The opening 10 has a non-linear profile, which causes the effective discharge area to increase as the far end of the rocker arm 12 lifts, thereby allowing the arm to fall back down and close the opening. As long as the user keeps applying sufficient expiratory pressure, the rocker arm 12 will rise and fall repeatedly as the opening 10 is opened and closed, causing a vibratory, alternating or oscillating interruption to expiratory breath flow through the device. Further information about the construction and operation of the device is not essential for an understanding of the invention but can be found in US6581598, US7059324 and US7699054.

The device also includes a mouthpiece 70 and a low cost flow sensor 50. The mouthpiece 70 is a simple push fit on the outside of the breathing inlet 7. The flow sensor 50 may be mounted in the mouthpiece 70 itself or in the breathing inlet 7 or anywhere along the expiratory flow path, such as in the air flow tube 6. It is preferable, however, for the sensor 50 to be located as close as possible to the user and the breathing inlet 7. The sensor 50 is of the kind including an electrically-heated resistive element having a temperature-dependent resistance, such as a thermistor. Low cost flow sensors of this kind are readily available, such as the "Wind Sensor" sold by moderndevice.com. The sensor 50 is connected with a processor 51 within the therapy device 100, which processes its output to derive a signal representative of flow rate. Power could be provided by a battery within the therapy device 100 or from a remote power source such as via a cable. The sensor includes a heated electrical resistive element exposed to breath flow through the device such that the rate of dissipation of heat from the resistive element is dependent on the user's breath flow rate. The processor 51 is connected with the sensor 50 and arranged to derive an output signal indicative of flow rate through the device from the response of the sensor.

The therapy device 100 may include a display mounted on the housing 2 and connected with the output of the processor 51. Alternatively, as illustrated, the processor 51 may include a wireless transmitter, such as a radio frequency transmitter operating on the Bluetooth protocol.

Importantly, the sensor 50 does not have any moving parts so does not obstruct or interfere with gas passage around it and does not affect the vibration pattern delivered to the user's respiratory passages. In this way, monitoring and feedback can take place without adversely affecting the vibratory treatment.

A remote unit 52 includes a receiver 53 arranged to receive the output from the processor 51. The unit 52 also includes a display 54 arranged to provide a representation of flow rate and a store 55 arranged to record information from the processor 51 for subsequent downloading. The display 54 may provide a visible representation of flow rate in real time as flow rises and falls. Alternatively, or additionally, the display 54 may display a chart showing flow change over a period of time. The display 54 may also represent maximum flow rate or flow integrated over a period of time. The processor 51 could also provide feedback to the user such as to indicate correct or incorrect usage, for example, flow being too low or for not long enough. The processor 51 could also indicate to the user when the user has completed the prescribed time for a therapy session. The feedback could be visual, audible or tactile (such as by vibration). The device could be used to provide a warning of a worsening condition.

Instead of using a dedicated remote unit the therapy device could be arranged to interact with a Bluetooth enabled computer such as a laptop, tablet or smart phone.

The sensor 50 used in the therapy device 100 of the present invention can be of low cost, small and lightweight so that it does not significantly obstruct air flow through the device. Such sensors can also be highly sensitive to gas flow at the typical flow rates produced in such therapy devices. The relatively constant temperature of the exhaled air helps ensure a relatively stable output.

If a pressure sensor were used to measure breath output this would require some form of constriction in the flow path, which would, be a disadvantage in therapy devices intended for use by patients with severely impaired breathing where the therapy device needs to give little or no resistance to exhalation. By contrast, the flow sensor of the present invention can provide a reliable output even if there is no constriction to flow, in free-flowing air.

The invention is not limited to vibratory expiratory therapy devices of the kind described above but could be used with other respiratory therapy devices.