A device for providing pain relief and / or sedation to a patient

Abstract

There is provided device for providing pain relief and / or sedation to a patient, and a method of providing pain relief and / or sedation to a patient. The device comprises: an input arrangement for actuation by the patient, a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, and a controller that is configured to receive an input signal from the input arrangement, process the input signal using a control algorithm to generate an output signal, and transmit the output signal to the delivery arrangement for controlling the delivery of the pain-relieving and / or sedative substance to the patient. The control algorithm comprises: a high response function that generates a high response delivery parameter, a low response function that generates a low response delivery parameter, and an output function that uses the high response delivery parameter and the low response delivery parameter to generate the output signal.

Description

[0001] Title - A device for providing pain relief and / or sedation to a patient

[0002] The present invention relates to the provision of pain relief and / or sedation to a patient, and in particular to a method and device for providing pain relief and / or sedation to a patient.

[0003] The use of sedation, rather than general anaesthesia, is beneficial for patients, clinicians and healthcare organisations. It has been shown to result in a lower incidence of postoperative cognitive dysfunction, shorter hospital stays, and a reduced environmental impact (Anaesthesia and Perioperative Medicine Getting It Right First Time Programme National Specialty Report (2021 )). However, sedation remains underutilised as an alternative to general anaesthesia, possibly due to patients’ and clinicians’ concerns about safety and intraoperative awareness and recall (Chatman N, Sutherland JR, van der Zwan R, Abraham N. A survey of patient understanding and expectations of sedation / anaesthesia for colonoscopy. Anaesth Intensive).

[0004] Sedation also has utility outside of the hospital and surgical setting. GP surgeries often perform minor procedures such as mole removal and IUD insertion, which cause pain and / or discomfort for the patient, but for which there are currently limited options for effective pain relief. Outside of the clinical setting, acute situations such as sports injuries or injuries resulting from accidents can lead to severe pain, for which effective pain relief may not be available until the patient has been moved to a clinical setting. In such situations, effective, portable sedation would have a significant impact on alleviating pain. Furthermore, many medical and surgical procedures currently conducted under general anaesthetic could be carried out in an outpatient setting given a suitable sedation approach. This would provide significant operational efficiency improvement and better utilise operating theatre resource.

[0005] Effective sedation is a balancing act between awareness and anaesthesia. If too little sedation is given, patients may continue to experience discomfort, and be able to recall intraoperative events. On the other hand, if too much sedation is given, patients may become fully anaesthetised and require airway, respiratory or cardiovascular support. Sedation can be delivered with intravenous or inhalational drugs, and the drug doses can be controlled by clinicians or by the patients themselves, with clinician-delivered intravenous sedation being the most common.

[0006] However, there are benefits associated with patient-controlled sedation / analgesia, including minimisation of drug doses and improved patient satisfaction (Sheahan CG, Mathews DM. Monitoring and delivery of sedation. Br J Anaesth. Dec 2014;113 Suppl 2.H37-47. doi:10. 1093 / bja / aeu378). Likewise, inhalational drugs offer advantages over intravenous delivery, including less inter-individual dose response variability and faster recovery (Sahinovic MM, Struys M, Absalom AR. Clinical Pharmacokinetics and Pharmacodynamics of Propofol. Clin Pharmacokinet. Dec 2018;57(12):1539-1558. doi:10. 1007 / s40262-018-0672-3; Ibrahim AE, Ghoneim MM, Kharasch ED, et al. Speed of recovery and side-effect profile of sevoflurane sedation compared with midazolam. Anesthesiology. Jan 2001 ;94(1):87-94. doi:10.1097 / 00000542-200101000-00018). However, potentially due to concerns about the delivery of unsafe dosages, and as a result, a lack of suitable administration apparatus, patient-controlled inhalational delivery has not been widely adopted.

[0007] More recent prior art goes some way towards mitigating these concerns, but improvements are still necessary.

[0008] W02022101491 discloses that an operator initially sets a predetermined background rate of delivery based on the physical condition of the patient, and that the rate is adjusted according to the frequency of the patient’s request, to meet the demand for pain relief. At the same time, the consciousness of the user is assessed, and the rate of drug delivery is altered accordingly, in order to ensure the patient does not become fully anaesthetised. The background rate is a minimum rate that is administered regardless of input caused by the patient. There is a need for an improved device for providing pain relief and / or sedation to a patient, which overcomes or substantially mitigates the above mentioned and / or other problems associated with the prior art.

[0009] According to a first aspect of the invention, there is provided a device for providing pain relief and / or sedation to a patient, the device comprising: an input arrangement for actuation by the patient, a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, and a controller that is configured to receive an input signal from the input arrangement, process the input signal using a control algorithm to generate an output signal, and transmit the output signal to the delivery arrangement for controlling the delivery of the pain- relieving and / or sedative substance to the patient, wherein the control algorithm comprises:

[0010] - a high response function that generates a high response delivery parameter,

[0011] - a low response function that generates a low response delivery parameter, and

[0012] - an output function that uses the high response delivery parameter and the low response delivery parameter to generate the output signal.

[0013] According to a second aspect of the invention, there is provided a method of providing pain relief and / or sedation to a patient, the method comprising the steps of: receiving an input signal from an input arrangement actuated by a patient, processing the input signal using a control algorithm to generate an output signal, and transmitting the output signal to a delivery arrangement for delivering a pain- relieving and / or sedative substance to the patient, wherein the control algorithm comprises: a high response function that uses the input signal to generate a high response delivery parameter, a low response function that uses the input signal to generate a low response delivery parameter, and an output function that uses the high response delivery parameter and the low response delivery parameter to generate the output signal. The invention according to these aspects of the invention may be advantageous in that the algorithm generates a high response delivery parameter and a low response delivery parameter from the same patient input, and the output function uses both of those delivery parameters to generate the output signal. In contrast, in the prior art devices, where a high response delivery parameter (e.g. a bolus delivery) and a low response delivery parameter (e.g. a background delivery rate) are determined, at least one of those delivery parameters (typically the background delivery rate) is predetermined and remains at a constant level. This often means that additional substance is delivered unnecessarily, when less pain- relieving and / or sedative substance could sufficiently manage the patient’s discomfort.

[0014] The output function may use the high response delivery parameter and the low response delivery parameter to generate the output signal in response to the patient input signal. The high response delivery parameter and / or the low response delivery parameter may be variable. The high response function and the output function may generate a variable output signal in a high response mode of the device. The low response function and the output function may generate a variable output signal in a low response mode of the device.

[0015] According to a third aspect of the invention, there is provided a device for providing pain relief and / or sedation to a patient, the device comprising: an input arrangement for actuation by the patient, a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, and a controller that is configured to receive an input signal from the input arrangement, process the input signal using a control algorithm to generate a variable output signal, and transmit the variable output signal to the delivery arrangement for controlling the delivery of the pain-relieving and / or sedative substance to the patient, wherein the control algorithm comprises: a high response output function that takes a parameter of the input signal and generates a variable output signal in a high response mode of the device, and a low response output function that takes a parameter of the input signal and generates a variable output signal in a low response mode of the device.

[0016] According to a fourth aspect of the invention, there is provided a method of providing pain relief and / or sedation to a patient, the method comprising the steps of: receiving an input signal from an input arrangement actuated by a patient, processing the input signal using a control algorithm to generate a variable output signal, and transmitting the variable output signal to a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, wherein the control algorithm comprises: a high response output function that takes a parameter of the input signal and generates a variable output signal in a high response mode of the device, and a low response output function that takes a parameter of the input signal and generates a variable output signal in a low response mode of the device.

[0017] The control algorithm may further generate one or more delivery parameter from the input signal. For example, the control algorithm may further generate a high response delivery parameter and a low response delivery parameter. The high response output function may use the high response delivery parameter to generate the variable output signal in the high response mode of the device. Alternatively, the high response output function may use the high response delivery parameter and the low response delivery parameter to generate the variable output signal in the high response mode of the device. The low response output function may use the low response delivery parameter to generate the variable output signal in the low response mode of the device.

[0018] The above aspects of the invention concern a device for relieving pain and / or delivering sedation. Pain may be relieved and / or sedation provided, through the administration of medicaments of a variety of types, but in particular through the administration of sedatives, analgesics and / or anaesthetics. These medicaments may be administered alone or in combination to achieve the desired physical effect. In the context of the invention, ‘sedative’ is intended to refer to a medicament which induces a state of calm or sleep, ‘analgesic’ to a medicament which induces pain relief without the loss of consciousness and without total loss of feeling or movement, and ‘anaesthetic’ to a medicament which induces the loss of physical sensation with or without loss of consciousness.

[0019] The device of the invention may relieve pain and / or deliver sedation through the administration of one or more analgesics, anaesthetics and / or sedatives. Suitable pain-relieving or sedative substances are known in the art and may include sevoflurane, methoxyflurane, remifentanil, fentanyl, remimazolam, propofol and / or isoflurane. The pain-relieving and / or sedative substance used in the present invention may particularly be a volatile fluid, and may be selected from the list comprising, for example, sevoflurane, methoxyflurane and isoflurane. The volatile pain-relieving and / or sedative substance may be inhaled by the patient.

[0020] Different analgesics, anaesthetics and sedatives take varying lengths of time to take effect in the body after administration begins (onset) and to cease acting on the body once administration finishes (offset). This depends at least in part on the way in which the medication is metabolised by the body and / or eliminated, the method of administration, and / or the way in the medication is redistributed within the body, e.g. whether it circulates in the bloodstream or migrates to fat and muscle tissues, reducing the clinical effect.

[0021] The medication for use in the present invention may particularly be a pain relieving and / or sedative substance having rapid onset and rapid offset, that is, that it begins acting in the body quickly after administration begins, and only remains clinically active for a short time after administration ceases. This enables rapid, responsive changes in the delivery of the pain-relieving and / or sedative substance, with changes in dosage being rapidly felt by the patient.

[0022] Typically, the pain-relieving and / or sedative substance used in the present invention has rapid offset, and exhibits complete reversal of clinical effect within 15 minutes, or within 10 minutes, or within 7 minutes, or within 5 minutes of the administration of a clinically effective dose. In particular, the medication may be an anaesthetic, for example sevoflurane. While commonly used as an anaesthetic, low doses of sevoflurane have been found to be an effective analgesic and sedative, with a typical offset time of 5 minutes or less, leading to quick patient recovery. Some memory loss of events occurring whilst under the influence of sevoflurane has also been reported by patients, which may be beneficial for patients in severe pain or undergoing a potentially traumatic procedure.

[0023] The input arrangement may comprise one or more inputs. The input arrangement may be actuated by the patient by any, or any combination of: a visual input, for example by waving or blinking, a haptic or tactile input, for example by squeezing or pressing, and an audio input, for example by speaking.

[0024] Actuation of the input arrangement by the patient may be indicative of a demand for pain relief and / or sedation. Actuation of the input arrangement by the patient may therefore be indicative of the patient requiring greater pain relief and / or sedation, and / or the amount of pain and / or sedation the patient is experiencing. The number and / or frequency and / or duration of actuations of the input arrangement may be indicative of the patient requiring greater pain relief and / or sedation, and / or the amount of pain and / or sedation the patient is experiencing. Similarly, the force and / or pressure and / or velocity and / or acceleration and / or audio volume of actuations of the input arrangement may be indicative of the patient requiring greater pain relief and / or sedation, and / or the amount of pain and / or sedation the patient is experiencing. The patient may therefore be instructed to actuate the patient input to demand greater pain relief and / or sedation.

[0025] The high response and low response delivery parameters may be dependent on one or more patient input parameter(s) associated with the patient input or patient input signal. The low response delivery parameter may be dependent on at least a first patient input parameter or first patient input parameters. The high response delivery parameter may be dependent on at least a second patient input parameter or second patient input parameters. The first and second patient input parameters may be the same patient input parameters or different patient input parameters associated with the same patient input.

[0026] The patient input parameters may be dependent on a frequency of the patient input signal, which may be indicative of a frequency of the patient input. In particular, a higher frequency of patient actuation of the input arrangement may be indicative of the patient’s desire for greater pain relief and / or sedation. The patient input parameters may be dependent on the time elapsed since the previous patient input, the time elapsed between a plurality of patient inputs, a change in the time elapsed between inputs over a plurality of patient inputs, or the average time elapsed between inputs over a plurality of patient inputs. Where the patient input parameters depend on a plurality of patient inputs, the dependency may be weighted, e.g. such that the most recent patient input holds greater weight.

[0027] The patient input parameters may be dependent on an amplitude of the patient input signal, which may be indicative of a velocity, force or acceleration associated with the patient input. In particular, a higher velocity, force or acceleration of patient actuation of the input arrangement may be indicative of the patient’s desire for greater pain relief and / or sedation. The patient input parameters may be dependent on the velocity, force or acceleration associated with a single patient input, the average velocity, force or acceleration associated with a plurality of patient inputs, or a change in the velocity, force or acceleration between patient inputs over a plurality of patient inputs. Where the patient input parameters depend on a plurality of patient inputs, the dependency may be weighted, e.g. such that the most recent patient input holds greater weight.

[0028] The patient input parameters may be dependent on a period of the patient input signal, and therefore on a duration of the patient input. In particular, a longer duration of patient actuation of the input arrangement may be indicative of the patient’s desire for greater pain relief and / or sedation. The patient input parameters may be dependent on the duration of a single patient input, the average duration of a plurality of patient inputs, or a change in the duration of patient inputs between patient inputs over a plurality of patient inputs. Where the patient input parameters depend on a plurality of patient inputs, the dependency may be weighted, e.g. such that the most recent patient input holds greater weight.

[0029] The low response delivery parameter may be a rate of delivery of the pain- relieving and / or sedative substance. The low response parameter may be a volume of the pain-relieving and / or sedative substance. The volume may be a volume for immediate delivery, e.g. as a bolus delivery, or a volume to be delivered over a time period, e.g. a single breath or inhalation of the patient. The low response delivery parameter may be a time period associated with delivery of the pain-relieving and / or sedative substance. For example, the low response delivery parameter may be a time period over which a volume of the pain-relieving and / or sedative substance should be delivered, e.g. a single breath or inhalation of the patient, or a time period over which a rate of delivery of the pain-relieving and / or sedative substance should be maintained.

[0030] The high response delivery parameter may be a rate of delivery of the pain- relieving and / or sedative substance. The high response delivery parameter may be a volume of the pain-relieving and / or sedative substance. The volume may be a volume for immediate delivery, e.g. as a bolus delivery, or a volume to be delivered over a time period, e.g. a single breath or inhalation of the patient. The high response delivery parameter may be a time period associated with delivery of the pain-relieving and / or sedative substance. For example, the high response delivery parameter may be a time period over which a volume of the pain-relieving and / or sedative substance should be delivered, e.g. a single breath or inhalation of the patient, or a time period over which a rate of delivery of the pain-relieving and / or sedative substance should be maintained.

[0031] The output signal may determine a rate of delivery of the pain-relieving and / or sedative substance from the delivery arrangement. The output signal may determine a volume of the pain-relieving and / or sedative substance. The volume may be a volume for immediate delivery, e.g. as a bolus delivery, or a volume to be delivered over a time period, e.g. a single breath or inhalation of the patient. The output signal may determine a time period associated with delivery of the pain-relieving and / or sedative substance. For example, the output signal may determine a time period over which a volume of the pain-relieving and / or sedative substance should be delivered, e.g. a single breath or inhalation of the patient, or a time period over which a rate of delivery of the pain-relieving and / or sedative substance should be maintained.

[0032] The device may be configured to operate in different modes dependent on the output function. The device may be configured to operate in a low response delivery mode when the output function uses the low response delivery parameter to generate the output signal. The device may be configured to operate in a high response delivery mode when the output function uses the high response delivery parameter to generate the output signal. The output signal may therefore be dependent on only one of the low response delivery parameter and the high response delivery parameter.

[0033] Alternatively, the output function may combine or add the low response delivery parameter and the high response delivery parameter. The output signal may therefore be dependent on both the low response delivery parameter and the high response delivery parameter.

[0034] Further alternatively, the output function may compare the low response delivery parameter and the high response delivery parameter, and generating the output signal may comprise selecting the higher of the low response delivery parameter and the high response delivery parameter. The output signal may therefore be dependent on only one of the low response delivery parameter and the high response delivery parameter.

[0035] The control algorithm may comprise one or more additional functions, i.e. in addition to the high response function and the low response function. The one or more additional functions may generate one or more additional delivery parameters, i.e. in addition to the high response delivery parameter and the low response delivery parameter. The output function may therefore use the one or more additional delivery parameters, i.e. in addition to the high response delivery parameter and the low response delivery parameter.

[0036] The device may be configured to operate in different modes dependent on the result of the comparison of the low response delivery parameter and the high response delivery parameter. Where the low response delivery parameter is higher than the high response delivery parameter, the device may be configured to operate in a low response delivery mode. Where the high response delivery parameter is higher than the low response delivery parameter, the device may be configured to operate in a high response delivery mode.

[0037] Prior to, or upon, startup of the device, the patient may be instructed to actuate the input arrangement to demand greater pain relief and / or sedation. Hence, upon startup of the device, in response to actuation of the input arrangement by the patient, the high response function may generate an increase in the high response delivery parameter, and the low response function may generate an increase in the low response delivery parameter. The output function may therefore generate an increase in output signal. The increase in the high response delivery parameter may be greater than the increase in the low response delivery parameter. Upon comparing the low response delivery parameter and the high response delivery parameter, the high response delivery parameter will therefore typically be higher, and the device will operate in the high response delivery mode, to satisfy the patient’s immediate need for pain relief and / or sedation.

[0038] In the high response delivery mode, the control algorithm may comprise a response and output function that uses at least a parameter of the input signal that is indicative of a demand for pain relief and / or sedation from the patient to generate the output signal.

[0039] In the high response delivery mode, the device may have a rate increase phase during which demand for pain relief and / or sedation from the patient, e.g. via actuation of the input arrangement, provides an increase in a non-zero rate of delivery of the pain-relieving and / or sedative substance to a higher non-zero rate of delivery.

[0040] In the rate increase phase, in response to an actuation of the input arrangement by the patient, the high response function may generate an increase in the high response delivery parameter. The increase in the high response delivery parameter may be dependent on the current value of the high response delivery parameter, i.e. at the time of actuation of the input arrangement by the patient. The output function may therefore generate an increase in the output signal. The increase in the output signal may be proportional to the increase in the high response delivery parameter. In response to actuation of the input arrangement by the patient, the low response function may also generate an increase in the low response delivery parameter. The increase in the low response delivery parameter may be a predetermined increase. The increase in the low response delivery parameter may be an instantaneous increase, or a gradual increase applied over time. The increase in the low response delivery parameter may therefore be constant for each actuation of the input arrangement by the patient.

[0041] In the absence of actuation of the input arrangement by the patient, the high response function may generate a decrease in the high response delivery parameter. The decrease in the high response delivery parameter may be dependent on the time elapsed since the input arrangement was last actuated by the patient. The decrease in the high response delivery parameter may be dependent on the current value of the high response delivery parameter, e.g. at the time of the most recent actuation of the input arrangement by the patient. The output function may therefore generate a decrease in the output signal. The decrease in the output signal may be proportional to the decrease in the high response delivery parameter. In the absence of actuation of the input arrangement by the patient, the low response function may generate a decrease in the low response delivery parameter. The decrease in the high response delivery parameter may be greater than the decrease in the low response delivery parameter. The decrease in the low response delivery parameter may be a predetermined decrease. The decrease in the low response delivery parameter may be a gradual decrease applied over time. The decrease in the low response delivery parameter may therefore be constant for any given time period in which there is an absence of actuation of the input arrangement by the patient. The decrease in the low response delivery parameter may be dependent on the time elapsed since the input arrangement was last actuated by the patient. The decrease in the low response delivery parameter may be dependent on the current value of the low response delivery parameter, e.g. at the time of the most recent actuation of the input arrangement by the patient.

[0042] The low response delivery parameter may have a maximum value. The maximum value may be a predetermined maximum value. The predetermined maximum value may correspond to a maximum rate of delivery that may be safely delivered to a patient over a prolonged period of time. In response to the low response delivery parameter reaching the maximum value, the device may enter a rate decrease phase.

[0043] Additionally or alternatively, the device may have a maximum limit on the time the device may operate in the high response delivery mode. The maximum limit may be a cumulative time during which the device may operate in the high response delivery mode. The maximum limit may be a cumulative time within a predetermined time period during which the device may operate in the high response delivery mode. In response to the time spent in the high response delivery mode reaching the maximum limit, the device may enter the rate decrease phase.

[0044] In the rate decrease phase, in response to an actuation of the input arrangement by the patient, the high response function may generate a decrease in the high response delivery parameter. The decrease in the high response delivery parameter may be dependent on the current value of the high response delivery parameter, i.e. at the time of actuation of the input arrangement by the patient. The output function may therefore generate a decrease in the output signal. The decrease in the output signal may be proportional to the decrease in the high response delivery parameter. In response to actuation of the input arrangement by the patient, the low response function may also generate maintenance in the low response delivery parameter.

[0045] Hence, in the rate decrease phase, demand for pain relief and / or sedation from the patient provides a decrease in a non-zero rate of delivery of the pain-relieving and / or sedative substance to a lower non-zero rate of delivery.

[0046] The above combination of features may be particularly beneficial, and hence, according to a fifth aspect of the invention, there is provided a device for providing pain relief and / or sedation to a patient, the device comprising: an input arrangement for actuation by the patient, a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, and a controller that is configured to receive an input signal from the input arrangement, process the input signal using a control algorithm to generate an output signal, and transmit the output signal to the delivery arrangement for controlling the delivery of the pain- relieving and / or sedative substance to the patient, the control algorithm comprising a response and output function that uses at least a parameter of the input signal that is indicative of a demand for pain relief and / or sedation from the patient to generate the output signal, wherein the device has a rate increase phase during which actuation of the input arrangement from the patient indicative of a demand for pain relief and / or sedation provides an increase in a non-zero rate of delivery of the pain-relieving and / or sedative substance to a higher non-zero rate of delivery, and the device has a rate decrease phase during which actuation of the input arrangement from the patient indicative of an equal or greater demand for pain relief and / or sedation provides a decrease in a non-zero rate of delivery of the pain-relieving and / or sedative substance to a lower non-zero rate of delivery.

[0047] Similarly, according to a sixth aspect of the invention, there is provided a method of providing pain relief and / or sedation to a patient, the method comprising the steps of: receiving an input signal from an input arrangement actuated by a patient, processing the input signal using a control algorithm to generate an output signal, and transmitting the output signal to a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, wherein the control algorithm comprises a response and output function that uses at least a parameter of the input signal that is indicative of a demand for pain relief and / or sedation from the patient to generate the output signal, wherein the method has a rate increase phase during which actuation of the input arrangement from the patient indicative of a demand for pain relief and / or sedation provides an increase in a non-zero rate of delivery of the pain-relieving and / or sedative substance to a higher non-zero rate of delivery, and the method has a rate decrease phase during which actuation of the input arrangement from the patient indicative of an equal or greater demand for pain relief and / or sedation provides a decrease in a non-zero rate of delivery of the pain-relieving and / or sedative substance to a lower non-zero rate of delivery.

[0048] These aspects of the invention may be advantageous in that the patient cannot continually increase the rate of delivery of the device beyond a safe dosage. Instead, the device recognises the point at which it would no longer be safe to increase or maintain the rate of delivery, and enters a rate decrease phase, without the need for input from a clinician or trained operator. In contrast, prior art devices typically increase the rate of delivery in response to a patient request for pain relief and / or sedation, and a clinician or trained operator determines when a safe dosage has been reached.

[0049] In the rate increase phase, actuation of the input arrangement from the patient generates an input signal that has a first value of the at least a parameter and provides an increase in the non-zero rate of delivery of the pain-relieving and / or sedative substance to the higher non-zero rate of delivery. In the rate decrease phase, actuation of the input arrangement from the patient generates an input signal that has a second value of the at least a parameter and provides a decrease in the non-zero rate of delivery of the pain-relieving and / or sedative substance to the lower non-zero rate of delivery. The second value of the at least a parameter may be egual to, or greater than, the first value of the at least a parameter. In the rate increase phase, the increase in the non-zero rate of delivery may be dependent on the current or instantaneous value of the rate of delivery, i.e. at the time of actuation of the input arrangement by the patient.

[0050] In the rate decrease phase, the decrease in the non-zero rate of delivery may be predetermined. For example, the decrease in the non-zero rate of delivery may be at a predetermined rate, or occur over a predetermined time period. Alternatively, the decrease in the non-zero rate of delivery may be dependent on the current or instantaneous value of the high response delivery parameter, i.e. at the time of actuation of the input arrangement by the patient.

[0051] In the rate decrease phase, in the absence of actuation of the input arrangement by the patient, the device may provide a decrease in a non-zero rate of delivery of the pain-relieving and / or sedative substance to a lower non-zero rate of delivery. The decrease in the non-zero rate of delivery may be predetermined. For example, the decrease in the non-zero rate of delivery may be at a predetermined rate, or occur over a predetermined time period. Alternatively, the decrease in the nonzero rate of delivery may be dependent on the current or instantaneous value of the non-zero rate of delivery. Further alternatively, the decrease in the non-zero rate of delivery may be dependent on the value of the non-zero rate of delivery at the time of the most recent actuation of the input arrangement by the patient, or the time elapsed since the most recent actuation of the input arrangement by the patient. The rate of the decrease in the non-zero rate of delivery in the absence of actuation of the input arrangement may be greater than the rate of the decrease in the non-zero rate of delivery when the patient is actuating the input arrangement.

[0052] The control algorithm of the fifth and sixth aspects may further comprise:

[0053] - a high response function that generates a high response delivery parameter,

[0054] - a low response function that generates a low response delivery parameter, and

[0055] - an output function that uses the high response delivery parameter and the low response delivery parameter to generate the output signal. The fifth and sixth aspects of the invention may relate to the high response delivery mode described above, for example where the high response delivery parameter is higher than the low response delivery parameter.

[0056] In the rate decrease phase, in the absence of actuation of the input arrangement by the patient, the high response function may generate a decrease in the high response delivery parameter. The decrease in the high response delivery parameter may be predetermined. Alternatively, the decrease in the high response delivery parameter may be dependent on the current or instantaneous value of the high response delivery parameter. Further alternatively, the decrease in the high response delivery parameter may be dependent on the non-zero rate of delivery at the time of the most recent actuation of the input arrangement by the patient, or the time elapsed since the most recent actuation of the input arrangement by the patient. The decrease in the high response delivery parameter in the absence of actuation of the input arrangement may be greater than the decrease in the high response delivery parameter when the patient is actuating the input arrangement. The output function may therefore generate a decrease in the output signal. The decrease in the output signal may be proportional to the decrease in the high response delivery parameter.

[0057] In the absence of actuation of the input arrangement by the patient, the low response function may generate a decrease in the low response delivery parameter. The decrease in the low response delivery parameter may be predetermined. Alternatively, the decrease in the low response delivery parameter may be dependent on the current or instantaneous value of the low response delivery parameter. Further alternatively, the decrease in the low response delivery parameter may be dependent on the low response delivery parameter at the time of the most recent actuation of input arrangement by the patient, or the time elapsed since the most recent actuation of input arrangement by the patient. The decrease in the high response delivery parameter in the absence of actuation of the input arrangement by the patient may be greater than the decrease in the low response delivery parameter in the absence of actuation of the input arrangement by the patient. The decrease in the low response delivery parameter may be a predetermined decrease. The decrease in the low response delivery parameter may therefore be constant for any given time period in which there is an absence of actuation of the input arrangement by the patient.

[0058] In the rate decrease phase, in the absence of actuation of the input arrangement by the patient, it is anticipated that the low response delivery parameter will at some point in time decrease below the maximum value. In response to the low response delivery parameter decreasing below the maximum value, the device may be permitted to return to the rate increase phase. The device may only return to the rate increase phase in response to the low response delivery parameter being below the maximum value by a predetermined amount, and / or in response to the low response delivery parameter being below the maximum value for a predetermined amount of time.

[0059] In the rate decrease phase, actuation of the input arrangement by the patient may prevent the device from re-entering the rate increase phase. In particular, actuation of the input arrangement by the patient may maintain the low response delivery parameter at or near the maximum value, e.g. so that the low response delivery parameter is not below the maximum value by the predetermined amount. In this scenario, the device may only be permitted to return to the rate increase phase once there is an absence of actuation of the input arrangement by the patient that is sufficient to decrease the low response delivery parameter below the maximum value, e.g. by the predetermined amount.

[0060] In the rate decrease phase, where actuation of the input arrangement from the patient results in a decrease in the high response delivery parameter, but maintenance of the low response delivery parameter at or near the maximum value, it is anticipated that at some point in time the low response delivery parameter will become higher than the high response delivery parameter, and the device will then begin to operate in the low response delivery mode. Similarly, where the decrease in the high response delivery parameter in the absence of actuation of the input arrangement by the patient is greater than the decrease in the low response delivery parameter in the absence of actuation of the input arrangement by the patient, it is anticipated that at some point in time the low response delivery parameter will become higher than the high response delivery parameter, and the device will then begin to operate in the low response delivery mode. Upon entering the low response delivery mode, actuation of the input arrangement by the patient indicative of a demand for pain relief and / or sedation may prevent the device from re-entering the rate increase phase. In particular, actuation of the input arrangement by the patient indicative of a demand for pain relief and / or sedation may maintain the low response delivery parameter at or near the maximum value, e.g. so that the low response delivery parameter is not below the maximum value by the predetermined amount.

[0061] The device may have a phase during which the control algorithm generates the output signal such that: (a) a non-zero rate of delivery decreases to a lower nonzero rate of delivery in the absence of actuation of the input arrangement by the patient, (b) the patient is requested to actuate the input arrangement, (c) if the patient successfully actuates the input arrangement in response to the request, the rate of delivery is adjusted to a first non-zero rate of delivery; and (d) if the patient does not successfully actuate the input arrangement in response to the request, the rate of delivery is adjusted to a zero rate of delivery or a second non-zero rate of delivery, wherein the first non-zero rate of delivery is higher than the second non-zero rate of delivery.

[0062] In the above-described phase, step (a) may be optional, i.e. the algorithm may also generate the output signal such that steps (b)-(d) occur, even when step (a) does not. This combination of features may be particularly beneficial, and hence, according to a seventh aspect of the invention, there is provided a device for providing pain relief and / or sedation to a patient, the device comprising: an input arrangement for actuation by the patient, a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, and a controller that is configured to receive an input signal from the input arrangement, process the input signal using a control algorithm to generate an output signal, and transmit the output signal to the delivery arrangement for controlling the delivery of the pain- relieving and / or sedative substance to the patient, wherein the device has a phase during which the control algorithm generates the output signal, such that: (a) a non-zero rate of delivery decreases to a lower non-zero rate of delivery in the absence of actuation of the input arrangement by the patient, (b) the patient is requested to actuate the input arrangement, and (c) if the patient successfully actuates the input arrangement in response to the request, the rate of delivery is adjusted to a first non-zero rate of delivery; and (d) if the patient does not successfully actuate the input arrangement in response to the request, the rate of delivery is adjusted to a second non-zero rate of delivery, wherein the first nonzero rate of delivery is higher than the second non-zero rate of delivery.

[0063] Similarly, according to an eighth aspect of the invention, there is provided a method of providing pain relief and / or sedation to a patient, the method comprising the steps of: receiving an input signal from an input arrangement actuated by a patient, processing the input signal using a control algorithm to generate an output signal, and transmitting the output signal to a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, wherein the method has a phase during which the control algorithm carries out the following steps: (a) decreasing a non-zero rate of delivery to a lower non-zero rate of delivery in the absence of actuation of the input arrangement by the patient, (b) requesting that the patient actuates the input arrangement, and (c) if the patient successfully actuates the input arrangement in response to the request, adjusting the non-zero rate of delivery to a first non-zero rate of delivery; and (d) if the patient does not successfully actuate the input arrangement in response to the request, the rate of delivery is adjusted to a second non-zero rate of delivery, wherein the first nonzero rate of delivery is higher than the second non-zero rate of delivery.

[0064] The patient may be requested to actuate the input arrangement to indicate that the current level of pain relief and / or sedation is sufficient and / or to indicate that the patient remains conscious. The adjustment in the non-zero rate of delivery in step (c) may be for a predetermined amount of time, after which step (a), and subsequently step (b) may be repeated. These aspects of the invention may be advantageous in that where the patient actuates the input arrangement, thereby indicating that they are conscious, the patient continues to receive a higher non-zero rate of delivery of the pain-relieving and / or sedative substance than if they do not actuate the input arrangement. At the same time, the rate of delivery is generally decreased in this phase to encourage the patient onto a lower rate of delivery to find the minimum level that provides the necessary pain relief and / or sedation.

[0065] The control algorithm of the seventh and eighth aspects may further comprise:

[0066] - a high response function that generates a high response delivery parameter,

[0067] - a low response function that generates a low response delivery parameter, and

[0068] - an output function that uses the high response delivery parameter and the low response delivery parameter to generate the output signal.

[0069] The seventh and eighth aspects of the invention may relate to the low response delivery mode described above, for example where the low response delivery parameter is higher than the high response delivery parameter.

[0070] The device may comprise at least one patient indicator. The request to the patient to actuate the input arrangement may be provided via the at least one patient indicator. The at least one patient indicator may be any, or any combination of, at least one visual indicator, at least one haptic or tactile indicator, and at least one audio indicator. The request may therefore be any of, or any combination of, a visual request, a haptic request, and an audio request.

[0071] The patient may be requested to actuate the input arrangement periodically throughout delivery of the substance in the low response delivery mode. The patient may be requested to actuate the input arrangement at predetermined intervals throughout delivery of the substance in the low response delivery mode. The request for a patient input may be a consciousness or sedation check. The patient actuating the input arrangement may therefore be indicative of the patient being conscious, or of the patient experiencing a comfortable or sufficient level of sedation. The absence of the patient actuating the input arrangement, or the patient actuating the input arrangement slowly, may therefore be indicative of the patient having a reduced level of consciousness or being over-sedated. Here, “slowly” may be defined as taking longer than a predetermined acceptable response time. A successful actuation of the input arrangement may therefore be defined as the patient actuating the input arrangement within a predetermined acceptable response time, and an unsuccessful actuation of the input arrangement may therefore be defined as the patient failing to actuate the input arrangement within the predetermined acceptable response time.

[0072] The variation in the rate of delivery over time may define a delivery profile. The delivery profile may have a plurality of periods. Each period may extend between adjacent actuations of the input arrangement by the patient. The rate of delivery at the time of a first actuation of the input arrangement by the patient may represent the start of a period. The rate of delivery at the time of a subsequent actuation of the input arrangement by the patient may represent the end of a period.

[0073] The rate of delivery at the start of a period may be higher than the rate of delivery at the end of the period. The rate of delivery at the end of a period may be lower than the rate of delivery at the start of the period. The rate of delivery may therefore cumulatively decrease over each period.

[0074] Where the patient successfully actuates the input arrangement in response to the request, adjusting the non-zero rate of delivery to a first non-zero rate of delivery may comprise increasing the non-zero rate of delivery to a higher non-zero rate of delivery. The increase in the non-zero rate of delivery may be for a predetermined amount of time, after which step (a), and subsequently step (b) may be repeated. The predetermined amount of time may be near-zero, e.g. where the increase in the non-zero rate of delivery is a step increase. The increase in the rate of delivery in response to the patient actuating the input arrangement may be less than the decrease in the rate of delivery since the previous actuation of the input arrangement by the patient. The increase in the rate of delivery in response to the actuation of the input arrangement may be less than the decrease in the rate of delivery over the previous period. Where the request in step (b) is the first request, the increase in the rate of delivery in step (c) may be less than the decrease in the rate of delivery since operation in the low response mode. The increase in the rate of delivery in response to the actuation of the input arrangement may be a percentage or fraction of the decrease in the rate of delivery over the previous period. The percentage may be less than 100%. The fraction may be less than 1 . The delivery profile may therefore have a sawtooth profile.

[0075] The decrease in the rate of delivery at step (a) may be by a predetermined amount over each period. Alternatively, the decrease in the rate of delivery over a period may be proportional to the rate of delivery at the start of the period. The decrease in the rate of delivery may therefore be higher where the rate of delivery is relatively higher, and lower where the rate of delivery is relatively lower. The increase in the rate of delivery in response to the actuation of the input arrangement may be by a predetermined amount over each period. Alternatively, the increase in the rate of delivery may be proportional to the rate of delivery at the start of the period. The increase may therefore be lower where the rate of delivery is relatively higher, and higher where the rate of delivery is relatively lower.

[0076] The control algorithm may request that the patient actuates the input arrangement at regular or irregular intervals. The time interval between requests may be a predetermined time interval. Alternatively, the time interval between requests may be dependent on, or proportional to, the current or instantaneous rate of delivery, or the rate of delivery at the start of the period. The time interval between requests may therefore be shorter where the rate of delivery is relatively higher, and longer where the rate of delivery is relatively lower.

[0077] Where the patient does not actuate the input arrangement in response to the request, the non-zero rate of delivery may continue to decrease to a lower nonzero rate of delivery. Hence, adjusting the non-zero rate of delivery to a second non-zero rate of delivery may comprise decreasing the non-zero rate of delivery to a lower non-zero rate of delivery. The rate of decrease in the rate of delivery may be increased in response to the patient failing to actuate the input arrangement in response to the request. Similarly, the rate of decrease in the rate of delivery may be increased in response to the patient actuating the input arrangement slowly in response to the request. Here, “slowly” may be defined as taking longer than a predetermined acceptable response time.

[0078] In alternative embodiments, where the patient successfully actuates the input arrangement in response to the request, adjusting the non-zero rate of delivery to a first non-zero rate of delivery may comprise maintaining the current or instantaneous non-zero rate of delivery. Maintenance of the current or instantaneous non-zero rate of delivery may be for a predetermined amount of time, after which step (a), and subsequently step (b), may be repeated. Where the patient does not successfully actuate the input arrangement in response to the request, adjusting the non-zero rate of delivery to a second non-zero rate of delivery may comprise decreasing the non-zero rate of delivery.

[0079] In a further alternative embodiment, where the patient successfully actuates the input arrangement in response to the request, adjusting the non-zero rate of delivery to a first non-zero rate of delivery may comprise decreasing the current or instantaneous non-zero rate of delivery, for example by maintaining the rate of decrease in the rate of delivery in step (a). Where the patient does not successfully actuate the input arrangement in response to the request, adjusting the non-zero rate of delivery to a second non-zero rate of delivery may comprise decreasing the non-zero rate of delivery, wherein the first non-zero rate of delivery is higher than the second non-zero rate of delivery.

[0080] In response to the patient failing to actuate the input arrangement in response to the request, or in response to the patient actuating the input arrangement slowly in response to the request, a secondary request may be issued to the patient to actuate the input arrangement, e.g. via the patient indicator. The secondary request may be issued to the patient in a short time frame relative to the timeframe between primary requests. That is, the time interval between a primary request and a secondary request may be less than the time interval between adjacent primary requests. This may be advantageous in that it is quickly confirmed whether the patient is actually experiencing a reduced level of consciousness or is sedated, or whether the patient missed the primary request. Alternatively, the time interval between a primary request and a secondary request may be the same as the time interval between adjacent primary requests. The secondary request may be distinguished from the primary request in a different way. For example, the request may be provided via a different one of the at least one patient indicators, and / or the request may be a different type of request, e.g. the primary request may be a visual request, and the secondary request may be a brighter or longer visual request.

[0081] In response to the patient failing to actuate the input arrangement in response to the secondary request, or in response to the patient actuating the input arrangement slowly in response to the secondary request, a further secondary request, i.e. a tertiary request, may be issued to the patient to actuate the input arrangement, or the rate of delivery may be set to zero. That is, the rate of delivery may be set to zero in response to the patient failing to respond to consecutive requests to actuate the input arrangement, or in response to the patient responding slowly to consecutive requests to actuate the input arrangement. Here, “slowly” may be defined as taking longer than a predetermined acceptable response time.

[0082] In response to the patient actuating the input arrangement in response to the secondary request, the rate of delivery may increase to a higher non-zero rate of delivery. The higher non-zero rate of delivery may be substantially equal to the rate of delivery at the time of issuing the primary request. Alternatively, the higher non-zero rate of delivery may be a percentage or fraction of the rate of delivery at the time of issuing the primary request. The percentage may be less than 100%. The fraction may be less than 1 . Alternatively, in response to the patient actuating the input arrangement in response to the secondary request, the rate of delivery may continue to decrease, for example by maintaining the rate of decrease in the rate of delivery in step (a). Where a tertiary request is issued, the tertiary request may be issued to the patient in a short time frame relative to the time frame between primary requests, and / or relative to the time frame between primary and secondary requests. That is, the time interval between a secondary request and a tertiary request may be less than the time interval between adjacent primary requests and / or less than the time interval between a primary request and a secondary request. This may be advantageous in that it is quickly confirmed whether the patient is actually experiencing a reduced level of consciousness or is sedated, or whether the patient missed the primary and secondary requests. Alternatively, the time interval between a secondary request and a tertiary request may be the same as the time interval between adjacent primary requests and / or the time interval between a primary request and a secondary request. The tertiary request may be distinguished from the primary and secondary requests in a different way. For example, the request may be provided via a different one of the at least one patient indicators, and / or the request may be a different type of request, e.g. the tertiary request may be a brighter or longer visual request than the primary and secondary requests.

[0083] In response to the patient failing to actuate the input arrangement in response to the tertiary request, or in response to the patient actuating the input arrangement slowly in response to the tertiary request, the rate of delivery may be set to zero. That is, the rate of delivery may be set to zero in response to the patient failing to respond to three consecutive requests to actuate the input arrangement, or in response to the patient responding slowly to three consecutive requests to actuate the input arrangement. Here, “slowly” may be defined as taking longer than a predetermined acceptable response time.

[0084] In response to the patient actuating the input arrangement in response to the tertiary request, the rate of delivery may increase to a higher non-zero rate of delivery. The higher non-zero rate of delivery may be substantially equal to the rate of delivery at the time of issuing the primary or secondary request. Alternatively, the higher non-zero rate of delivery may be a percentage or fraction of the rate of delivery at the time of issuing the primary or secondary request. The percentage may be less than 100%. The fraction may be less than 1 . Alternatively, in response to the patient actuating the input arrangement in response to the secondary request, the rate of delivery may continue to decrease, for example by maintaining the rate of decrease in the rate of delivery in step (a).

[0085] The patient failing to actuate the input arrangement in response to any request to actuate the input arrangement may cause the device to enter the rate decrease phase. The device may be prevented from entering the rate increase phase until the patient successfully actuates the input arrangement in response to a request.

[0086] The patient failing to actuate the input arrangement in response to consecutive (e.g. two or three consecutive) requests may result in the rate of delivery remaining at zero until the patient successfully actuates the input arrangement in response to a request. The rate of delivery may be prevented from being non-zero for a predetermined amount of time. The patient may be requested to actuate the input arrangement once the predetermined amount of time has elapsed.

[0087] Once the rate of delivery has been set to zero, the patient may continue to be requested to actuate the input arrangement periodically, e.g. at predetermined intervals. The predetermined intervals may be shorter than the predetermined intervals at which the primary requests to actuate the input arrangement are made.

[0088] In response to the patient failing to actuate the input arrangement in response to these further requests, or in response to the patient actuating the input arrangement slowly in response to these further requests, the periodic requests to actuate the input arrangement may be continued, and / or the rate of delivery may remain set to zero. Here, “slowly” may be defined as taking longer than a predetermined acceptable response time.

[0089] In response to the patient actuating the input arrangement in response to one of these further requests, the rate of delivery may increase to a higher non-zero rate of delivery. The higher non-zero rate of delivery may be substantially equal to the rate of delivery at the time of issuing the primary, secondary or tertiary request. Alternatively, the higher non-zero rate of delivery may be a percentage or fraction of the rate of delivery at the time of issuing the primary, secondary or tertiary request. The percentage may be less than 100%. The fraction may be less than 1. The percentage or fraction may be dependent on the value of the non-zero rate of delivery at the time of the most recent actuation of the input arrangement by the patient. Alternatively, the percentage or fraction may be dependent on the number of requests to actuate the input arrangement and / or the time elapsed, since the most recent actuation of the input arrangement by the patient.

[0090] The above combination of features may be particularly beneficial, and hence, according to a ninth aspect of the invention, there is provided a device for providing pain relief and / or sedation to a patient, the device comprising: an input arrangement for actuation by the patient, a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, and a controller that is configured to receive an input signal from the input arrangement, process the input signal using a control algorithm to generate an output signal, and transmit the output signal to the delivery arrangement for controlling the delivery of the pain- relieving and / or sedative substance to the patient, wherein the device has a phase during which the control algorithm generates the output signal, such that: (a) a patient is requested to actuate the input arrangement; (b) if the patient does not successfully actuate the input arrangement in response to the request, the rate of delivery decreases and further requests to actuate the input arrangement are issued to the patient; (c) if the patient successfully actuates the input arrangement in response to one of the further requests, the rate of delivery increases to a higher rate of delivery, the higher rate of delivery being dependent on the number of further requests to actuate the input arrangement since the most recent actuation of the input arrangement by the patient and / or the time elapsed since the most recent actuation of the input arrangement by the patient.

[0091] Similarly, according to a tenth aspect of the invention, there is provided a method of providing pain relief and / or sedation to a patient, the method comprising the steps of: receiving an input signal from an input arrangement actuated by a patient, processing the input signal using a control algorithm to generate an output signal, and transmitting the output signal to a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, wherein the method has a phase during which the control algorithm carries out the following steps: (a) requesting that a patient actuates the input arrangement; (b) if the patient does not successfully actuate the input arrangement in response to the request, decreasing the rate of delivery to a lower rate of delivery and issuing further requests to the patient to actuate the input arrangement; (c) if the patient successfully actuates the input arrangement in response to one of the further requests, increasing the rate of delivery to a higher rate of delivery, the higher rate of delivery being dependent on the number of further requests to actuate the input arrangement since the most recent actuation of the input arrangement by the patient and / or the time elapsed since the most recent actuation of the input arrangement by the patient.

[0092] Preferably, where the higher rate of delivery is dependent on the number of further requests to actuate the input arrangement since the most recent actuation of the input arrangement by the patient and / or the time elapsed since the most recent actuation of the input arrangement by the patient, the most recent actuation of the input arrangement is in response to a request to actuate the input arrangement.

[0093] The lower rate of delivery may be zero. The higher rate of delivery may be a percentage or fraction of the rate of delivery at the time of issuing one of the previous requests. The percentage may be less than 100%. The fraction may be less than 1 . The percentage or fraction may be dependent on the value of the rate of delivery at the time of the most recent actuation of the input arrangement by the patient.

[0094] In the above, where it is described that the rate of delivery of the pain-relieving and / or sedative substance is increased or decreased, the increase or decrease may be an instantaneous increase or decrease in the rate of delivery. This may be the case where, for example, the delivery arrangement has a continuous and adjustable rate of delivery. Alternatively, the increase or decrease may be an increase or a decrease to be applied over time. For example, the increase or decrease may be an increase or a decrease to the volume to be delivered over a time period. The increase or decrease may therefore be an increase or decrease in the time that the delivery arrangement delivers pain-relieving and / or sedative substance within a time period. This may be the case where, for example, the pain-relieving and / or sedative substance is provided in pulses, in which the delivery arrangement alternates between delivering the pain-relieving and / or sedative substance, and not delivering the pain-relieving and / or sedative substance. The increase or decrease may therefore be an increase or decrease in the width of the pulses.

[0095] The patient may also be requested to actuate the patient input arrangement during operation in the high response delivery mode, and / or when the device is in the rate increase phase, e.g. to indicate that the current level of pain relief and / or sedation is sufficient and / or to indicate that the patient remains conscious. In this mode or phase, in response to the patient failing to actuate the input arrangement in response to a request, or in response to the patient actuating the input arrangement slowly in response to a request, the rate of delivery may be prevented from increasing. For example, the device may enter the rate decrease phase.

[0096] The input arrangement of the seventh and eighth aspects of the invention may be the input arrangement of the first-sixth aspects of the invention. That is, the same controller may be configured to receive input signals from the same input arrangement to control the delivery of the pain-relieving and / or sedative substance to the patient in the ways described in each of the first-eighth aspects of the invention.

[0097] The input arrangement may therefore be actuatable by the patient in at least two ways. The input arrangement may be actuatable in a first way to indicate a demand for pain relief and / or sedation. The input arrangement may be actuatable in a second, different way to indicate that the current level of pain relief and / or sedation is sufficient and / or to indicate that the patient remains conscious. The above combination of features may be particularly beneficial, and hence, according to an eleventh aspect of the invention, there is provided a device for providing pain relief and / or sedation to a patient, the device comprising: a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, an input arrangement for actuation by the patient, the input arrangement being actuatable in a first way to provide an input signal that is indicative of a demand for pain relief and / or sedation and being actuatable in a second way to provide an input signal that is indicative of the patient remaining conscious and / or that the current level of pain relief and / or sedation is sufficient, and a controller that is configured to receive an input signal from the input arrangement, process the input signal using a control algorithm generate an output signal, and transmit the output signal to the delivery arrangement for controlling the delivery of the pain- relieving and / or sedative substance to the patient.

[0098] Similarly, according to a twelfth aspect of the invention, there is provided a method of providing pain relief and / or sedation to a patient, the method comprising the steps of: receiving an input signal from an input arrangement actuated by a patient, processing the input signal using a control algorithm to generate an output signal, and transmitting the output signal to a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, wherein the input arrangement is actuatable in a first way to provide an input signal that is indicative of a demand for pain relief and / or sedation and is actuatable in a second way to provide an input signal that is indicative of the patient remaining conscious and / or that the current level of pain relief and / or sedation is sufficient.

[0099] The control algorithm may process the input signal to determine whether the input signal is indicative of a demand for pain relief and / or sedation, or if the input signal is indicative of the patient remaining conscious and / or that the current level of pain relief and / or sedation is sufficient. The control algorithm may generate the output signal dependent on the input signal, the input signal being dependent on the way in which the input arrangement is actuated. The output signal may therefore depend on the way in which the input arrangement is actuated, and delivery of the pain relief and / or sedation to the patient may therefore depend on the way in which the input arrangement is actuated.

[0100] The input arrangement may be actuatable in the first and second way in at least one mode of operation. In particular, the input arrangement may be actuatable in the first and second way in at least in the low response delivery mode, where the patient may be periodically requested to actuate the input arrangement to indicate that the patient remains conscious and / or that the current level of pain relief and / or sedation is sufficient. The input arrangement may be actuatable in the first and second way in multiple modes of operation. For example, the input arrangement may be actuatable in the first and second way in the low response delivery mode and the high response delivery mode.

[0101] The input arrangement may comprise a single input, such as a single actuator, e.g. a single button. This may be particularly advantageous in that a single input can be actuated by the patient to control various functionalities of the device. In particular, a single input can be actuated to indicate a demand for pain relief and / or sedation, and to indicate that the current level of pain relief and / or sedation is sufficient and / or to indicate that the patient remains conscious. In turn, this only requires training the patient to actuate a single input.

[0102] Prior to, or upon, startup of the device, the patient may be instructed to actuate the input arrangement in the first way to demand greater pain relief and / or sedation.

[0103] Prior to, or upon, startup of the device, the patient may be instructed to actuate the input arrangement in the second way to indicate consciousness and / or to indicate that the current level of pain relief and / or sedation is sufficient.

[0104] The input arrangement may have an actuated state or position and an unactuated state or position. The input arrangement may be biased towards the unactuated state. The actuated state of the input arrangement may therefore be any state in which the input arrangement is moved from its unactuated state. In one example, the input arrangement may comprise a button. The button may be pressed or pushed into an actuated state, and may be biased towards the unactuated state once released.

[0105] The frequency and / or the amplitude and / or the duration / and or the pressure of an actuation of the input arrangement may be indicative of the way in which the input arrangement has been actuated. The frequency and / or the amplitude and / or the period of the input signal may therefore be indicative of the way in which the input arrangement has been actuated.

[0106] In particular, the frequency of the actuation of the input arrangement being less than a predetermined threshold and / or the amplitude of the actuation of the input arrangement being greater than a predetermined threshold and / or the duration of the actuation of the input arrangement being greater than a predetermined threshold may be indicative of the input arrangement being actuated in the first way, and may therefore be indicative of a demand for pain relief and / or sedation. In contrast, the frequency of the input signal being greater than a predetermined threshold and / or the amplitude of the input signal being less than a predetermined threshold and / or the period of the input signal being less than a predetermined threshold may be indicative of the input arrangement being actuated in the second way, and may therefore be indicative of the patient remaining conscious and / or that the current level of pain relief and / or sedation is sufficient.

[0107] Alternatively, the frequency of the actuation of the input arrangement being within a first range or range(s) and / or the amplitude of the actuation of the input arrangement being within a first range or range(s) and / or the duration of the actuation of the input arrangement being within a first range or range(s) may be indicative of the input arrangement being actuated in the first way, and may therefore be indicative of a demand for pain relief and / or sedation. In contrast, the frequency of the input signal being within a second range or range(s) and / or the amplitude of the input signal being second range or range(s) and / or the period of the input signal being second range or range(s) may be indicative of the input arrangement being actuated in the second way, and may therefore be indicative of the patient remaining conscious and / or that the current level of pain relief and / or sedation is sufficient, the first range(s) and the second range(s) being different.

[0108] Preferably, actuating the input arrangement in the first way comprises actuating the input arrangement for an amount of time that is greater than a predetermined threshold. Actuating the input arrangement for an amount of time that is greater than a predetermined threshold may therefore be indicative of a demand for pain relief and / or sedation.

[0109] Preferably, actuating the input arrangement in the second way comprises actuating the input arrangement for an amount of time that is less than the predetermined threshold.

[0110] The second way of actuating the input arrangement may require the input arrangement to be actuated from an unactuated state. Thus, if the input arrangement is in an actuated state when the patient is requested to actuate the input arrangement in step (b) of the seventh and eighth aspects of the invention, the second way of actuating the input arrangement may require that the input arrangement is first returned to the unactuated state before actuating the input arrangement. The second way of actuating the input arrangement may further require the input arrangement to be returned to the unactuated state, i.e. following actuation.

[0111] The above features may be particularly advantageous in that where the patient is already actuating the input arrangement to indicate a demand for greater pain relief and / or sedation, it prevents the device from accidentally registering this actuation as an indication from the patient of their consciousness and / or that the current level of pain relief and / or sedation is sufficient.

[0112] The device may comprise a patient interface. The patient interface may comprise the aforementioned patient indicator. The patient interface may comprise at least one breath detection sensor. The at least one breath detection sensor may comprise any of, or any combination of: a pressure sensor, a temperature sensor, and a flow sensor, though other sensors are anticipated. The at least one breath detection sensor may detect that the patient is breathing based on fluctuations in measurements. The fluctuations may be periodic or cyclical.

[0113] The device may comprise a delivery interface arranged to deliver the pain-relieving and / or sedative substance to the patient. The patient interface and the delivery interface may be the same interface, for example where the pain-relieving and / or sedative substance is delivered to the patient via a respiratory mask. Alternatively, the patient interface and the delivery interface may be distinct interfaces.

[0114] The controller may be further configured to receive a sensor signal from the at least one sensor. The control algorithm may further comprise a breath detection function that generates a breathing parameter based on the sensor signal. The breathing parameter may indicate whether a patient’s breathing has been detected. The output function may use the breathing parameter to generate the output signal. Where breathing has not been detected, the output function may generate an output signal to prevent or cease delivery of the pain-relieving and / or sedative substance to the patient. Where the pain-relieving and / or sedative substance is currently being delivered to the delivery interface, the output function may generate an output signal to cease delivery to the delivery interface. Where delivery of the pain-relieving and / or sedative substance to the delivery interface is yet to commence, the output function may generate an output signal to prevent commencing delivery to the delivery interface.

[0115] The above combination of features may be particularly beneficial, and hence, according to a thirteenth aspect of the invention, there is provided a device for providing pain relief and / or sedation to a patient, the device comprising a patient interface, at least one sensor for detecting the breath of a patient within the patient interface, a delivery arrangement for delivering a pain-relieving and / or sedative substance to a delivery interface, and a controller that is configured to receive a sensor signal from the at least one sensor, process the sensor signal using a control algorithm to generate an output signal, and transmit the output signal to the delivery arrangement for controlling the delivery of the pain-relieving and / or sedative substance to the patient, wherein in the absence of breath detection, the control algorithm generates an output signal that prevents or ceases delivery of the pain-relieving and / or sedative substance to the delivery interface.

[0116] Similarly, according to an fourteenth aspect of the invention, there is provided a method of providing pain relief and / or sedation to a patient, the method comprising the steps of: receiving a sensor signal from at least one sensor for detecting the breath of a patient within a patient interface, processing the sensor signal using a control algorithm to generate an output signal, and transmitting the output signal to a delivery arrangement for delivering a pain-relieving and / or sedative substance to a delivery interface, wherein in the absence of breath detection, the control algorithm generates an output signal that prevents or ceases delivery of the pain- relieving and / or sedative substance to the delivery interface.

[0117] The invention according to these aspects of the invention may be advantageous in that by detecting the breathing of the patient, the device is able to determine when the mask is not being worn (or being worn incorrectly by a patient). By preventing or ceasing delivery of the pain-relieving and / or sedative substance to the delivery interface in the absence of breath detection, the device ensures that the substance is not unnecessarily delivered and emitted into ambient surroundings, which is important with some of the volatile substances that are used in this field. This also prevents buildup of the pain-relieving and / or sedative substance within the delivery interface, which could otherwise lead to overdose should the delivery interface be temporarily removed and repositioned on the patient after such buildup.

[0118] Where the pain-relieving and / or sedative substance is currently being delivered to the delivery interface, the output signal may be to cease delivery to the delivery interface. The output signal may also generate or trigger an alarm signal to indicate that breathing is no longer detected.

[0119] The output signal generated by the control algorithm in the absence of breath detection may be the absence of an output signal to deliver the pain-relieving and / or sedative substance to the delivery interface. Specifically, rather than actively generating an output signal that prevents or ceases delivery of the pain- relieving and / or sedative substance to the delivery interface, the control algorithm may prevent or cease delivery of the pain-relieving and / or sedative substance to the delivery interface by not sending an output signal that initiates or continues delivery of the pain-relieving and / or sedative substance to the delivery interface.

[0120] Where the at least one sensor is a pressure sensor, the pressure sensor may detect a decrease in pressure within the patient interface in response to the patient inhaling, and / or an increase in pressure within the patient interface in response to the patient exhaling. The respective increase and decrease in pressure may therefore be indicative of the patient breathing into the patient interface. If an increase or a decrease in pressure is not detected, this may be indicative of the mask not being worn (or being worn incorrectly) by a patient.

[0121] Where the at least one sensor is a pressure sensor, the sensor signal may be indicative of the tidal volume of the patient. In particular, the magnitude of the fluctuations in the pressure measurements may be indicative of the tidal volume of the patient. The controller may therefore be configured to receive the sensor signal from the at least one sensor, and process the sensor signal to calculate the tidal volume of the patient. The controller may be further configured, using the control algorithm, to generate an output signal, and transmit the output signal to the delivery arrangement to control the delivery of the pain-relieving and / or sedative substance dependent on the tidal volume of the patient.

[0122] Where the at least one sensor is a temperature sensor, the temperature sensor may detect natural increases and decreases in temperature that occur as a result of the patient breathing. Specifically, the temperature sensor may detect an increase within the patient interface in response to the patient exhaling and the sensor may detect a decrease within the patient interface in response to the patient inhaling.

[0123] Where the patient interface and the delivery interface are the same interface, because of the nature of some pain-relieving and / or sedative substances, upon delivery of the pain-relieving substance into the patient interface, the intake of breath by the patient draws air flow through the patient interface, causing the pain- relieving and / or sedative substance to evaporate, in turn causing a decrease in temperature within the delivery interface. Hence, the temperature sensor may detect a decrease in the temperature within the patient interface in response to the patient inhaling, and the temperature sensor may detect an increase in temperature within the patient interface in response to the patient exhaling.

[0124] The respective increase in temperature may therefore be indicative of the patient exhaling into the patient interface. If an increase in temperature is not detected, this may be indicative of the mask not being worn (or being worn incorrectly) by a patient. Similarly, the respective decrease in temperature may be indicative of the patient inhaling through the patient interface. If a decrease in temperature, or a reduced decrease in temperature, is not detected, this may be indicative of the mask not being worn (or being worn incorrectly) by a patient.

[0125] The device may further comprise a status indicator arrangement. The patient interface may comprise the status indicator arrangement. The patient interface may be a respiratory mask. The device may further comprise a supply of pain- relieving and / or sedative substance. The status indicator arrangement may be configured to indicate at least one state of the device.

[0126] The above combination of features may be particularly beneficial, and hence, according to a fifteenth aspect of the invention, there is provided a device for providing pain relief and / or sedation to a patient, the device comprising at least one supply of a pain-relieving and / or sedative substance, a patient interface having a status indicator arrangement for indicating at least one state of the device, and a controller that is configured to determine at least one state of the device, and transmit an output signal to the status indicator arrangement indicative of the at least one state of the device.

[0127] Similarly, according to a sixteenth aspect of the invention, there is provided a method of providing pain relief and / or sedation to a patient, the method comprising the steps of: determining at least one state of the device, generating an output signal indicative of the at least one state of the device, and transmitting the output signal to a status indicator arrangement at a patient interface for indicating the at least one state of the device.

[0128] The invention according to these aspects of the invention may be advantageous in that the device provides clear and identifiable information about the at least one state of the device via a status indicator arrangement positioned on the patient interface.

[0129] The at least one state of the device may be indicative of the priming status of the device, e.g. whether the device is currently priming, or whether priming has been completed. Priming may be defined as the process of preparing the device for delivery of the pain-relieving and / or sedative substance. Priming may occur between turning on the device and initiation of delivery of the pain-relieving and / or sedative substance. The at least one state of the device may be indicative of the delivery status of the device, e.g. whether the device is currently delivering pain- relieving and / or sedative substance to the delivery interface. The at least one state of the device may be indicative of the status of the at least one supply of a pain- relieving and / or sedative substance, e.g. how much of the pain-relieving and / or sedative substance remains. The at least one state of the device may be indicative of the usage of the device, e.g. whether the device has been used before.

[0130] The status indicator arrangement may comprise one or more visual indicator, such as one or more light emitting diode. The one or more visual indicator may be configured to provide a different visual indication dependent on the at least one state of the device being indicated. For example, the one or more visual indicator may be illuminated in a different colour, dependent on the at least one state of the device being indicated.

[0131] The status indicator arrangement may comprise a plurality of indicators. The plurality of indicators may be configured to indicate a level or extent of completion of an operation associated with the device. In particular, the amount of the plurality of indicators that are activated may be indicative of the level or extent of completion of an operation associated with the device. For example, the amount of the plurality of indicators that are activated may be indicative of the level or extent of completion of priming of the device. Similarly, the amount of the plurality of indicators that are activated may be indicative of the level or volume of pain- relieving and / or sedative substance remaining in the device.

[0132] The plurality of indicators may be arranged in a formation. The formation may be a loop. The loop may be circular or otherwise. The portion of the formation that is activated may be indicative of a level or extent of completion of an operation associated with the device. In particular, the size of the portion of the formation that is activated may be indicative of the level or extent of completion of an operation associated with the device. For example, the size of the portion that is activated may be indicative of the level or extent of completion of priming of the device. Similarly, the size of the portion that is activated may be indicative of the level or volume of pain-relieving and / or sedative substance remaining in the device.

[0133] The device may further comprise an input arrangement for actuation by the patient. The device may further comprise a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient.

[0134] The method may further comprise transmitting an output signal to the delivery arrangement to control or adjust the delivery of the pain-relieving and / or sedative substance. The output signal may be dependent on the determined at least one state of the device.

[0135] Any of the features described in relation to each of the individual aspects of the invention may be applicable to other aspects of the invention. In particular, where different features of the control algorithm are described in relation to each of the individual aspects of the invention, any combination, or all, of those features may be combined to form a single control algorithm. According to a further aspect of the invention there is provided a device for providing pain relief and / or sedation to a patient, the device comprising at least one processor configured to perform the above-described method steps.

[0136] According to a further aspect of the invention there is provided a data carrier or data storage medium comprising machine readable instructions for the control of one or more processor to perform the above-described method steps.

[0137] According to further aspects of the invention there is provided one or more processors comprising machine readable instructions for performing or controlling any, any combination of, or all of the aforementioned method steps. According to further aspects of the invention there is provided a data carrier or data storage medium comprising machine readable instructions for controlling one or more processor to perform said step(s).

[0138] Practicable embodiments of the invention are described in further detail below with reference to the accompanying drawings, of which:

[0139] Figure 1 shows a perspective view of a pain management system;

[0140] Figure 2 shows a front view of a facemask from the system of Figure 1 ;

[0141] Figure 3 shows a perspective view of the facemask of Figure 2;

[0142] Figure 4 shows an exploded view of the facemask of Figures 2 and 3;

[0143] Figures 5a to 5c show part of an assembly sequence for the facemask of Figures 2 and 3;

[0144] Figure 6 is a part perspective view of the partly assembled facemask of Figures 2 and 3; Figure 7 is a cross-sectional view thorough a delivery chamber of the facemask of Figures 2 and 3;

[0145] Figure 8 is perspective view of an air / gas inlet component from the facemask of Figures 2 and 3;

[0146] Figure 9 is perspective view from the top of the partially assembled facemask of Figures 2 and 3;

[0147] Figure 10 is a cross-sectional view of the facemask of Figures 2 and 3;

[0148] Figure 11 shows an exploded view of a filter cartridge from the facemask of Figures 2 and 3;

[0149] Figure 12 shows a perspective view of a handset from the system of Figure 1 ;

[0150] Figures 13a and 13b show front and rear exploded views of the handset of Figure 12;

[0151] Figure 14 shows a horizontal cross-sectional view of the handset of Figure 8, viewed from above;

[0152] Figures 15a and 15b show front and rear perspective views of a spring used in the handset of Figure 8;

[0153] Figure 16 shows a rear perspective view of the handset of Figure 8, with the hinged lid in an open position;

[0154] Figures 17a and 17b show an expandable reservoir and medicament bottle for use in conjunction with the pain management system of the invention;

[0155] Figures 18a, 18b and 18c show the connection between the expandable reservoir and medicament bottle of Figures 17a and 17b, Figures 18b and 18c showing a cross-sectional view of the expandable reservoir and medicament bottle during (18c) and after (18b) connection;

[0156] Figure 19 shows the barrel and plunger which form the component parts of an expandable reservoir for use in conjunction with the pain management system of the invention;

[0157] Figure 20 shows an underside of the handset of Figure 12;

[0158] Figure 21 shows a perspective view of a transmission tube from the system of Figure 1 ;

[0159] Figure 22 shows an exemplary simulation of medicament delivery in use;

[0160] Figure 23 shows an exemplary simulation of medicament delivery in use;

[0161] Figures 24a-24d show a first notification sequence indicated by the mask of Figures 2 and 3 during operation of the pain management system of Figure 1 ;

[0162] Figures 25a-25d show a second notification sequence indicated by the mask of Figures 2 and 3 during operation of the pain management system of Figure 1 ;

[0163] Figures 26a-26d show a third notification sequence indicated by the mask of Figures 2 and 3 during operation of the pain management system of Figure 1 ;

[0164] Figure 1 generally shows a patient-controlled pain relief and / or sedation device 1 . Briefly, the device 1 comprises a facemask 10, to be placed around the nose and mouth of a user, and a handset 301 connected to the facemask 10 by a transmission tube 307. As will be described in detail later, the handset 301 comprises a reservoir of sevoflurane, or other medicament, for use as an analgesic and / or a sedative, and a user input to trigger delivery of the medicament to the facemask 10 via the transmission tube 307. The device 1 provides user-controlled delivery of a medicament for inhalation to manage pain. Numerous design features are provided to address, mitigate, or overcome the concerns and risks associated both with patient-controlled sedation and with the use of inhalational delivery.

[0165] The mask 10 is shown in isolation in Figures 2 and 3, and comprises a shell or body 100 and a compliant / compressible seal 25, formed of elastomeric material, around the periphery of the body 100. The outer shape of the body 100 and design of the seal 25 are generally similar to those described in the applicant’s earlier patent application WO 2022 / 122974. As well as a chin cup 26 and nose engaging portion 27, the seal 25 comprises extended side portions 28 that, in use, extend laterally across the cheeks of the wearer. The seal 25 thus provides a large area to engage with the face, including over the softer skin of the cheeks, and thus improves the quality and reliability of the sealing provided. It has been found that extending the seal 25 laterally across the softer tissue of the cheeks allows an effective seal to be provided with a lower than usual degree of flexibility in the sealing member, at least in these regions. The minimal movement of the cheeks / cheekbones during talking or other jaw movement also helps to ensure that the seal is not compromised.

[0166] The seal 25 shown in Figures 2 and 3 is more curved at the ends of the side portions 28 than that shown in WO 2022 / 122974. This curvature at both sides of the seal 25 has been found to further improve the sealing performance across a wider range of face sizes, making a single mask size more universal.

[0167] Elasticated straps 20 are provided to secure the facemask 10 to a wearer during use. The ends of the elasticated straps 20 are received in tabs 102 extending from the sides of the mask body 100. The tabs 102 provide a frictional engagement with the elasticated straps 20 so that the tension of the elasticated straps 20 can be adjusted in the conventional way. The relatively large mask shell / body 100 supports and stabilises the compliant seal 25 where needed and also provides sufficient space for a centrally positioned delivery chamber 200 and for a pair of large capacity filter cartridges 50, one on either side of the delivery chamber 200. The depth and overall size of the chamber 200 and filter cartridges 50 can best be seen in the perspective view of Figure 3.

[0168] The delivery chamber 200 comprises a chamber housing 202 secured to the mask body 100. A generally tubular air / gas inlet 204 extends forwardly and downward from a lower side of the chamber 200. A pair of diametrically opposed cut-outs 206 are provided at the free end of the inlet 204, allowing connection to a standard T-piece if / when supplementary oxygen needs to be supplied to the mask 10 during use. Behind the inlet 204 can be seen a gas monitoring connector, e.g. an end tidal CO2 monitor connector 104, which is fluidly connected to the interior of the mask 10 through a monitoring port in the lower part of the mask body 100. It should be understood that the connector 104 could also monitor administered drug concentration, and allow peak concentration and end tidal concentration to be measured.

[0169] An outwardly facing display 500 is provided on a front face of the chamber 200 to provide information about operation of the device 1 to an external observer such as a clinician.

[0170] Figure 4 shows an exploded view of the various components that make up the mask 10.

[0171] The exploded view shows that the mask body 100 can be considered to define separate regions. A central region 120 provides the rear part of the delivery chamber 200, and includes a locating boss 208 for the chamber housing 202. A filter cartridge aperture 150 is provided on either side of the central region 120.

[0172] Each filter cartridge 50 is independently insertable into and removable from one of the filter apertures 150 the mask body 100 from the rear or cavity side. This avoids potential tampering or inadvertent disconnection of the filter cartridges 50 from outside the mask 10 during use. A peripheral lip 52 and groove 54 are provided around a rear side of each of the filter cartridges 50. The filter cartridges 50 are received in the mask body 100 with a ‘pop’ fit, with the periphery of each filter aperture 150 engaging with the peripheral groove 54 of a respective cartridge 50. The peripheral lip 52 then abuts an inner surface of the mask body 100 to prevent removal of the cartridges 50 from the front / outside of the mask 10.

[0173] Each filter cartridge 50 comprises an aperture 60 through which a cavity within the cartridge 50 can be supplied with activated carbon granules.

[0174] A circular wall 210 extends outwardly from the central region 120 of the mask body 100, and surrounds an opening through the mask body 100. A vertical bar 212 spans the opening and provides support for a locator pin 214 which extends along the central axis defined by the circular wall 210. A flexible inhalation valve member 216 is received on the locator pin 214, followed by a gauze / pad 218 from which a delivered dose of sevoflurane evaporates and is inhaled in use.

[0175] Figure 4 also shows that the generally tubular air / gas inlet 204 is a separate component from the mask body 100. A generally circular cup 220 is provided at an upper end of the tubular inlet, and is sized to fit over the end of the circular wall 210 to enclose the inhalation valve member 216 and pad 218. A medicament inlet port 222 is provided through the cup 220 so that sevoflurane can be delivered onto the pad 218 on demand.

[0176] Finally, Figure 4 shows a PCB 224 to be mounted in front of the other components within the chamber housing 202. The PCB in the illustrated example comprises a ring 502 of front facing LEDs which form a part of the display 500 visible from the front of the housing 202. Several housing mounting bosses 226 extend forward of the circular wall 210 to support and secure the PCB 224 and chamber housing 202 to the mask body via screw holes 228 provided in the chamber housing 202. For various reasons, it is important that the mask can provide a reliable seal with a patients’ face. As already described, the overall shape and size of the mask body 100 and seal 25 has been found to provide a good level of sealing, but a further consideration is that a single mask should ideally be suitable for a range of different face sizes and / or shapes. It is typically easier to accommodate a range of face sizes and shapes when a mask has a high degree of inherent flexibility, and is thus able to deform and conform to a particular face size and shape. In the present invention, the mask body 100 is required to support several relatively large components / modules, and the required strength and stability of construction is generally incompatible with a desire for a flexible mask body.

[0177] The design of the described mask body 100 in three different sections helps to maintain a reasonable degree of flex in the mask body 100 while still providing suitable support for the delivery chamber 200 and the filter cartridges 50. Separately mounting the filter cartridges 50 and the components making up the delivery chamber 200 ensures that these components do not prevent the mask body 100 from flexing as they would if all mounted together. For example, the mask body 100 can still flex between the component mountings, and this particularly helps to maintain a good degree of lateral flexibility, so that the extended side portions 28 of the seal 25 can maintain contact with the cheeks of a wearer.

[0178] Figures 5a, 5b and 5c show the assembly of the central components within the delivery chamber 200.

[0179] Figure 5a shows the inhalation valve member 216 installed on the locator pin 214 within the circular wall 210. The vertical bar 212 is shown faintly in Figure 5a, but is positioned behind the inhalation valve member 216 as shown. A retaining ring 230 extends inwardly from the circular wall 210 to hold the inhalation valve member 216 in place against the vertical bar. Evenly spaced radial fingers 232 extend inwardly from the retaining ring 230 across the outer face of the inhalation valve member 216. It will be understood that the retaining ring 230 and radial fingers 232 prevent deformation of the inhalation valve member 216 towards the outside of the mask 10, while the single vertical bar 212 still allows deformation and / or deflection of the inhalation valve member 216 to the interior of the mask on inhalation. A one-way valve is therefore provided to allow flow on inhalation but to prevent flow on exhalation.

[0180] A hollow tubular boss 234 is centrally provided above the one-way valve, and provides a passageway into the interior of the mask body.

[0181] Figure 5b shows the pad 218 also assembled on the locator pin 214. The pad 218 is arranged outside and overlying the inhalation valve member 216 retaining ring 230 and radial fingers 232. The pad 218 thus further helps to prevent outward deflection or deformation of the inhalation valve member 216. The retaining ring 230 and radial fingers 232 maintain a small space behind the pad 218 so that the inhalation valve member 216 does not directly abut a surface of the pad and potentially inhibit the evaporation of a medicament. The spacing also helps to avoid the risk of the inhalation valve member 216 sticking to the wet pad 218 once medicament is delivered.

[0182] The installation of the air / gas inlet 204 is shown in Figure 5c. The cup 220 closes the opening provided by the circular wall 210, leaving the medicament inlet port 222 open to receive an end of the transmission tube 307 for delivering sevoflurane or another medicament to the pad 218. A pair of pegs 225 is also provided on the front / outer surface of the cup 220 to help guide and retain the transmission tube 307, as will be described further below.

[0183] It will be understood from Figures 5a-5c that air and / or any supplemental oxygen or other gas can enter only through the air / gas inlet 204 as indicated by arrow 236. Any gas flow must, therefore, pass through the pad 218 and then through the oneway valve to enter the cavity of the mask 10. Directing inhaled air / gas flow through the pad 218 helps to drive evaporation of the medicament, and is more efficient than simply passing a flow over a wicking surface or reservoir. The gauze / pad 218 in the illustrated example is provided as a disc of material 28mm in diameter and 1 ,3mm thick. The pad 218 has a multi-layer construction, specifically comprising five layers of perforated cotton, forming a 'core’ of the pad 218, faced with unperforated cotton on both sides. The perforations in adjacent perforated layers are offset so that the holes in the core do not line up. Testing has shown that it is possible to deliver a 3-4% concentration of sevoflurane from such a pad 218 by delivering 2ml per minute onto a pad in a breathing simulator at 20 breaths per minute and 500ml tidal flow. The evaporation rate has found to be such that a single dose delivered to the pad 218 at the end of an exhalation can fully evaporate during the following inhalation.

[0184] The system and its control architecture are designed to avoid a buildup of sevoflurane within the mask, and specifically to try and ensure that each delivered dose from the handset 301 evaporates from the pad 218 and is inhaled in a single inhalation event. Nonetheless, the capacity of the pad 218 can be selected so that a small amount of additional medicament delivered to the pad 218 can be retained if desired, for example if the demanded flow is greater than the evaporation rate for a short time. Retaining a small amount of additional medicament on / in the pad helps to avoid immediate leaking or pooling of liquid, which could result in inhalation or ingestion in excessive or unsafe concentrations.

[0185] Cotton provides a good level of fluid retention, strong wicking properties for distributing the medicament across the pad 218, and a relatively low resistance to breathing. However, other similar materials could be used with minimal changes to the design. A foam pad or foam core faced with cotton or similar could, for example, be used.

[0186] Figure 6 shows a perspective view of part of the mask 10, from below. The transmission tube 307 is shown entering the mask 10 from below to help minimise the risk of the tube 307 tangling or snagging on other equipment or interfering with movements of a patient or a clinician during use. The tube 307 enters the delivery chamber 200 behind the air / gas inlet 204 and then coils between the pegs 225 and then between the two upper housing mounting bosses 226 and the hollow tubular boss 234 before being received in the medicament inlet port 222. For simplicity, the end of the transmission tube 307 is, in use, received in the medicament inlet port 222 with a friction fit. The tortuous path taken by the transmission tube 307, as shown in Figure 6, provides some additional support and frictional resistance to help avoid inadvertent removal or disconnection from the medicament inlet port 222 during use, for example if a user pulls on the tube 307 or handset 301 .

[0187] The interior of the delivery chamber 200 of the fully assembled mask can be seen in the cross-sectional view of Figure 7. The cross-section shows the arrangement of the inhalation valve member 216 and pad 218, with a space in between, and additionally shows several sections of the transmission tube 307 as it winds through the delivery chamber 200 and is received in the medicament inlet port 222 for delivering a dose of sevoflurane onto the pad 218 on demand. A grate 238 within the air / gas inlet 204 is also shown.

[0188] A pressure monitoring port 134, at the interior end of the hollow tubular boss 234, can also be seen in cross section. The hollow tubular boss 234 provides a fluid passageway from the pressure monitoring port 134 to a pressure sensor 240 mounted on the rear side of the PCB 224, allowing real-time pressure measurements to be taken from within the mask 10, which in turn enables monitoring of the patient’s breathing in use. It would also be possible to use a temperature sensor within the delivery chamber 200, adjacent the pad 218, to monitor breathing, based on the temperature changes resulting from evaporation of the medicament from the pad 218 during use, and this may also assist in determining whether medicament is building up on the pad so that delivery rates can be adjusted.

[0189] Above the pressure sensor 240, also on the rear of the PCB 224, is a rear facing LED 242b for providing stimuli and / or feedback to a wearer of the mask. The visible LED 242b is a central LED of a group of three laterally spaced LEDs, collectively referred to as 242, provided on the rear of the PCB 224. A light guide may also be provided by the material making up an upper part of the mask body 100, for example the mounting boss 208, to direct the light from one or more of the LEDs 242 towards the eyes of the wearer.

[0190] Figure 8 shows a rear view of the air / gas inlet 204 and cup 220. Various features can be seen on the rear of the cup 220, most notably the outlet of the medicament inlet port 222 and a central hole 244 for receiving the end of the locator pin 214. As can be seen from Figure 7, these features contact the outermost face of the pad 218 so that the medicament inlet port 222 opens directly onto the pad 218. This helps to avoid medicament dripping from the port 222 and pooling within the delivery chamber 200 rather than being absorbed by the pad 218. However, it can also be seen from Figure 8 (and from Figure 10 below) that a space / void is provided within the cup 220 to help ensure airflow across the whole diameter of the pad 218. A cutout 207, for receiving the transmission tube 307 as it enters the chamber 200, is also shown in Figure 8.

[0191] Figure 9 shows a perspective view from the top of the assembled mask 10 with the housing cover 202 removed. The view shows part of the internal cavity 110 defined by the mask body. It can also be seen that the gas monitoring connector 104 extends into this cavity 110 to monitor readings from within the mask body 100. The inhalation valve member 216 can also be seen, positioned centrally between the two filter cartridges 50. The three spaced LEDs 242a, 242b and 242c (collectively 242) can also be seen on the rear surface of the PCB 224. It will be understood that the left and right LEDs 242a, 242c are best placed to be seen by a wearer during use. However, all three LEDs 242 may be used to send alerts and / or stimuli to a wearer, with the use of light guides allowing even quite directional light from the central LED 242b to be directed towards the eyes of the user. Alternative embodiments may, therefore, use only two laterally spaced LEDs, or even just a single LED. Using more than one LED allows alternate flashing of separate LEDs or some other ‘pattern flashing’ of a group of LEDs. These more unusual light patterns can be more effective in attracting the attention of a wearer. A complete cross section through the mask 10 is shown in Figure 10. Unlike in Figure 7, the cross-section of Figure 10 is taken off-centre, and shows that an open cavity / void 246 in front of the pad 218 is provided by the cup 220, as discussed above in relation to Figure 8. The majority of a front surface of the pad 218 is open to this cavity 246 to maximise the area that inhaled air / gas can reach to reduce flow resistance and aid with vaporisation of a medicament, particularly at high flow rates. There is a challenging balance for the pad 218 to strike between providing suitable fluid retention / evaporation characteristics and minimising flow resistance, so it is important to ensure as much of the pad as possible remains open to flow.

[0192] The cross-section of Figure 10 also passes through one of the radial fingers 232 that maintains a spacing between the pad 218 and inhalation valve member 216 as previously described, and through the rightmost rear facing LED 242c.

[0193] The rear surface of one of the filter cartridges 50 can also be seen in Figure 10, with the peripheral lip 52 abutting an internal wall 106 of the mask body 100. An opening 56 in the rear of the filter cartridge 50 provides a one-way exhalation valve. The mask 10 therefore provides a flow path whereby all inhaled air / gas passes through the pad 218 and the one-way inhalation valve, and all exhaled air and other substances from within the cavity 110 exit the mask 10 through the filter cartridges 50.

[0194] One factor potentially preventing or limiting the wider adoption of inhalational analgesics and / or sedatives is the risk of contamination of the atmosphere in an operating theatre. Gases or vapours from volatile liquids that are either not inhaled or remain in a patients exhaled air can, if not controlled, quickly build up in a confined space and be detrimental to clinicians or others in the space. Any breathing mask used in the administration of such substances should, therefore, mitigate these risks by providing a robust / reliable seal (as described above) and through effective / efficient filtration of excess and / or exhaled substances. The large filter cartridges 50 provided on the mask body help to ensure that the filtering of exhaled gases and / or vapours is sufficient to avoid a build-up. The construction of each filter cartridge 50 is shown in the exploded view of Figure 11 .

[0195] The filter cartridges 50 comprise a front casing 58, which defines a cavity to receive the activated carbon, and a rear casing 64 to close the cavity. The rear casing 64 comprises the opening 56 which, together with an exhalation valve member 66, forms the one-way exhalation valve. A first hydrophobic scrim 68 is provided on a scrim support 70 located between the front casing 58 and the exhalation valve member 66. A second hydrophobic scrim 74 is provided inside the front casing across the exhaust openings 76 in the front of the front casing 58. The first and second hydrophobic scrims 74,76 in the illustrated example are formed from polypropylene.

[0196] Activated carbon is a preferred filter medium in many applications due to its low weight and efficient performance. However, it is typically avoided in moist environments because the adsorbent properties of the material tend to absorb moisture first, leading to reduced capacity or even saturation of the filter. The first and second hydrophobic scrims 74,76 prevent moisture ingress into the cavity of the filter cartridge, ensuring that the filtering remains effective and thus allowing the use of activated carbon to filter moist exhaled air. The scrim support 70 additionally helps to secure the exhalation valve member 66 in place within the filter cartridge 50.

[0197] When assembled, the components provide a filter cartridge 50 with a contained internal volume to receive the activated carbon. A cover 62 is provided to close the aperture 60, which is in a wall of the front casing 58 that is obscured from view in Figure 11 . this means that the cartridge 50 is potentially refillable / rechargeable. As an alternative, the filter cartridge may be made completely disposable. Various sizes of cartridge, either re-fillable or disposable, may be provided to account for different volumes of sevoflurane stored in the handset. The rear casing 64 comprises the peripheral lip 52, around the rear of the filter cartridge 50, that engages with an internal wall 106 of the mask body 100 as the filter cartridges 50 are inserted from the cavity 110 side. The rear casing 64 also defines the base of the groove 54 that provides the ‘pop’ fit with the filter aperture 150.

[0198] The capacity or fill level of the filter cartridges 50 may be defined by or selected based on the volume of medicament contained in the handset 301 prior to use. That is, the capacity of the filter cartridges 50 may be specifically selected so that they provide sufficient filtering for the entire volume of sevoflurane available for use during a particular procedure. As will be explained below, the volume of medicament held in handset is set prior to use of the device, and cannot then be adjusted, i.e. the reservoir cannot be refilled once the device is in use. A particular filter volume can thus be selected based on the intended use of the device with confidence that the filter capacity will be sufficient.

[0199] The handset 301 of the device 1 is shown in Figure 12. The handset 301 comprises a housing having a wrist portion 302 and an end portion 303. The end portion 303 is rounded, with a bulbous shape which fits comfortably within the user’s hand. The wrist portion 302 extends outwardly from the end portion 303, the wrist and end portions 302,303 being joined together by a concave curved surface on an upper side of the housing, and by a substantially planar surface on the underside of the housing.

[0200] The construction and overall structure of the handset can be seen in Figures 13a and 13b. The underside of the housing comprises a cradle 409 which forms the underside of both the wrist and end portions 302, 303, and the lower part of the front face of the end portion 303. The cradle 409 comprises mounting bosses 413 which extend upwardly from the cradle, and the lower part of the front face comprises a substantially semi-ovular cut-out 415 with a recessed wall 416 positioned behind. The cradle 409 further comprises loops 314, 315 and slots for the receipt of the straps 305, 306, as described in further detail in relation to Figure 20. The cradle 409 receives and engages with a central section 410, the central section 410 comprising the side walls 412 of the handset between which are retained the battery and reservoir compartments 309, 310, guide member 407, horizontal bar 417, activation switch 406 and peristaltic pump 334. The transmission tube 307 is fluidly connected to the peristaltic pump 334 and extends from the rear of the handset 301 , and, as described above, is connected to the delivery chamber 200 of the facemask 10. These features are discussed in further detail below.

[0201] The upper side of the housing is formed of two components: a domed lid 411 and a hinged lid 308. The domed lid 411 forms the upper side, and the upper part of the front face, of the end portion 303. Similarly to the cradle, the upper part of the front face of the domed lid 411 comprises a substantially semi-ovular cut-out 418 with a recessed wall 419 positioned behind. The domed lid 411 engages with the mounting bosses 413 which support and secure the domed lid 411 to the cradle 409, covering the peristaltic pump 334, guide member 407, horizontal bar 417 and activation switch 406 within the central section 410, but leaving the battery and reservoir compartments 409, 410 exposed.

[0202] The hinged lid 308, which forms the upper surface of the wrist portion 302, is hingedly attached to the domed lid 411 and, when closed, covers the battery and reservoir compartments 309, 310 as described in further detail in relation to Figure 16 below.

[0203] The handset 301 further comprises a button 304 and a spring 403, which together form the user input.

[0204] The button 304 is located on a front face of the end portion 303 of the handset 301. It is retained between the semi-ovular cut-outs 415, 418 of the cradle 409 and domed lid 411. The button 304 is substantially oval in shape, and extends over a significant portion of the front face of the rounded end portion 303, providing a large surface area for the user to press. The button 304 has a convex form, and its shape follows the contours of the bulbous end portion 303 of the handset 301 . In use, the user’s palm lies across and over the domed lid 411 such that their fingers rest on the button 304 on the front face of the end portion 303, while their wrist rests on the hinged lid 308, which forms the upper surface of the wrist portion 302.

[0205] The button 304 is a floating button which can be pressed from almost any angle, increasing usability for patients with restricted movement. The button 304 comprises a domed surface 401 with an integrally formed central column 402, the central column 402 extending rearwardly from the concave face of the domed surface 401. A rearwardly extending wall 423 extends outwardly from the periphery of the concave face of the domed surface 401 , the rearwardly extending wall 423 further comprising four tabs 424 spaced at regular intervals about its outer circumference. In use, the convex face of the domed surface 401 is pressed by the user to activate the device. A spring 403, comprising an arcuate resilient strip 404, is mounted within the handset and positioned behind the concave face of the domed surface 401 , such that the end of the central column 402 distal to the domed surface 401 contacts the resilient strip 404, and the spring 403 is orientated such that the resilient strip 404 is biased towards the central column 402.

[0206] The spring 403 is shown in isolation in Figures 15a and 15b, and comprises an arcuate resilient strip 404 retained within a rectangular mount 408. Within the central section 410 of the handset a horizontal bar 417 extends between the sidewalls 412, with a guide member 407 depending from a central point on the horizontal bar 417 and extending outwardly towards the front of the handset 301 . When installed in the handset, the rectangular mount 408 of the spring abuts the horizontal bar 417, locating the spring 403 in the correct position. A hollow post 405 extends rearwardly from the centre of the resilient strip 403 and receives the guide member 407, the hollow post being movable longitudinally along the guide member 407. The end of the hollow post 405 distal to the resilient strip 404 is positioned adjacent to or in contact with an activation switch 406, such that longitudinal movement of the hollow post 405 along the guide member 407 causes the activation switch 406 to be pressed.

[0207] The spring 403 is mounted within the handset behind the button 304, such that the end of the central column 402 distal to the domed surface 401 contacts the spring. When pressure is applied to the domed surface 401 of the button 304 by the user, pushing it towards the spring 403 and pushing the rearwardly extending wall 423 into abutment with the recessed walls 416, 419 on the cradle 409 and domed lid 411 , the central column 402 exerts a force on the spring, pushing against the bias of the resilient strip 404. This force causes the resilient strip 404 to deform and consequently move the post 405 longitudinally along the guide member 407, pressing the activation switch 406 and thereby registering a user input. When the pressure on the button 304 is released the resilient strip 404 returns to its original arcuate shape, pushing the central column 402 and domed surface 401 back into their original positions such that the tabs 424 engage with the internal periphery of the semi ovular cut-outs on the dome and cradle 415, 418, retaining the button 304 within the handset. This moves the post 405 out of engagement with and hence releases the activation switch 406. Engagement of the tabs 424 with the internal periphery of the semi ovular cut-outs 415, 418 also creates pivot points about the edge of the button 304 such that, if pressure is only applied to one edge of the button 304 by the user, the button 304 will pivot about the tab or tabs 424 adjacent to an opposing edge of the button. This causes the centre of the button and hence the central column 402 to move towards the spring, ensuring that pressure is still applied to the resilient strip 404 by the central column 402 regardless of the angle or position from which the button is pressed.

[0208] Referring back to Figure 12, the handset 301 further comprises straps 305, 306 for attaching the handset 301 to the user’s arm and / or wrist. The straps 305, 306 extend from a first side of the handset to a second side of the handset, forming a loop for retaining the patient’s arm and / or wrist. The straps 305, 306 are adjustable, and can be adjusted to fit the patient’s arm and prevent undue movement of the handset relative to the patient’s arm, even if the patient’s arm moves or falls. The attachment of the straps 305, 306 to the handset 301 is described in further detail in relation to Figure 20.

[0209] The wrist portion 302 of the handset comprises an openable housing, as shown in Figure 16. The openable housing comprises a hinged lid 308 which opens to reveal a battery compartment 309 and reservoir compartment 310 (batteries and reservoir not shown). The reservoir compartment 310 comprises a channel 328 for receiving an expandable reservoir filled with a pain-relieving and / or sedative substance, and an aperture 329 shaped to receive a connecting portion of the reservoir. The aperture 329 is broadly circular, and further comprises a laterally extending cut-out 311 shaped to receive a flange 330 which extends outwardly from the reservoir, as will be described in more detail later. Once inserted through the aperture 329, the reservoir 322 is engaged by a reservoir receiver (not shown), the reservoir receiver being connected to the inlet of the tube 335 of a peristaltic pump 334 housed within the end portion 303 as shown in Figure 13a. A peristaltic pump 334 has a fixed displacement and so, when in operation, the pump draws fixed aliquots of medication from the reservoir 322, transferring it to the transmission tube 307.

[0210] Two buttons 312, 313 are also located within the housing, proximate to the hinge of the hinged lid 308. The two buttons 312, 313 may be used to adjust parameters for correct operation of the device, for example to adjust the dosage and / or to set the dose profile of the medicament. Also visible are loops 314, 315, integrally formed with the body of the handset 301 , which provide retention means for the straps 305,306 (not shown in Figure 16). The transmission tube 307 is clearly shown extending from the rear of the handset 301 .

[0211] Figure 17a shows an expandable reservoir 322 for use with the handset 301 of the invention.

[0212] The expandable reservoir 322 comprises a barrel 325 having a proximal end and a distal end, and a plunger 326, the plunger 326 being inserted into the barrel 325 at the distal end and being slidable longitudinally within the barrel 325. The proximal end of the barrel 325 comprises a connection formation 323 to enable the syringe to be connected to a proprietary adaptor 324 on a medicament bottle, as shown in Figure 17b. The connection formation 323 additionally forms the connecting portion which forms a fluid connection between the reservoir and the handset 301 , as described above.

[0213] The connection formation 323 enables a secure connection between the proximal end of the barrel 325 and a proprietary adaptor 324 on the medicament bottle , while permitting the transfer of a pain-relieving and / or sedative substance between the bottle and reservoir 322. The connection formation 323 comprises two concentric rings 331 , 332 which extend outwardly from the proximal end of the barrel 325. The outer ring 331 extends outwardly from the periphery of the proximal end of the barrel 325 and forms a friction fit with the proprietary adaptor 324, creating a fluid-tight seal. The wall of the outer ring 331 comprises two cutout sections 420 to engage with corresponding formations 421 on the proprietary adaptor 324. The inner ring 332 is shorter than the outer ring 331 and comprises cut-out sections 333, such that at least an upper section of the inner ring 332 is broken into three segments. In use, the inner ring 332 presses on the spigot 422 of the adaptor 324, breaking the seal and allowing medicament to flow out of the bottle. The cut-out sections 333 provide spaces through which the medicament can flow to the centre of the connection formation and through a channel 424 which extends through the inner ring 332 and into the barrel 325.

[0214] The reservoir 322 is filled with a predetermined amount of a pain-relieving and / or sedative substance prior to insertion in the handset 301 . Prior to filling the reservoir 322, the plunger 326 is depressed. Once the reservoir 322 is attached to the proprietary adaptor 324 on the medicament bottle, the reservoir 322 and bottle 324 are inverted and the plunger 326 drawn out (as shown in Figure 18a, and in cross-section in Figures 18b and 18c), thus creating a vacuum which sucks the medicament into the reservoir 322. The outer ring prevents loss of medicament to the atmosphere during this process. The connection formation 323 prevents the reservoir from being connected to any vessel which does not carry the proprietary connector 324, thus ensuring that the syringe can only be filled with the medicament for which the device and its safety mechanisms have been designed.

[0215] The plunger 326 comprises a narrowed section forming a defined point of weakness 327, which can be seen in Figure 19. The point of weakness 327 is positioned such that, when the plunger 326 has been drawn out to fill the barrel 325 with the correct dosage of medicament, the point of weakness 327 is located at or just above the distal end of the barrel 325. Once the expandable reservoir 322 has been filled with medicament, the plunger 326 is snapped off at the point of weakness 327. Snapping off a portion of the plunger 326 in this manner prevents the reservoir from being refilled and reused. The requirement to snap off the plunger 326 is enforced as the reservoir compartment 310 in the handset 301 is sized such that a full reservoir 322 will only fit into the syringe compartment 310 when the plunger 326 has been snapped off.

[0216] The barrel 325 further comprises a flange 330 protruding from a side close to or at its proximal end. The flange 330 extends outwardly from, and extends a short distance longitudinally along, the outer ring 331 of the connection formation 323, as shown in Figure 19. When the full reservoir 322 is inserted into the reservoir compartment 310 on the handset 301 , the connection formation 323 and flange 330 on the barrel 325 pass through the aperture 329 and associated laterally extending cut-out 311 . When correctly inserted, the flange 330 engages with a micro-switch (not shown) within the aperture 329. Actuation of the micro-switch confirms that the reservoir 322 has been correctly loaded into the handset 301 , and activates the device 1 .

[0217] The underside of the handset 301 is shown in Figure 20. The underside of the handset 301 comprises a window 316 in a position corresponding to the position of the reservoir compartment 310 in the interior of the handset 301 , such that the reservoir 322 is visible through the window 316. This enables the level of medicament remaining within the reservoir 322 to be monitored while the device is in use.

[0218] Also visible are two loops 314, 315 and two slots 317, 318 for attachment of the straps 305, 306, the straps being used to secure the handset 301 to the user’s wrist and hand and prevent dislodgement or dropping during use. Strap 305 passes from the interior of the handset 301 , where it is secured, and through the slot 318 to the exterior of the handset. The strap 305 then passes over the upper side of the handset and through the corresponding loop 315. The tension of the strap is adjusted by altering the amount of the strap 305 which is pulled through the loop 315. The free end of the strap 305 (that which has passed through the loop 315) may comprise a buckle, toggle, cleat or other adjustable locking means (not shown) to prevent the strap from sliding back through the loop 315 and permit future adjustment. The second strap 306 is attached to the second slot 317 and loop 314 in the same manner.

[0219] The transmission tube 307 (shown in further detail in Figure 21 ) extends from the rear of the handset 301 and, as described above, is connected to the delivery chamber 200 of the facemask 10, operationally connecting the handset 301 and facemask 10.

[0220] The transmission tube 307 comprises a tube having a silicone body, and having first and second lumens 319, 320 extending longitudinally through the tube. The first lumen 319 has a diameter of approximately 2.5mm and carries electrical wires 321 , electronically connecting the mask 10 and the handset 301 . The second lumen 320 has a narrower diameter than the first lumen 319, of approximately 1 mm, and carries the medicament from the handset 301 to the mask 10, where it is evaporated for inhalation by the user as previously described.

[0221] The transmission tube 307 enters the rear of the handset 301 . Inside the handset 301 , the second lumen 320 of the tube is connected to the tube of the peristaltic pump 334 at its outlet. As previously described, the reservoir 322 is fluidly connected to the tube of the peristaltic pump at its inlet 335. Thus, when the pump 334 is in operation, predetermined aliquots of medication are drawn from the expandable reservoir 322, through the peristaltic pump 334, and pass into the second lumen 320 of the transmission tube 307 to be carried to the facemask 10.

[0222] In use, delivery of the medicament from the handset 310 to the facemask 10 is controlled by a control algorithm that is carried out by a controller. The control algorithm consists of a number of components that in combination determine an output signal that controls the delivery rate of the medicament. Although described individually below, each of the algorithm components runs simultaneously, each influencing the output signal that controls the delivery rate of the medicament.

[0223] Breath detection

[0224] A breath detection component of the algorithm is initiated upon turning on of the device 1 . At regular intervals of approximately 10 milliseconds, the controller requests an input signal from the pressure sensor 240 that is indicative of a realtime pressure within the mask 10. Since fluctuations in the pressure within the mask 10 are indicative of a patient’s breathing, the controller is able to sense, from the input signal, whether the mask is being worn by a patient.

[0225] Before commencing delivery of the medicament from the handset 301 to the facemask 10, if patient breathing is detected, then delivery of the medicament to the pad 218 is enabled. If patient breathing is not detected, then delivery of the medicament to the pad 218 is disabled. This ensures that medicament is not delivered to the pad 218 when the facemask 10 is not being worn, reducing waste and preventing buildup of medicament on the pad 218, which could otherwise lead to overdose should the mask be temporarily removed and repositioned on the patient after such buildup.

[0226] During delivery of the medicament from the handset 301 to the facemask 10, if patient breathing is detected, then delivery of the medicament is allowed to continue. If patient breathing is no longer detected, then delivery of medicament is ceased immediately. This enables detection of the mask having been removed, ensuring that medicament is not delivered to the facemask 10 when not being worn, reducing waste and preventing exposure of the medicament to the ambient environment, as well as preventing buildup of medicament on the pad 218, which could otherwise lead to overdose should the mask be temporarily removed and repositioned on the patient after such buildup.

[0227] Fluctuations in the pressure within the mask 10 are also indicative of the patient’s breathing cycle, i.e. when they are in an inhalation phase and when they are in an exhalation phase. In particular, a drop in pressure within the facemask 10 is indicative of the patient breathing in, and an increase in pressure within the facemask 10 is indicative of the patient breathing out.

[0228] By receiving regular input signals from the pressure sensor 240, the controller is therefore able to determine when the patient is inhaling, and when the patient is exhaling. In some embodiments, this may enable the controller to control the timing of the pump to deliver medicament to the pad 218 of the facemask 10, such that the medicament is available for inhalation from the pad 218 when the patient next inhales.

[0229] The medicament delivery can also be controlled to provide a single dose size suitable for a single inhalation event. This individual dose size can be pre-set based on established clinical data, or can be tuned for a specific case (for example based on the age, size, weight, and / or lung capacity of a patient).

[0230] Determination of delivery rate

[0231] A continuous delivery component of the algorithm calculates a continuous medicament delivery rate based at least in part on a patient input received via button 304. The continuous delivery component and the continuous medicament delivery rate may otherwise be referred to as a low response component and a low response medicament delivery rate. A rapid delivery component of the algorithm calculates a rapid medicament delivery rate based at least in part on a patient input received via button 304. The rapid delivery component and the rapid medicament delivery rate may otherwise be referred to as a high response component and a high response medicament delivery rate. These components of the algorithm run simultaneously to provide a combined output delivery rate that is based at least in part on the same patient input received via button 304.

[0232] Figure 22 illustrates the response of these components of the algorithm to various patient inputs received during medicament delivery.

[0233] In this example, the controller compares the continuous delivery component and the rapid delivery component, and the output delivery rate is equivalent to the higher of the two components. Hence, the output delivery rate is not plotted in Figure 22. Where the continuous delivery component is higher than the rapid delivery component, the device is described herein as delivering medicament in a continuous mode. Where the rapid delivery component is higher than the continuous delivery component, the device is described herein as delivering medicament in a rapid mode.

[0234] The graph of Figure 22 is split into four phases 900, 910, 920, 930 for illustrative purposes and ease of description. In reality, the graph represents an ongoing simulation of these components of the algorithm for a given scenario.

[0235] At the start of phase 900, medicament delivery is yet to commence, as the button 304 has not been pressed by the patient. Around halfway through phase 900, the patient first presses button 304, initiating medicament delivery. In response to the patient pressing button 304, the controller sends a signal to the rear facing LED(s) 242 to flash, thereby confirming to the patient that the button press has been successful and registered by the device 1 .

[0236] At this early stage of medicament delivery, both the continuous delivery component and the rapid delivery component experience a small increase, by the same amount, i.e. with a step-like rise, and the output delivery rate is therefore equal to both components, and deemed to be in the continuous mode. In the second half of phase 900, the patient presses button 304 a further four times, as can be seen by the four incremental step increases in both the continuous delivery component and the rapid delivery component. The increases in the rapid delivery component are much larger than those in the continuous delivery component at this early stage of requesting pain relief and / or sedation, to rapidly respond to the patient’s needs.

[0237] The step increase in the rapid delivery component is dependent on the value of the rapid delivery component at the time of the button press. In particular, each press of the button 304 increases the rapid delivery component by a fraction or percentage of the difference between the instantaneous value of the rapid delivery component and a maximum delivery rate. The maximum delivery rate may be a maximum delivery rate permitted of the pump, or a preset maximum delivery rate that is dependent on the patient, for example based on their weight. Hence, where the rapid delivery component is higher, the step increase is lower, and where the rapid delivery component is lower, the step increase is higher.

[0238] In contrast, the step increases in the continuous delivery component are equal for each press of the button 304, irrespective of the value of the continuous delivery component at the time of the press. For example, each press of the button 304 may increase the continuous delivery component by 0.2ml / min, up to a predetermined maximum threshold.

[0239] These four presses of the button 304 in a short time period cause the rapid delivery component to increase at a much quicker rate than the continuous delivery component, and thus the output delivery rate is governed by the rapid delivery component throughout the remainder of phase 900, and the pump is operating in the rapid mode.

[0240] In phase 910 of Figure 22, the patient does not press the button 304, and the rapid delivery component decreases towards the continuous delivery component. In turn, the output delivery rate also decreases in the same way, still being governed by the rapid delivery component, because the rapid delivery component remains higher than the continuous delivery component.

[0241] The continuous delivery component also decreases, but at a much slower rate such that the decrease is imperceptible in phase 910 of Figure 22. In this embodiment, the rate of decrease of the continuous delivery component is a predetermined constant rate of decrease throughout delivery of the medicament.

[0242] However, in alternative embodiments, it is envisaged that the rate of decrease could be variable, for example dependent on the instantaneous rate of delivery, or the rate of delivery at the last press of the button 304.

[0243] In this example, because the rapid delivery component is still higher than the continuous delivery component, and thus the pump is operating in the rapid mode, the continuous delivery component continuously decreases throughout the absence of a button press by the patient. However, if the rapid delivery component were to decrease enough to become lower than the continuous delivery component, and the pump began to operate in the continuous mode, then the continuous delivery component would vary as described in relation to the breath detection component of the algorithm and Figure 23 below.

[0244] In phase 920 of Figure 22, the process described in relation to phases 900 and 910 is repeated a plurality of times. Each time the patient presses button 304, the continuous delivery component experiences a step increase by the fixed amount, and the rapid delivery component experiences a step increase that is typically larger than the step increase in the continuous delivery component, but varies dependent on the value of the rapid delivery component at the time of the button press.

[0245] In the absence of the patient pressing the button 304, the rapid delivery component decreases in the same way as in phase 910, and the continuous delivery component decreases at a constant rate, as described above. It can be seen from phase 920 of Figure 22 that the rate of the decrease in the rapid delivery component is different for each of the button presses. This rate of decrease in the rapid delivery component is dependent on the time that has passed since the button was last pressed. Specifically, the longer it has been since the button 304 was last pressed, the quicker the rate of decrease in the rapid delivery component. This protects the patient from prolonged exposure to higher doses of medicament when unnecessary for pain relief and / or sedation.

[0246] Throughout phase 920, because the rapid delivery component remains higher than the continuous delivery component throughout, the pump continues to operate in the rapid mode. Although the pump is operating in the rapid mode, the algorithm continues to calculate and monitor the continuous delivery component, as can be seen by the continued increases in the continuous delivery component throughout phase 920, in response to the patient pressing button 304.

[0247] At the start of phase 930 of Figure 22, a dosage monitoring component of the algorithm determines that the continuous delivery component has reached a predetermined threshold. The dosage monitoring component of the algorithm operates by continuously monitoring the continuous delivery component against said predetermined threshold, and intervening when the continuous delivery component reaches said predetermined threshold, by decreasing the rapid delivery component. In alternative embodiments, the dosage monitoring component may additionally or alternatively continuously monitor the time the device has spent in the rapid mode against a predetermined threshold, and intervening when the cumulative time the device has spent in the rapid mode reaches said predetermined threshold, by decreasing the rapid delivery component.

[0248] Once the dosage monitoring component of the algorithm determines that the continuous delivery component has reached a predetermined threshold, the rapid delivery component is disabled such that further presses of the button 304 do not cause an increase in the rapid delivery component. Hence, although the patient continues to press the button 304 between 24 and 30 seconds, the rapid delivery component decreases towards the continuous delivery component. In this embodiment, in response to the dosage monitoring component reducing the rapid delivery component, the rapid delivery component decreases at a rate that is slower than the rate of decrease in the rapid delivery component during normal operation of the device 1 in the rapid mode. However, it is envisaged that in alternative embodiments, the rate of decrease may be similar to, or faster than, the rate of decrease in the rapid delivery component during normal operation of the device 1 in the rapid mode.

[0249] At the end of phase 930, the rapid delivery component decreases to a level that is below the continuous delivery component, and at this point the pump begins to operate in the continuous mode, i.e. the output delivery rate becomes governed by the continuous delivery component.

[0250] This transition from the rapid mode into the continuous mode is illustrated in Figure 23, which illustrates the transition from phase 930 of Figure 22 into phase 935. Phase 935 represents medicament delivery in the continuous mode, where the continuous delivery component is greater than the rapid delivery component, and the output delivery rate is therefore equivalent to the continuous delivery component. Hence, the continuous delivery rate is not plotted in phase 935 of Figure 23. Phase 935 is described in greater detail in relation to consciousness checks below.

[0251] Once the device 1 has been forced out of operating in the rapid mode, the device 1 remains locked out of operating in the rapid mode until the continuous delivery component decreases below the predetermined threshold again, or in the alternative embodiment described above, until the cumulative time spent in the rapid mode by the device 1 decreases below the predetermined threshold.

[0252] In the meantime, whilst operating in the continuous mode, continued presses of the button 304 would cause the continuous delivery component to increase by the fixed step increase, until the continuous delivery component reaches a predetermined maximum, or maintain the continuous delivery component at the predetermined maximum if presses of the button 304 are frequent.

[0253] In one particular embodiment, in order to indicate a demand for medicament delivery, the patient is instructed to press and hold the button 304 down. In order to register the demand, the button 304 must be depressed for longer than a predetermined interval, e.g. 0.5 seconds. If one or more presses occur that result in the button 304 being depressed for less than 0.5 seconds, then the demand is not registered. Similarly, whilst the button 304 is not depressed, it is assumed that there is no demand for medicament delivery. In this embodiment, the pressing and holding of button 304 over time provides the equivalent functionality to the frequent pressing of button 304 in the previously described embodiment.

[0254] With this arrangement, whilst the button 304 is being held down, the continuous delivery component and the rapid delivery component are increased in the same way as described above, except that rather than providing incremental increases to those components every time the button 304 is pressed, increases to those components are effected periodically throughout the duration of the button 304 being held down.

[0255] Consciousness checks

[0256] A consciousness component of the algorithm monitors the consciousness of the patient during operation of the pump. Although in Figure 23, consciousness checks are only illustrated in relation to the continuous mode of delivery, it is also anticipated that consciousness checks could be carried out in the rapid mode.

[0257] When carrying out consciousness checks, the controller regularly performs a consciousness check by sending output signals to illuminate the rear facing LED(s) 242, e.g. with a single flash or multiple flashes, or flashing patterns using the three spaced LEDs 242a, 242b and 242c, which indicates to the patient to confirm that they remain conscious, by pressing the button 304. In relation to consciousness checks, where the device requires the patient to press and hold button 304 down for longer than a predetermined interval in order to indicate a demand for medicament delivery, to successfully register a response to the consciousness check (and therefore pass the consciousness check), if the button 304 is currently not being held down, a single press is required to indicate consciousness, i.e. the button 304 does not need to be continually held, just pressed. If the button 304 is already being held down at the time of the consciousness check, i.e. because the patient is requesting increased medicament delivery, then the patient must first let go of the button 304, and then press the button 304. If the patient simply continues to hold button 304 down, then the check is failed. This prevents the patient accidentally passing the consciousness check because they are requesting medicament delivery. This functionality of button 304 enables the same patient input to be simultaneously used for demand of medicament delivery and response to consciousness checks.

[0258] In response to the patient successfully responding to the consciousness check, the controller sends a signal to the rear facing LED(s) 242 to flash, thereby confirming to the patient that the button press has been successful and registered by the device 1 .

[0259] Once the LED(s) 242 has / have been illuminated, the controller monitors the time taken for the patient to respond to the consciousness check. The controller then compares the patient response time with a predetermined threshold response time to determine whether the patient is conscious enough. Typically, it is deemed that if the patient responds within 0.8 seconds, then they are deemed to be conscious enough.

[0260] If the patient response time is less than the threshold response time, then delivery of the medicament continues, and a further consciousness check is conducted in due course. If the patient response time is longer than the threshold response time, then the controller determines that the consciousness check has been failed, and that the patient has become too sedated. In response to the patient failing a primary consciousness check, delivery of the medicament continues, but the patient is no longer able to demand increased delivery, i.e. by further unprompted pressing of button 304. Following failure of the primary consciousness check, a secondary consciousness check is performed in the same way as the primary consciousness check, for example 10 seconds after the failed primary consciousness check, with a more noticeable illumination of the rear facing LED(s) 242, such as a flashing pattern that may be brighter or quicker than previous illuminations.

[0261] Again, the controller monitors the time taken for the patient to respond by pressing the button 304, and if the patient response time is within 0.8 seconds, the patient is deemed to be conscious enough. As a result, the demand functionality of the button 304 is re-enabled, and the output delivery rate is restored to a percentage, e.g. 70%, of that being delivered prior to the failed primary consciousness check.

[0262] In response to passing a secondary consciousness check, the controller returns to performing primary consciousness checks at predetermined time intervals, or time intervals that are dependent on the current medicament delivery rate. This ensures that delivery does not cease where the patient has simply missed the response to a primary consciousness check by accident. In alternative embodiments, the secondary consciousness check may be performed at the same predetermined time interval as the primary consciousness checks.

[0263] In response to failing a secondary consciousness check, delivery of the medicament continues, but the patient remains unable to demand increased delivery. Following failure of the secondary consciousness check, a tertiary consciousness check is performed, for example 5 seconds after the failed secondary consciousness check, again with a more noticeable illumination of the rear facing LED(s) 242.

[0264] Again, the controller monitors the time taken for the patient to respond by pressing the button 304, and if the patient response time is within 0.8 seconds, the patient is deemed to be conscious enough. As a result, the demand functionality of the button 304 is re-enabled, and the output delivery rate is restored to a percentage, e.g. 70%, of that being delivered prior to the failed primary consciousness check.

[0265] In response to passing a tertiary consciousness check, the controller returns to performing primary consciousness checks at predetermined time intervals. This ensures that delivery does not cease where the patient has simply missed the response to primary and secondary consciousness checks by accident. In alternative embodiments, the tertiary consciousness check may be performed at the same predetermined time interval as the primary consciousness checks.

[0266] In response to failing a tertiary consciousness check, delivery of the medicament ceases completely, and a zero-delivery consciousness check regime is initiated. After a predetermined time interval (that is typically shorter than the predetermined time interval between normal primary consciousness checks), a zero-delivery primary consciousness check is performed.

[0267] Again, the controller monitors the time taken for the patient to respond by pressing the button 304, and if the patient response time is within 0.8 seconds, the patient is deemed to be conscious enough, the demand functionality of the button 304 is re-enabled, the output delivery rate is restored to a percentage, e.g. 70%, of that being delivered prior to the originally failed primary consciousness check, and the controller returns to performing primary consciousness checks at predetermined time intervals.

[0268] In response to failing the zero-delivery primary consciousness check, delivery of the medicament remains at zero, and a zero-delivery secondary consciousness check is performed, for example 10 seconds after the failed zero-delivery primary consciousness check.

[0269] Again, the controller monitors the time taken for the patient to respond by pressing the button 304, and if the patient response time is within 0.8 seconds, the patient is deemed to be conscious enough, the demand functionality of the button 304 is re-enabled, the output delivery rate is restored to a percentage, e.g. 70%, of that being delivered prior to the originally failed primary consciousness check, and the controller returns to performing primary consciousness checks at predetermined time intervals.

[0270] In response to failing the zero-delivery secondary consciousness check, delivery of the medicament remains at zero, and the zero-delivery consciousness check regime restarts, and continues until the patient is deemed to be conscious enough. Failure to pass the zero-delivery secondary consciousness check may also result in an alarm signal being raised.

[0271] Phase 935 of Figure 23 illustrates a series of successful primary consciousness checks, where the output delivery rate is plotted over time. The first primary consciousness check is performed shortly after the pump starts to operate in the continuous mode, i.e. shortly after the end of phase 930 and shortly after the start of phase 935 in the example of Figure 23. The first consciousness check is typically conducted after a predetermined time interval following the last press of the button 304 in the rapid mode, or following commencement of delivery in the continuous mode. In alternative embodiments, the timing of the first consciousness check may additionally or alternatively depend on the time that has elapsed since the button 304 was last pressed by the patient to request pain relief and / or sedation, and the output delivery rate at that moment. Specifically, in this alternative, the longer it has been since the button 304 was last pressed, and the higher the output delivery rate was at the moment, the quicker the first consciousness check occurs once the pump begins to operate in the continuous mode. This is because as more time elapses, particularly after delivery of a high volume of medicament to the patient, the need to check on the status of the patient becomes more urgent, i.e. because they are more likely to have become too sedated.

[0272] When operating in the continuous mode, the primary consciousness checks are performed at regular time intervals, for example every 15 seconds. In alternative embodiments, the length of the time intervals between primary consciousness checks may be dependent on the output delivery rate at that moment in time, and may therefore be irregular. In particular, where the output delivery rate is higher, the primary consciousness checks are performed more regularly, because the risk of losing consciousness is higher. In contrast, where the output delivery rate is lower, the primary consciousness checks are performed less regularly, because the risk of losing consciousness is lower. Indeed, where the output delivery is particularly low, for example below a predetermined threshold, consciousness checks may cease altogether, i.e. because the chance of the patient being unconscious is significantly low.

[0273] At point in time 940, the device 1 begins to operate in the continuous mode, and thus at point in time 950, it is determined that a first primary consciousness check should be performed, because 15 seconds has elapsed since commencing operation in the continuous mode. An output signal is sent to illuminate the rear facing LED(s) 242, and because the patient presses the button 304 to confirm their consciousness within 0.8 seconds, the check is deemed to have been passed. In response, at point in time 955, the continuous delivery component, and hence the output delivery rate, are increased, because it is deemed safe to deliver more medicament to the patient to maintain their current level of pain relief and / or sedation.

[0274] After the initial step increase in the continuous delivery component and the output delivery rate, the continuous delivery component, and hence the output delivery rate, begin to decrease again. At point in time 960, following a further 15 seconds, a further primary consciousness check is performed, and an output signal is again sent to illuminate the rear facing LED(s) 242.

[0275] Again, the patient presses the button 304 to confirm their consciousness, and because the patient’s response is within 0.8 seconds, the check is deemed to have been passed. In response, at point in time 965, the continuous delivery component, and hence the output delivery rate, are increased, because it is deemed safe to deliver more medicament to the patient to maintain their current level of pain relief and / or sedation. After the initial step increase in the continuous delivery component and the output delivery rate, the continuous delivery component, and hence the output delivery rate, begin to decrease again.

[0276] Whilst the patient continues to pass the primary consciousness checks, this process continues until a) the patient presses the button 304 without being requested, indicating that they are in pain and wish to receive more pain relief and / or sedation, triggering the continuous delivery component and the rapid delivery component of the algorithm to function as described above, or b) the patient fails a primary consciousness check, thereby triggering the procedure of subsequent consciousness checks described above.

[0277] In response to each passed primary consciousness check, the delivery rate is increased by a fraction or percentage of the decrease in the delivery rate enforced between checks. For example, between points in time 940 and 950, the delivery rate is decreased by a predetermined amount, and in response to passing the primary consciousness check at point in time 950, the delivery rate is increased by 80% of that predetermined amount. This creates a cumulative decrease in the delivery rate during operation in the continuous mode, enabling fine adjustment of the delivery rate to the minimum rate required to maintain sufficient pain relief and / or sedation for the patient, whilst allowing the patient to reduce the delivery rate as they begin to feel more comfortable.

[0278] In this embodiment, the output delivery rate decreases at a constant rate between primary consciousness checks. However, in alternative embodiments it is envisaged that the decrease in the delivery rate may decrease at an alternative rate. For example, the decrease in the delivery rate may be dependent on the instantaneous delivery rate, e.g. at the time of pressing the button 304 in response to the most recent consciousness check. In particular, the rate of decrease may be higher where the delivery rate is higher, and lower where the delivery rate is lower.

[0279] In an alternative embodiment, it is envisaged that if the patient fails to respond to a primary consciousness check, the decrease in delivery rate continues at the same rate, but if the patient successfully responds to the primary consciousness check, the delivery rate decreases, but at a slower rate. In another alternative embodiment, it is envisaged that if the patient fails to respond to a primary consciousness check, the delivery rate decreases at a faster rate, but if the patient successfully responds to the primary consciousness check, the delivery rate continues to decrease at the same rate. In another alternative embodiment, it is envisaged that if the patient fails to respond to a primary consciousness check, the delivery rate continues to decrease at the same rate, or a faster rate, but if the patient successfully responds to the primary consciousness check, the delivery rate is maintained at the current or instantaneous rate, e.g. for a predetermined amount of time.

[0280] Where the above description of the specific embodiments discusses a “delivery rate” of medicament, in reality, it is envisaged that for some pumps in this field this may be better defined by reference to a volume of medicament delivered in a certain time period. For example, a delivery rate of 2ml / min may be delivered by delivering 4ml / min for 30 seconds, and stopping delivery for 30 seconds. The output rate of the pump is therefore 4ml / min, but the delivery rate of medicament to the facemask 10 is 2ml / min. Increasing the delivery rate to 3ml / min may therefore be implemented by delivering 4ml / min for 45 seconds, and stopping delivery for 15 seconds. Similarly, a delivery rate of 2ml / min may be delivered by alternating between delivering 4ml / min for 3 seconds, and stopping delivery for 3 seconds, for 10 intervals of each, giving an overall delivery rate of medicament to the facemask 10 of 2ml / min. Increasing the delivery rate to 3ml / min may therefore be implemented by alternating between delivering 4ml / min for 4.5 seconds for and stopping delivery for 1 .5 seconds, for 10 intervals of each.

[0281] Hence, the output of the pump may be the same, but may be pulsed to the facemask 10 over a different time period, to achieve a different delivery rate to the facemask 10. This may be particularly relevant when using a stepper motor to drive delivery of the medicament, which may be beneficial in ensuring accurate and precise dosing / delivery.

[0282] LED ring The LEDs of display 500 shown in Figures 2-4 are used during operation to provide various status updates to a user or operator. The following notification sequences are described in relation to the specific LED ring 502 of Figures 2-4, which has eight LEDs in a circular shape. However, it will be understood that the same notification sequences could be provided by a plurality of LEDs provided in a different shape, and / or being different in number, and that different colours could be used to indicate different statuses from those specifically described below.

[0283] Figures 24a-24d illustrate a first notification sequence, in which one or more of the LEDs is illuminated in purple to indicate that the device is priming. Once the reservoir 322 has been correctly inserted into the handset 301 and the microswitch activated by the flange 330 as previously described, provided the battery is connected, the device 1 begins the priming process. During priming of the device 1 , the peristaltic pump 334 draws and transmits sufficient medication from the reservoir 322 to the transmission tube 307 to fill the transmission tube 307 between the handset 301 and the mask 10, but does not begin delivery of the medication onto the gauze / pad 218. During priming, actuation of the button 304 will not cause delivery of medication to the mask 10. During priming, medicament will be delivered to the facemask 10 regardless of the breath detection component of the algorithm, but not to the pad 218.

[0284] Here, the number of illuminated LEDs of LED ring 502 corresponds to a proportion or percentage of the priming completed. The number of illuminated LEDs therefore increases in a clockwise direction as priming progresses, starting from the LED positioned towards the top of the outwardly facing display 500.

[0285] For example, each LED that is illuminated in purple may be indicative of the device being approximately 12.5% primed. Hence, the first LED showing being illuminated in purple may indicate that the device is approximately 12.5% primed, two LEDs being illuminated in purple may indicate that the device is 25% primed (as illustrated in Figure 24a), four LEDs being illuminated in purple may indicate that the device is 50% primed (as illustrated in Figure 24b), 6 LEDs being illuminated in purple may indicate that the device is 75% primed (as illustrated in Figure 24c), and so on. These percentages are an example only, and in general, each LED being illuminated is indicative of the device being further towards being fully primed.

[0286] Once the device is fully primed, all eight of the LEDs are illuminated in purple, to indicate that priming is complete (as illustrated in Figure 20d). Upon completion of priming, the device 1 checks whether the device battery is full., The device 1 may also check whether the reservoir 322 is full, for example by issuing a request to the operator to confirm that the reservoir 322 is new, thereby confirming that it is full. Upon confirmation of the full battery (and the full reservoir, where applicable), all eight of the LEDs are illuminated in green, indicating to the user or operator that the device is fully primed and ready for normal operation, i.e. the handset 301 is ready to deliver medicament to the facemask 10.

[0287] Figures 25a-25d illustrate a second notification sequence, which runs during delivery of the medicament from the handset 301 to the facemask 10. In this second notification sequence, 7 of the 8 LEDs in the LED ring 242 remain illuminated in green, whilst a single LED is illuminated in blue. The LED illuminated in blue changes over time, so that the blue LED appears to move in a clockwise manner around the LED ring over time, as illustrated in Figures 20a-20b, indicating that breathing is continually being detected and delivery of the medicament is ongoing.

[0288] Figures 26a-26d illustrate a third notification sequence, which runs in combination with the second notification sequence during delivery of the medicament from the handset 301 to the facemask 10. In this third notification sequence, the number of LEDs illuminated in green is indicative of the amount of medicament remaining in the medicament bottle 324. The number of LEDs illuminated in green therefore reduces in an anticlockwise direction during delivery of the medicament to the facemask 10, finishing with the LED positioned towards the top of the outwardly facing display 500. As with the first notification sequence, each LED that is illuminated in green is indicative of how full the medicament bottle 324 is. For example, each LED that is illuminated in green may represent the medicament bottle 324 being approximately 12.5% full. Hence, when the eighth LED is the last LED illuminated in green, as in Figure 26a, the medicament bottle 324 is approximately 100% full. When the sixth LED is the last LED illuminated in green, as in Figure 26b, the medicament bottle 324 is approximately 75% full. When the fourth LED is the last LED illuminated in green, as in Figure 26c, the medicament bottle 324 is approximately 50% full. When the second LED is the last LED illuminated in green, as in Figure 26d, the medicament bottle 324 is approximately 25% full.

[0289] Once the medicament bottle 324 drops to being approximately 10% full, the last two LEDs are illuminated in yellow, and pulse or flash to indicate to the operator that the medicament bottle 324 is almost empty.

[0290] Once the medicament bottle 324 is completely empty, the last LED is illuminated in yellow, and pulses or flashes to indicate to the operator that the medicament bottle 324 is empty.

[0291] A single, yellow, flashing or pulsing LED may be used during the setup of a device 1 to notify the operator that the device 1 has been used before. All 8 LEDs flashing or pulsing in yellow during the setup of a device 1 may be used to notify the operator that the device 1 has a software or hardware fault. That fault may be, for example, that the battery is low, or that a component of the device 1 is missing or misconnected.

[0292] Various other modifications of the embodiments described above would also be apparent to a skilled reader. As such, it is emphasised that the forgoing description is provided by way of example only, and is not intended to limit the scope of protection as defined with reference to the appended claims.

Claims

1. Claims1 . A device for providing pain relief and / or sedation to a patient, the device comprising: an input arrangement for actuation by the patient, a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, and a controller that is configured to receive an input signal from the input arrangement, process the input signal using a control algorithm to generate an output signal, and transmit the output signal to the delivery arrangement for controlling the delivery of the pain-relieving and / or sedative substance to the patient, wherein the control algorithm comprises:- a high response function that generates a high response delivery parameter,- a low response function that generates a low response delivery parameter, and- an output function that uses the high response delivery parameter and the low response delivery parameter to generate the output signal.

2. A device according to Claim 1 , wherein the high response delivery parameter and / or the low response delivery parameter is dependent on one or more patient input parameter associated with the patient input signal.

3. A device according to Claim 2, wherein the one or more patient input parameter is dependent on any of, or any combination of: a frequency of the patient input signal, an amplitude of the patient input signal, or a period of the patient input signal.

4. A device according to any preceding claim, wherein the low response delivery parameter and / or the high response delivery parameter is a rate ofdelivery of the pain-relieving and / or sedative substance, or a volume of the pain-relieving and / or sedative substance to be delivered.

5. A device according to any preceding claim, wherein the device is configured to operate in a low response delivery mode when the output function uses the low response delivery parameter to generate the output signal, and the device is configured to operate in a high response delivery mode when the output function uses the high response delivery parameter to generate the output signal.

6. A device according to any of Claims 1 -5, wherein the output function compares the low response delivery parameter and the high response delivery parameter, and generating the output signal comprises selecting the higher of the low response delivery parameter and the high response delivery parameter.

7. A device according to Claim 6, wherein the device is configured to operate in a low response delivery mode when the low response delivery parameter is higher than the high response delivery parameter, and configured to operate in a high response delivery mode when the high response delivery parameter is higher than the low response delivery parameter.

8. A device according to any preceding claim, wherein the low response delivery parameter has a maximum value, and in response to the low response delivery parameter reaching the maximum value, the device enters a rate decrease phase.

9. A device according to any preceding claim, wherein the device has a rate increase phase during which actuation of the input arrangement from the patient indicative of a demand for pain relief and / or sedation provides an increase in a non-zero rate of delivery of the pain-relieving and / or sedative substance to a higher non-zero rate of delivery, and the device has a rate decrease phase during which actuation of the input arrangement from thepatient indicative of an equal or greater demand for pain relief and / or sedation provides a decrease in a non-zero rate of delivery of the pain- relieving and / or sedative substance to a lower non-zero rate of delivery.

10. A device according to Claim 9, wherein in the rate increase phase, actuation of the input arrangement from the patient generates an input signal that has a first value of the at least a parameter and provides an increase in the non-zero rate of delivery of the pain-relieving and / or sedative substance to the higher non-zero rate of delivery, and in the rate decrease phase, actuation of the input arrangement from the patient generates an input signal that has a second value of the at least a parameter and provides a decrease in the non-zero rate of delivery of the pain-relieving and / or sedative substance to the lower non-zero rate of delivery, wherein the value of the at least a parameter is indicative of demand for pain relief and / or sedation, and the second value of the at least a parameter is egual to, or greater than, the first value of the at least a parameter.11 .A device according to any of Claims 8-10, wherein in the rate decrease phase, in the absence of actuation of the input arrangement by the patient, the device provides a decrease in a non-zero rate of delivery of the pain- relieving and / or sedative substance to a lower non-zero rate of delivery, wherein the rate of the decrease in the non-zero rate of delivery in the absence of actuation of the input arrangement is greater than the rate of the decrease in the non-zero rate of delivery when the patient is actuating the input arrangement.

12. A device according to any preceding claim, wherein the device has a phase during which the control algorithm generates the output signal, such that:(a) a non-zero rate of delivery decreases to a lower non-zero rate of delivery in the absence of actuation of the input arrangement by the patient,(b) the patient is requested to actuate the input arrangement, and (c) if the patient successfully actuates the input arrangement in response to therequest, the rate of delivery is adjusted to a first non-zero rate of delivery; and (d) if the patient does not successfully actuate the input arrangement in response to the request, the rate of delivery is adjusted to a second nonzero rate of delivery, wherein the first non-zero rate of delivery is higher than the second non-zero rate of delivery.

13. A device according to Claim 12, further comprising at least one patient indicator, wherein the request to the patient to actuate the input arrangement in step (b) is provided via the at least one patient indicator.

14. A device according to Claim 12 or Claim 13, wherein in step (b), the patient is requested to actuate the input arrangement to indicate that the current level of pain relief and / or sedation is sufficient and / or to indicate that the patient remains conscious.

15. A device according to any of Claims 12-14, wherein the adjustment in the non-zero rate of delivery in step (c) is for a predetermined amount of time, after which step (a) is repeated.

16. A device according to any of Claims 12-15, wherein when the patient successfully actuates the input arrangement in response to the request, adjusting the non-zero rate of delivery to a first non-zero rate of delivery comprises increasing the non-zero rate of delivery to a higher non-zero rate of delivery.

17. A device according to Claim 16, wherein the increase in the rate of delivery in response to the patient actuating the input arrangement is less than the decrease in the rate of delivery since the previous actuation of the input arrangement by the patient in response to step (b).

18. A device according to any preceding claim, the device further comprising a patient interface, and at least one sensor for detecting the breath of a patient within the patient interface, and a delivery interface, wherein the delivery arrangement is arranged to deliver the pain-relieving and / orsedative substance to the delivery interface, and the controller is further configured to receive a sensor signal from the at least one sensor, process the sensor signal using a control algorithm to generate an output signal, and transmit the output signal to the delivery arrangement for controlling the delivery of the pain-relieving and / or sedative substance to the patient, wherein in the absence of breath detection, the control algorithm generates an output signal that prevents or ceases delivery of the pain-relieving and / or sedative substance to the delivery interface.

19. A method of providing pain relief and / or sedation to a patient, the method comprising the steps of: receiving an input signal from an input arrangement actuated by a patient, processing the input signal using a control algorithm to generate an output signal, and transmitting the output signal to a delivery arrangement for delivering a pain-relieving and / or sedative substance to the patient, wherein the control algorithm comprises:- a high response function that uses the input signal to generate a high response delivery parameter,- a low response function that uses the input signal to generate a low response delivery parameter, and- an output function that uses the high response delivery parameter and the low response delivery parameter to generate the output signal.

20. A device for providing pain relief and / or sedation to a patient, the device comprising: at least one supply of a pain-relieving and / or sedative substance, a patient interface having a status indicator arrangement for indicating at least one state of the device, and a controller that is configured to determine at least one state of the device, and transmit an output signal to the status indicator arrangement indicative of the at least one state of the device.21 .A device according to Claim 20, wherein the at least one state of the device is indicative of the priming status of the device, the delivery status of the device, the status of the at least one supply of a pain-relieving and / or sedative substance, or the usage of the device.

22. A device according to Claim 20 or Claim 21 , wherein the status indicator arrangement comprises one or more visual indicator, the one or more visual indicator being configured to provide a different visual indication dependent on the at least one state of the device being indicated.

23. A device according to any of Claims 20-22, wherein the status indicator arrangement comprises a plurality of indicators, the plurality of indicators being configured to indicate a level or extent of completion of an operation associated with the device.

24. A device according to Claim 23, wherein the amount of the plurality of indicators that are activated is indicative of the level or extent of completion of an operation associated with the device.

25. A device according to Claim 23 or Claim 24, wherein the plurality of indicators is arranged in a formation, and the portion of the formation that is activated is indicative of a level or extent of completion of an operation associated with the device.

26. A device according to Claim 25, wherein the size of the portion of the formation that is activated is indicative of the level or extent of completion of an operation associated with the device.

27. A method of providing pain relief and / or sedation to a patient, the method comprising the steps of: determining at least one state of the device,generating an output signal indicative of the at least one state of the device, and transmitting the output signal to a status indicator arrangement at a patient interface for indicating the at least one state of the device.

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