Patent Description:
In the UK in <NUM> approximately <NUM> million operations were carried out. Of these, <NUM> million were performed with the patient unconscious (under general anaesthesia), and <NUM> million were carried out with the patient awake. Operations performed with the patient awake are associated with an increased risk of patient anxiety and pain, whereas operations under general anaesthesia carry risks associated with the anaesthetic. For many operations, deep sedation and anaesthesia is not necessary, provided the problems of anxiety and pain can be managed. This can be achieved by careful control of a level of sedation of the patient, in combination with local anaesthesia where appropriate. The ideal level of sedation during a procedure is highly patient dependent. Pharmacokinetic factors (how the body deals with the sedative agent) include age, weight and less easily determined factors such as metabolic rate and proportion of body fat. Most importantly though, patients differ widely in their anxiety levels and their need for sedation during the procedure. Sedatives are usually administered by an anaesthetist. The patient is therefore not in control of how much sedation they receive. In this situation the patient may receive too little sedation; resulting in increased anxiety and a poor subjective experience. Conversely the patient may receive too much sedation; with possible complications such as low blood pressure, respiratory depression, airway obstruction and desaturation (low oxygen levels).

An alternative to anaesthetist-delivered boluses of sedative drugs is the use of a pharmacokinetic infusion pump, as for example disclosed in <CIT>. This type of approach can provide a smoother blood concentration of the sedative but is still delivered by the anaesthetist and therefore open to over and under sedation of the patient as described above.

Another option is patient-controlled sedation, in which the patient is at least partly in control of the amount of sedative they receive. The patient may control the sedation they receive using a switch, such as a push button, that is actuated to signal to a dose metering pump that more sedative is required. The dose metering pump then responds to the activation of the switch, within pre-set limits, which may for example limit the maximum amount capable of being administered over time. Repeated presses by the patient will cause gradual increases in the amount of sedative being administered until the patient considers the amount effective, or until a pre-set upper limit is reached. An advantage of this approach is that the patient is able to control their own sedation and thereby receive the optimum amount of sedative. A further advantage is that the total amount of sedative consumed has been shown in studies to be substantially reduced as compared with anaesthetist-administered sedation. In addition, patients able to control their own level of sedation tend to feel less anxious and have a shorter recovery time. To date there has been no commercially produced device capable of delivering patient controlled sedation using a pharmacokinetic pump to deliver the drug.

<CIT> discloses an apparatus and method for alleviating pain or discomfort while enabling safe drug delivery in correlation with monitoring of patient health conditions, in which a blood pressure cuff capable of being wrapped around a patient's wrist is affixed to a palm support portion with a depressible query response switch capable of being depressed by the patient's thumb and a drug dosage request switch is integrated into a finger support portion.

<CIT> discloses a system for remotely controlling medication infusion and analyte monitoring, in which a monitoring device has a hosing and strap which allows it to be worn on a limbic region such as the arm, the device having a display and control keys for receiving input data and commands from the user.

<CIT> discloses an automated programmable transdermal administrative system for providing pulsed doses of medications.

<CIT> discloses a dose request device for a medicament delivery device including a housing, a dose request button, a short-range non-contact identifier, a communication interface configured to communicate with the medicament delivery device and a controller.

<CIT> discloses an injection device having a miniaturized drug delivery portion, the device including a housing having an interior volume and the drug delivery portion having a volume enclosed within the housing.

<CIT> discloses an apparatus and system for the self-dosing of a liquid machine, in which a push button is attached to a piston capable of being pressed by the patient a desired number of times corresponding to an amount of dosed liquid medicine.

In accordance with a first aspect of the invention there is provided a hand-operated device for a patient-controlled sedation system, the device comprising:.

An advantage is that fitting the device around the wrist of a patient and operating the switch by compression allows the device to be operated more easily by the patient. The device is also less likely to fall out of reach during an operation if it is attached around the patient's wrist.

To allow for the patient to identify when the switch has been operated, the device may have an indicator configured to provide one or more indications upon activation of the switch. The indicator may be one or more of: a light configured to illuminate the device upon activation of the switch; a vibration motor arranged to provide haptic feedback upon activation of the switch; and a sounder arranged to emit an audible signal upon activation of the switch.

The device may comprise a strap configured to connect proximal and distal ends of the elongate arcuate portion for securing the device around the patient's wrist.

The device may comprise a connection cable for connecting the switch to an interface for a dose metering device. In alternative examples the device may comprise a wireless transceiver for wirelessly transmitting an actuation signal when the switch is operated. The wireless transceiver may for example be a Bluetooth type transceiver.

The elastomeric material may for example be a silicone rubber. The hollow tubular element may be translucent or transparent, thereby enabling the element to be illuminated from within to provide visual feedback.

The switch may comprise a pressure sensor and a switching module, the switching module configured to receive a pressure signal from the pressure sensor and activate the switch when a sensed pressure exceeds a pre-set value.

In accordance with a second aspect there is provided a system for patient-controlled sedation, the system comprising:.

The invention is described in further detail below by way of example and with reference to the accompanying drawings, in which:.

<FIG> illustrates an example system <NUM> for patient-controlled sedation. The system <NUM> comprises a patient button interface <NUM> having a wired connection to a computer interface <NUM> for an anaesthetist. The computer interface <NUM> is connected to an infusion pump <NUM>, which provides a controlled dose of sedative to a cannula <NUM> attached to a drip bag <NUM>. The computer interface <NUM> may allow the anaesthetist to view the amount and rate of sedative being provided to the patient and to override this if necessary.

The anaesthetist-operated computer interface <NUM> may be a conventional (typically ruggedized) portable computer with a first two-way wired interface to the patient button interface <NUM> and a second two-way wired interface with the infuser pump <NUM>. Both interfaces may for example be made using conventional USB connections. The infuser pump <NUM> may for example be a Perfusor fm® infusion pump, available from B. Braun Melsungen AG. In some arrangements the computer interface <NUM> may be incorporated into the infusion pump <NUM>.

An example hand-operated device <NUM> for use as a patient button interface <NUM> is illustrated in <FIG>. The device <NUM> comprises a grip portion <NUM> for fitting within a patient's hand and a button <NUM> at a distal end <NUM> of the device <NUM>. A cable <NUM> extends from a proximal end <NUM> of the device <NUM> for connecting the device <NUM> to a computer interface via a connector <NUM>. In use, the patient grips the device <NUM> and presses the button <NUM> with their thumb to request an increase in the level of sedation.

A problem with the type of device <NUM> in <FIG> is that the patient may lose grip of the device <NUM> and not be able to operate the button <NUM>. This may be partially solved by adding a wrist band to attach the device <NUM> to the patient's wrist. If the patient's grip loosens and the device falls but is held by the wrist band, the patient would need to pick up the device and reorient it before being able to press the button again. This may be difficult for the patient to do, particularly when partially sedated, and can potentially result in increased patient anxiety, which could lead to problems during an operation.

A schematic sectional view of an example hand-operated device <NUM> for a patient-controlled sedation system is shown in <FIG>. The device <NUM> is in the form of a partial section of a ring, comprising an elongate arcuate portion <NUM> that is arranged to fit around the wrist of a patient. The inner diameter of the device <NUM> may therefore be in the region of around <NUM> to <NUM>. The device <NUM> comprises a switch <NUM> that is arranged to operate upon compression across a width of the elongate arcuate portion <NUM>. The patient may operate the switch by squeezing the device <NUM> at any point along the length of the arcuate portion <NUM>, making the operation significantly easier than that of finding and pressing a button, particularly when the patient is partially sedated. Being wrist-mounted, the device <NUM> is also far less prone to being misplaced and is always immediately to hand for the patient to operate.

A cable <NUM> connects a proximal end <NUM> of the device <NUM> to a connector <NUM> for connection to a dose metering device. Electrical power to the device <NUM> may be provided via the cable <NUM>. In alternative examples the device <NUM> may comprise a wireless transceiver, for example a Bluetooth module, for wirelessly transmitting an actuation signal when the switch <NUM> is activated, and the device <NUM> may be powered internally with a battery. In a surgical operating environment, a cable connection may be preferable to avoid the possibility of interference with other sensitive electronic equipment.

The elongate arcuate portion <NUM> of the device <NUM> is formed of a flexible elastomeric material such as a silicone rubber, which allows the device to be positioned and held in place around the patient's wrist. The elongate arcuate portion <NUM> is hollow such that a compressive force applied at any point along the length of the portion <NUM> causes an increase in pressure within an internal volume <NUM>, which is transmitted to the switch <NUM>. The switch <NUM> then responds to the increase in pressure by activating, causing a signal to be sent to an infusion pump to request an increase in sedation. The switch <NUM> may for example be in the form of a pressure-activated switch that is configured to close above a pre-set pressure. Alternatively the switch <NUM> may comprise a pressure sensor <NUM> and a switching module <NUM> that receives a pressure signal from the pressure sensor <NUM> and activates the switch <NUM> when a sensed pressure exceeds a pre-set value. The switch <NUM> may be disposed at a proximal end <NUM> of the elongate arcuate portion <NUM>. An advantage of using a pressure sensor <NUM> and switching module <NUM> is that the switch <NUM> may be activated not only according to the absolute value of pressure but also according to the length of time the pressure increase lasts. Spurious readings caused by momentary increases in pressure can thereby be discounted, and the switch <NUM> activated only when a sustained increase in pressure is applied. A further advantage is that the device <NUM> can be calibrated according to the particular patient before use, for example by having the patient apply pressure to the device <NUM> to set a pre-set value for subsequently activating the switch. An average pressure taken from a number of readings may be used. Different grip strengths can thereby be accommodated, for example allowing patients with reduced strength or impairment such as arthritis to use the device.

The device <NUM> may comprise a feedback mechanism to provide an indication to the patient of when the switch is activated. The feedback mechanism may involve haptic, aural or visual feedback. Haptic feedback may be provided by the device <NUM> comprising a vibratory motor <NUM>, which is activated when the switch <NUM> is operated. The switching module <NUM> may be arranged to drive the vibratory motor <NUM> when activating the switch <NUM>. Visual feedback may be provided by the device <NUM> comprising one or more lights <NUM> arranged to be lit when the switch <NUM> is activated. The lights <NUM> may be arranged in the internal volume <NUM> so that the device <NUM> is illuminated from within when the switch <NUM> is activated, which is particularly relevant when the arcuate portion <NUM> is in the form of a hollow tubular element composed of a translucent or transparent material such as a silicone rubber.

Aural feedback may be provided by the device <NUM> comprising a sounder <NUM> arranged to emit an audible alert such as a beep when the switch <NUM> is activated. The sounder may be activated by the switching module <NUM>.

An advantage of the elongate arcuate portion <NUM> being in the form of a hollow tubular element formed of an elastomeric material, in combination with the switch <NUM> being activated by an increase in pressure being detected, is that the device may be used by the patient in different ways. A usual way of activating the switch <NUM> would be for the patient to wear the device <NUM> on their wrist and activate the switch <NUM> by squeezing with the other hand. The device <NUM> may alternatively be held around the patient's hand, where it will tend to stay in place by the resilient nature of the tubular element, and activated by squeezing the same hand. The device <NUM> may alternatively be used in other positions such as under the patient's chin, around the knee or in other positions where a squeezing action can be applied. Haptic feedback is particularly useful for when the device may be in positions that are not immediately visible to the patient and for environments that may have background noise that could make aural feedback indistinct.

<FIG> is a drawing of an example device <NUM> of the type shown in <FIG>, in which the elongate arcuate portion <NUM> is a hollow ring formed of silicone rubber. An exterior surface of the elongate arcuate portion <NUM> is textured to improve grip and enable the patient to recognise the device by touch alone. A strap <NUM> removably connects the proximal and distal ends <NUM>, <NUM> of the elongate arcuate portion <NUM> for securing the device <NUM> in place around a patient's wrist. The device <NUM> may comprise features described above in relation to the device <NUM> in <FIG>.

<FIG> is a drawing of a further example device <NUM>, in which an alternative way of securing the device <NUM> to the patient is used, in this case an adjustable strap <NUM> with a toggle <NUM> connects the proximal and distal ends <NUM>, <NUM> of the elongate arcuate portion <NUM>. A gown clip <NUM> may also be provided for securing the cable <NUM> to the patient's clothing. The device <NUM> comprises lights <NUM> within the hollow elongate arcuate portion <NUM> that illuminate the device <NUM> from within when the switch is activated. Other features described above in relation to the device <NUM> in <FIG> may also be present.

<FIG> illustrates schematically an example method of operating a device of the type described herein, where the device comprises a pressure sensor and switching module together with a feedback mechanism. In a first step <NUM> the switching module obtains a pressure reading from the pressure sensor. In a second step <NUM>, the switching module compares the pressure reading with a pre-set pressure threshold. If the pressure reading is below the pre-set pressure threshold, the method returns to step <NUM> and repeats. If the pressure reading is above the pre-set pressure threshold, at step <NUM> the switch is activated, sending a signal to request an increase in sedation level. At step <NUM> the switching module activates the feedback mechanism, for example a vibration motor, to provide feedback to the patient that the switch has been activated. The method then returns to step <NUM> and repeats. The method may pause before repeating the process to prevent multiple requests being transmitted from a single press. Step <NUM> may also involve determining whether the pressure threshold has been exceeded for a minimum time before proceeding to step <NUM> to prevent spurious momentary pressure increases from triggering an activation signal.

Claim 1:
A hand-operated device (<NUM>, <NUM>) for a patient-controlled sedation system, the device (<NUM>, <NUM>) comprising:
an elongate arcuate portion (<NUM>) arranged to fit around a wrist of a patient; and characterized by
a switch (<NUM>) arranged to activate upon compression across a width of the elongate arcuate portion (<NUM>),
wherein the elongate arcuate portion (<NUM>) comprises a hollow tubular element formed of an elastomeric material,
wherein the switch (<NUM>) is configured to be actuated by an increase in air pressure within the hollow tubular element upon compression of the elongate actuate portion (<NUM>).