Patent Application
20220323675
The invention relates to patient-maintained sedation and in particular to a novel hand-operated device for enabling patients to control their own level of sedation.
In the UK in 2013 approximately 3.6 million operations were carried out. Of these, 2.8 million were performed with the patient unconscious (under general anaesthesia), and 0.8 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 U.S. Pat. No. 8,038,645 B2. 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.
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 elongate arcuate portion may comprise a hollow tubular element formed of an elastomeric material. 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 be configured to be actuated by an increase in air pressure within the hollow tubular element upon compression of the elongate actuate portion.
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:
In accordance with a third aspect there is provided a method of operating the system according to the second aspect, wherein the switch comprises a pressure sensor and a switching module, the switching module configured to receive a pressure signal from the pressure sensor, the method comprising:
The method may comprise the switching module activating a feedback mechanism in the device upon activation of the switch. The feedback mechanism may be one or more of a vibratory motor, one or more lights and a sounder.
The invention is described in further detail below by way of example and with reference to the accompanying drawings, in which:
The anaesthetist-operated computer interface 102 may be a conventional (typically ruggedized) portable computer with a first two-way wired interface to the patient button interface 101 and a second two-way wired interface with the infuser pump 103. Both interfaces may for example be made using conventional USB connections. The infuser pump 103 may for example be a Perfusor fm® infusion pump, available from B. Braun Melsungen AG. In some arrangements the computer interface 102 may be incorporated into the infusion pump 103.
An example hand-operated device 200 for use as a patient button interface 101 is illustrated in
A problem with the type of device 200 in
A schematic sectional view of an example hand-operated device 300 for a patient-controlled sedation system is shown in
A cable 310 connects a proximal end 304 of the device 300 to a connector 311 for connection to a dose metering device. Electrical power to the device 300 may be provided via the cable 310. In alternative examples the device 300 may comprise a wireless transceiver, for example a Bluetooth module, for wirelessly transmitting an actuation signal when the switch 302 is activated, and the device 300 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 301 of the device 300 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 301 is hollow such that a compressive force applied at any point along the length of the portion 301 causes an increase in pressure within an internal volume 303, which is transmitted to the switch 302. The switch 302 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 302 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 302 may comprise a pressure sensor 306 and a switching module 307 that receives a pressure signal from the pressure sensor 306 and activates the switch 302 when a sensed pressure exceeds a pre-set value. The switch 302 may be disposed at a proximal end 304 of the elongate arcuate portion 301. An advantage of using a pressure sensor 306 and switching module 307 is that the switch 302 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 302 activated only when a sustained increase in pressure is applied. A further advantage is that the device 300 can be calibrated according to the particular patient before use, for example by having the patient apply pressure to the device 300 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 300 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 300 comprising a vibratory motor 305, which is activated when the switch 302 is operated. The switching module 307 may be arranged to drive the vibratory motor 305 when activating the switch 302. Visual feedback may be provided by the device 300 comprising one or more lights 308 arranged to be lit when the switch 302 is activated. The lights 308 may be arranged in the internal volume 303 so that the device 300 is illuminated from within when the switch 302 is activated, which is particularly relevant when the arcuate portion 301 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 300 comprising a sounder 309 arranged to emit an audible alert such as a beep when the switch 302 is activated. The sounder may be activated by the switching module 307.
An advantage of the elongate arcuate portion 301 being in the form of a hollow tubular element formed of an elastomeric material, in combination with the switch 302 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 302 would be for the patient to wear the device 300 on their wrist and activate the switch 302 by squeezing with the other hand. The device 300 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 300 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.
Other embodiments are intentionally within the scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1914214.0 | Oct 2019 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2020/052422 | 10/2/2020 | WO |
