GB2392242A

GB2392242A - Apparatus with multiple pulse-oximetry sensors

Info

Publication number: GB2392242A
Application number: GB0313529A
Authority: GB
Inventors: Geoffrey Richard Mathews; Veronica Mary Mathews
Original assignee: Electrode Co Ltd
Current assignee: Electrode Co Ltd
Priority date: 2002-06-14
Filing date: 2003-06-12
Publication date: 2004-02-25
Also published as: WO2003105683A3; WO2003105683A2; GB0213836D0; GB0313529D0; AU2003240083A1

Abstract

An apparatus comprises a number of separate pulse oximetry sensors 6, 8, 10 respectively measuring pulsatile signals at different locations within the peripheral tissue of a body part. A further sensor (30, figure 2) associated with each pulse oximetry sensor may be provided to determine if a body part overlies the pulse oximetry sensor. The apparatus is used to assess the level of tissue oxygenation in the body and so can detect localised abnormalities in peripheral blood oxygenation levels, indicative of existing or potential tissue damage. The apparatus may be incorporated into a prosthetic limb 2 and also may be used to control a variable pressure mattress (22, figure 2) or cushion, compression devices (e.g. to prevent DVT), and reconfigurable articles of furniture.

Description

J Analytical Apparatus The present invention relates to an analytical

apparatus and, more particularly, to an apparatus for analysing the peripheral tissue of a body part.

5 Vascular disease is the cause of much morbidity and mortality and may cause poor local tissue oxygenation. Poor local tissue oxygenation may be due to local peripheral or more central vascular occlusion/narrowing of vessel lumen.

It is therefore a first object of the present invention 10 to provide an arrangement for assessing levels of peripheral tissue oxygenation to assist health workers in assessing levels of disease/pathology in a patient, so as to allow them to determine the most appropriate method of treating that patient.

Presently, in Europe alone, approximately one hundred 15 thousand lower limb amputations are performed every year.

To restore the mobility of a lower limb amputee, it has long been known to replace the missing part of a limb with a prosthesis, having a socket shaped to receive a residual limb portion, the residual limb portion typically being cushioned 20 within the socket by an elastomeric sleeve.

However, a number of studies have shown that a poorly fitting prosthesis can cause discomfort to its wearer and, in extreme cases, irreparable tissue damage, as a result of under or over-pressurisation of a surface portion of a residual limb.

25 It is therefore a second object of the present invention to provide an arrangement by which the limitations of existing prosthetic devices may be overcome.

A variety of devices are known for intermittently compressing a body part, for example to prevent deep-vein 30 thrombosis (DVT), and it is a third object of the present invention to provide a means for improving the efficacy of such devices. A variety of reconfigurable articles of furniture and variable pressure cushions and mattresses are also known, for

varying the pressure applied to different parts of a body supported thereon, and it is a fourth object of the present invention to provide a means for improving the efficacy of such devices. S According to a first aspect of the present invention, there is provided an analytical apparatus comprising a plurality of pulse-oximetry sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of a body part and electronic means for 10 monitoring the output of said sensors.

The apparatus may thus be used to detect localized abnormalities in peripheral blood oxygenation levels, indicative of existing tissue damage or the potential therefor.

For example, the apparatus could be used to monitor 15 blood oxygenation around varicose ulcers, around healing; wounds, either during or after vascular or amputation surgery, or around the sites of existing or potential pressure sores.

The apparatus could also be used for investigating vascular disease, e.g claudication, best level of amputation, 20 response to surgery. In the assessment of claudication, the i apparatus could be used to monitor and record changes in levels of tissue oxygenation after exercise or resulting from a change in ambient conditions, e.g. a drop in temperature.

Furthermore, the apparatus could be used to indicate 25 the need to move a patient to prevent or limit the formation of pressure sores, for example by alerting health workers after a pre-determined level of tissue anoxia has been exceeded over a pre-determined period of time.

Preferably the electronic monitoring means comprise 30 means for processing the measured signals and preferably for displaying the processed signals.

Said processing means may comprise respective processors for processing the signals measured by each of said pulse-oximetry sensors or a single processor for processing 35 each of the measured signals in turn.

Preferably each of the plurality of pulse-oximetry sensors comprises a reflectance or a transmission mode sensor.

The sensors may be arranged in a sheath, strip, pad or mat, which may be either rigid or flexible, for applying to or 5 wrapping around a body part and may be incorporated into a material such as adhesive strapping, cotton fabric, a hydrogel or silicone., Preferably each sensor comprises a respective light; emitter and receiver.

10 Alternatively the sensors may be provided by each of a plurality of light receivers arranged to receive signals from a single light emitter or by a single light receiver arranged to receive signals from each of a plurality of light emitters.

Where the apparatus comprises a plurality of light 15 emitters, the emitters may be arranged to emit light at; different respective frequencies and/or may be operated in sequence to reduce optical cross talk, the sequence of operation of the emitters being either random or pre-defined.

Additionally or alternatively, where the apparatus comprises 20 a plurality of light receivers, the receivers may be arranged to receive light at different respective frequencies.

Preferably the apparatus comprises a telemetric apparatus, arranged for sensor outputs to be monitored remotely t of the sensor array, by the transmission of the sensor outputs i 25 to a remote site, either continuously or periodically, via a telecommunications link.

Preferably, a further respective sensor is provided, adjacent each of said pulse-oximetry sensors, for detecting the presence of an adjacent body part. For example, the further 30 sensor may comprise a photo- electric sensor arranged to detect light falling thereon at frequencies other than those used by its respective pulse-oximetry sensor, or a pressure sensor.

In a first preferred embodiment, the sensors are incorporated into the residual-limb-receiving socket of a] 35 prosthetic device, most preferably into a cushioning liner of

the socket, e.g. a silicone or hydrogel liner, which liner preferably comprises an elastomeric sleeve or sock for fitting over the residual limb.

In a second preferred embodiment, the measured 5 pulsatile signals are used to provide feedback for controlling the operation of a device arranged to intermittently compress a body part, for example to prevent deep-vein thrombosis (DVT).

In a third preferred embodiment, the measured pulsatile signals are used to provide feedback for controlling the 10 operation of a reconfigurable article of furniture, such as a chair or bed, or of a variable pressure cushion or mattress.

According to a second aspect of the present invention, there is provided a prosthetic device having a socket for receiving a residual limb, the socket having a liner for 15 cushioning the residual limb and incorporating a plurality of pulse-oximetry sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of the residual limb.

According to a third aspect of the present invention, 20 there is provided a liner for the socket of a prosthetic device and incorporating a plurality of pulse-oximetry sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of a residual limb to which the prosthetic device may be fitted.

25 According to a fourth aspect of the present invention, there is provided a device for intermittently compressing a body part and comprising electronic control means responsive to feedback signals provided by a plurality of pulse-oximetry sensors arranged to measure pulsatile signals at separate 30 respective locations within the peripheral tissue of the body part. According to a fifth aspect of the present invention, there is provided a reconfigurable article of furniture comprising electronic control means responsive to feedback 35 signals provided by a plurality of pulse-oximetry sensors

arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of a body supported by the article of furniture.

According to a sixth aspect of the present invention, S there is provided a variable-pressure cushion or mattress comprising electronic control means responsive to feedback signals provided by a plurality of pulseoximetry sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of a body supported by 10 the cushion or mattress.

Embodiments of the present invention will now be described by way of examples only and with reference to the accompanying drawings, of which: Figure 1 is a schematic view of a first embodiment of 15 apparatus in accordance with the present invention; and; Figure 2 is a schematic view of a second embodiment of; apparatus in accordance with the present invention.

Referring to Figure 1 of the drawings, a first embodiment of analytical apparatus is shown comprising a 20 prosthetic device comprising a rigid shell 2 for receiving a residual limb and a substantially transparent, elastomeric liner 4 for cushioning the residual limb within the shell 2, the liner incorporating a plurality of pulse-oximetry sensors t 6,8,10 arranged to measure pulsatile signals at separate i 25 respective locations within the peripheral tissue of the residual limb.

The sensors 6,8,10 are arranged to communicate, via a shared ribbon-cable 12, with electronic control means 14 arranged to process and relay output signals from each of the 30 sensors to remote means 16 for further processing, displaying and/or storing the output signals.

Each sensor 6,8,10 comprises a respective light emitter, e.g. 18, for emitting light at a plurality of frequencies and an associated light receiver, e.g. 20, for] 35 measuring the amount of light reflected by the peripheral

tissue underlying the sensor, at each of said frequencies, the electronic control means 14 being arranged to derive, from the ratio of the amounts of light reflected at each of said frequencies, a measure of the level of localized blood 5 oxygenation.

To avoid optical cross-talk, which might otherwise occur between the sensors 6,8,10 due to their close proximity to one another, the electronic control means 16 are arranged to synchronize the reading of output signals from the light 10 receivers, e.g. 20, of each of the sensors 6,8,10, with the sequential illumination of their associated light emitters, e.g. 18.

Thus the apparatus allows a health worker to remotely monitor the condition of a residual limb, to identify any 15 abnormalities in the level of peripheral blood oxygenation at various locations within the socket of a prosthetic device, which may be indicative of an over- or under-pressurisation of the surface of the limb at those locations or to more centralized vascular problems.

20 It will be appreciated that whilst an apparatus has been described for identifying abnormalities in the level of peripheral blood oxygenation at various locations within the socket of a poorly fitted prosthetic device, the present invention also extends to apparatus, for example in the form 25 of strips, pads or sheaths, for applying to or wrapping around body parts to assist health workers in assessing levels of disease/pathology in a patient, so as to allow them to determine the most appropriate method of treating that patient.

Referring to Figure 2, a second embodiment of apparatus 30 is shown, comprising a variable pressure mattress 22 supported by a reconfigurable support-frame 24 and electronic control means 26 arranged to vary the configuration of support-frame 24 and/or the degree of support provided by the mattress 22 at different locations across its surface, in accordance with 35 output signals provided by a plurality of pulse- oximetry

sensors 28 arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of a body supported by the mattress 22, to achieve desired levels of peripheral tissue oxygenation at each of said locations.

5 A further respective sensor 30, e.g. a photoelectric or pressure sensor, associated with each pulse-oximetry sensor 28, provides a means for determining whether a body part overlies the pulse-oximetry sensor 28, and thus whether the output of the pulse-oximetry sensor 28 provides any valid physiological 10 information.

The apparatus thus described provide effective means for detecting localised abnormalities in peripheral blood oxygenation levels, indicative of existing tissue damage or the potential therefor.

Claims

Claims

1) An analytical apparatus comprising a plurality of pulse-oximetry sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue 5 of a body part and electronic means for monitoring the output of said sensors.

2) An analytical apparatus as claimed in Claim 1, wherein said electronic monitoring means comprise means for processing 10 said measured signals.

3) An analytical apparatus as claimed in Claim 2, wherein said electronic monitoring means comprise means for displaying the processed signals.

4) An analytical apparatus as claimed in Claim 2 or Claim 15 3, wherein said processing means comprise respective processors for processing the signals measured by each of said pulse-

oximetry sensors.

5) An analytical apparatus as claimed in Claim 2 or Claim 3, wherein said processing means comprise a single processor 20 for processing, in turn, the signals measured by each of said pulse-oximetry sensors.

6) An analytical apparatus as claimed in any preceding claim, wherein each of said plurality of pulse-oximetry sensors comprises a reflectance mode sensor.

25 7) An analytical apparatus as claimed in any of Claims 1 to 5, wherein each of said plurality of pulse-oximetry sensors comprises a transmission mode sensor.

8) An analytical apparatus as claimed in any preceding claim, wherein each sensor comprises a respective light emitter and receiver.

9) An analytical apparatus as claimed in any of Claims 1 5 to 7, wherein the sensors are provided by each of a plurality of light receivers arranged to receive signals from a single light emitter.

10) An analytical apparatus as claimed in any of Claims 1 to 7, wherein the sensors are provided by a single light 10 receiver arranged to receive signals from each of a plurality of light emitters.

11) An analytical apparatus as claimed in Claim 8 or Claim 10, wherein the light emitters are arranged to emit light at different respective frequencies to reduce optical cross talk.

15 12) An analytical apparatus as claimed in Claim 8 or Claim 10, wherein the light emitters are arranged to be operated in sequence to reduce optical cross talk.

13) An analytical apparatus as claimed in Claim 8 or Claim 9, wherein the receivers are arranged to receive light at 20 different respective frequencies.; 14) An analytical apparatus as claimed in any preceding claim, arranged for sensor outputs to be monitored remotely of the sensor array, by the transmission of the sensor outputs to a remote site, via a telecommunications link.

25 15) An analytical apparatus as claimed in any preceding claim, wherein a further respective sensor is provided, adjacent each of said pulseoximetry sensors, for detecting the presence of an adjacent body part.

16) An analytical apparatus as claimed in Claim 15, wherein said further sensor comprises a photo-electric sensor arranged to detect light falling thereon at frequencies other than those used by its respective pulseoximetry sensor.

5 17) An analytical apparatus as claimed in Claim 15, wherein said further sensor comprises a pressure sensor.

18) An analytical apparatus as claimed in any preceding claim, wherein said pulse-oximetry sensors are incorporated into the residual-limbreceiving socket of a prosthetic device.

10 19) An analytical apparatus as claimed in Claim 18, wherein, wherein said pulse-oximetry sensors are incorporated into a cushioning liner of said socket.

20) An analytical apparatus as claimed in Claim 19, wherein said liner comprises an elastomeric sleeve or sock for fitting 15 over the residual limb.

21) An analytical apparatus as claimed in any of Claims 1 to 17, wherein the measured pulsatile signals are used to provide feedback for controlling the operation of a device arranged to intermittently compress a body part, for example 20 to prevent deep-vein thrombosis (DVT).

22) An analytical apparatus as claimed in any of Claims 1 to 17, wherein the measured pulsatile signals are used to provide feedback for controlling the operation of a reconfigurable article of furniture, such as a chair or bed, 25 or of a variable pressure cushion or mattress.

23) A prosthetic device having a socket for receiving a residual limb, the socket having a liner for cushioning the residual limb and incorporating a plurality of pulse-oximetry

sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of the residual limb.

24) A liner for the socket of a prosthetic device and 5 incorporating a plurality of pulse-oximetry sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of a residual limb to which the prosthetic device may be fitted.

25) A device for intermittently compressing a body part and 10 comprising electronic control means responsive to feedback signals provided by a plurality of pulse-oximetry sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of the body part.

Z6) A reconfigurable article of furniture comprising 15 electronic control means responsive to feedback signals provided by a plurality of pulse-oximetry sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of a body supported by the article of furniture.

20 27) A variable-pressure cushion or mattress comprising electronic control means responsive to feedback signals provided by a plurality of pulse-oximetry sensors arranged to measure pulsatile signals at separate respective locations within the peripheral tissue of a body supported by the cushion 25 or mattress.

28) An analytical apparatus substantially as herein described with reference to the accompanying drawings.

29) A prosthetic device substantially as herein described with reference to Figure 1 of the accompanying drawings.

30) A liner for the socket of a prosthetic device, the liner being substantially as herein described with reference to the Figure 1 of the accompanying drawings.

31) A device for intermittently compressing a body part, 5 the device being substantially as herein described with reference to Figure 2 of the accompanying drawings.

32) A reconfigurable article of furniture substantially as herein described with reference to Figure 2 of the accompanying drawings. 10 33) A variable-pressure cushion or mattress substantially as herein described with reference to Figure 2 of the accompanying drawings.