WO2020121229A1

WO2020121229A1 - Respiratory monitoring device

Info

Publication number: WO2020121229A1
Application number: PCT/IB2019/060682
Authority: WO
Inventors: Reagan Kurniadwiputra SUSANTO; Jason Chiang; Lee James GIBSON
Original assignee: Curatek Pty Ltd
Priority date: 2018-12-12
Filing date: 2019-12-12
Publication date: 2020-06-18

Abstract

A respiratory monitoring device comprising: a housing comprising an adhesive surface adapted to adhere to a patient; a stretchable resistive element housed in the housing, the resistive element comprising: a metal ink conductor printed on a flexible substrate; wherein a resistance of the stretchable resistive element varies in proportion to a distance by which the stretchable resistive element is stretched; and a measuring circuit connected to the stretchable resistive element, for measuring changes in resistance of the stretchable resistive element.

Description

RESPIRATORY MONITORING DEVICE

Field

[0001 ] The present invention relates to respiratory monitoring devices.

Background

[0002] Respiratory monitoring devices are used to determine respiratory rate which can serve as an indicator for patient health. For example, respiratory rate may be used as an indication of patient discomfort or show symptoms of an underlying condition requiring treatment.

[0003] Devices used in respiratory monitoring generally fall into two categories. Direct measurement devices, measuring air flow into and out of the lungs directly, or indirect measurement devices, that measure changes in body volume as an approximation of respiratory rate. Further, as an alternative to both direct and indirect measuring devices, trained medical staff may conduct periodic manual respiratory counts to determine changes in respiratory rate.

[0004] Conventional respiratory monitoring devices suffer from several drawbacks. Direct measurement devices, such as a spirometer, interferes with normal breathing and renders the patient immobile. Indirect measurement devices, such as a strain based monitoring belt located around the chest of a patient, allows the patient to be ambulant, but may cause discomfort when measuring expansion and contraction of the patient's chest. Due to the complexity and cost of existing indirect measurement devices, these devices need to be maintained and are often reused, which, entails some risk of contamination between patients. Manually conducted respiratory counts are prone to human error and consume further occupies the limited time available to trained medical staff.

[0005] In this context, there is a need for improved respiratory monitoring devices.

Summary

[0006] According to the present invention, there is provided a respiratory monitoring device comprising:

a housing comprising an adhesive surface adapted to adhere to a patient; a stretchable resistive element arranged housed in the housing, the restive element comprising:

a metal ink conductor printed on a flexible substrate;

wherein a resistance of the stretchable resistive element varies in proportion to a distance by which the stretchable resistive element is stretched; and a measuring circuit connected to the stretchable resistive element, for measuring changes in resistance of the resistive element..

[0007] The respiratory monitoring device may further comprise a controller arranged on the housing wherein an output signal of the measuring circuit is connected as an input to the controller; and wherein the controller is configured to transmit output data of the measuring circuit to an external device.

[0008] The housing may take the form of an adhesive patch.

[0009] The adhesive surface may comprise two adhesive sections arranged on opposite ends of the adhesive patch.

[0010] The stretchable resistive element may be arranged to span between the two adhesive sections.

[001 1 ] The housing may comprise two stretchable layers, wherein the stretchable resistive element is housed between the two stretchable layers.

[0012] The respiratory monitoring device may further comprise a communication module.

[0013] The communication module may comprise a wireless transceiver.

[0014] The respiratory monitoring device may further comprise a removable backing strip for retaining the housing in a pre-stretched condition before applying the respiratory monitoring device to a patient.

[0015] The metal ink may comprise gold or silver materials.

[0016] The flexible substrate may be a silicon substrate. [0017] The metal ink conductor may comprise a plurality of parallel conductive strips spanning along a length of the flexible substrate. The plurality of parallel conductive strips may undulate across a breadth of the flexible substrate. The plurality of parallel conductive strips may undulate in alternate angled right and left turns.

[0018] The respiratory monitoring device may comprise a visual indicator of the degree of stretch of the stretchable resistive element.

[0019] The respiratory monitoring device may be shaped to visually provide an indication for positioning the device relative to a preferred target location on a patient.

[0020] The respiratory monitoring device may be shaped to comprise only rounded corners to avoid snagging with other objects.

[0021 ] According to the present invention, there is provided a respiratory monitoring system comprising: a respiratory monitoring device as described above and a display in communication with the respiratory monitoring device, wherein the display is configured to display a respiratory rate.

[0022] The display may be configured to calculate the respiratory rate.

[0023] The respiratory monitoring device may be in wireless communication with the display.

Brief Description of Drawings

[0024] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is an exploded perspective view of a respiratory monitoring device in accordance with some embodiments;

Figure 2 is a diagram showing the respiratory monitoring device of Figure 1 attached to a patient;

Figure 3 is an exploded view of a respiratory monitoring device in accordance with some embodiments;

Figure 4 is a perspective view of the respiratory monitoring device of Figure 3; Figure 5a is a schematic representation of a printed resistive element according to some embodiments;

Figure 5b is a schematic representation of a printed resistive element according to further embodiments;

Figure 6 is a schematic representation of various possible configurations of respiratory monitoring devices in accordance with some embodiments;

Figure 7 is a block diagram of the system architecture for a respiratory monitoring device in accordance with some embodiments;

Figure 8 is a flow chart outlining an algorithm used to process the oscillator circuit output signal;

Figure 9 is a flow chart outlining a further algorithm used to calculate a respiratory rate;

Figure 10 is a plot of respiratory rate measured in breaths per minute against time; and

Figure 1 1 is a diagram showing a respiratory monitoring system according to a further aspect of the invention.

Description of Embodiments

[0025] Referring to Figures 1 and 2, a respiratory monitoring device 100 in accordance with the invention, generally comprises a housing, which as shown for the example embodiment of Figure 1 may take the form of an adhesive patch 102 comprising an adhesive surface 104 adapted to attach the monitoring device 100 to a patient 106. The respiratory monitoring device 100 further comprises a stretchable resistive element 108 housed within the housing, the resistive element comprising a metal ink conductor printed on a flexible base layer 1 16 wherein a resistance of the stretchable resistive element 108 varies in proportion to a distance by which the stretchable resistive element 108 is stretched. The respiratory monitoring device 100 further comprises a measuring circuit 1 10 connected to the stretchable resistive element 108 for measuring changes in the resistance of the stretchable resistive element 108.

[0026] Referring to Figure 1 , for the example embodiment shown, the adhesive patch 102 may comprise a backing layer 1 14 and a base layer 1 16. The combination of the backing layer 1 14 and base layer 1 16 may be configured to house the measuring circuit 1 10 and the stretchable resistive element 108 therebetween. For example, the stretchable resistive element 108 may be printed on or in the base layer 1 16 and covered by the backing layer 1 14. The respiratory monitoring device 100 may comprise one or more further sealing layers 1 15 for sealing the stretchable resistive element 108. For example, a sealing layer 1 15 may be provided between the base layer 1 16 and the backing layer 1 14 as shown in Figure 1 . A sealing layer 1 15 may also be provided between the base layer 1 16 and the adhesive surface 104, if required. The measuring circuit 1 10 may be covered by a protective cap 1 17 for shielding the electrical components of the respiratory monitoring device 100. The respiratory monitoring device 100 may be powered by a battery 1 12. The adhesive layer 104 may be sealed until use by means of adhesive backing tape 1 19 to prevent adhesion of the patch prior to use. One or more of the layers forming the patch may be stretchable. In some embodiments, the base layer 1 16 on which the resistive element 108 is printed, will be adapted to stretch in conjunction with the resistive element 108. Similarly, the sealing layer 1 15, the adhesive layer 104 and/or the backing layer 1 14 may be configured to stretch in conjunction with the resistive element 108 and other stretchable layers.

[0027] As, for example shown in Figure 2, the adhesive patch 102 may be connected to the chest of a patient 106 such that the stretchable resistive element 108 is in a partially stretched condition. In use, the respiratory monitoring device 100 can be arranged in proximity and parallel to a clavicle of the patent 106 being monitored. Alternatively, as shown for example in Figure 1 1 , the respiratory monitoring device can be arranged on a lower rib or diaphragm region of the patient 106 on the abdomen, proximate the costal arch. Typically the lower rib region will only be used if the upper clavicle region is being used for other monitoring devices. In both of these positions, the stretch of the patient’s skin can be measured to represent the patient’s breathing.

[0028] The stretchable resistive element 108 may take the form of metallic ink which may comprise gold or silver materials, such as gold or silver particles. The metallic ink may be printed onto a flexible silicon substrate such as a PDMS substrate. For example, as shown in Figure 5a the metallic ink may be printed to form a conductor having multiple parallel conductive strips 109 along a length of the base layer 1 16. Appreciably, by arranging the connected parallel conductive strips 109 along the length of the base layer 1 16, any change in length of the base layer 1 16 is multiplied by a proportionate change in length of each of the parallel conductors 109. Referring to Figure 5b, a further example of a stretchable resistive element 108 is shown, in the form of a metallic ink conductor printed on a flexible base layer 1 16. Similar to the example shown in Figure 5a, the resistive element 108 may comprise parallel conductors 109 spanning along a length of the flexible base layer 1 16. The parallel conductors 109 may further be arranged to undulate across a breadth of the flexible base layer 1 16. The parallel conductors 109 may undulate or zigzag in, for example, alternate left and right turns. The conductors 109 zigzag horizontally from one end to the other of the patch 102. The conductors 109 zigzag in a horizontal plane of the base layer 1 16. These alternating turns may be gradual or may be abrupt angled turns as shown, for example, in Figure 5b. Appreciably, the zigzag arrangement of the conductors 109 over the breadth of the base layer 1 16 will allow additional stretch of the stretchable resistive element 108 along the length of the base layer 1 16 prior to irreparable deformation of the resistive element 108. The zigzag arrangement may therefore extend the operating lifetime of the respiratory monitoring device 100. The stretchable resistive element 108 may comprise contacts 1 1 1 for connecting to the measuring circuit 1 10.

[0029] The measuring circuit 1 10 may take any suitable form to measure changes in resistance, for example the measuring circuit may take the form of a wheat stone bridge circuit to measure changes in resistance. Alternatively, the measuring circuit may take the form of an oscillator circuit which may measure changes in resistance as a function of frequency which may enable resistance measurements to be made using lower power consumption.

[0030] Referring to Figures 3 and 4, a respiratory monitoring device 100 in accordance with some embodiments may comprise an upper support film in the form of a removable backing strip 130 for retaining the respiratory monitoring patch 100 in the correct pre stretched state prior to adhering the device 100 to a patient. Once the device 100 is attached to the patient, the backing strip 130 can be removed to allow the respiratory monitoring device 100 to stretch and contract in correlation with expansion and contraction of the patient’s chest. Advantageously, having the monitoring device 100 secured in the pre-stretched state by the backing strip 130, prior to adhesion, limits the likelihood of the device being applied incorrectly, with, for example, insufficient margin to stretch or contract. Applying pre-stretched monitoring devices may also remove the requirement to calibrate each device 100 specifically to each patient. The respiratory monitoring patch 100 may comprise a battery tab 132 for disconnecting the battery 1 12 from the measuring circuit and the controller. The battery 1 12 may be housed within a battery slot 121.

[0031 ] Figure 6, shows example shapes and configurations of respiratory monitoring devices in the form of patches in accordance with some embodiments. Although the patches shown comprise various design shapes, the changes in resistance are correlated with linear stretch and contraction of the metal ink conductor housed within the patch. As shown in the figures, the patches may preferably have curved and/or rounded edges. Advantageously, using patches with curved and rounded edges will help to avoid the patches snagging or catching on clothing, wiring or other articles and equipment that may be found in environments where the device is likely to be used, such as, hospitals and clinics. The patches may further be functionally shaped to provide a physical indicator of placement relative to a preferred target location, orientated against specific body landmarks, such as the collarbone or costal arch. For example, one edge of the patch may be shaped to project toward the centre a patient’s collarbone when correctly applied, thereby providing the user with a reference for properly applying the patch to the patient. The shape of the patch may also be suited to fit the aesthetics of the environment in which it used, such as a hospital.

[0032] Referring to Figures 3 and 4, the respiratory monitoring device 100 may comprise one or more visual indicators to assist in the application and operation of the device 100. The monitoring device 100 may include a visual indicator of the degree of stretch of the stretchable resistive element 108. The patch 102 may comprise a printed backing pattern 131 to serve as indicator of the current degree of stretch of contraction the patch 102 is under. For the example shown, the pattern 131 of alternating^ coloured and curved (accordion) lines will deform depending on the degree of strain applied along the length of the patch 102. Appreciably, the correct level of tension required for operation can be matched to a specific visual arrangement of the indicator prior to application. The monitoring device may further include numbered tabs to assist with operation of the device. This may include numbered battery tab 132 for operating activation of the measuring circuit. The numbered tabs may include an adhesive tab 134 arranged on the adhesive backing tape 1 19. The numbered tabs may also include a backing tab 136 arranged on the backing strip 130. The numbered tabs may indicate a proper sequence of removal to follow during application. For example, in use, when applying the patch 102 the user will first remove the battery tab 132 numbered“1” to activate the patch 102. Thereafter the user will remove the adhesive backing 1 19 indicated by adhesive tab 134 numbered“2” before adhering the patch 102 to the patient. Finally, once the patch 102 is attached, the user will proceed to remove the backing strip 130 indicated by backing tab136 numbered“3” releasing the patch 102 and allowing the stretchable resistive element 108 to stretch and contract. The patch 102 may further include a visual indication of its function in order to differentiate the patch 102 from other patches that may be applied to a patient. For example, the embodiment shown includes the text “RESP” to indicate that the patch is used for respiratory monitoring.

[0033] The patch 102 may be approximately 130 mm in length and may be approximately 40 mm wide.

[0034] Figure 7 shows a block diagram of the system level architecture of a respiratory monitoring system. In order to conserve data processing requirements, data output from the sensing circuit 1 10 is transmitted to the processor 140 by means of controller 128, removing the need to perform respiratory rate calculations on the device 100.

[0035] Referring to Figure 8, the processor 140 may implement processing algorithm 200 to process the output signal of the oscillator circuit 1 10. The processing algorithm 200 starts at 202 by initialising a buffer array at 204. Once the buffer array is initialised, at 206 incoming data from the measuring circuit 1 10 is saved to a buffer array at 208 this is repeated until the buffer is full. Once the buffer is full at 300, a calculation algorithm described below with reference to Figure 9 is executed to calculate a respiratory rate. At 210 the calculated respiratory rate is saved. At 212 a check is conducted to determine whether the testing sequence is still within a predetermined time limit. Once the time limit is exceeded, at 214, the process is ended.

[0036] Referring to Figure 9, the processor 140 may use calculation algorithm 300 to calculate the respiratory rate of the patient. At 302 the mean of the measured data stored in the buffer is calculated. At 304 the standard deviation of the measured data is calculated. Thereafter, at 306 a respiratory counter is initialised to zero and each individual segment of data is analysed at 308 to see if the data is above the mean and below the threshold, if yes, at 310 the state is determined to be unknown, and if no, at 312 a check is conducted to see if the data is above the threshold. If yes, at 314 the current state is set to high, and if no, at 316 the current state is set low. At 318 each of n individual pieces of data is analysed at 320 to check if the current data is less than the mean. At 322, if the data is less than the mean, the state is set to low, otherwise, if at 324 the state is not high and the data is above the threshold, then at 326 the current state is set to high and at 328 the respiratory count is increased by one. At 330 the data is checked to confirm if it is the end of a loop. If yes, at 332 the calculation stops and the data is stored. The example algorithms described with reference to Figures 8 and 9 are described with references examples where respiratory rate is calculated as a function of change in frequency due to change in resistance. Other algorithms and calculation techniques may also be used to determine respiratory rate.

[0037] Figure 10 shows a plot of respiratory rate in breaths per minute against time as calculated using algorithm 300.

[0038] Figure 1 1 shows a respiratory monitoring system 400 including a respiratory monitoring device 100 as described above configured to communicate with a display 404. The display 404 may comprise a graphic user interface to display the number of breaths per minute, the real time respiratory rate, trend data over time, the sinusoidal movement of breathing, regularity or irregularity of a patients breathing pattern and may be able to show the amount of effort required by the patient to breathe. Multiple patches 102 may connect to the respiratory monitoring system, by, for example, interfacing with a hospital network to allow transmission of data to a central database. Each patch 102 collects respiratory data with may then be transmitted to a remote processor to calculate one or more of respiratory rate, trend, effort, pattern and any warnings that may be generated from these calculations.

[0039] Embodiments of the present invention provide a respiratory monitoring device that is useful for use in medical applications to determine the respiratory rate of a patient by using a variable resistance element.

[0040] For the purpose of this specification, the word“comprising” means“including but not limited to”, and the word "comprises" has a corresponding meaning.

[0041 ] The above embodiments have been described by way of example only and modifications are possible within the scope of the claims that follow.

Claims

1 . A respiratory monitoring device comprising:

a housing comprising an adhesive surface adapted to adhere to a patient;

a stretchable resistive element housed in the housing, the resistive element comprising:

a metal ink conductor printed on a flexible substrate;

wherein a resistance of the stretchable resistive element varies in proportion to a distance by which the stretchable resistive element is stretched; and

a measuring circuit connected to the stretchable resistive element, for measuring changes in resistance of the stretchable resistive element.

2. The respiratory monitoring device as claimed in claim 1 , further comprising:

a controller arranged on the housing;

wherein an output signal of the measuring circuit is connected as an input to the controller; and

wherein the controller is configured to transmit output data of the measuring circuit to an external device.

3. The respiratory monitoring device as claimed in either claim 1 or claim 2, wherein the housing is an adhesive patch.

4. The respiratory monitoring device as claimed in claim 3, wherein the adhesive surface comprises two adhesive sections arranged on opposite ends of the adhesive patch.

5. The respiratory monitoring device as claimed in claim 4, wherein the stretchable resistive element spans between the two adhesive sections.

6. The respiratory monitoring device as claimed in any one of the preceding claims, wherein the housing comprises two stretchable layers, and wherein the stretchable resistive element is housed between the two stretchable layers.

7. The respiratory monitoring device as claimed in any one of the preceding claims further comprising a communication module.

8. The respiratory monitoring device as claimed in claim 7, wherein the communication module comprises a wireless transceiver.

9. The respiratory monitoring device as claimed in any one of the preceding claims further comprising a removable backing strip for retaining the housing in an operative pre-stretched condition before applying the respiratory monitoring device to a patient.

10. The respiratory monitoring device as claimed in any one of the preceding claims wherein the metal ink comprises gold or silver materials.

1 1. The respiratory monitoring device as claimed in any one of the preceding claims wherein the flexible substrate is a silicon substrate.

12. The respiratory monitoring device as claimed in any one of the preceding claims, wherein the metal ink conductor comprises a plurality of parallel conductive strips spanning along a length of the flexible substrate.

13. The respiratory monitoring device as claimed in claim 12, wherein the plurality of parallel conductive strips undulate across a breadth of the flexible substrate.

14. The respiratory monitoring device as claimed in claim 13, wherein the plurality of parallel conductive strips undulate in alternate angled right and left turns.

15. The respiratory monitoring device as claimed in any one of the preceding claims, comprising a visual indicator of the degree of stretch of the stretchable resistive element.

16. The respiratory monitoring device as claimed in any one of the preceding claims, wherein the device is shaped to visually provide an indication for positioning the device relative to a preferred target location on a patient.

17. The respiratory monitoring device as claimed in any one of the preceding claims, wherein the device is shaped to comprise only rounded corners to avoid snagging with other objects.

18. A respiratory monitoring system comprising:

a respiratory monitoring device as claimed in any one of claims 1 to 17;

a display in communication with the respiratory monitoring device, wherein the display is configured to display a respiratory rate.

19. The respiratory monitoring system as claimed in claim 18 wherein the display is configured to calculate the respiratory rate.

20. The respiratory monitoring system as claimed in claim 18 wherein the respiratory monitoring device is in wireless communication with the display.