Method and device for monitoring the perspiration of a living being

Abstract

The invention relates to a method for monitoring the perspiration of a living being, said perspiration causing the creation of a bodily fluid, said method comprising: A step of filling a measuring cavity (103) with a volume of bodily fluid (F) during perspiration, said measuring cavity (103) having an internal volume V1 intended to be filled with the bodily fluid; A step of measuring an electrical signal between a first measuring electrode (20) and a second measuring electrode (21); A step of absorbing the bodily fluid (F) when the bodily fluid reaches a volume V2 which is equal to the internal volume V1 of the measuring cavity (103), and in that said measurement step is triggered when said volume V2 of bodily fluid (F) is equal to the internal volume V1 of the measuring cavity (103). Figure to be published with the abstract: Figure 1

Description

Title of the invention: Method and device for monitoring the perspiration of a living being Technical field of the invention

[0001] The present invention relates to a method and device for monitoring the perspiration of a living being. State of the art

[0002] Various measurement sensors are now known to monitor certain physiological parameters of a living being in real time, such as blood glucose levels and heart rate. Recently, sweat sensors have also been developed to monitor the fluid losses experienced by a living being. These sensors can provide early warning of possible dehydration, for example during physical activity, or be used for other purposes, such as measuring the stress level of the living being.

[0003] US patent application 2022 / 257131A1 describes, in particular, the development of a wearable device in the form of a patch to be applied to the skin of a living being. The patch may be equipped with a measurement system capable of measuring physiological parameters of the living being by analyzing bodily fluids, i.e., sweat secreted by the living being. The parameters monitored include, for example, sodium levels, lactate levels, and glucose levels.

[0004] US patent 10405794B2 describes a sweat detector using in particular a coiled capillary capable of filling with body fluid, electrodes being distributed along the capillary to determine the volume of fluid captured and track the volume of sweat secreted.

[0005] The referenced publication “Hashimoto, Y.; Ishihara, T.; Kuwabara, K.; Amano, T.; Togo, H. Wearable Microfluidic Sensor for the Simultaneous and Continuous Monitoring of Local Sweat Rates and Electrolyte Concentrations. Micromachines 2022, 13, 575. https: / / doi.org / 10.3390 / mil3040575” describes a device suitable for measuring small volumes of sweat collected regularly, in order to deduce the sweat rate throughout exercise.

[0006] Each drop of sweat formed is detected before being absorbed, ensuring real-time monitoring of the volume of sweat emitted by the skin. Electrical detection using two electrodes allows counting the number of drops generated and determining the time between the collection of two consecutive drops.

[0007] The accuracy of this sensor relies on the reproducibility of the formed drops. Indeed, the volume allocated to the drops is considered constant and solely dependent on of the geometry of the device. The contact of the droplet between the two electrodes allows the measurement of the conductivity of the sweat, which makes it possible to monitor the ionic composition of the sweat during exercise.

[0008] However, this measuring device has several drawbacks: - It relies on the principle of reproducibility of the formed droplets, which are considered to always have the same volume. However, nothing precisely defines this volume. The volume of the droplet is in fact dependent on the space between the exit channel and the absorbing element. This space can vary. During physical exertion, vibrations due to the person's movement (running, cycling, etc.) will indeed modify this space and / or the shape of the droplet, which will generate uncertainty about the droplet's volume and therefore about the resulting measurements. - The contact time of the drop with the two electrodes is very short, which does not allow for a very reliable measurement of the conductivity of the sweat drop.

[0009] The aim of the invention is to propose a suitable solution for monitoring the perspiration of a living being, which is independent of the size of the collected drops and as little as possible of the operating constraints (movement, vibrations,...). Description of the invention

[0010] This objective is achieved by a method for monitoring the perspiration of a living being, said perspiration causing the creation of a bodily fluid, said method comprising: - A step of filling a measuring cavity with a volume of bodily fluid during perspiration, said measuring cavity having an internal volume V1 intended to be filled with the bodily fluid, - A measurement step of an electrical signal between a first measuring electrode and a second measuring electrode, triggered when the first and second electrodes come into contact with the body fluid present in the measuring cavity, - The process includes: - A step of absorption of body fluid when the body fluid reaches a volume V2 which is equal to the internal volume VI of the measuring cavity, - Said measurement step being triggered when said volume V2 of body fluid is equal to the internal volume VI of the measurement cavity.

[0011] According to one particular feature, the measurement step is also triggered when the volume V2 of body fluid is less than the internal volume VI of the cavity of measure.

[0012] The invention also relates to a device for monitoring the perspiration of a living being, said perspiration causing the creation of a bodily fluid, said device comprising: - A measuring cavity comprising an internal volume capable of filling with bodily fluid during perspiration, - A first measuring electrode and a second measuring electrode, placed in contact with the internal volume of the measuring cavity, - Means for measuring an electrical signal between the first measuring electrode and the second measuring electrode, - An absorbent element placed in contact with said internal volume of the measuring cavity, - The device being configured to implement the perspiration monitoring process as defined above.

[0013] According to one particular feature, the first measuring electrode has a conductive end immersed in said internal volume of the measuring cavity.

[0014] According to another feature, the second measuring electrode has a conductive end immersed in said internal volume of the measuring cavity.

[0015] According to another feature, the device includes a body fluid collection cavity, positioned upstream of the measuring cavity, and a connecting channel having an inlet connected to the collection cavity and an output connected to said measuring cavity.

[0016] According to another feature, the inlet of the connecting channel is equipped with a drip-breaker device.

[0017] According to another feature, the outlet of the connecting channel is flared.

[0018] According to another characteristic, the electrical signal is an impedance signal electric. Brief description of the figures

[0019] Other features and advantages will become apparent in the detailed description that follows, given in relation to the accompanying drawings in which: - Fig. 1 schematically represents the perspiration monitoring device according to the invention, according to a first advantageous embodiment; - Figures 2A to 2C schematically show several other embodiment configurations of the sweat monitoring device of the invention; - Figures 3A to 3C illustrate the operating principle of the sweating device of the invention; - Fig. 4 shows a diagram illustrating the variation in impedance during the steps of the process of the invention;

[0020] Detailed description of at least one embodiment

[0021] With reference to [Fig. 1], the invention relates to a device 1 for monitoring the perspiration of a living being, for example a human being. Through perspiration, the living being releases a bodily fluid called sweat through the skin P.

[0022] The device may be in the form of a patch to be applied to the skin P of the living being.

[0023] The device has an architecture developed along a principal direction X, this direction being intended to be perpendicular to the surface of the skin P when the device is applied against it. The terms "upper", "lower", "above" and "below" are to be considered with reference to this principal direction.

[0024] The device may thus comprise a single support 10 that adheres to the skin of the living being. Without limitation, the support 10 may have a surface area of ​​between 5 cm² and 15 cm².

[0025] The support 10 is presented for example in the form of a strip or disc of flexible material, having an underside called active 100 intended to be applied against the skin P of the living being.

[0026] The support 10 includes a body fluid collection cavity 101, intended to be positioned opposite the skin P. This collection cavity has a lower opening on the side of its lower face, through which the body fluid F enters during perspiration.

[0027] The support 10 includes a so-called measuring cavity 103. This measuring cavity 103 is located above the collecting cavity 101. The collecting cavity 101 and the measuring cavity 103 are connected to each other by at least one connecting channel 102 made in the support 10. This connecting channel 102 thus has an inlet connected to the collecting cavity 101 and an outlet connected to the measuring cavity 103. The connecting channel 102 can be made in the form of a capillary.

[0028] The device also includes a first measuring electrode 20 and a second measuring electrode 21. The device includes measuring means M adapted to measure an electrical signal between the first measuring electrode and the second measuring electrode.

[0029] The first measuring electrode 20 and the second measuring electrode 21 are configured and arranged to be in contact with the internal volume of the measuring cavity 103, and to come into contact with the body fluid F during partial and / or total filling of the measuring cavity 103.

[0030] The measuring means M are dedicated to measuring at least one electrical parameter. This electrical parameter is, for example, the electrical impedance (denoted Z) and / or the electrical conductivity of the fluid and / or any other relevant electrical parameter. In the remainder of the description and in the drawings, the electrical impedance measurement Z will be used.

[0031] It has been observed that, as is known, the impedance Z decreases as the volume of body fluid present in the measuring cavity increases. In other words, the more body fluid the measuring cavity contains, the lower the electrical impedance measured by the sensor will be.

[0032] The connecting channel 102 has a cross-section smaller than that of the collecting cavity 101 and smaller than that of the measuring cavity 103.

[0033] At its inlet, the connecting channel 102 advantageously features a drip-breaker device, which breaks the droplet that forms in the collection cavity 101 and is then directed to spread into the connecting channel 102. To implement this drip-breaker device, the connecting channel 102 must form, at its inlet, an angle Al of no more than 90° with the collection cavity 101. This drip-breaker device may also have at least one deposit of a layer of hydrophobic material 30 made at the periphery of the inlet of the connecting channel. This device makes it possible to break a liquid film always at the same point and thus increase the accuracy of the absorbed volume each time the measuring cavity 103 is filled.

[0034] Furthermore, at its outlet, the connecting channel 102 may have a flared area at its junction with the measuring cavity 103. This widening allows the body fluid F that passes through the connecting channel 102 and enters the measuring cavity 103 via the outlet to easily fill the measuring cavity 103 by capillary action along the lateral walls of the measuring cavity 103. The body fluid F thus spreads into the measuring cavity by rising up the lateral walls of the measuring cavity 103. Without limitation, the flare may be made at an angle A2 of at least 120°.

[0035] As regards the measuring cavity 103, it can take different forms. It can be parallelepiped, spherical, ovoid ([Fig.2C]).

[0036] According to the invention, the measuring cavity 103 has a total internal volume denoted VL.

[0037] Within the scope of the invention, the device also includes an absorbing element 40 made of an absorbing material. This absorbing element is intended to absorb the volume of body fluid present in the measuring cavity when this volume, denoted V2, becomes equal to the volume VI of the measuring cavity 103, that is, when the measuring cavity 103 is sufficiently filled with body fluid for the latter to then be absorbed by the absorbing element 40. In other words, the volume VI of the measuring cavity is defined by the position of the absorbing element 40 relative to the cavity.

[0038] The absorbing element 40 is, for example, positioned above the measuring cavity 103 and covers, for example, the top of the measuring cavity, bringing at least one of its faces into contact with the internal volume of the measuring cavity 103. Thus, when the volume VI of the measuring cavity 103 is filled with body fluid F, the latter comes into contact with the absorbing element 40 and is automatically absorbed in full, thus allowing the measuring cavity 103 to be emptied and the process to be restarted (see below).

[0039] Device 1 also includes a processing unit UC.

[0040] The processing unit CU can be integrated into the support 10, mounted on the support 10, or located remotely from the support 10. Wired or wireless communication means can be integrated into the support 10 to send the data measured by the measuring means to the processing unit CU. A wired connection is used, for example, between the measuring means and the processing unit CU.

[0041] The processing unit CU can be, for example, that of a smart portable object, such as, for example, a mobile phone, a computer or a smartwatch.

[0042] It is connected to the measuring means M to receive the measurement data.

[0043] Each measuring electrode may have a particular shape: - Straight conductive rod shape (as in [Fig. 1]), - Angled conductive rod shape, - Planar shape engraved on a printed circuit board or substrate, - Shape of conductive plate,...

[0044] Furthermore, it is also possible to provide different positioning configurations for each electrode: - Electrode immersed vertically in the measuring cavity, - Electrode immersed horizontally in the cavity, - Electrode running along the side wall of the measuring cavity,...

[0045] From this, it is possible to foresee different arrangements of the measuring electrodes. Figure 1, already discussed above, and Figures 2A to 2C show a selection of several possible arrangements. These arrangements are not limiting. It should be noted that the electrode shape and positioning configurations described above can be combined, while remaining within the scope of the invention.

[0046] [Fig. 1]: Two measuring electrodes 20, 21 in the form of conductive rods, inserted parallel and vertically into the measuring cavity 103. This configuration allows a first measurement to be triggered as soon as the level of body fluid present in the measuring cavity 103 reaches the two electrodes. Then, as As the body fluid F rises in the measuring cavity, the measuring means produce several measurements over time, until the internal volume VI of the cavity is filled and the volume V2 of body fluid F reaches this volume VI. When V2 = V1, the measuring cavity 103 is completely filled with body fluid, and the measuring means M can produce a final measurement before the body fluid is absorbed by the absorbing element. In this configuration, the electrical impedance will vary as the measuring cavity fills. The impedance will decrease as the chamber fills.

[0047] [Fig. 2A]: Two measuring electrodes 20, 21 extending horizontally in the measuring cavity 103. In this configuration, the variation in impedance is less noticeable because when the body fluid level F exceeds the positioning level of the two electrodes, the impedance will drop sharply and then remain at that level until absorption by the absorbing element 40. In this configuration, when the volume of body fluid reaches a volume V2 which is equal to the volume VI of the measuring cavity, the measured impedance is low, then it drops sharply as soon as this volume V2 is absorbed by the absorbing element 40. It would also be possible to use two identical fluidic cards, one inverted onto the other, with the two measuring electrodes made between the two cards sealed together.

[0048] [Fig. 2B]: This is, for example, a configuration where one of the two measuring electrodes is positioned in the measuring cavity 103 and the other electrode is positioned so as to come into contact with the body fluid when this volume of body fluid reaches a volume V2, which is equal to the volume VI of the cavity. The measurement will be triggered when the volume V2 reached by the body fluid reaches the volume VL. The second measuring electrode is therefore positioned above, at the level of the absorbing element 40.

[0049] [Fig.2C]: this is for example a configuration showing a measurement cavity of at least partially ovoid shape.

[0050] Figures 3A, 3B, 3C and 4 illustrate the operating principle of the invention, based on the configuration of Figure 1. The same principle applies to all the configurations also described above.

[0051] The device is positioned against the skin of the living being to monitor its perspiration.

[0052] E1: A first drop of bodily fluid F forms on the surface of the skin, penetrating the collection cavity 101. The two measuring electrodes 20, 21 are in air, the measured electrical impedance Z_0 is therefore high.

[0053] E2: The drop grows inside the collection cavity 101.

[0054] E3: As it grows, the droplet begins to pass through the connecting channel 102. By means of the droplet-breaking device present at the entrance of the channel, the droplet is broken, and the body fluid F fills the connecting channel 102.

[0055] E4: The body fluid F begins to fill the measuring cavity. Since the drop was previously broken and the channel has a flare at its outlet, the body fluid F tends to rise, occupying the entire cross-section of the measuring cavity 103.

[0056] E5: The level of body fluid in the measuring cavity 103 reaches the two measuring electrodes, triggering a strong variation in electrical impedance (or other electrical parameter) at the level of the measuring means M. The measured electrical impedance Z_1 varies sharply downwards.

[0057] E6: As the level of body fluid rises in the measuring cavity, it is possible to take several successive measurements. The higher the level, the lower the measured electrical impedance (Z_i).

[0058] E7: The volume V2 reached by the body fluid in the measuring cavity becomes equal to the internal volume VI of the measuring cavity. The body fluid reaches the absorbing element. The measuring means produce a final measurement Z_n.

[0059] E8: The absorbing element absorbs the body fluid present in the measuring cavity. A sudden rise in electrical impedance (to Z_0) is then observed, as the two measuring electrodes are again in the air after the measuring cavity 103 has been emptied. A new droplet can then form in the collection cavity 101.

[0060] The process can then be repeated for a new drop. The diagram in [Fig. 4] also illustrates the variation in impedance at each stage. Abrupt breaks are observed when the body fluid comes into contact with the two measuring electrodes and when the measuring cavity 103 empties.

[0061] The invention has many advantages, including: - The measurement is carried out on a volume that is always known, independent of the size of the initial drop; this is made possible by the fact that the body fluid F comes to occupy the entire section of the measuring cavity 103 until it completely fills the measuring cavity whose volume V1 is known. - The drop-breaking device ensures uniform filling of the measuring cavity 103, regardless of the shape of the drop initially taken. - By taking into account the filling time of the measuring cavity 103 (time interval between two distinct absorptions), it is possible to know the sweat rate in real time. - It is possible to determine the total volume of body fluid F collected by multiplying the collection volume of the device (volume of the measuring cavity) + volume of the linking channel + volume of the collection cavity) by the number of times the measuring cavity was filled. The number of times the reservoir is refilled in a given time allows for precise measurement of the evolution of the perspiration rate over time. The overall concentration of the solution (osmolarity) can be determined during the filling of the measuring cavity, as soon as the body fluid comes into contact with the measuring electrodes. Each new intake of body fluid is separated from the previous intake by the presence of an air space; therefore, there is no possible back-diffusion of compounds from one intake to the next.

Claims

Demands

1. A method for monitoring the perspiration of a living being, said perspiration causing the creation of a bodily fluid, said method comprising: - A step of filling a measuring cavity (103) with a volume of bodily fluid (F) during perspiration, said measuring cavity (103) having an internal volume V1 intended to be filled with the bodily fluid, - A step of measuring an electrical signal between a first measuring electrode (20) and a second measuring electrode (21), triggered when the first and second electrodes are brought into contact with the bodily fluid (F) present in the measuring cavity, - Characterized in that it comprises: - A step of absorbing the bodily fluid (F) when the bodily fluid reaches a volume V2 which is equal to the internal volume VI of the measuring cavity (103),and in that - Said measurement step is triggered when said volume V2 of body fluid (F) is equal to the internal volume VI of the measurement cavity (103).

2. Method according to claim 1, characterized in that the measurement step is also triggered when the volume V2 of body fluid (F) is less than the internal volume VI of the measurement cavity (103).

3. A device for monitoring the perspiration of a living being, said perspiration causing the creation of a bodily fluid, said device comprising: - A measuring cavity (103) comprising an internal volume capable of filling with bodily fluid (F) during perspiration, - A first measuring electrode (20) and a second measuring electrode (21), brought into contact with the internal volume of the measuring cavity (103), - Means for measuring an electrical signal between the first measuring electrode (20) and the second measuring electrode (21), - An absorbing element (40) brought into contact with said internal volume of the measuring cavity, - Characterized in that the device is configured to implement the sweat monitoring method as defined in claim 1 or 2.

4. Device according to claim 3, characterized in that the first measuring electrode (20) has a conductive end immersed in said internal volume of the measuring cavity (103).

5. Device according to claim 3 or 4, characterized in that the second measuring electrode has a conductive end immersed in said internal volume of the measuring cavity (103).

6. Device according to any one of claims 3 to 5, characterized in that it comprises a body fluid collection cavity (101), positioned upstream of the measuring cavity (103), and a connecting channel (102) comprising an inlet connected to the collection cavity and an outlet connected to said measuring cavity.

7. Device according to claim 6, characterized in that the inlet of the connecting channel (102) is provided with a drip-breaking device.

8. Device according to claim 6 or 7, characterized in that the outlet of the connecting channel (102) is flared.

9. Device according to any one of claims 3 to 8, characterized in that the electrical signal is an electrical impedance signal.

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