DEVICE AND METHOD FOR DETECTING A PRESSURE IN A RUMEN OF A RUMINANT

Abstract

The invention relates to a device (1) for detecting a pressure in a mammal's stomach, particularly in a rumen of a ruminant, the device (1) comprising at least the following components: a sensing volume (12), a pressure sensor (9) configured and arranged to detect a gas pressure in the sensing volume (12), an elastic membrane (5) forming a deformable wall portion of the sensing volume (12), wherein the elastic membrane (5) is configured and arranged to deform in response to a pressure difference over the elastic membrane (5), wherein the elastic membrane (5) comprises a gas-permeable portion allowing a pressure difference over the elastic membrane (5) to equalize.

Claims

1. A device (1) for detecting a pressure in a mammal's stomach, particularly in a rumen of a ruminant, the device (1) comprising at least the following components: a gas-filled sensing volume (12), a pressure sensor (9) configured and arranged to detect an atmospheric gas pressure in the sensing volume (12), an elastic membrane (5) liquid-tight forming a deformable wall portion of the sensing volume (12), wherein the elastic membrane (5) covers an opening of the sensing volume (12) and is configured and arranged to deform over the opening in response to a pressure difference over the elastic membrane (5), such that an atmospheric gas pressure change in the rumen is instantaneously detectable in the sensing volume (12), characterized in that the elastic membrane (5) comprises a gas-permeable portion allowing a pressure difference over the elastic membrane (5) to equalize, wherein the gas permeable portion of the membrane (5) has a thickness between 100 μm and 700 μm.

2. The device (1) according to claim 1, wherein the gas-permeable portion of the membrane (5) has a thickness that is larger than 300 μm and/or smaller than 500 μm.

3. The device (1) according to claim 1, wherein the device (1) is configured and adapted to record the pressure in the sensing volume (12) with a time resolution better than 10 seconds, wherein a pressure change over the elastic membrane (5) is transmitted to the sensing volume instantaneously.

4. The device (1) according to claim 1, wherein the pressure sensor (9) is a piezo-resistive pressure sensor, configured to detect an atmospheric gas pressure in the sensing volume.

5. The device (1) according to claim 1, wherein the elastic membrane (5) consists of the gas-permeable portion.

6. The device (1) according to claim 1, wherein the sensing volume (12) is enclosed liquid tight by the device (1).

7. The device (1) according to claim 1, wherein the elastic membrane (5), such as a mesh, gauze, or an elastic fabric.

8. The device (1) according to claim 1, wherein the gas-permeable portion comprises or consists of Polytetrafluoroethylene (PTFE).

9. The device (1) according to claim 1, wherein the gas permeable portion of the membrane is made by a milling process.

10. The device (1) according to claim 1, wherein the device (1) comprises a rigid casing (7, 14), wherein said casing (7) comprises the pressure sensor (9) and wherein the elastic membrane (5) is attached to the casing (7) such as to form or limit the sensing volume (12).

11. The device (1) according to claim 1, wherein the device (1) has an average density and a volume, adjusted such that that the device (1) permanently remains in a rumen of a ruminant.

12. The device (1) according to claim 1, wherein the device (1) comprises a radio wave transmission module (8) configured to wireless transmit sensor data generated by the pressure sensor (9).

13. The device (1) according to claim 1, wherein the device (1) does not comprise a valve configured to adjust a gas pressure in the sensing volume (12).

14. The device (1) according to claim 1, wherein the elastic membrane (5) covers an area of more than 0.5 cm.sup.2.

15. The device (1) according to claim 1, wherein the elastic membrane (5) extends planar over the sensing volume (12).

16. The device according to claim 1, wherein gas permeable portion of the membrane is configured to equalize the pressure difference over the membrane within a time interval, wherein said time interval is in the range of one second to 1.200 seconds.

17. A method for measuring a stomach pressure in a rumen of a ruminant with a device (1) according to claim 1, the method comprising the following steps of: Applying the device (1) to the rumen of the ruminant, Periodically or continuously detecting an atmospheric pressure in the sensing volume (12), wherein the pressure is sampled with a time resolution better than ten seconds wherein a time resolution of the device for detecting a pressure change is better than or equal to 1 second, Storing the detected pressure and/or the detected pressure change on a data storage (11) of the device (1) and/or periodically or intermittently transmitting the detected pressure and/or the detected pressure change to a receiver arranged on an outside of the ruminant.

18. The method according to claim 17, wherein the method further comprises the steps of: From the detected pressure and/or the detected pressure change determining rumen contractions, Determining a rumen activity, particularly a rumen contraction frequency, from the rumen contractions, Informing a person about the determined rumen activity.

19. The device according to claim 1, wherein pressure sensor (9) is configured and arranged to detect an atmospheric gas pressure only and not a partial gas pressure.

Description

[0111] FIG. 1 shows two views of the device according to the invention. In the upper part of the FIG. 1 a top view of the device 1 is shown, wherein in the lower part of FIG. 1 a cross-sectional view is depicted. The device 1 has a bolus form, also optionally denoted bolus for short. The device 1 is subdivided into a first region or portion 101 and second region or portion 102. The first region 101 has a cylindrical casing 7 of POM. The second region 102 has a cylindrical casing 15 that is releasable attachable to the casing 7 of the first portion. The casing 7 comprises a packing piece 3, in which the electronics 4 of the device 1 are arranged. Selection of the polymer ensures on the one hand radio wave transmissibility and simultaneously on the other hand biocompatibility of the material.

[0112] The electronics 4 in this example comprise inter alia a transmission module 8, a pressure sensor 9 and a microcontroller 10 and a data storage 11. The pressure-sensitive part of the pressure sensor is accommodated in a sensing volume 12 (or can communicate therewith), the wall of which is at least in part likewise configured from the casing 7 of the first region 101 and the top of which is formed by an elastic, gas-permeable PTFE-membrane 5, i.e. a membrane that consists of PTFE, i.e. the whole membrane consists of a gas-permeable portion. The PTFE-membrane 5 has a thickness of 400 μm. The sensing volume 12 is located at one end of the first region 101 of the device 1 and is preferably arranged on the end face of the elongate device 1.

[0113] Deformation of the elastic PTFE-membrane 5 as a result of application of force brings about a change in pressure in the sensing volume 12 which can be detected by the pressure sensor 9. The sensing volume 12 is closed with a closure means in the form of a ring 6 which fixes the membrane 5 in place. The electronics 4 are internally interconnected in such a way that the measurement data from the pressure sensor 9 can be processed by the microcontroller 10, stored on the data storage 11 and sent by the transmission module 8 to an external computer. The measurement data can furthermore also be processed by the electronics 4 itself.

[0114] The second region 102 of the device 1 adjoins below the first region 101. The second region 102 has a cylindrical casing 14 (for example of a stainless steel) which comprises an energy source in the form of a battery 2 for supplying the electronics 4 with electricity.

[0115] The electronics 4 are for example activated by means of a latching circuit which is triggered with a reed contact. To this end, a magnet closes the reed contact from outside and so activates the electronics 4.

[0116] The electronics 4 can turn back off as a result of an appropriate level on reset of the latching circuit, so enabling a test run of the entire device 1.

[0117] FIG. 2 shows a further configuration of the device 1. In the upper part of the FIG. 2 a top view of the device 1 is shown, wherein in the lower part of FIG. 2 a cross-sectional view is depicted. FIG. 2 shows the casing 14 of the second portion 102 of the device 1, which protectively encloses the energy source 2, the packing piece or alternatively weighting body 3, the electronics 4, the elastic gas-permeable PTFE-membrane 5, together with the sealing cap 6, the casing 7 of the first portion 101, the transmission module 8, the pressure sensor 9, as well as the microcontroller 10 and the data storage 11, and the sensing volume 12.

[0118] In contrast to the example shown in FIG. 1, the closure means 6 is configured as an annular sealing cap 6 which is configured to be screwed together with the device 1, in particular the casing 7, wherein the PTFE-membrane 5 is fixed in place over the sensing volume 12. To this end, the closure means 6, when screwed together as intended with the device 1 or casing 7, presses the PTFE-membrane 5 against a circumferential contact surface of the casing 7, wherein the PTFE-membrane 5 is fixed to the device 1 or the casing 7.

[0119] In particular, in an embodiment with a circumferential region, said annular sealing cap 6 presses against a circumferential edge region of the in particular circular PTFE-membrane 5. The PTFE-membrane 5 does not project beyond the sealing cap 6 in the axial direction of the device 1, as a result of which the PTFE-membrane 5 is provided with additional protection.

[0120] FIG. 3 shows a schematic and cross-sectional view of embodiment of the invention. The device 1 comprises a first portion 101 and a second portion 101 that are attached to each other along an axial direction of the device 1 and form a protective enclosure of the cylindrically-shaped device 1.

[0121] The first portion 101 comprises a cylindrical casing 7 forming a wall portion of the device 1, wherein at an upper opening, the device 1 is limited by an elastic, gas-permeable membrane 5 consisting of PTFE. The membrane 5 covers a gas-filled sensing volume 12 that is enclosed by the casing 7 and the membrane 5. The sensing volume 12 is fluidically connected by means of at least one channel (not shown) in the device 1 to a pressure sensor component 9. The pressure sensor component comprises the pressure sensor 9, a transmission module 4 for sending measured sensor data and for receiving external control data from an external device. Moreover, the pressure sensor component 9 comprises a microcontroller 10, as well as a data storage 11 for storing measured sensor data and received control data.

[0122] The device 1 comprises a mounting body 17 for an antenna and an antenna (not shown) that is arranged in specific channels 15 in the first portion 101 of the device 1 enclosed by the casing 7. The casing 7 is made from a radio-wave transparent material, such that transmission from and to the antenna of the device 1 is possible.

[0123] The second portion 102 comprises a casing 14 enclosing the energy source, namely the battery 2. The casing 14 is made from stainless steel in order to provide an inert but robust and stable casing for the second portion 102.

[0124] The membrane 5 is attached and fixed to the device by means of a membrane sealing ring 6 that is arranged circumferentially around an outer perimeter of the membrane 5. At a top portion of the casing 7, the casing 7 has a radially inward pointing protrusion 16 that is configured to protect and hold the sealing ring 6 onto the membrane 5.

[0125] The device shown in FIG. 3 is based on the same working principle as the devices shown in FIG. 1 and FIG. 2.

[0126] In FIG. 4 a schematic comparison of pressure measurements of conventional device for measuring ruminal activity to pressure measurement performed with a device according to the invention. Conventional device feature non-gas-permeable membranes. In both graphs the rumen activity, particularly contractions of the rumen can be seen as “ripples” on the graph. These contractions have a duration of only a few seconds (typically in the range of 1 to 10 seconds), such that the temporal resolution of pressure detection is of the essence.

[0127] As can be seen in the upper panel (A), underlying the pressure changes caused by ruminal activity a slow build-up in pressure inside the sensing volume can be observed until the pressure sensor is at its upper pressure range limit, where the pressure in the rumen cannot be recorded anymore (flat line due to saturation). The pressure build up can have various sources. For example it might be caused by outgassings of the battery, chemical or physical processes of some of the materials in the device, temperature variations, such that a gas pressure builds up inside the sensing volume that is not connected to actual pressure changes in the rumen and therefore does not reflect the true pressure in the rumen of the animal.

[0128] In comparison in the lower panel (B) of FIG. 4, the gas-permeable portion of the membrane of the device according to the invention allows for continuous pressure equalization between the sensing volume and the rumen, such that additional pressure components caused by the device are omitted to full extend.

[0129] Each time the rumen contracts the membrane might bent to obey to the pressure difference caused over the membrane. Due to its gas-permeability the membrane can relax in its original state as the gas permeates between the rumen and the sensing volume. A stiff membrane, that might be caused by a too large thickness will lead to a slow response time, such that time resolution of the device is affected such that the pressure changes caused by contractions in the rumen cannot be observed.

[0130] On the other hand if the membrane is too thin, e.g. thinner than 0.1 mm, the membrane is not stable enough to cope with the pressure changes and would rip apart during operation.

[0131] Surprisingly, while being prone to an elaborate manufacturing procedure with a milling device, when using PTFE membranes a membrane thickness allowing for a sufficiently high time resolution and stability towards external forces has been found, despite the unfavorable processing properties of PTFE in the claimed thickness regime.

[0132] The gas-permeability of the membrane therefore allows for a precise and more importantly long-term monitoring of the pressure in the rumen of an animal.