WO2012001557A1 - Strain gauge extensometer sensor for medical or industrial use in general - Google Patents

Strain gauge extensometer sensor for medical or industrial use in general Download PDF

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Publication number
WO2012001557A1
WO2012001557A1 PCT/IB2011/052493 IB2011052493W WO2012001557A1 WO 2012001557 A1 WO2012001557 A1 WO 2012001557A1 IB 2011052493 W IB2011052493 W IB 2011052493W WO 2012001557 A1 WO2012001557 A1 WO 2012001557A1
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WO
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Patent type
Prior art keywords
characterized
according
sensor
sheath
tape
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Application number
PCT/IB2011/052493
Other languages
French (fr)
Inventor
Antonio Berto
Giorgio Bergamo
Sandro Tognana
Original Assignee
Microlab Elettronica Sas
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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00Measuring arrangements characterised by the use of electric or magnetic means
    • G01B7/16Measuring arrangements characterised by the use of electric or magnetic means for measuring deformation in a solid, e.g. by resistance strain gauge
    • G01B7/18Measuring arrangements characterised by the use of electric or magnetic means for measuring deformation in a solid, e.g. by resistance strain gauge using change in resistance
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/103Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/107Measuring physical dimensions, e.g. size of the entire body or parts thereof
    • A61B5/1073Measuring volume, e.g. of limbs
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/103Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
    • A61B5/113Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb occurring during breathing
    • A61B5/1135Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb occurring during breathing by monitoring thoracic expansion
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/02Details of sensors specially adapted for in-vivo measurements
    • A61B2562/0261Strain gauges
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/68Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813Specially adapted to be attached to a specific body part
    • A61B5/6823Trunk, e.g., chest, back, abdomen, hip
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/68Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813Specially adapted to be attached to a specific body part
    • A61B5/6824Arm or wrist
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/68Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813Specially adapted to be attached to a specific body part
    • A61B5/6828Leg
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/68Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/683Means for maintaining contact with the body
    • A61B5/6831Straps, bands or harnesses

Abstract

The invention is a new strain gauge extensometer sensor (1) comprising at least one tubular duct (2) with small diameter, inside which there is mercury or gallium-indium alloy or another conductive liquid, said duct (2) being contained in an elastic sheath or body (3) having a flat-tape shape. Each end (31, 32) of said tape-like sheath (3) is constrained to an electrical connector (4, 5), wherein said electrical connectors (4, 5) are suited to be mutually coupled in a direct way achieving both the electrical connection and the mechanical connection.

Description

STRAIN GAUGE EXTENSOMETER SENSOR FOR MEDICAL OR INDUSTRIAL USE IN GENERAL DESCRIPTION

This patent is related to strain gauge extensometer sensors and in particular concerns a new strain gauge extensometer sensor for medical or industrial use in general.

So-called "strain gauge" extensometer sensors which measure the change in volume of a generally tubular body, or at least equipped with a section of which to measure the change in sizes are known.

The pathology of the venous system called venous insufficiency, which results in a condition in which the veins do not favour the return of blood flow to the heart is known. This condition often occurs in the veins of the lower limbs.

Thus in cases of venous insufficiency there is a slowing of blood flow, so the blood tends to stagnate in the lower legs. The slowing of blood flow due to venous insufficiency also reduces the supply of oxygen and nutrients to the blood vessel walls.

Venous stasis, which, as mentioned, is mainly located at the level of the limbs, typically lower limbs, may cause hypoxia, delayed perfusion, reduced drainage of catabolites, increased transmural pressure, and intense inflammatory activation of small veins and nearby tissue.

The diagnosis of venous insufficiency involves various methods, including venous plethysmography, which enables the assessment of overall venous function by measuring changes in the volume of venous blood in the leg. This measurement can be made with one of three plethysmographic techniques in use today: photo-pulse-plethysmography/reflected light rheography (PPG/RLR), strain gauge plethysmography (strain, SGP) and air plethysmography (APG).

In strain gauge plethysmography the measurement of changes in volume of a limb is replaced by the measurement of changes in limb circumference with the use of a strain gauge extensometer sensor.

Said strain gauge extensometer sensor comprises a tube with a very thin diameter made of elastic material, usually silicon, inside of which there is mercury or an alloy of indium/gallium, which is placed around the limb. An electric current is passed through the metal contained in the tube which, properly amplified and processed, is able to detect the stretching and thus the change in volume caused by leg vein occlusion.

The venous occlusion, obtained with a pneumatic cuff placed around the thigh and inflated up to values of 60mm Hg, causes an increase in volume of the leg and thus the circumference of the calf, resulting in a lengthening of the tube with a consequent variation in electrical resistance of the liquid in the tube.

By inflating the cuff until a pressure of 60 mm Hg, lower than the systolic blood pressure, limb volume below the cuff increases until the venous pressure equals the pressure of occlusion. Rapidly deflating the cuff, the venous outflow of the limb is attained, with a reduction of the circumference of the calf.

The limb circumference reduction rate provides a measure of the speed of venous outflow, which depends on whether there are obstacles in the venous channels.

The use of strain gauge extensometer sensors of the known type has some drawbacks.

First, the cooperation of the patient is required to properly place the cuff and the sensor, otherwise the results may be skewed. The strain gauge sensors of the known type also have the drawback of applying very high pressure on the limb, inasmuch as said tubes are extremely thin and thus, even when pressed against the surface of the limb with minimal force, being very elastic and very soft, they mark the skin, causing discomfort to the patient.

Thus the strain gauge extensometer sensors of the known type are not suitable to be used, for example, on particularly thin skin, or on sensitive parts of the body or body parts in the presence of edema.

These strain gauge sensors of the known type cannot be left on for long, but only for the shortest possible time.

Another drawback of the strain gauge sensors of the known type is that their connection is laborious and their very shape increases the chance of improperly positioning the sensor.

In fact, the strain gauge sensors of the known type generally comprise said tube in a U-shape with both ends connected to the same connector, while at the curve identified by the tube an element is placed for the mechanical connection with said connector or with a further connecting element to the conducting wires.

The U-shaped tube must be wrapped around the limb and then properly connected to carry out the measurements.

In this way, moreover, the U-shaped tube wrapped around the limb identifies on the skin of the limb itself essentially a double line of pressure, with additional discomfort for the patient.

Another drawback of the known strain gauge sensors is that the tubes, made of an elastic material, after various uses deform, stretch, and lose their elasticity, reducing the accuracy of the measurement.

These tubes, in fact, are extremely thin and flexible, so that minimal force is necessary to be able to extend and place the strain gauge sensor on the limb and to have high sensitivity to small changes in length.

For this reason, the tube is also more prone to breakage, even after a few uses.

In contrast, a tube with a larger diameter and/or made of material that is less elastic and therefore less deformable, would have lower sensitivity, and therefore lowered measurement accuracy.

Another drawback of strain gauge sensors of the known type is the fact that the tube, having a substantially circular-shaped section, undergoes torsional deformation as it is positioned, resulting in twisting and leading to measurement errors.

To overcome these drawbacks a new type of strain gauge extenso meter sensor was designed and constructed, particularly suitable for use in the medical field but also in any other area, industrial or otherwise, which involves the measurement of the change in volume of a body.

The main task of this invention is to ensure a more accurate reading of the data, since its correct positioning is facilitated with respect to sensors of the known type.

Another aim of the present invention is to ensure comfortable use by the user.

Another aim of the present invention is to enable quick placement and coupling, since the electrical connectors are integrated into a single coupling element.

Another aim of the present invention is to be able to apply it to the limbs, lower or upper, but also to other parts of the body, like the trunk.

Another aim of the present invention is to maintain its shape for longer and not sustain torsional deformations that compromise the proper positioning. These and other aims, direct and complementary, are achieved by the new strain gauge extensometer sensor for medical or industrial use in general, comprising, in its main parts, at least one small diameter duct, inside which there is mercury or indium/gallium alloy or another liquid conductor, and where said duct is contained in a body or flexible sheath, preferably made of silicon, with a flat tape-like shape.

This tape-like sheath made of silicone elastic material has many advantages. On one hand it reduces the pressure on a particularly narrow area on the skin of the limb or body part on which it is applied, making its use more comfortable, and furthermore can also be left in place for longer until completion of the measurement.

For this reason, the new strain gauge extensometer sensor is particularly suitable for use on any area on which it is possible to measure a change in volume, and in particular on parts of the body that are sensitive or in the presence of edema.

Thus the new strain gauge sensor can be effectively used for the diagnosis and evaluation of venous insufficiency.

The new strain gauge sensor is furthermore suitable for the evaluation of arterial blood flow, venous capacitance, the evaluation of the arteriosclerotic process, and all the evaluations that typically involve the measurement of a change in volume.

In addition, the elastic tape-like sheath can be deformed by lengthening it but returns to its original shape, unlike the known tube which, like in the strain gauge sensors of the known type, do not recover their original shape, as they are made of extremely thin and flexible tubes to maximize sensitivity, however not guaranteeing the return to their original shape when subjected to repeated stress. The new strain gauge sensor, in contrast, while being extremely extensible and sensitive to variations in length, ensuring the required accuracy in the measurement, is very elastic and returns to its original shape even after many uses.

A connector is constrained to each of the two opposite ends of said tape-like sheath, said connectors being suited to be mutually electrically connected in a direct way, also achieving the mechanical connection of the two ends of the tape-like sheath.

At least one of said two electrical connectors is in turn directly connected to at least one conductor cable, such as for example a four-wire cable.

In the preferred embodiment, each of said connectors comprises four contacts and in particular a first connector, or female connector, comprises four female electrical contacts for the four corresponding male electrical contacts of the second male connector.

Thus said electrical connectors quickly achieve the electrical connection and also the mechanical connection. Its application is quick and simple and positioning errors are minimized.

In fact, besides the fact that the mechanical and electrical connections are made quickly, the torsional deformations are minimized thanks to the flat shape of the tape-like sheath, which is thus properly positioned without twisting.

The attached drawing presents a practical embodiment of the invention by way of non-limiting example.

Figure 1 shows the invention fully assembled according to a first embodiment.

Figure la shows a section of the duct (2) housed in a tape-like sheath (3), while Figure 2a shows a section of the duct (2) comprising in turn one small tube (23) buried in said tape-like sheath (3).

Figure 2 shows how it is possible to electrically and mechanically connect the two connectors (4, 5) to both ends of the tape-like sheath (3).

Figure 3 shows the connectors (4, 5) according to the preferred embodiment. Figures 4a, 4b and 4c show three examples of use on the limbs (A, B) and trunk (C) of a patient (P), for plethysmographic measurements.

This is a strain gauge extenso meter sensor (1) comprising at least one elastic duct (2), with a small diameter, inside which there is mercury or gallium- indium alloy or another conductive liquid, and where said duct (2) is contained in an elastic sheath or body (3), preferably made of silicone or another elastic material, having a flat tape-like shape.

In the preferred solution, said duct (2) is obtained directly in said tape-like sheath or body (3), for example during the extrusion of the sheath (3) itself, as shown in Figure la.

According to a possible alternative embodiment, said duct (2) comprises at least one small elastic tube (23) that defines the duct (2) itself, said small tube (23) being completely buried in said tape-like sheath (3), as in Figure lb.

Said tape-like sheath (3) therefore has a length substantially equal to the length of said duct (2), without the ends (31, 32) which are connected to electrical connectors (4, 5), and a thickness greater than the diameter of the duct (2), as in Figures la and lb, and a width greater than its thickness. For example, considering a duct (2) with a diameter substantially equal to or on the order of 1 mm, said tape-like sheath (3) has a thickness of 2 mm and a width of 1 cm.

Therefore, this tape-like sheath (3) has a flat surface (33) for contact with the body part on which it is applied, unlike the strain gauge sensors of the known type which rest in contrast on the part essentially along a line identified by the small tube alone, thus exercising much greater pressure. Each end (31, 32) of said tape-like sheath (3) is constrained to at least one electrical connector (4, 5), in turn connected to the corresponding end (21, 22) of the duct (2), and wherein said electrical connectors (4, 5) are suited to be mutually coupled in a direct way achieving both the electrical connection and the mechanical connection.

At least one of said two electrical connectors (4) is in turn directly connected to at least one electric cable (6) with two or four wires.

As shown in Figure 1, each of said connectors (4, 5) comprises four contacts

(41, 51) and in particular a first connector or female connector (4), comprises four female electrical contacts (41) for the four corresponding male electrical contacts (51) of the second male connector (5).

Said electrical connectors thus quickly realize the electrical connection and also the mechanical connection, as shown in Figure 2.

In the preferred embodiment, shown in Figure 3, said connectors (4, 5) also comprise further mechanical connection means (42, 43, 52, 53) suited to ensure and protect the correct mechanical coupling, preventing said connectors (4, 5) from accidentally coming off or from being displaced.

In particular, said male connector (5) comprises walls (52) enveloping said male electrical contacts (51), with edges (53) suited to rest on the corresponding parts (43) of the female connector (4) and with cut-out seats or slots (521) suited for the insertion of protrusions (42) positioned correspondingly on said female connector (4).

The new strain gauge sensor (1) can be used in plethysmography to measure changes in volume of a limb (A, B) in the diagnosis and evaluation of chronic venous insufficiency, in the evaluation of arterial blood flow, the arteriosclerotic process, venous capacitance and other phenomena or processes that require measurement of changes in limb volume, be it for example a leg (A) or an arm (B).

For these measurements, said tape-like sheath (3) is designed to wrap around the limb (A, B) of the patient (P), as in Figures 4a and 4b.

Said sensor (1) can also be used for the measurement of changes in volume of the trunk (C), where said tape-like sheath (3) is designed to wrap around the trunk (C) of the patient (P), as shown in Figure 4c.

It is foreseen that the measurement takes place with the patient's body (P) in motion, to naturally create an inflow of blood in a part of the body, and subsequent outflow, measuring the change in volume.

The new strain gauge sensor (1) is suited to measure one or more volume variations, or series of consecutive volume variations in a given time interval, with the body stationary or moving.

The new strain gauge sensor (1) further comprises one or more electronic components and/or conditioning interfaces and/or signal digitization.

The new strain gauge sensor (1) can also be used alone or combined with other kinds of sensors.

Therefore with reference to the preceding description and the attached drawings the following claims are made.

Claims

L Strain gauge extenso meter sensor (1) comprising at least one tubular duct (2) with small diameter, inside which there is mercury or gallium- indium alloy or another conductive liquid, characterized in that said duct (2) is contained in an elastic sheath or body (3) having a flat-tape shape.
2. Extenso meter sensor (1) according to claim 1, characterized in that said duct (2) is obtained in said tape-like sheath or body (3) during the production stage of said tape-like sheath (3).
3. Extenso meter sensor (1) according to claim 1, characterized in that said duct (2) comprises at least one small elastic tube (23) that defines the same duct (2), said small tube being completely buried in said tape-like sheath (3).
4. Extensometer sensor (1) according to claims 1, 2, 3, characterized in that said tape-like sheath (3) is made of silicone or another elastic material.
5. Extensometer sensor (1) according to claims 1, 2, 3, and 4, characterized in that said tape-like sheath (3) has a length substantially equal to the length of said duct (2), without the ends (21, 22) of the same duct (2) which are connected to electrical connectors (4, 5), and a width greater than its thickness, defining a contact surface (33) suited to rest against the body the volume variation of which has to be measured.
6. Extensometer sensor (1) according to claims 1, 2, 3, 4, and 5, characterized in that each end (31, 32) of said tape-like sheath (3) is constrained to at least one electrical connector (4, 5) connected to the corresponding end (21, 22) of said duct (2), and wherein said electrical connectors (4, 5) are suited to be mutually coupled in a direct way achieving both the electrical connection and the mechanical connection.
7. Extenso meter sensor (1) according to the preceding claims, characterized in that a first one of said connectors, or female connector (4) comprises four female electrical contacts (41) for the corresponding four male electrical contacts (51) of the second connector, or male connector (5).
8. Extenso meter sensor (1) according to the preceding claims, characterized in that said connectors (4, 5) comprise further mechanical connection means (42, 43, 52, 53) suited to guarantee and protect the correct mechanical fixing, preventing said connectors (4, 5) from accidentally coming off or from being displaced.
9. Extenso meter sensor (1) according to one or more of the preceding claims, characterized in that it has a useful length for utilization in plethysmography for measuring the volume variation of a limb (A, B), wherein said tape-like sheath (3) is arranged so as to wrap a limb (A, B) of the patient (P).
10. Extenso meter sensor (1) according to one or more of the preceding claims, characterized in that it has a useful length for utilization in plethysmography for measuring the volume variation of the trunk (C), wherein said tape-like sheath (3) is arranged so as to wrap the trunk (C) of the patient (P).
11. Extensometer sensor (1) according to claims 9 and 10, characterized in that it can be used in plethysmography with the body of the patient (P) in motion.
12. Extensometer sensor (1) according to the preceding claims, characterized in that it is suited to measure one or more volume variations or series of consecutive volume variations in a given time interval.
13. Extensometer sensor (1) according to the preceding claims, characterized in that it further comprises one or more electronic components and/or conditioning interfaces and/or signal digitization.
14. Extensometer sensor (1) according to the preceding claims, characterized in that it can be used alone or combined with other kinds of sensors.
PCT/IB2011/052493 2010-07-02 2011-06-08 Strain gauge extensometer sensor for medical or industrial use in general WO2012001557A1 (en)

Priority Applications (2)

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ITPD2010A000206 2010-07-02
ITPD20100206 2010-07-02

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3081162A3 (en) * 2015-03-24 2017-01-18 Covidien LP Vascular disease detection device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3731184A (en) * 1948-12-21 1973-05-01 H Goldberg Deformable pick up coil and cooperating magnet for measuring physical quantities, with means for rendering coil output independent of orientation
US20020032388A1 (en) * 2000-09-13 2002-03-14 Helgi Kristbjarnarson Disposable sensor for measuring respiration and method of forming the same
US6375620B1 (en) * 1996-08-09 2002-04-23 Domed Medizintechnik Gmbh Process and device for carrying out a venous plethysmography using compression
US20090007685A1 (en) * 2007-07-02 2009-01-08 The Hong Kong Polytechnic University Piezoresistive strain gauge using doped polymeric fluid
US20100132476A1 (en) * 2008-11-28 2010-06-03 Ching-Hsiang Cheng Strain sensor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3731184A (en) * 1948-12-21 1973-05-01 H Goldberg Deformable pick up coil and cooperating magnet for measuring physical quantities, with means for rendering coil output independent of orientation
US6375620B1 (en) * 1996-08-09 2002-04-23 Domed Medizintechnik Gmbh Process and device for carrying out a venous plethysmography using compression
US20020032388A1 (en) * 2000-09-13 2002-03-14 Helgi Kristbjarnarson Disposable sensor for measuring respiration and method of forming the same
US20090007685A1 (en) * 2007-07-02 2009-01-08 The Hong Kong Polytechnic University Piezoresistive strain gauge using doped polymeric fluid
US20100132476A1 (en) * 2008-11-28 2010-06-03 Ching-Hsiang Cheng Strain sensor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3081162A3 (en) * 2015-03-24 2017-01-18 Covidien LP Vascular disease detection device

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