GB2234344A - Fibre optic pressure or temperature transducers - Google Patents

Fibre optic pressure or temperature transducers Download PDF

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Publication number
GB2234344A
GB2234344A GB8912878A GB8912878A GB2234344A GB 2234344 A GB2234344 A GB 2234344A GB 8912878 A GB8912878 A GB 8912878A GB 8912878 A GB8912878 A GB 8912878A GB 2234344 A GB2234344 A GB 2234344A
Authority
GB
United Kingdom
Prior art keywords
sleeve
transducer
fibre optic
end
seal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB8912878A
Other versions
GB8912878D0 (en
Inventor
Norman Barrie Jones
George L Papageorgion
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Medical & Diagnostic Systems Ltd
Medical & Diagnostic Systems L
Original Assignee
Medical & Diagnostic Systems Ltd
Medical & Diagnostic Systems L
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Medical & Diagnostic Systems Ltd, Medical & Diagnostic Systems L filed Critical Medical & Diagnostic Systems Ltd
Priority to GB8912878A priority Critical patent/GB2234344A/en
Publication of GB8912878D0 publication Critical patent/GB8912878D0/en
Publication of GB2234344A publication Critical patent/GB2234344A/en
Application status is Withdrawn legal-status Critical

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Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/02Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/021Measuring pressure in heart or blood vessels
    • A61B5/0215Measuring pressure in heart or blood vessels by means inserted into the body
    • A61B5/02154Measuring pressure in heart or blood vessels by means inserted into the body by optical transmission
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01DMEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infra-red, visible, or ultra-violet light
    • G01D5/268Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infra-red, visible, or ultra-violet light using optical fibres
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01KMEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K5/00Measuring temperature based on the expansion or contraction of a material
    • G01K5/32Measuring temperature based on the expansion or contraction of a material the material being a fluid contained in a hollow body having parts which are deformable or displaceable
    • G01K5/46Measuring temperature based on the expansion or contraction of a material the material being a fluid contained in a hollow body having parts which are deformable or displaceable with electric conversion means for final indication
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01LMEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material by electric or magnetic means
    • G01L9/0001Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means
    • G01L9/0007Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means using photoelectric means

Abstract

A catheter tip transducer, capable of measuring temperature or pressure, suitable for biomedical applications comprises a fibre optic 10 and a substantially cylindrical sleeve 12 positioned over and extending beyond one end of the fibre optic. The sleeve is sealed to entrap a volume of gas at the end of the fibre optic, the seal 14 and/or the sleeve being flexible and capable of deformation upon changes in temperature or pressure so as to modulate an optical signal transmitted from the fibre optic 10 and reflected inside the sleeve back into the fibre optic. The sleeve 12 may be formed by cutting or deforming the protective cladding of the fibre and may be sealed by dipping in a rubber solution to form a seal 14 or by the sides of the end of the sleeve being compressed and bonded together. <IMAGE>

Description

FIBRE OPTIC PRESSURE OR TEMPERATURE TRANSDUCERS This invention relates to fibre optic transducers capable of measuring temperature or pressure and in particular to catheter tip transducers suitable for Biomedical applications and to their fabrication.

Pressure or temperature transducers suitable for insertion into the vascular system of humans or animals are known and are disclosed, for example, in U.S. Patent Nos. 3,273,447, 3,911,902, 3,942,382 and 4,176,551. One type of known transducers contains a displacable element in the form of a diaphragm which moves or deforms in response to pressure or temperature fluctuations. The displacement of the diaphragm may be used to modulate electrical, ultrasonic or optical signals to provide an indication of the pressure or temperature change.

Another type of transducer contains a gas/liquid interface which moves in response to pressure or temperature fluctuations. The movement of the gas/liquid interface may be used to modulate signals as described above. Fibre optic transducers are usually based on the change in the quantity of light reflected by the diaphragm or gas/liquid interface upon displacement, deformation etc.

Recent medical advances have made it possible for catheters to be introduced into many parts of the vascular system without causing damage. Such procedures have led to a demand for miniaturised transducers so that internal pressure and temperature measurements may be taken at different parts of the vascular system. Many known devices are too large to be used in smaller arteries and veins and the commercially available catheter tip transducers are sufficiently expensive that they must be reused in the interests of economy. It is necessary for the transducers to be sterilised between successive uses which adds to the expense and there is a significant risk of damage to the transducer during each re-sterilisation.

U.S. Patent No. 3,273,447 discloses a fibre optic transducer in which the end of the fibre optic comprises or communicates with an aspherical bulbous portion which tends to be distorted under pressure to a spherical form.

To improve the reflective properties of the bulbous portion the outer surface thereof is preferably coated with a reflective material. There is no disclosure as to how the proposed transducers may be fabricated and in spite of this publication being in excess of twenty years old there has been no known reduction to commercial practice of the proposals.

It is an aim of the present invention to provide a catheter tip transducer having a structure which may be simply and economically fabricated such that the transducer may be disposable.

According to one aspect of the present invention there is provided a transducer for measuring pressure or temperature comprising; a fibre optic, and, a substantially cylindrical sleeve positioned over and in sealing engagement with one end of the fibre optic and extending beyond said end, wherein the end of the sleeve extending beyond the end of the fibre optic has a seal to entrap a volume of gas within the sleeve, between the seal and the end of the fibre optic, the seal and/or the sleeve being flexible and capable of deformation upon changes in temperature or pressure.

The invention provides a catheter tip transducer which is highly sensitive to fluctuations in temperature or pressure and has a simple construction which is readily applicable to mass production allowing the transducer to be produced at a price which will allow disposal of the transducer after a single use.

The transducer of the invention comprises a single fibre optic which is used to transmit and receive an optical signal i.e. the fibre chosen must be multi-modal to prevent interference affecting the signal. The fibre optic will generally have a core diameter in the range 50 to 2000 microns, preferably 50 to 1000 microns. One end of the fibre optic is cut and polished to generate a smooth surface for optimum transmission and receiving of the optical signal.

The transducer of the invention comprises an entrapped volume of gas which causes displacement of a movable element upon changes in pressure or temperature.

The optical signal transmitted by the fibre optic is reflected from the movable element and passes back through the fibre optic to a receiver. Movement of the element in response to pressure or temperature change modulates the reflected signal thereby providing an indication of said change.

The gas is entrapped by the provision of a cylindrical sleeve which is secured over the end of the fibre optic in sealing engagement therewith and the open end of the sleeve sealed thereby entrapping gas with the sleeve. The cylindrical sleeve may be displacable upon fluctuation in temperature or pressure or may be rigid and the seal formed as a displacable membrane. In one embodiment of the invention the sleeve is flexible and has a wall thickness of 20 to 100 microns more preferably, about 30 microns. The flexible sleeve preferably compresses an elastic material e.g. silicon rubber. The sleeve may comprise a metal, or a polymer e.g. p.v.c., nylon, polyurethane, polyethylene or a fluorinated polymer.If the sleeve is flexible it may be sealed at its end remote from the fibre by compressing the end and bonding the compressed surfaces together or by forming a seal across the open end e.g. with a membrane such as silicone rubber. For efficient transducer function it is most preferable that the sleeve or membrane deformation is precise and repeatable i.e.

the sleeve displaces in a predetermined manner in response to a given change in temperature or pressure.

The internal or external surface of the sleeve or seal may be treated to improve its reflective properties e.g. by coating with a reflective material such as a metal or white pigment. The coating should not deteriously affect the flexibility of the sleeve or seal.

In a preferred embodiment of the invention the cylindrical sleeve is formed from the protective cladding which conventionally envelopes fibre optics. The protective cladding normally comprises a polymer, particularly a fluorinated polymer such as those commercially available under the Trade Marks Teflon and Teflex. The polymer cladding may be cut e.g. with a blade, a short distance before the end of the fibre optic and displaced so that the cladding extends beyond the end of the fibre optic. Alternatively, a heated element may be used to cut or soften the cladding and thereafter displace a portion of the cladding beyond the end of the fibre optic.

The fibre optic bearing the cylindrical sleeve may readily be sealed to entrap a volume of gas by dipping in a film forming liquid e.g. a silicon rubber solution in toluene or similar solvent, rubber latex etc. Silicon rubber is preferred because of its inert nature i.e. it is readily biocompatible. The dipping operation readily allows the formulation of a membrane across the open end of the sleeve or may act as an adhesive if the open end of the sleeve is compressed immediately after dipping.

Also, by dipping the fibre optic to a sufficient depth it is readily possible to obtain a gas tight seal over the end of the sleeve extending over the fibre optic.

The length of the sleeve and volume of gas entrapped will depend upon the size of the fibre optic and degree of flexibility of the sleeve and seal. The closer the movable element (sleeve or seal) is to the end of the fibre optic the greater the signal strength. However, the movable element must be sufficiently flexible to displace to a measurable extent in response to minor variations in pressure or temperature. In practice it is readily possible to produce a sensitive catheter tip having a sleeve extending beyond the fibre optic by a distance of less than lmm.

In some applications it is desirable for the entrapped gas to be maintained under constant pressure to render the transducer immune to temperature variation.

This may be achieved by provision of a conduit extending to the volume of gas within the sleeve. For example, a capillary tube may be secured along the fibre optic, extending beyond its end, before the cylindrical sleeve is applied.

The invention will now be described with reference to the accompanying drawings in which: Figures 1 to 4 represent longitudinal sections through different transducers in accordance with the invention, Figure 5 represents a transducer of the invention positioned within a flushing tube, and, Figures 6 to 8 represent longitudinal sections showing manufacturing stages of a transducer in accordance with the invention.

Referring to Figure 1, the transducer comprises a fibre optic (10) having a polished end (11) over which extends a sleeve (12) sealed to the fibre optic at (13).

The end (14) of the sleeve (12) is sealed to entrap a volume of gas within the sleeve. The sealed sleeve defines an enclosed cylindrical tube which will collapse or bulge as shown in dashed lines (15) and (16) upon increase and decrease in external pressure or temperature. This deformation will modulate an optical signal which is transmitted from the fibre optic, reflected from the inside of the sleeve and the reflected signal passed back through the fibre optic.

Referring to Figure 2, the transducer comprises a deformable partially collapsed elastic sleeve (21), the free end of the sleeve being compressed and bonded to form seal (22). The other end of the sleeve is sealed to optic fibre (23) to entrap a volume of gas within the sleeve such that change in temperature or pressure produces collapse or bulge of the sleeve walls as shown in dashed lines (24), (25) respectively.

The transducer of Figure 3 is similar to that of Figure 1 with the exception that the sleeve (31) has been treated such that it will undergo a predetermined deformation upon pressure fluctuation. In the embodiment illustrated the sleeve will bond and adopt the configuration shown by dashed line (32) since one area of the surface of the sleeve is more rigid e.g. possesses a greater thickness, than an opposing area of the surface of the sleeve.

Referring to Figure 4, the transducer of Figure 2 is modified by the inclusion of a vent tube (41) inserted into elastic sleeve (21). Venting the gas volume entrapped in the sleeve provides for a pressure responsive transducer immune to temperature variation.

Deformation of sleeve (21), as depicted in Figure 2, in response to pressure change is detected by fibre optic (23).

Referring to Figure 5, the transducer illustrated in Figure 2 is positioned within a fluid filled accessory tube (51). Tube (51) protects the transducer during insertion and may be used to flush the transducer with e.g. liquid to clear debris, blood clots etc. from impairing efficient transducer function. Tube (51) may additionally be connected to an external pressure transducer to provide a reference pressure for a drift compensated transducer system as describ our co Elo.

pending British Patent Applicationlof even date.

Referring to Figure 6, the transducer comprises a rigid sleeve (61) sealed to optic fibre (62) at (63).

Elastic membrane (64) entraps a volume of gas within the sleeve such that changes in temperature or pressure produce collapse (65) or bulging (66) of the membrane.

Deformation of the membrane indicated by dashed lines is detected by optic fibre (62).

Figure 7 illustrates a stage in the fabrication of a transducer in which a sleeve (71) is formed by cutting fibre optic protective cladding (72) with a blade and displacing the cut section in the direction of the depicted arrow. Membrane (73) and seal (74) are formed by dipping the fibre optic (75) and sleeve (71) in a film forming liquid e.g. a solution of silicone rubber in toluene. It is readily possible to dip a plurality of tubes simultaneously.

Figure 8 illustrates a modification of the manufacturing process of Figure 7 in which the fibre optic cladding (81) is cut or deformed at (a) with a hot element (not shown) causing displacement of cladding to form a sleeve (82) extending beyond the end of the fibre optic (83). Membrane (84) and optionally a seal in the region (a) may be formed by a dipping technique as described above.

Claims (28)

1. A transducer for measuring pressure or temperature comprising; a fibre optic, and, a substantially cylindrical sleeve positioned over and in sealing engagement with one end of the fibre optic and extending beyond said end, wherein the end of the sleeve extending beyond the end of the fibre optic has a seal to entrap a volume of gas within the sleeve, between the seal and the end of the fibre optic, the seal and/or the sleeve being flexible and capable of deformation upon changes in temperature or pressure.
2. A transducer as claimed in Claim 1 in which the optic fibre has a core diameter in the range of 50 to 2000 clam.
3. A transducer as claimed in Claim 1 or Claim 2 in which the optic fibre has a core diameter in the range 50 to 1000 m.
4. A transducer as claimed in any one of Claims 1 to 3 in which the sleeve and/or the seal comprises an elastic material.
5. A transducer as claimed in Claim 4 in which the sleeve and/or seal material is silicon rubber or natural rubber.
6. A transducer as claimed in Claim 4 or Claim 5 in which the sleeve thickness is in the range 20 to 100 pm.
7. A transducer as claimed in Claim 6 in which the sleeve thickness is 30 ym.
8. A transducer as claimed in any preceding claim in which the end of the sleeve extending beyond the end of said fibre is flattened and bonded together to form a seal.
9. A transducer as claimed in Claim 8 in which the bonding is formed utilising silicon rubber or natural rubber.
10. A transducer as claimed in any preceding claim constructed and arranged such that the seal and/or sleeve displaces in response to a change in temperature or pressure.
11. A transducer as claimed in any preceding claim in which the sleeve is configured such that it displaces in a predetermined manner in response to a change in temperature or pressure.
12. A transducer as claimed in any one of Claims 1 to 3 in which the sleeve comprises a rigid material.
13. A transducer as claimed in any preceding claim in which the sleeve comprises nylon, polyvinylchloride or polyurethane.
14. A transducer as claimed in any preceding claim in which the fibre optic has a protective outer coating.
15. A transducer as claimed in Claim 14 in which the sleeve comprises the fibre optic protective outer coating.
16. A transducer as claimed in Claim 15 in which the protective outer coating comprises a fluorinated polymer.
17. A transducer as claimed in any one of Claims 1 to 7 and Claims 10 to 16 in which the seal comprises a membrane.
18. A transducer as claimed in any preceding claim in which the sleeve and/or the seal is coated with a reflective material.
19. A transducer as claimed in any preceding claim in which the transducer is mounted in a catheter tip.
20. A transducer as claimed in any preceding claim additionally comprising an open conduit extending into said entrapped volume of gas.
21. A method of manufacturing a transducer as defined in Claim 1 which comprises positioning a cylindrical sleeve over one end of a fibre optic such that an end of the sleeve extends beyond the end of the fibre optic, securing the sleeve to the fibre optic and sealing the open end of the sleeve remote from the fibre optic so as to entrap a volume of gas between the end of the fibre optic and the sealed end of the sleeve.
22. A method as claimed in Claim 21 in which the open end of the sleeve is sealed by dipping in a film forming liquid.
23. A method as claimed in Claim 22 in which the film forming liquid is selected from silicon rubber solution and rubber latex.
24. A method as claimed in Claim 22 or 23 in which the sleeve is sealed to the fibre optic by said dipping.
25. A method as claimed in any one of Claims 21 to 24 in which the open end of the tube is compressed during sealing.
26. A method as claimed in any one of Claims 21 to 25 in which the sleeve is formed from the protective cladding of the fibre optic by displacing a section thereof beyond the end of the fibre optic.
27. A method as claimed in Claim 26 in which the cladding is cut with a blade prior to displacement.
28. A method as claimed in Claim 26 in which a hot element is applied to the cladding to cut and/or displace the cladding beyond the end of the fibre optic.
GB8912878A 1989-06-05 1989-06-05 Fibre optic pressure or temperature transducers Withdrawn GB2234344A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8912878A GB2234344A (en) 1989-06-05 1989-06-05 Fibre optic pressure or temperature transducers

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8912878A GB2234344A (en) 1989-06-05 1989-06-05 Fibre optic pressure or temperature transducers

Publications (2)

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GB8912878D0 GB8912878D0 (en) 1989-07-26
GB2234344A true GB2234344A (en) 1991-01-30

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992002796A1 (en) * 1990-07-27 1992-02-20 Cosurvey Optics Fibre-optical pressure sensor
GB2331580A (en) * 1997-11-22 1999-05-26 Karlsruhe Forschzent Heart catheter with means for measuring contact pressure
WO1999045352A1 (en) * 1998-03-06 1999-09-10 Leiv Eiriksson Nyfotek As Optical pressure sensor

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1001809A (en) * 1963-04-19 1965-08-18 American Optical Corp Improvements in or relating to pressure transducers
US3273447A (en) * 1963-08-26 1966-09-20 Franklin Institute Detection and measurement device having a small flexible fiber transmission line
US4201222A (en) * 1977-08-31 1980-05-06 Thomas Haase Method and apparatus for in vivo measurement of blood gas partial pressures, blood pressure and blood pulse
EP0074055A2 (en) * 1981-09-03 1983-03-16 Honeywell Inc. Fiber optic pressure sensor
US4487206A (en) * 1982-10-13 1984-12-11 Honeywell Inc. Fiber optic pressure sensor with temperature compensation and reference
EP0208545A2 (en) * 1985-07-10 1987-01-14 Hitachi, Ltd. Method and apparatus for detecting combustion pressure in engine
WO1988000023A1 (en) * 1986-06-25 1988-01-14 Radisensor Ab Miniaturized sensor for physiological pressure measurements
GB2193310A (en) * 1986-08-01 1988-02-03 Boc Group Plc Pressure sensor
US4787396A (en) * 1987-06-18 1988-11-29 Fiberoptic Sensor Technologies, Inc. Fiberoptic pressure transducer

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1001809A (en) * 1963-04-19 1965-08-18 American Optical Corp Improvements in or relating to pressure transducers
US3273447A (en) * 1963-08-26 1966-09-20 Franklin Institute Detection and measurement device having a small flexible fiber transmission line
US4201222A (en) * 1977-08-31 1980-05-06 Thomas Haase Method and apparatus for in vivo measurement of blood gas partial pressures, blood pressure and blood pulse
EP0074055A2 (en) * 1981-09-03 1983-03-16 Honeywell Inc. Fiber optic pressure sensor
US4487206A (en) * 1982-10-13 1984-12-11 Honeywell Inc. Fiber optic pressure sensor with temperature compensation and reference
EP0208545A2 (en) * 1985-07-10 1987-01-14 Hitachi, Ltd. Method and apparatus for detecting combustion pressure in engine
WO1988000023A1 (en) * 1986-06-25 1988-01-14 Radisensor Ab Miniaturized sensor for physiological pressure measurements
GB2193310A (en) * 1986-08-01 1988-02-03 Boc Group Plc Pressure sensor
US4787396A (en) * 1987-06-18 1988-11-29 Fiberoptic Sensor Technologies, Inc. Fiberoptic pressure transducer

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992002796A1 (en) * 1990-07-27 1992-02-20 Cosurvey Optics Fibre-optical pressure sensor
US5425273A (en) * 1990-07-27 1995-06-20 Cosurvey Optics Fiber optic pressure sensor with inclusions in a compressible transparent material
GB2331580A (en) * 1997-11-22 1999-05-26 Karlsruhe Forschzent Heart catheter with means for measuring contact pressure
GB2331580B (en) * 1997-11-22 2002-05-15 Karlsruhe Forschzent Heart catheter with a means for measuring the contact pressure
WO1999045352A1 (en) * 1998-03-06 1999-09-10 Leiv Eiriksson Nyfotek As Optical pressure sensor

Also Published As

Publication number Publication date
GB8912878D0 (en) 1989-07-26

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