WO2004026128A1 - Apparatus and method for monitoring condition of a patient - Google Patents

Apparatus and method for monitoring condition of a patient Download PDF

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Publication number
WO2004026128A1
WO2004026128A1 PCT/GB2003/004136 GB0304136W WO2004026128A1 WO 2004026128 A1 WO2004026128 A1 WO 2004026128A1 GB 0304136 W GB0304136 W GB 0304136W WO 2004026128 A1 WO2004026128 A1 WO 2004026128A1
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WO
WIPO (PCT)
Prior art keywords
sensor
analyte
sensor device
pressure
tissue
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Application number
PCT/GB2003/004136
Other languages
French (fr)
Inventor
Barry Colin Crane
Nicholas James Barnett
Mark B. Knudson
Original Assignee
Diametrics Medical Limited
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
Priority claimed from GB0224661A external-priority patent/GB0224661D0/en
Application filed by Diametrics Medical Limited filed Critical Diametrics Medical Limited
Priority to AU2003267632A priority Critical patent/AU2003267632A1/en
Publication of WO2004026128A1 publication Critical patent/WO2004026128A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/14539—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring pH
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/03—Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs
    • A61B5/031—Intracranial pressure
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • A61B5/1459—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters invasive, e.g. introduced into the body by a catheter
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
    • A61B2560/02—Operational features
    • A61B2560/0242—Operational features adapted to measure environmental factors, e.g. temperature, pollution
    • A61B2560/0247—Operational features adapted to measure environmental factors, e.g. temperature, pollution for compensation or correction of the measured physiological value
    • A61B2560/0252—Operational features adapted to measure environmental factors, e.g. temperature, pollution for compensation or correction of the measured physiological value using ambient temperature
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0002—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, 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
    • A61B5/021—Measuring pressure in heart or blood vessels
    • A61B5/0215—Measuring pressure in heart or blood vessels by means inserted into the body
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, 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
    • A61B5/026—Measuring blood flow
    • A61B5/0275—Measuring blood flow using tracers, e.g. dye dilution
    • A61B5/028—Measuring blood flow using tracers, e.g. dye dilution by thermo-dilution

Definitions

  • the invention relates to an apparatus for monitoring the condition of a patient.
  • the measurement in blood or other bodily fluids of certain analytes for example, dissolved oxygen, dissolved carbon dioxide and hydrogen ions as oxygen partial pressure (p0 2 ) , carbon dioxide partial pressure (pC0 2 ) and pH, can be important during surgery, post-operatively and during hospitalisation under intensive care.
  • a probe can be placed in the patient, for example in a blood vessel, in other bodily fluid or in tissue.
  • the probe contains indicators, for example absorption and fluorescent indicators, which are arranged to provide data regarding certain analytes in the fluid or tissue, and to transmit that data to a base unit which in use of the sensor device is located outside the patient's body.
  • thermocouple for determining the local temperature. Temperature data collected by the thermocouple is intended to be used in order to correct the measured analyte concentrations for any changes in temperature.
  • UK Patent Specification GB 2371360A describes a multiple parameter fibre optic probe containing one or more optical fibers which are arranged to be responsive in terms of variations in mechanical strain to certain body parameters such as pressure.
  • General reference is made therein to determination of certain analytes including dissolved blood gases, but the document does not disclose any arrangement suitable for determining dissolved blood gases.
  • the accuracy of the measurements made by the device depends upon excluding extraneous influences on mechanical strain experiences by the fibers, it is apparently essential in practice for the sensing portion of the probe of GB 2371360 ⁇ to be rigid, which can in practice reduce the usefulness of the probe, for example, in fine vasculature.
  • the invention provides a sensor device having a sensor portion for insertion into tissue or a bodily fluid of a patient, the sensor comprising an analyte sensor for determining an analyte in the tissue or bodily fluid selected from p0 2 , pC0 2 and pH, and a sensor for determining a parameter relating to flow of a bodily fluid (hereafter "flow parameter sensor”) .
  • the parameter relating to flow of a bodily fluid may be any physical parameter the value or variation of which is attributable wholly or in part to flow of a bodily fluid. It will be appreciated that those parameters include in particular pressure.
  • a preferred embodiment of the invention is a sensor device having a sensor portion for insertion into tissue or a bodily fluid of a patient, the sensor portion comprising an optical analyte sensor for determining an analyte in the tissue or bodily fluid selected from p0 2 , pC0 2 and pH and a sensor for determining pressure in the tissue or bodily fluid.
  • an optical analyte sensor for determining an analyte in the tissue or bodily fluid selected from p0 2 , pC0 2 and pH
  • a sensor for determining pressure in the tissue or bodily fluid.
  • Thermal diffusion which, in a bodily fluid or in tissue, may include a first component attributable to simple thermal conduction through the bodily fluid or tissue and a second, convectional, component attributable to flow of the bodily fluid per se or, in the case of measurements in tissue, flow of a bodily fluid through the tissue; and Parameters relating to blood velocity, for example, blood velocity itself.
  • the flow parameter to be monitored will normally be pressure, although a variety of other flow parameters may be measurable. For convenience, however, pressure is referred to below in many places. Except where the contrary is apparent from the context, analogous statements apply to other flow parameters.
  • a single sensor device for the measurement of pressure and analyte concentration may involve reduced tissue damage and/or trauma to the patient, and may also simplify the equipment required.
  • a tubular passageway known as a cranial bolt
  • the device of the invention allows a cranial bolt with a single passageway to be used to obtain data relating to both analyte concentration and intracranial pressure.
  • the aperture cut in the patient' s skull can be smaller and only one tract is required through the cerebral tissue, reducing the volume of disrupted tissue.
  • a sensor device of the invention data can be obtained relating to the local pressure in the vicinity of the sensor portion.
  • a build-up of pressure can have considerable clinical significance.
  • Inclusion of a pressure sensor and an analyte sensor in a common sensor portion enables information regarding the pressure to be made available without the need for introduction of a separate sensor device.
  • pressure data is obtained relating to substantially the same location as the analyte measurements of the analyte sensor, reducing the risk that information will be obtained which is not consistent or may be misleading as a result of pressure measurement and analyte measurement being effected at different locations.
  • the sensor portion is of elongate configuration and comprises a distal portion, which in use can be positioned in the tissue or bodily fluid, and a proximal portion. Said analyte sensor and said pressure sensor are advantageously associated with the distal portion.
  • the sensor device may further comprise a connector portion, a proximal end of the sensor portion being attached to the connector portion for communication of data from the analyte sensor and pressure sensor to the connector portion.
  • the connector portion is arranged to permit connection of the sensor device to a base unit for communication of the data to the base unit.
  • the connector unit may be used to connect the sensor device to appropriate data processing means, from which data collected by the device may be passed to a display device.
  • the analyte sensor and the pressure sensor may be housed within the sensor device, for example in the distal portion thereof. It will be appreciated that, where the pressure sensor is housed within the sensor device, it will be necessary for the sensor device to be so constructed that the pressure obtaining within the pressure sensor in the vicinity of the pressure sensor is such that the sensor can give a reliable indication of the pressure obtaining outside the sensor device, for example such that little or substantially no damping of the pressure signal or changes therein occurs as a result of the device's construction. In a preferred embodiment that can be achieved by locating the pressure sensor in a polyacrylamide gel within a microporous housing having pores of diameter at least 0.05 ⁇ m, and preferably at least O.l ⁇ m.
  • the pressure sensor may be located outside the sensor portion.
  • the pressure sensor is located at or in the vicinity of the distal end of the distal portion.
  • the pressure sensor may be a pressure transducer.
  • the pressure sensor may be a strain-gauge.
  • the pressure sensor may be connected to a fibre optic cable for permitting optical interrogation of the pressure sensor.
  • the pressure sensor may be connected to an electrically conductive cable for transmission of the measured pressure data.
  • the analyte sensor is suitable for determining an analyte selected from p0 2 , pC0 2 and pH.
  • the analyte sensor is arranged for optical determination of the respective analyte.
  • the sensor device comprises a second analyte sensor, preferably also an optical sensor, for determining at least one further analyte.
  • the sensor device is suitable for determining two analytes selected from p0 2 , pC0 2 and pH .
  • the sensor device is suitable for determining p0 2 , pC0 2 and pH.
  • Suitable optical sensors include in particular sensors comprising an indicator, especially an indicator solution, the optical characteristics of which are dependent on the concentration of the analyte to be measured.
  • the indicator is an absorption indicator, a fluorescence indicator or a chemiluminescence indicator. Examples of such sensors for blood gases are known, for example, in the Paratrend (trade mark) device previously mentioned.
  • the device further comprises a temperature measuring device, for example, a thermocouple.
  • the invention also provides a method of monitoring a patient, comprising inserting into tissue or a bodily fluid of said patient a sensor portion of a sensor device comprising an analyte sensor and a sensor for determining a parameter relating to flow of a bodily fluid, determining the concentration of an analyte selected from p0 2 , pC0 2 and pH and determining a value of a parameter relating to flow of a fluid, and treating the patient in dependence upon the determined analyte concentration and value of the parameter relating to fluid flow.
  • the sensor device is advantageously arranged to monitor the parameter relating to flow and concentration of at least one analyte in substantially the same location within said soft tissue.
  • the sensor device is inserted into a blood vessel for monitoring blood therein.
  • two or more analytes are measured.
  • the parameter relating to fluid flow is pressure.
  • the sensor portion is suitable for insertion into cerebral spinal fluid.
  • the sensor portion will be required to be of a strength such that it can penetrate tissue surrounding the cerebral spinal fluid.
  • the sensor portion is suitable for insertion into soft tissue. A sensor portion for insertion into soft tissue may require greater strength than, for example, a sensor portion for use in a blood vessel.
  • the term “strength” is intended to refer in particular to stiffness and resistance to kinking.
  • the sensor portion will, however, preferably be flexible along at least those parts thereof that will be introduced into a blood vessel or soft tissue.
  • the term “flexible” is to be interpreted as requiring at least sufficient flexibility for the sensor portion to be sited in the convoluted pathways that may be present in vasculature or soft tissue to be examined without causing significant distortion of those pathways.
  • data relating to the pressure is transmitted optically from the pressure sensor to a monitoring device.
  • data relating to the pressure may be transmitted electrically from the pressure sensor to a monitoring device.
  • Fig. 1 is a schematic section through a distal end of a sensor device according to the invention suitable for use as a blood sensor;
  • Fig. 2 is an enlarged view of a part of Fig. 1;
  • Fig. 3 is a schematic view of the proximal end of a sensor portion of the device and an associated connector portion.
  • a sensor device 1 which is suitable for use in a blood vessel for measuring parameters relating to blood, has an elongate sensor portion having a distal portion 2 terminating at distal end 3.
  • the distal portion 2 has a wall 4 enclosing a number of analyte sensors 5, 6, 7 and a pressure sensor 8.
  • the wall 4 is of a microporous material 9 having micropores 10 which are filled with a hydrophilic material which when hydrated forms a gel and allows the passage of water-bound ions.
  • the microporous material may be a membrane made from a hydrophobic polymer, for example polyethylene.
  • the hydrophilic material may be, for example, a polyacrylamide which when hydrated forms a gel and allows the passage of water-bound ions, as well as gases.
  • the micropores 10 may be of diameter of, for example, 0.1 ⁇ m.
  • Analyte sensors 5, 6 7 are optical sensors of known construction.
  • Analyte sensor 5 is a pH sensor comprising an optical fibre 11 through a distal sensing portion of which extends a helical array of apertures, which are so arranged that all parts of the cross sectional area of the fibre are interrupted by at least one of the apertures.
  • Each of the apertures is filled with a pH sensitive indicator, for example phenol red in a gel.
  • the optical fibre 11 also has an optical transmission portion 12 extending from the distal sensing portion to a connector (not included in Fig. 1) by means of which it can be connected to a light source and a data collection and/or processing device.
  • a mirror (not shown in Fig. 1) is provided embedded in the end of the fibre 11. Optical radiation transmitted along fibre 11 is reflected by the mirror and passes back along the fibre. The transmitted and reflected light passes through the indicator- containing apertures and the amount of light absorbed gives an indication of the pH of the medium in which the sensor is located.
  • Analyte sensor 6 is of similar construction to sensor 5 except that it contains an indicator sensitive to oxygen, for example, a fluorescent indicator.
  • Analyte sensor 7 is a pC0 2 sensor which is of broadly similar construction to sensor 5 except that the indicator is suitable for detection of C0 2 .
  • the indicator may be phenol red in a solution which is a source of bicarbonate ions.
  • Sensor 6 is enveloped by a tubular membrane of C0 2 - permeable polymer, for example polyethylene (not shown in Fig. 1) .
  • Analyte sensors of the kind described above are present, for example, in the sensor devices described in US 5 596 988.
  • the pressure sensor 8 is located adjacent to the distal portions of analyte sensors 5, 6 and 7, and close to the microporous wall 9.
  • the sensor 8 is a fibre-optic sensor, for example, a fibre-optic pressure transducer of the kind made by FISO Technologies, which has a diameter of 550 ⁇ m.
  • Sensor 8 is connected to an optical fibre 13 by means of which the sensor 8 can be interrogated using white light interferometry .
  • the sensor 8 shown is a fibre optic pressure transducer. Any other suitable pressure sensor may, however, be used.
  • the sensor 8 may be a guidewire mounted pressure sensor of the kind may by RADI Medical and known as the Pressure Wire 0 (trade mark) . That sensor uses essentially a strain gauge piezo-resistance technique, using a pressure sensitive diaphragm micro- machined in silicon. Another suitable strain-gauge is that included in a catheter manufactured by Millar Instruments Inc. under the trade mark Mikro-Tip.
  • the sensor device also includes a thermocouple 14.
  • the elongate sensor portion is connected at its proximal end to a connector unit which comprises connection means for connection to a light source from which light of wavelengths suitable for interrogation of the sensors may be transmitted to the optical fibres 11, 13 and to a data processing unit from which the data received from those optical fibres, optionally after analysis, may be transmitted to a display device, for example, a monitor.
  • the analyte sensors 5, 6, 7, the pressure sensor 8 and the thermocouple 14 are embedded in a matrix 15, which fills the interior of the distal portion 2 of the sensor portion and maintains the sensors 5, 6, 7, 8 and thermocouple 14 substantially in their relative positions.
  • the pressure in the immediate vicinity of the sensor device can equilibrate with the pressure in the interior of the device by means of the adjacent microporous wall 9 and the matrix 15 and can be measured by the sensor 8.
  • the matrix 15 is of a hydrophilic material that is permeable to the analyte (s) to be measured and may be, for example, a hydrogel, especially a hydrophilic polyacrylamide gel.
  • the matrix must be suitable for transmission of the pressure outside the wall 4 to the sensor device 8.
  • the matrix will be of the same material as the hydrophilic material filling micropores 10.
  • the sensor device may be introduced into a blood vessel of the patient by known means, for example, by advancing it through a previously introduced cannula. Once in place, and following a short time in which the pressure within the sensor portion can equilibrate with the external pressure, the pressure sensor 8 is interrogated using a suitable source of light.
  • the analyte sensors 5 to 7 are similarly interrogated using respective appropriate light sources.
  • the analyte and pressure measurements may be exhibited on any suitable display device, for example, a monitor.
  • the data from the sensors 5 to 7 may be used, usually after any appropriate temperature correction based on temperature measurements from thermocouple, together with pressure measurements from sensor 8 to make a variety of clinically important determinations which may assist in diagnosis of patient condition. For example, that data may be used to calculate oxygen saturation, bicarbonate concentration and base excess. Those determinations, with knowledge of the local pressure, can provide the clinician with a wealth of information to assist in diagnosis.
  • the sensor device described above is suitable for use in blood vessels.
  • the construction of a suitable device might be the same, except that the device and especially wall 9 would require strengthening to prevent kinking of the device on insertion.
  • the invention includes sensor devices comprising an analyte sensor and a physical sensor for determining a physical parameter relating to flow of a bodily fluid, for example, thermal diffusion.
  • a physical sensor for determining a physical parameter relating to flow of a bodily fluid for example, thermal diffusion.
  • thermal diffusion is a physical parameter relating to flow of a bodily fluid.
  • thermistors of the kind included in the Thermal Diffusion Probe (trade mark) of Hemedex, Inc. of Cambridge,
  • That thermistor arrangement allows both thermal conduction within tissue and thermal convection due to blood flow to be determined.
  • a velocimeter for example, a laser Doppler device.
  • the invention is primarily for use in human patients, but it will be appreciated that devices adapted for use in animals, in particular other mammals, are not excluded.

Abstract

A sensor device (1) for monitoring patient condition has a sensor portion comprising an analyte sensor (15, 6, 7) for determining an analyte in tissue or a bodily fluid and a physical sensor (8) for determining a physical parameter in the tissue or bodily fluid. Illustrative of physical parameters that may be determined are pressure and physical parameters relating to flow of a bodily fluid.

Description

Apparatus and method for monitoring condition of a patient
The invention relates to an apparatus for monitoring the condition of a patient. The measurement in blood or other bodily fluids of certain analytes, for example, dissolved oxygen, dissolved carbon dioxide and hydrogen ions as oxygen partial pressure (p02) , carbon dioxide partial pressure (pC02) and pH, can be important during surgery, post-operatively and during hospitalisation under intensive care. In certain known forms of sensor device, a probe can be placed in the patient, for example in a blood vessel, in other bodily fluid or in tissue. The probe contains indicators, for example absorption and fluorescent indicators, which are arranged to provide data regarding certain analytes in the fluid or tissue, and to transmit that data to a base unit which in use of the sensor device is located outside the patient's body. One such sensor device, known as the Paratrend Continuous Blood Gas Monitor available from Diametrics Medical Limited of High Wycombe, England, can measure p02, pC02 and pH. That device incorporates a thermocouple for determining the local temperature. Temperature data collected by the thermocouple is intended to be used in order to correct the measured analyte concentrations for any changes in temperature.
UK Patent Specification GB 2371360A describes a multiple parameter fibre optic probe containing one or more optical fibers which are arranged to be responsive in terms of variations in mechanical strain to certain body parameters such as pressure. General reference is made therein to determination of certain analytes including dissolved blood gases, but the document does not disclose any arrangement suitable for determining dissolved blood gases. Because the accuracy of the measurements made by the device depends upon excluding extraneous influences on mechanical strain experiences by the fibers, it is apparently essential in practice for the sensing portion of the probe of GB 2371360Α to be rigid, which can in practice reduce the usefulness of the probe, for example, in fine vasculature.
The invention provides a sensor device having a sensor portion for insertion into tissue or a bodily fluid of a patient, the sensor comprising an analyte sensor for determining an analyte in the tissue or bodily fluid selected from p02, pC02 and pH, and a sensor for determining a parameter relating to flow of a bodily fluid (hereafter "flow parameter sensor") . The parameter relating to flow of a bodily fluid may be any physical parameter the value or variation of which is attributable wholly or in part to flow of a bodily fluid. It will be appreciated that those parameters include in particular pressure. Thus, a preferred embodiment of the invention is a sensor device having a sensor portion for insertion into tissue or a bodily fluid of a patient, the sensor portion comprising an optical analyte sensor for determining an analyte in the tissue or bodily fluid selected from p02, pC02 and pH and a sensor for determining pressure in the tissue or bodily fluid. Other illustrative examples of parameters relating to flow of a bodily fluid are:
Thermal diffusion which, in a bodily fluid or in tissue, may include a first component attributable to simple thermal conduction through the bodily fluid or tissue and a second, convectional, component attributable to flow of the bodily fluid per se or, in the case of measurements in tissue, flow of a bodily fluid through the tissue; and Parameters relating to blood velocity, for example, blood velocity itself.
The flow parameter to be monitored will normally be pressure, although a variety of other flow parameters may be measurable. For convenience, however, pressure is referred to below in many places. Except where the contrary is apparent from the context, analogous statements apply to other flow parameters.
Use of a single sensor device for the measurement of pressure and analyte concentration may involve reduced tissue damage and/or trauma to the patient, and may also simplify the equipment required. For example, for measurements to be made in the intracranial region, a tubular passageway, known as a cranial bolt, is generally required. The device of the invention allows a cranial bolt with a single passageway to be used to obtain data relating to both analyte concentration and intracranial pressure. In consequence, the aperture cut in the patient' s skull can be smaller and only one tract is required through the cerebral tissue, reducing the volume of disrupted tissue.
Using a sensor device of the invention, data can be obtained relating to the local pressure in the vicinity of the sensor portion. A build-up of pressure can have considerable clinical significance. Inclusion of a pressure sensor and an analyte sensor in a common sensor portion enables information regarding the pressure to be made available without the need for introduction of a separate sensor device. Further, pressure data is obtained relating to substantially the same location as the analyte measurements of the analyte sensor, reducing the risk that information will be obtained which is not consistent or may be misleading as a result of pressure measurement and analyte measurement being effected at different locations.
Advantageously, the sensor portion is of elongate configuration and comprises a distal portion, which in use can be positioned in the tissue or bodily fluid, and a proximal portion. Said analyte sensor and said pressure sensor are advantageously associated with the distal portion. The sensor device may further comprise a connector portion, a proximal end of the sensor portion being attached to the connector portion for communication of data from the analyte sensor and pressure sensor to the connector portion. Advantageously, the connector portion is arranged to permit connection of the sensor device to a base unit for communication of the data to the base unit. In practice, the connector unit may be used to connect the sensor device to appropriate data processing means, from which data collected by the device may be passed to a display device.
The analyte sensor and the pressure sensor may be housed within the sensor device, for example in the distal portion thereof. It will be appreciated that, where the pressure sensor is housed within the sensor device, it will be necessary for the sensor device to be so constructed that the pressure obtaining within the pressure sensor in the vicinity of the pressure sensor is such that the sensor can give a reliable indication of the pressure obtaining outside the sensor device, for example such that little or substantially no damping of the pressure signal or changes therein occurs as a result of the device's construction. In a preferred embodiment that can be achieved by locating the pressure sensor in a polyacrylamide gel within a microporous housing having pores of diameter at least 0.05μm, and preferably at least O.lμm.
If desired, the pressure sensor may be located outside the sensor portion.
Advantageously, the pressure sensor is located at or in the vicinity of the distal end of the distal portion. The pressure sensor may be a pressure transducer. The pressure sensor may be a strain-gauge. The pressure sensor may be connected to a fibre optic cable for permitting optical interrogation of the pressure sensor. The pressure sensor may be connected to an electrically conductive cable for transmission of the measured pressure data. As indicated above, the analyte sensor is suitable for determining an analyte selected from p02, pC02 and pH. Preferably, the analyte sensor is arranged for optical determination of the respective analyte. Advantageously, the sensor device comprises a second analyte sensor, preferably also an optical sensor, for determining at least one further analyte. Advantageously, the sensor device is suitable for determining two analytes selected from p02, pC02 and pH . Preferably, the sensor device is suitable for determining p02, pC02 and pH. Suitable optical sensors include in particular sensors comprising an indicator, especially an indicator solution, the optical characteristics of which are dependent on the concentration of the analyte to be measured. Preferably the indicator is an absorption indicator, a fluorescence indicator or a chemiluminescence indicator. Examples of such sensors for blood gases are known, for example, in the Paratrend (trade mark) device previously mentioned. Advantageously, the device further comprises a temperature measuring device, for example, a thermocouple. The invention also provides a method of monitoring a patient, comprising inserting into tissue or a bodily fluid of said patient a sensor portion of a sensor device comprising an analyte sensor and a sensor for determining a parameter relating to flow of a bodily fluid, determining the concentration of an analyte selected from p02, pC02 and pH and determining a value of a parameter relating to flow of a fluid, and treating the patient in dependence upon the determined analyte concentration and value of the parameter relating to fluid flow. In that method, the sensor device is advantageously arranged to monitor the parameter relating to flow and concentration of at least one analyte in substantially the same location within said soft tissue. In another especially advantageous method, the sensor device is inserted into a blood vessel for monitoring blood therein. Preferably, two or more analytes are measured. Preferably, the parameter relating to fluid flow is pressure. Advantageously, the sensor portion is suitable for insertion into cerebral spinal fluid. For that purpose, the sensor portion will be required to be of a strength such that it can penetrate tissue surrounding the cerebral spinal fluid. Advantageously, the sensor portion is suitable for insertion into soft tissue. A sensor portion for insertion into soft tissue may require greater strength than, for example, a sensor portion for use in a blood vessel. In the context of this specification, the term "strength" is intended to refer in particular to stiffness and resistance to kinking. The sensor portion will, however, preferably be flexible along at least those parts thereof that will be introduced into a blood vessel or soft tissue. In that connection, the term "flexible" is to be interpreted as requiring at least sufficient flexibility for the sensor portion to be sited in the convoluted pathways that may be present in vasculature or soft tissue to be examined without causing significant distortion of those pathways.
Advantageously, data relating to the pressure is transmitted optically from the pressure sensor to a monitoring device. Alternatively, data relating to the pressure may be transmitted electrically from the pressure sensor to a monitoring device.
One illustrative embodiment of the invention will now be described in detail with reference to the accompanying drawings, in which:
Fig. 1 is a schematic section through a distal end of a sensor device according to the invention suitable for use as a blood sensor; Fig. 2 is an enlarged view of a part of Fig. 1; and
Fig. 3 is a schematic view of the proximal end of a sensor portion of the device and an associated connector portion.
With reference to Fig. 1, a sensor device 1, which is suitable for use in a blood vessel for measuring parameters relating to blood, has an elongate sensor portion having a distal portion 2 terminating at distal end 3. The distal portion 2 has a wall 4 enclosing a number of analyte sensors 5, 6, 7 and a pressure sensor 8. The wall 4 is of a microporous material 9 having micropores 10 which are filled with a hydrophilic material which when hydrated forms a gel and allows the passage of water-bound ions. For example, the microporous material may be a membrane made from a hydrophobic polymer, for example polyethylene. The hydrophilic material may be, for example, a polyacrylamide which when hydrated forms a gel and allows the passage of water-bound ions, as well as gases. The micropores 10 may be of diameter of, for example, 0.1 μm.
Analyte sensors 5, 6 7 are optical sensors of known construction. Analyte sensor 5 is a pH sensor comprising an optical fibre 11 through a distal sensing portion of which extends a helical array of apertures, which are so arranged that all parts of the cross sectional area of the fibre are interrupted by at least one of the apertures. Each of the apertures is filled with a pH sensitive indicator, for example phenol red in a gel. The optical fibre 11 also has an optical transmission portion 12 extending from the distal sensing portion to a connector (not included in Fig. 1) by means of which it can be connected to a light source and a data collection and/or processing device. A mirror (not shown in Fig. 1) is provided embedded in the end of the fibre 11. Optical radiation transmitted along fibre 11 is reflected by the mirror and passes back along the fibre. The transmitted and reflected light passes through the indicator- containing apertures and the amount of light absorbed gives an indication of the pH of the medium in which the sensor is located.
Analyte sensor 6 is of similar construction to sensor 5 except that it contains an indicator sensitive to oxygen, for example, a fluorescent indicator.
Analyte sensor 7 is a pC02 sensor which is of broadly similar construction to sensor 5 except that the indicator is suitable for detection of C02. For example, the indicator may be phenol red in a solution which is a source of bicarbonate ions. Sensor 6 is enveloped by a tubular membrane of C02- permeable polymer, for example polyethylene (not shown in Fig. 1) .
Analyte sensors of the kind described above are present, for example, in the sensor devices described in US 5 596 988. The pressure sensor 8 is located adjacent to the distal portions of analyte sensors 5, 6 and 7, and close to the microporous wall 9. The sensor 8 is a fibre-optic sensor, for example, a fibre-optic pressure transducer of the kind made by FISO Technologies, which has a diameter of 550μm. Sensor 8 is connected to an optical fibre 13 by means of which the sensor 8 can be interrogated using white light interferometry .
As mentioned above, the sensor 8 shown is a fibre optic pressure transducer. Any other suitable pressure sensor may, however, be used. For example, the sensor 8 may be a guidewire mounted pressure sensor of the kind may by RADI Medical and known as the Pressure Wire 0 (trade mark) . That sensor uses essentially a strain gauge piezo-resistance technique, using a pressure sensitive diaphragm micro- machined in silicon. Another suitable strain-gauge is that included in a catheter manufactured by Millar Instruments Inc. under the trade mark Mikro-Tip.
The sensor device also includes a thermocouple 14. With reference to Fig. 2, the elongate sensor portion is connected at its proximal end to a connector unit which comprises connection means for connection to a light source from which light of wavelengths suitable for interrogation of the sensors may be transmitted to the optical fibres 11, 13 and to a data processing unit from which the data received from those optical fibres, optionally after analysis, may be transmitted to a display device, for example, a monitor.
As may be seen from Fig. 3, the analyte sensors 5, 6, 7, the pressure sensor 8 and the thermocouple 14 are embedded in a matrix 15, which fills the interior of the distal portion 2 of the sensor portion and maintains the sensors 5, 6, 7, 8 and thermocouple 14 substantially in their relative positions. In use, the pressure in the immediate vicinity of the sensor device can equilibrate with the pressure in the interior of the device by means of the adjacent microporous wall 9 and the matrix 15 and can be measured by the sensor 8. The matrix 15 is of a hydrophilic material that is permeable to the analyte (s) to be measured and may be, for example, a hydrogel, especially a hydrophilic polyacrylamide gel. It will be appreciated that the matrix must be suitable for transmission of the pressure outside the wall 4 to the sensor device 8. In practice, the matrix will be of the same material as the hydrophilic material filling micropores 10. The sensor device may be introduced into a blood vessel of the patient by known means, for example, by advancing it through a previously introduced cannula. Once in place, and following a short time in which the pressure within the sensor portion can equilibrate with the external pressure, the pressure sensor 8 is interrogated using a suitable source of light. The analyte sensors 5 to 7 are similarly interrogated using respective appropriate light sources. The analyte and pressure measurements may be exhibited on any suitable display device, for example, a monitor. The data from the sensors 5 to 7 may be used, usually after any appropriate temperature correction based on temperature measurements from thermocouple, together with pressure measurements from sensor 8 to make a variety of clinically important determinations which may assist in diagnosis of patient condition. For example, that data may be used to calculate oxygen saturation, bicarbonate concentration and base excess. Those determinations, with knowledge of the local pressure, can provide the clinician with a wealth of information to assist in diagnosis.
As mentioned, the sensor device described above is suitable for use in blood vessels. For use in tissue or in cerebral spinal fluid, the construction of a suitable device might be the same, except that the device and especially wall 9 would require strengthening to prevent kinking of the device on insertion.
As already mentioned, the invention includes sensor devices comprising an analyte sensor and a physical sensor for determining a physical parameter relating to flow of a bodily fluid, for example, thermal diffusion. Illustrative of physical sensors for determining thermal diffusion are thermistors of the kind included in the Thermal Diffusion Probe (trade mark) of Hemedex, Inc. of Cambridge,
Massachussetts, USA. That thermistor arrangement allows both thermal conduction within tissue and thermal convection due to blood flow to be determined.
For determination of blood velocity and related parameters such as perfusion, there may be incorporated instead of, or as well as, the pressure sensor 8 a velocimeter, for example, a laser Doppler device.
The invention is primarily for use in human patients, but it will be appreciated that devices adapted for use in animals, in particular other mammals, are not excluded.

Claims

1. A sensor device having a sensor portion for insertion into tissue or a bodily fluid of a patient, the sensor comprising an optical analyte sensor for determining an analyte in the tissue or bodily fluid selected from p02, pC02 and pH, and a sensor for determining a parameter relating to flow of a bodily fluid.
2. A sensor device according to claim 1, in which the sensor is a pressure sensor.
3. A sensor device according to claim 2 in which the pressure sensor is a pressure transducer.
4. A sensor device according claim 2 in which the pressure sensor is a strain-gauge. 5. A sensor device according to any one of the preceding claims, in which the sensor portion is of elongate configuration having a distal portion which in use can be positioned in the tissue or bodily fluid and a proximal portion. 6. A sensor device according to any one of the preceding claims, further comprising a connector portion, a proximal end of the sensor portion being attached to the connector portion for communication to the connector portion of data from the analyte sensor and flow parameter sensor
7. A sensor device according to claim 6, in which the connector portion is arranged to permit connection of the sensor device to a base unit for communication of the data to the base unit.
8. A sensor device according to any one of the preceding claims, in which the analyte sensor and the sensor for a parameter relating to flow are housed within a distal portion of the sensor portion.
9. A sensor device according to any one of the preceding claims, in which the flow parameter sensor is located at or in the vicinity of the distal end of the distal portion.
10. A sensor device according to any one of the preceding claims, in which the flow parameter sensor is connected to an optical fibre for permitting optical interrogation of that sensor .
11. A sensor device according to any one of claims 1 to 9. in which the flow parameter sensor is connected to an electrically conductive cable for transmission of the measured pressure data.
12. A sensor device according to any one of the preceding claims, in which there is a second analyte sensor, for determining at least one further analyte.
13. A sensor device according to claim 15, which is suitable for determining p02, pC02 and pH. 1 . A sensor device according to any one of the preceding claims, in which the or each analyte sensor is arranged for optical determination of the respective analyte.
15. A sensor device according to any one of the preceding claims, which further comprises a temperature measurement device.
16. A sensor device according to any one of the preceding claims, which is suitable for insertion into cerebral spinal fluid.
17. A sensor device according to any one of claims 1 to 15, which is suitable for insertion into soft tissue.
18. A sensor device having a sensor portion for insertion into tissue or a bodily fluid of a patient, the sensor portion comprising an analyte sensor for determining an analyte in the tissue or bodily fluid and a physical sensor for determining pressure in the tissue or bodily fluid.
19. A method of monitoring a patient, comprising inserting into tissue or a bodily fluid of said patient a sensor portion of a sensor device comprising an analyte sensor and a sensor for determining a parameter relating to flow of a bodily fluid, determining the concentration of an analyte selected from p02, pC02 and pH and determining a value of a parameter relating to flow of a fluid, and treating the patient in dependence upon the determined analyte concentration and the value of the parameter relating to fluid flow.
20. A method according to claim 19, in which the sensor device is arranged to monitor the flow parameter and concentration of at least one analyte in substantially the same location within said tissue or bodily fluid.
21. A method according to claim 19 or claim 2_0 in which two or more analytes are measured. 22. A method according to any one of claims 19 to 21 in which the physical sensor is a pressure sensor.
23. A method according to claim 22, in which the pressure is measured using a pressure transducer.
24. A method according to claim 22, in which the pressure is measured using a strain gauge.
25. A method according to any one of claims 19 to 24, in which data relating to the flow parameter is transmitted optically to a monitoring device.
26. A method according to any one of claims 19 to 24, in which data relating to the flow parameter is transmitted electrically to a monitoring device. 27. A method according to any one of claims 19 to 26, in which there is at least one optical analyte sensor arranged for optical determination of an analyte.
28. A method according to any one of claims 19 to 27, in which the sensor portion is inserted into a blood vessel. 29. A method according to any one of claims 19 to 27, in which the sensor portion is inserted into cerebral spinal fluid.
30. A method according to any one of claims 19 to 27, in which the sensor portion is inserted into soft tissue.
PCT/GB2003/004136 2002-09-17 2003-09-17 Apparatus and method for monitoring condition of a patient WO2004026128A1 (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009109215A1 (en) * 2008-03-03 2009-09-11 Geisert Square Gmbh Intervertebral disc analysis system and method
WO2014033101A1 (en) * 2012-08-30 2014-03-06 Siemens Aktiengesellschaft Device and method for in vivo determination of at least one blood value within an object to be examined
CN105686811A (en) * 2016-02-24 2016-06-22 南京航空航天大学 Minimally-invasive encephalic multi-parameter detection probe
US11559218B2 (en) 2014-04-04 2023-01-24 St. Jude Medical Coordination Center Bvba Intravascular pressure and flow data diagnostic systems, devices, and methods

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5704353A (en) * 1992-05-27 1998-01-06 Kalb; Irvin M. Urinary diagnostic catheter
US6248080B1 (en) * 1997-09-03 2001-06-19 Medtronic, Inc. Intracranial monitoring and therapy delivery control device, system and method
DE20116460U1 (en) * 2001-10-08 2002-01-17 Schregel Werner Device for insertion into hollow body organs
US20020052563A1 (en) * 1997-09-03 2002-05-02 Penn Richard D. Device and method to measure and communicate body parameters
US20020072679A1 (en) * 2000-12-12 2002-06-13 Schock Robert B. Intra-aortic balloon catheter having a fiberoptic sensor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5704353A (en) * 1992-05-27 1998-01-06 Kalb; Irvin M. Urinary diagnostic catheter
US6248080B1 (en) * 1997-09-03 2001-06-19 Medtronic, Inc. Intracranial monitoring and therapy delivery control device, system and method
US20020052563A1 (en) * 1997-09-03 2002-05-02 Penn Richard D. Device and method to measure and communicate body parameters
US20020072679A1 (en) * 2000-12-12 2002-06-13 Schock Robert B. Intra-aortic balloon catheter having a fiberoptic sensor
DE20116460U1 (en) * 2001-10-08 2002-01-17 Schregel Werner Device for insertion into hollow body organs

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009109215A1 (en) * 2008-03-03 2009-09-11 Geisert Square Gmbh Intervertebral disc analysis system and method
WO2014033101A1 (en) * 2012-08-30 2014-03-06 Siemens Aktiengesellschaft Device and method for in vivo determination of at least one blood value within an object to be examined
US11559218B2 (en) 2014-04-04 2023-01-24 St. Jude Medical Coordination Center Bvba Intravascular pressure and flow data diagnostic systems, devices, and methods
CN105686811A (en) * 2016-02-24 2016-06-22 南京航空航天大学 Minimally-invasive encephalic multi-parameter detection probe
CN105686811B (en) * 2016-02-24 2019-02-05 南京航空航天大学 A kind of minimal removed of intracranial parameter detecting probe

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