WO2006135293A1 - Capteur d’écoulement et procédé de mesure d’écoulement d’un fluide corporel - Google Patents

Capteur d’écoulement et procédé de mesure d’écoulement d’un fluide corporel Download PDF

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Publication number
WO2006135293A1
WO2006135293A1 PCT/SE2005/000945 SE2005000945W WO2006135293A1 WO 2006135293 A1 WO2006135293 A1 WO 2006135293A1 SE 2005000945 W SE2005000945 W SE 2005000945W WO 2006135293 A1 WO2006135293 A1 WO 2006135293A1
Authority
WO
WIPO (PCT)
Prior art keywords
heating
sensing element
temperature
flow
body fluid
Prior art date
Application number
PCT/SE2005/000945
Other languages
English (en)
Inventor
Kenth Nilsson
Original Assignee
St. Jude Medical Ab
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 St. Jude Medical Ab filed Critical St. Jude Medical Ab
Priority to PCT/SE2005/000945 priority Critical patent/WO2006135293A1/fr
Publication of WO2006135293A1 publication Critical patent/WO2006135293A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
    • G01F1/6886—Pyroelectric elements
    • 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 present invention relates to an Implantable flow sensor intended to be implanted into the circulatory system of a human being for sensing the flow of a body fluid, comprising a heating element for heating a pyroelectric sensing element of a pyroelectric detector which is adapted to generate a temperature signal representing changes in temperature of its sensing element after interruption of the heating, and a flow determining means for determining from said temperature signal data about the body fluid flow rate from cooling of said sensing element after interruption of the heating.
  • the invention also relates to a method for measuring the flow of a body fluid in the circulatory system of a human being, wherein a pyroelectric sensing element, intended to be implanted into said circulatory system, is heated by a heating element, whereupon a pyroelectric signal from said sensing element is detected when the temperature changes after interrupted heating for determining the cooling of the sensing element, and data about the body fluid flow rate is determined from the cooling after interrupted heating.
  • the senor is intermittently heated, and after the heating has been switched off, the sensor body cooling speed is recorded.
  • the speed of cooling gives information about the flow.
  • An example of such a sensor is disclosed in US 5 598 847.
  • the sensor according to this document includes a rigid cylindrical tube, sized to fit within a blood vessel. Inside the tube a heating element and a pyroelectric sensing element are situated. A signal processor is provided for generating a signal indicating the blood flow rate on the basis of the temperature signal received from the sensing element.
  • a cleaning element in the form of a piezoelectric actuator is coupled to the sensor.
  • the piezoelectric actuator When the piezoelectric actuator is set to vibrate, the vibrations are transferred to the sensor for removal of deposits.
  • the purpose of the present invention is to propose a simple and reliable technique for measuring the flow rate of fluids in the circulatory system of a human being, wherein the problem of ingrowths and overgrowths, adhering protein layers, deposits etc. on an implanted sensing surface is also eliminated.
  • the pyroelectric effect is inherent in a very pronounced way in all piezoelectric material. Often this is a disadvantage which has to be compensated for, especially in low frequency applications.
  • the pyroelectric properties of piezoelectric materials are utilized for providing a simple, reliable and quick sensor for determining the flow of a body fluid.
  • the element By applying an AC excitation voltage over the piezoelectric element the element is vibrated, and due to losses in the piezoelectric material the element is heated. After interruption of the excitation the fluid, normally blood, flowing past the sensing element will cool it until the element reaches the temperature of the surrounding fluid. From this cooling of the sensing element data about the fluid flow rate are determined.
  • a separate heating element is not needed, but one and the same element is used for heating and sensing, and the above-mentioned cooling is measured by the sensor itself.
  • the heating and sensing element can also be made with a very small thermal mass, and consequently a low thermal inertia, such that a quick sensor is obtained which makes it possible to sense temperature variations during single cardiac cycles. Also in situations with slow pressure variations in the fluid in question the temperature variation can be correctly followed in short time windows.
  • the voltage source of the sensor according to the invention is therefore arranged to apply on said combined heating and sensing element a vibration exciting voltage which is adapted to clean the surface of said heating and sensing element from tissue overgrowth and adhering proteins.
  • the above- mentioned vibration of the sensing element for heating purposes has thus appeared to also have an efficient cleaning effect on the surface of the sensing element. This cleaning action is a very important advantage of the invention.
  • the flow determining means is adapted to determine the decay of the temperature of said combined heating and sensing element after interruption of the heating and to determine said data about the body fluid flow rate from said decay.
  • the temperature decay curve after interruption of the heating important flow data are derived.
  • figure 1 is a schematic drawing of an electrode lead having a ring electrode suitable for use in the sensor according to the invention
  • figures 2 and 3 illustrate qualitatively the temperature decay curves sensed by the sensing element from which flow rate data are determined in two different ways.
  • Figure 1 shows an electrode lead 11 for a pacemaker with a tip electrode 200 and an indifferent ring electrode 100.
  • the lead 11 also includes three conductors, one conductor 12 connected to the tip electrode 200 and two conductors 13, 14 connected to the ring electrode 100.
  • the ring electrode 100 is coated by piezoelectric material which is vibrated by application of an excitation voltage on this electrode. The piezoelectric material is then heated by the vibrations as explained above. After interruption of the excitation the cooling is determined from the pyroelectric signal obtained from the piezoelectric material.
  • this cooling is depending on the flow of body fluid past the ring electrode 100. From the cooling, flow data of the fluid can consequently be derived.
  • Such a sensor can preferably be designed as a piezoelectric sensor, for instance of the kind described in WO 99/53972. From such a sensor not only a pyroelectric signal can be obtained but also e.g. pressure signals including several components from which different kinds of information can be filtered out.
  • FIGS 2 and 3 illustrate qualitatively the temperature variation as a function of time when practising the invention.
  • the excitation voltage is applied to the sensing element which is heated as explained above.
  • the temperature T then increases from T 0 which is the temperature of the body fluid in question, normally blood.
  • T 7 e.g. 1 °C
  • the excitation voltage is switched off, at time t 0 , and the heating is stopped. If this predetermined time period does not result in a sufficient heating, the excitation heating is continued during a second predetermined time period.
  • the blood flowing past the sensing element then cools the element and its temperature is decreasing until the temperature T 0 of the surrounding blood is reached again.
  • the temperature decay curve starting at the time to is an exponential curve generally described by an equation of the type
  • T (T 7 - T 0 ) e -t/ ⁇
  • T denotes the temperature of the sensing element for t >t o .
  • ⁇ is a constant determined by the thermal mass of the sensing element. The shape of the temperature decay curve after the time t 0 can thus be determined from the temperature T and the time t which are measurable quantities. Since the temperature decay in its turn depends on the flow rate of blood flowing past the sensing element and cooling it, data for this flow are thus derivable from the temperature decay curves.
  • Curve I illustrates a slower cooling than curve II which in its turn indicates that curve I represents a situation of a lower flow than curve II, provided that other conditions are similar.
  • FIG. 3 shows a corresponding diagram, illustrating an alternative way of determining the temperature decay, by measuring the times tj, t 2 , t 3 , U, t 5 and t 6 , at which three predetermined temperatures T', T", and T" ' are reached after interrupting the heating at t 0 for the two situations illustrated. Also from this figure it directly appears that the time for the temperature to drop from e.g. T' to T" is longer in the situation according to curve I than according to curve II, viz.
  • curve I is illustrating a situation of slower cooling than curve II.

Landscapes

  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Cardiology (AREA)
  • Physiology (AREA)
  • General Physics & Mathematics (AREA)
  • Biophysics (AREA)
  • Pathology (AREA)
  • Fluid Mechanics (AREA)
  • Biomedical Technology (AREA)
  • Hematology (AREA)
  • Medical Informatics (AREA)
  • Molecular Biology (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)

Abstract

L’invention concerne un capteur d’écoulement implantable destiné à être implanté dans le système circulatoire d’une personne pour détecter l’écoulement d’un fluide corporel comprenant un élément de chauffage permettant de chauffer un élément de détection pyroélectrique d’un détecteur pyroélectrique qui est adapté pour générer un signal de température représentant des changements de température de son élément de détection après interruption du chauffage. Un moyen de détermination d’écoulement est disposé pour déterminer à partir des données de signaux de température le débit de fluide corporel à partir du refroidissement dudit élément de détection après interruption du chauffage. L’élément de chauffage et l’élément de détection sont un seul et même l’élément combiné de chauffage et de détection (100). L’élément combiné de chauffage et de détection est piézoélectrique, et une source de tension est installée pour appliquer une tension d’excitation de vibrations sur l’élément combiné de chauffage et de détection permettant de chauffer l’élément. Un procédé correspondant de mesure d’écoulement du fluide corporel est également décrit.
PCT/SE2005/000945 2005-06-16 2005-06-16 Capteur d’écoulement et procédé de mesure d’écoulement d’un fluide corporel WO2006135293A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/SE2005/000945 WO2006135293A1 (fr) 2005-06-16 2005-06-16 Capteur d’écoulement et procédé de mesure d’écoulement d’un fluide corporel

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE2005/000945 WO2006135293A1 (fr) 2005-06-16 2005-06-16 Capteur d’écoulement et procédé de mesure d’écoulement d’un fluide corporel

Publications (1)

Publication Number Publication Date
WO2006135293A1 true WO2006135293A1 (fr) 2006-12-21

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Family Applications (1)

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PCT/SE2005/000945 WO2006135293A1 (fr) 2005-06-16 2005-06-16 Capteur d’écoulement et procédé de mesure d’écoulement d’un fluide corporel

Country Status (1)

Country Link
WO (1) WO2006135293A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8224421B2 (en) 2006-01-31 2012-07-17 St. Jude Medical Ab Implantable cardiac stimulator, device and system for monitoring the status of a cardiac lead
WO2018096168A1 (fr) 2016-11-28 2018-05-31 Koninklijke Philips N.V. Capteur de débit et méthode de mesure d'un débit

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3798967A (en) * 1971-04-21 1974-03-26 Philips Corp Probe for measuring the flow of liquids
US4770037A (en) * 1986-04-08 1988-09-13 Battelle Memorial Institute Method for determining the flow of a fluid
US5598847A (en) * 1994-12-28 1997-02-04 Pacesetter, Inc. Implantable flow sensor apparatus and method
US6524256B2 (en) * 2000-07-22 2003-02-25 Biotronik Mess-und Therapiegeraete GmbH & Co. Ingenieürbuero Berlin Implantable measuring device, particularly a pressure measuring device for determining the intracardial or intraluminal blood pressure
US6571130B1 (en) * 1998-04-22 2003-05-27 St. Jude Medical Ab Medical implant with piezoelectric material in contact with body tissue
US20040007245A1 (en) * 2002-07-15 2004-01-15 Hans Hecht Method for cleaning of a measuring element passed over by a gas flow

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3798967A (en) * 1971-04-21 1974-03-26 Philips Corp Probe for measuring the flow of liquids
US4770037A (en) * 1986-04-08 1988-09-13 Battelle Memorial Institute Method for determining the flow of a fluid
US5598847A (en) * 1994-12-28 1997-02-04 Pacesetter, Inc. Implantable flow sensor apparatus and method
US6571130B1 (en) * 1998-04-22 2003-05-27 St. Jude Medical Ab Medical implant with piezoelectric material in contact with body tissue
US6524256B2 (en) * 2000-07-22 2003-02-25 Biotronik Mess-und Therapiegeraete GmbH & Co. Ingenieürbuero Berlin Implantable measuring device, particularly a pressure measuring device for determining the intracardial or intraluminal blood pressure
US20040007245A1 (en) * 2002-07-15 2004-01-15 Hans Hecht Method for cleaning of a measuring element passed over by a gas flow

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8224421B2 (en) 2006-01-31 2012-07-17 St. Jude Medical Ab Implantable cardiac stimulator, device and system for monitoring the status of a cardiac lead
WO2018096168A1 (fr) 2016-11-28 2018-05-31 Koninklijke Philips N.V. Capteur de débit et méthode de mesure d'un débit
CN110022760A (zh) * 2016-11-28 2019-07-16 皇家飞利浦有限公司 流量传感器和测量流速的方法
JP2020503502A (ja) * 2016-11-28 2020-01-30 コーニンクレッカ フィリップス エヌ ヴェＫｏｎｉｎｋｌｉｊｋｅ Ｐｈｉｌｉｐｓ Ｎ．Ｖ． 流量を測定するフロー・センサー及び方法
JP7000428B2 (ja) 2016-11-28 2022-02-10 コーニンクレッカ フィリップス エヌ ヴェ 流量を測定するフロー・センサー及び方法
RU2768159C2 (ru) * 2016-11-28 2022-03-23 Конинклейке Филипс Н.В. Датчик потока и способ измерения скорости потока

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