WO2009072023A1 - Système de pléthysmographie à impédance monté sur le front, et procédé associé - Google Patents

Système de pléthysmographie à impédance monté sur le front, et procédé associé Download PDF

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Publication number
WO2009072023A1
WO2009072023A1 PCT/IB2008/054841 IB2008054841W WO2009072023A1 WO 2009072023 A1 WO2009072023 A1 WO 2009072023A1 IB 2008054841 W IB2008054841 W IB 2008054841W WO 2009072023 A1 WO2009072023 A1 WO 2009072023A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrodes
patient
headband
forehead
drive
Prior art date
Application number
PCT/IB2008/054841
Other languages
English (en)
Inventor
Earl Herleikson
William Crone
Original Assignee
Koninklijke Philips Electronics, N.V.
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 Koninklijke Philips Electronics, N.V. filed Critical Koninklijke Philips Electronics, N.V.
Publication of WO2009072023A1 publication Critical patent/WO2009072023A1/fr

Links

Classifications

    • 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
    • A61B5/024—Detecting, measuring or recording pulse rate or heart rate
    • A61B5/02438—Detecting, measuring or recording pulse rate or heart rate with portable devices, e.g. worn by the patient
    • 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
    • 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
    • A61B5/0295—Measuring blood flow using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/053—Measuring electrical impedance or conductance of a portion of the body
    • A61B5/0535—Impedance plethysmography
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6814—Head

Definitions

  • This invention generally relates to systems and methods for determining changes in blood volume or flow from measurements of impedance, and more particularly, to determining changes in blood volume or flow from impedance measurements taken from the forehead of a patient.
  • Impedance plethysmography is a non-invasive medical test that measures small changes in electrical resistance of the chest, calf or other regions of the body. These measurements reflect blood volume changes. This procedure provides an alternative to venography, which is invasive and requires a great deal of skill to execute adequately and interpret accurately. With impedance plethysmography, a number of electrodes need only be secured to the patient and changes in impedance measured.
  • an apparatus for determining blood volume changes in a patient.
  • the apparatus includes a plurality of electrodes adapted to be secured to a patient's forehead.
  • the apparatus further includes a signal driving circuit, a sensing circuit, and a processor.
  • the signal driving circuit is coupled to at least one of the electrodes and is configured to drive an alternating signal to the patient's forehead.
  • the sensing circuit is coupled to at least one other of the electrodes and is configured to sense from the patient's forehead electrical signals resulting from the alternating signal.
  • the processor is coupled to the signal driving circuit and the sensing circuit and is configured to calculate impedance from the alternating signal and electrical signals sensed from the patients forehead to determine changes in blood volume.
  • a plurality of electrodes are positioned on a patient's forehead. Alternating current is passed through a first group of the plurality of electrodes into the patient's forehead. A voltage is detected at each of a second group of the plurality of electrodes. The patient's change in blood volume is then measured by processing the detected voltage.
  • the first group includes first and second drive electrodes and the second group includes first and second sense electrodes located between the first and second drive electrodes.
  • the first sense electrode is closer to the first drive electrode than to the second sense electrode.
  • the electrodes are mounted to a headband comprising a pressure transducer and/or force sensor and a visual indicator.
  • a visual indication is outputted when the pressure and/or force indicated by the respective transducer falls within a range of values corresponding to tension in the headband suitable for maintaining the electrodes in contact with the patient's forehead while not overly restricting blood flow.
  • Figure 1 is an illustration of a patient wearing a headband suitable for measuring a patient's heart rate in accordance with an embodiment of the present invention.
  • Figure 2 is a top plan view of a headband suitable for measuring a patient's blood perfusion in accordance with an embodiment of the present invention.
  • Figure 3 is a schematic block diagram of a system for determining a patient's blood perfusion using the headband of Figures 1 and 2.
  • Figure 4 is a top plan view of an alternative embodiment of a headband suitable for measuring a patient's blood perfusion in accordance with an embodiment of the present invention.
  • Figure 5 is a schematic block diagram of a system for determining a patient's blood perfusion using the headband of Figure 4.
  • a system 10 for measuring blood volume characteristics includes a headband 12 worn around the head of a patient 14.
  • the headband 12 may extend completely around the patients head, be adhered to the patient's forehead by an adhesive, or partially encircle the patient's head and be maintained in place by the elasticity of the headband or a headband strap biasing itself against the head of the patient.
  • a plurality of electrodes 16a-16d are secured to the inner surface of the headband 12 such that they are in contact with the skin of the patient's forehead when the headband 12 is placed on the patient's head.
  • the electrodes 16a-16d include an adhesive surface for adhering the electrodes 16a-16d to the patient's head.
  • the headband 12 is omitted and the electrodes 16a-16d are secured to the patient's head only by means of adhesive in the pattern shown.
  • the electrodes 16a, 16b are located on one side of the patient's forehead and the electrodes 16c, 16d are located on the other side of the forehead.
  • the distance between the pairs of electrodes is preferably much greater than the separation between the electrodes within a pair.
  • the separation between the medial electrodes 16b and 16c may be between three and fifteen times the separation between the electrodes 16a and 16b or the separation between the electrodes 16c and 16d.
  • the separation between the medial electrodes 16b and 16c may be between eight and twelve times the separation between the electrodes of each pair.
  • the electrodes 16a-16d are preferably formed of a material providing short term stability of the electrode-to-skin half-cell potential and providing overall short term stability of the interface impedance within the driving frequency of signals applied to the electrodes 16a-16d.
  • the electrodes 16a, 16d contact the skin by means of a hydrogel, such as RG 63T hydrogel.
  • the headband 12 encircles the patient's head, as shown, and includes a fastener 18 for securing ends 20a, 20b of the headband 12 to one another.
  • the fastener 18 is a hook and loop fastening system such as VELCRO, however other fastening systems such as buckles, snaps, a knot, or the like may be used to secure the ends 20a, 20b to one another.
  • the headband 12 is a continuous loop with elastic portions to enable the headband 12 to bias itself against the patient's head.
  • the headband 12 includes both elastic portions and a fastener 18.
  • a controller 22 is secured to the headband 12 and includes circuits for driving the electrodes 16a-16d and for detecting voltages therefrom.
  • the controller 22 is coupled to a monitoring device 24 by means of wires or wirelessly to transmit measurements and/or to receive control signals.
  • the device 24 may be embodied as an automatic external defibrillator (AED), CPR feedback device, or the like.
  • a power source 26, such as a battery, is also secured to the headband 12. In an alternative embodiment, the power source 26 and controller 22 are separate from the headband 12 and are electrically coupled to the headband 12 by means of wires.
  • visual indicators 28 are positioned on the headband 12 in relation to the headband electrode pairs such that a user may determine the location of one or more of the electrodes when the electrodes 16a-16d are facing the patient's forehead.
  • the visual indicators 28 are LEDs each positioned over one of the medial electrodes 16b, 16c.
  • the visual indicators 28 are each positioned over one of the lateral electrodes 16a, 16d.
  • the visual indicators 28 are located at a position between the lateral electrode 16a and the medial electrode 16b and a position between the medial electrode 16c and the lateral electrode 16d.
  • the visual indicators 28 are marks made on the outside surface of the headband 12 rather than LEDs.
  • the controller 22 in this embodiment includes a driving module 30 that generates signals coupled to some of the electrodes 16a-16d.
  • the driving module 30 couples signals only to the lateral electrodes 16a, 16d.
  • the driving module 30 couples an alternating signal to the electrodes 16a, 16d, such that the polarity of the electrodes 16a, 16d change cyclically and the direction of current flow changes cyclically.
  • the frequency of the alternating signal is preferably between about 1 and 100 kHz and the RMS current of the signal is preferably between 10 microamperes and 1 milliampere. In some embodiments, the RMS current of the driving signal is proportional to its frequency.
  • the RMS current may be equal to about 10 microamperes times the frequency measured in kilohertz.
  • a 100khz carrier times 10 microamps would result in a 100 times 10 ua rms current or 1000 ua (1 ma).
  • the controller 22 of Figure 3 includes a sensing module 32 coupled to some of the electrodes 16a-16d.
  • the sensing module 32 receives signals only from the medial electrodes 16b, 16c.
  • the sensing module 32 preferably does not draw a significant amount of current.
  • the sensing module 32 may include a voltage follower that outputs a voltage exerted at its input, but which has a high input impedance and therefore does not draw a significant amount of current.
  • the sensing module 32 may further process the sensed voltage by demodulating the sensed voltage to remove the carrier frequency components.
  • the sensed voltage may be demodulated using the in-phase (I) and quadrature (Q) signals of the carrier frequency, as known in the art.
  • the sensing module may further condition either the sensed or demodulated signal by, for example, amplifying or filtering as known in the art.
  • the controller 22 of Figure 3 includes a processing module 34 that processes the output of the sensing module 32 in order to extract information regarding blood volume changes in the patient 14.
  • the processing module 34 may, for example, extract a measure of blood perfusion, heart rate, or the like.
  • the heart rate may be analyzed to determine breathing rate by detecting changes in the R to R interval of the cardiac cycle caused by respiration.
  • Another method may include measurement of the amplitude modulation of the carrier caused by changes in impedance. The impedance will change as a function of respiration and this can also be measured.
  • the processing module 34 may extract the information according to impedance plethysmography techniques known in the art, such as those used to extract blood volume change information through impedance measurements performed on the patient's thorax. In some embodiments, extraction of information regarding blood volume changes occurs in a device remote from the headband 12. In such embodiments the processing module 34 may be omitted from the headband 12.
  • the controller 22 of Figure 3 includes a transmitting module 36.
  • the transmitting module 36 receives an output from the sensing module 32 or processing module 34 and transmits the signal over a wire or wirelessly to a remote device.
  • the remote device may include an automatic external defibrillator (AED), electrocardiogram (ECG) monitor, or other device for monitoring physiological attributes or vital signs.
  • AED automatic external defibrillator
  • ECG electrocardiogram
  • the controller may be integrated into the remote device.
  • the system 10 further includes a load cell (or piezo-electric type of force sensor) 38, or pressure transducer 38, secured to the headband 12.
  • the force sensor 38 is embodied as a piezoelectric film positioned on the headband 12 between the headband 12 and the patient's skin.
  • the force sensor 38 may detect one or both of tension in the headband 12 and force of the headband 12 against the head of the patient 14. Monitoring one or both of tension and force helps the operator to secure the headband 12 in proper contact with the head of the patient 14 without constricting blood flow through vascular structures beneath the headband 12.
  • the force sensor 38 is shown coupled to the controller 22, which is further coupled to one or more indicators 40, which may be embodied as an audible alarm or LED.
  • the controller 22 includes a tensioning module 42 which activates one of the one or more indicators 40 when an output from the force sensor 38 indicates that the tension in the headband 12 is within a range of values found to have a high likelihood of maintaining the electrodes 16a-16d in good electrical contact with the patient's forehead without excessive constriction of blood flow.
  • the controller 22 deactivates the indicator 40 when the tension exceeds the acceptable range of values.
  • the controller 22 may activate a different indicator 40 if the tension exceeds the acceptable range of values.
  • the controller 22 activates the same indicator when tension exceeds the acceptable range but in a different manner.
  • the controller 22 may cause an indicator 40 embodied as an LED to remain off where tension is below an acceptable range, to emit steadily if the tension lies within the acceptable range, and to emit intermittently if tension exceeds the acceptable range.
  • the output of the force sensor 38 may be either recorded on the headband or transmitted and recorded by another device such that the tension in the headband 12 may be used to interpret data transmitted from the headband 12.
  • the indicator 40 can be omitted and the tensioning indication provided by one or both of the indicators 28.
  • a separate force sensor 38 is associated with each pair of electrodes, monitoring the forehead contact at each electrode pair location. The indicators 28 are then used to signal the effectiveness of patient contact for each of the electrode pairs, respectively.
  • the various systems 10 disclosed hereinabove enable rapid mounting of electrodes to a patient in emergency situations. Measurements taken using the disclosed systems also provide a more accurate measurement of blood volume changes in the patient 14 in emergency situations than prior systems. Due to mounting of the electrodes on the patient's head, the impedance between the electrodes is not as affected by chest compressions as is for thorax mounted electrodes. Furthermore, due to the rigidity of the skull, changes in the volume through which current passes is not significantly affected by movement of the patient, which results in reduced motion artifacts even when the patient's head moves or CPR compressions are being applied.
  • Blood perfusion at the forehead is also relatively unaffected by the patient being in a state of shock. As noted above, blood flow to the limbs of a patient experiencing shock is reduced. In contrast, blood flow to the patient's head continues until the latest stages of shock. Measuring blood flow at the forehead is therefore useful for measuring blood perfusion in patients experiencing major trauma or receiving CPR.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Medical Informatics (AREA)
  • Physics & Mathematics (AREA)
  • Veterinary Medicine (AREA)
  • Biophysics (AREA)
  • Pathology (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Public Health (AREA)
  • General Health & Medical Sciences (AREA)
  • Molecular Biology (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • Cardiology (AREA)
  • Physiology (AREA)
  • Hematology (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Radiology & Medical Imaging (AREA)
  • Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)
  • Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)

Abstract

La présente invention concerne un système et un procédé destinés à déterminer des changements de volume/de flux sanguin chez un patient. Des électrodes sont placées sur le front d'un patient, puis l'on fait passer un courant alternatif à travers un premier groupe de la pluralité d'électrodes (16a, 16d) dans le front du patient. Une tension est détectée dans chacune d'une pluralité d'électrodes (16c, 16b) d'un second groupe. Une impédance est ensuite calculée à partir des tensions détectées, cette impédance étant utilisée pour permettre de déterminer les changements de volume/de flux sanguin chez le patient. La présente invention concerne également un bandeau frontal (12) sur lequel sont montées des électrodes de détection et d'activation. Les électrodes de détection sont situées entre les électrodes d'activation et séparées les unes des autres par une distance supérieure à celle qui sépare une électrode de détection d'une électrode d'activation adjacente. Un transducteur de pression ou de force (38) monté sur le bandeau frontal fournit un retour sur la tension dans le bandeau.
PCT/IB2008/054841 2007-12-05 2008-11-18 Système de pléthysmographie à impédance monté sur le front, et procédé associé WO2009072023A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US99247007P 2007-12-05 2007-12-05
US60/992,470 2007-12-05

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WO2009072023A1 true WO2009072023A1 (fr) 2009-06-11

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2604183A1 (fr) * 2011-12-16 2013-06-19 General Electric Company Procédé et agencement permettant de détecter un artefact de mouvement à partir de signaux bioélectriques mesurés à partir de la tête d'un patient
JP2014519352A (ja) * 2011-04-12 2014-08-14 オルサン メディカル テクノロジーズ リミテッド 頭蓋内圧および追加の頭蓋内血行動態パラメータを監視するための装置および方法
EP2672883A4 (fr) * 2011-02-09 2015-07-01 Orsan Medical Technologies Ltd Dispositifs et procédés permettant de surveiller des états hémodynamiques cérébraux

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3845757A (en) * 1972-07-12 1974-11-05 Minnesota Mining & Mfg Biomedical monitoring electrode
WO1999065390A1 (fr) * 1998-06-17 1999-12-23 Nimeda Ltd. Surveillance non-invasive de parametres physiologiques
US20020165462A1 (en) * 2000-12-29 2002-11-07 Westbrook Philip R. Sleep apnea risk evaluation
WO2005084537A1 (fr) * 2004-03-08 2005-09-15 Medicus Engineering Aps Methode et instrument pour mesurer des parametres physiologiques
GB2415051A (en) * 2004-06-10 2005-12-14 Quantum Applied Science & Res Garment with adjustably attached physiological sensors
US20050283082A1 (en) * 2004-06-21 2005-12-22 Geddes Leslie A Optical noninvasive vital sign monitor
WO2006103422A1 (fr) * 2005-03-29 2006-10-05 Pres-Sure Medical Ltd Capteur de pression d’un bandage

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3845757A (en) * 1972-07-12 1974-11-05 Minnesota Mining & Mfg Biomedical monitoring electrode
WO1999065390A1 (fr) * 1998-06-17 1999-12-23 Nimeda Ltd. Surveillance non-invasive de parametres physiologiques
US20020165462A1 (en) * 2000-12-29 2002-11-07 Westbrook Philip R. Sleep apnea risk evaluation
WO2005084537A1 (fr) * 2004-03-08 2005-09-15 Medicus Engineering Aps Methode et instrument pour mesurer des parametres physiologiques
GB2415051A (en) * 2004-06-10 2005-12-14 Quantum Applied Science & Res Garment with adjustably attached physiological sensors
US20050283082A1 (en) * 2004-06-21 2005-12-22 Geddes Leslie A Optical noninvasive vital sign monitor
WO2006103422A1 (fr) * 2005-03-29 2006-10-05 Pres-Sure Medical Ltd Capteur de pression d’un bandage

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2672883A4 (fr) * 2011-02-09 2015-07-01 Orsan Medical Technologies Ltd Dispositifs et procédés permettant de surveiller des états hémodynamiques cérébraux
US9307918B2 (en) 2011-02-09 2016-04-12 Orsan Medical Technologies Ltd. Devices and methods for monitoring cerebral hemodynamic conditions
JP2014519352A (ja) * 2011-04-12 2014-08-14 オルサン メディカル テクノロジーズ リミテッド 頭蓋内圧および追加の頭蓋内血行動態パラメータを監視するための装置および方法
EP2696755A4 (fr) * 2011-04-12 2015-07-01 Orsan Medical Technologies Ltd Dispositifs et procédés pour surveiller la pression intracrânienne et des paramètres hémodynamiques intracrâniens supplémentaires
EP2604183A1 (fr) * 2011-12-16 2013-06-19 General Electric Company Procédé et agencement permettant de détecter un artefact de mouvement à partir de signaux bioélectriques mesurés à partir de la tête d'un patient

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