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WO1997000045A1 - Stethoscope - Google Patents

Stethoscope Download PDF

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Publication number
WO1997000045A1
WO1997000045A1 PCT/CA1996/000408 CA9600408W WO9700045A1 WO 1997000045 A1 WO1997000045 A1 WO 1997000045A1 CA 9600408 W CA9600408 W CA 9600408W WO 9700045 A1 WO9700045 A1 WO 9700045A1
Authority
WO
WIPO (PCT)
Prior art keywords
time
heart
stethoscope
wave form
time elapsed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CA1996/000408
Other languages
English (en)
Inventor
Katz Hart
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HEART SOUNDS Inc
Original Assignee
HEART SOUNDS Inc
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 HEART SOUNDS Inc filed Critical HEART SOUNDS Inc
Priority to AU61186/96A priority Critical patent/AU6118696A/en
Publication of WO1997000045A1 publication Critical patent/WO1997000045A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B7/00—Instruments for auscultation
    • A61B7/02—Stethoscopes
    • A61B7/04—Electric stethoscopes
    • 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 for evaluating the cardiovascular system, e.g. pulse, heart rate, blood pressure or blood flow
    • A61B5/024—Measuring pulse rate or heart rate

Definitions

  • This invention has as its object the achievement of this feat and to thereby provide a substantial advance in the art of probative medicine with a stethoscope.
  • the invention preferably uses a hybrid computer which accepts the analog sound wave form detected by the stethoscope and converts it to digital form, and then processes it to produce a digital output of heart rate.
  • the ability to measure heart rate in the computer can be combined with the ability to simultaneously convey to the user the customary sounds made by the heart. It can also be combined with the ability to make a simultaneous record of the sounds of the heart and of heart beat rate.
  • an electronic heart rate sensing device comprising: means for producing a wave form that tracks the wave form of sound produced by the heart as derived from stethoscope contact with the patient in the area of the heart; means for establishing a wave form threshold beyond which cyclic reference complexes appear and are identified; means for measuring the time elapsed between similar moments on adjacent reference complexes as an indicator of rate of heart beat; and means for converting the measurement of time elapsed to a reading of rate of heartbeat.
  • Figure 1 is an illustration of a stethoscope with a heartbeat rate indicator according to this invention.
  • Figure 2 is a sectional and side view illustration showing the means for processing the heart rate of the stethoscope of Figure 1 ;
  • Figure 4 is the wave of Figure 3 full-wave rectified and illustrating the manner in which it is divided into time segments for the purpose of producing threshold amplitudes that detect cyclic complexes from which heart rate can be determined.
  • FIG. 1 is an illustration of an electronic stethoscope according to this invention. It has a cup 10 that is placed over a patient in the area of the heart. The cup has a microphone that tracks the sound of the heart and conducts it through cable 12 to a receiver in the housing 14 for amplification and transmission to the ear phones 16 for a user. This much of the device is old and not part of the invention.
  • the digital computer in the housing includes a micro-controller, an analog-digital converter to convert the analog wave form provide by the microphone to digital data that can be processed by the micro-controller. There is also provided a digital-analog converter which converts the digital data back to analog-wave form before transmission to the ear phones 16 for hearing.
  • the micro-controller is code-embedded with an algorithm for calculating heart rate, information which it then passes on to a display driver, which in turn causes the heart rate to be displayed on the display screen 13.
  • a micro-controller having a speed of 3 MgHz, a read-only memory of 12 kilobytes and a random access memory of 128 kilobytes is used.
  • Such a microcontroller is inexpensive but yet permits data to be saved for periods of several seconds for processing before it is replaced by other incoming data.
  • the microcontroller is programmed to keep the data collected for periods of at Ieast six seconds before erasing it from memory to make room for new data.
  • the stethoscope can run off of a standard power source such as battery, which can be initiated by pressing start-up button 25, and the operation of the stethoscope's electronic features can be controlled by standard circuitry using switches 17 mounted to the cup 10.
  • Ejection button 29 can be used to eject storage disk 26 from the housing 14. Further switches, like switch 25, can be added to the housing 14 for specific functions if required.
  • the arrangement of the switch means is a matter of personal preference of the designer and is not part of the invention.
  • Figure 3 is a drawing of a wave form of a typical heartbeat. It has a lupp, generally referred to by the numeral 28, representing the systolic (contracting) actions of the heart and a dupp, generally referred to by the numeral 30, representing the diastolic (expanding) actions of the heart during the cardiac cycle.
  • the periods between the systolic actions and the diastolic actions are generally referred to by the numeral 32.
  • the heart rate determinable from the wave-form illustrated is sixty cardiac cycles per minute, i.e. there is one cardiac cycle per second.
  • the lupp 28 is usually louder, longer and duller in sound than the dupp 30 and it is bigger on the graph. However, in some people, and in varying conditions for listening, the opposite is true. This and other differences do not interfere with the isolation of cyclic complexes associated with a maximum from which I calculate heart beat rate.
  • the wave form, as at 32, is substantially constant between lupp 28 and dupp 30 and between dupp 30 and lupp 28 formations.
  • the heart makes substantially no noise here and the base line of the derived wave form is taken as zero at this level.
  • the embodiment described determines heart beat rate by isolating reference complexes that are related to either a lupp 28 or a dupp 30 (whichever is the largest) complex of pulses and which occur once each cycle of the waveform.
  • the full wave rectified wave form of Figure 4 is divided into sequential time segments of one second each, separated by time segment dividers 33, 34 and 35.
  • This time segment usually is long enough to include both a lupp and a dupp.
  • the object is to identify the time between sequential cyclic complexes associated with a maximum amplitude of the wave and this is done by determining the maximum amplitude in a time segment and establishing a threshold amplitude across the next time segment that is below the maximum and above which a cyclic complex appears.
  • the threshold amplitude must, for example, be well above the base line.
  • numeral 36 refers to the maximum amplitude of the first one second time segment and a threshold amplitude 38 is established in the second time segment.
  • Numeral 40 refers to the maximum amplitude in the second time segment and a threshold amplitude 42 is established in the third time segment.
  • Numeral 44 is the maximum in the third time segment and numeral 46 refers to the threshold in the fourth time segment. This sequence is continuous. I have found that a threshold of .5 of the maximum measured works well.
  • the waveform will cross the threshold just before the maximum is reached, as is the case at 48, 50 and 52, and that the cross over is identified with the maximum. Further, the time between two adjacent maximums (under most conditions) represents the time of one cycle from which heart rate can be calculated.
  • the relationship between the maximum and minimum or no noise amplitude is significant and an examination of the total time that the amplitude is above the threshold in a predetermined time after crossover is significant as a test of a time cyclic maximum.
  • the time durations of the reference pulses i.e. the portion of the pulses of the reference complex having an amplitude greater than the threshold amplitude
  • the time durations of the reference pulses are added up and compared in proportion to the time of the testing period.
  • the inventor For heart rates of between 40 and 170 (cardiac cycles per minute), the inventor has found a testing period of 100 milli-seconds satisfactory and that, if the time durations of the component pulses 34 added up constituted thirty per cent or more of that testing period, a bona fide threshold complex has been found. If the sum is less than 30 per cent, the measured reference complex is probably not cyclically related and should be rejected for calculation. The algorithm then continues its search looking for the next intersection of the threshold.
  • the algorithm does not start looking for the next reference complex until after a refractory period has ended.
  • the refractory period is taken as having begun at the same moment in time that the bona fide reference complex began and continues on long enough after the testing period has ended such that, in most cases, any other complex of the same cycle that would render an inaccurate reading of heart rate will have been passed over.
  • both the amplitude of both the lupp and the dupp complexes within the same cardiac cycle as the reference complex are substantially reduced to amplitude below the threshold. If the heart rate is greater than 170 beats or less than 40 beats per minute, than an adjustment has to be made to the length of the refractory period. For instance, for heart rates greater than 150, the testing period must be shortened. For heart rates less than 40, the testing period must be lengthened.
  • a reference complex should also be rejected for calculation of heart beat rate if a next following reference complex is not located within 1200 milliseconds from the start of the time of measurement of a reference complex. That is taken as an indication that a cycle has been missed. In that case, the next second period is used to calculate a new maximum and the process is re-initialized. For heart rates that are less than 40 beats per minute, this 1200 millisecond period must be increased.
  • the heart sound wave will be input to a digital computer that will convert it to a corresponding voltage form, convert it to digital form and perform all of the other operations described above to finally supply a digital reading of heart beat rate per minute on its screen. It will full-wave rectify the waveform; divide the base into time segments of one second; determine the maximum amplitude in each second and o determine from it the cut-off amplitude for the next following time segment; determine the cyclically related reference complexes for each cycle; use a testing period to check to see that each reference segment is a valid cyclically related complex and reject it from measurement if it is not; determine the time between the beginning of the reference complex in a first cardiac cycle and the beginning of the reference complex in the next following cardiac cycle; and calculate the heart beat rate per minute and display it on the window read-out dial. It will do these things every second (determine maximum amplitude to provide threshold for next second period) and every cardiac cycle (identify and calculate time difference between the beginning of consecutive reference complexes) on a continuing basis.
  • the computer calculates the heart beat rate from the cycle time as derived from the first crossover point of the rectified waveform on the threshold of two adjacent cycles and checks the validity of the cross-over point by measuring the total time the waveform is over the threshold in the first 100 milliseconds after cross-over and by checking for the expected occurrence of a next following reference complex after the refractory period has ended. It thus is an accurate measurement because measurements likely to be in error as based on a reference complex that is not cyclic have been eliminated. Modifications to the device described are contemplated within the scope of the invention.
  • the threshold line location, the length of the testing period, the proportion of pulse to testing period tested for, can all be varied to suit particular circumstances.
  • Full wave rectification might be eliminated by putting a threshold amplitude line below the base line and adding the times of amplitude across over above and below the line.
  • the crucial aspect is to break out cyclic complexes at regular intervals from which heart rate can be calculated and to provide means for checking the validity of these complexes as being cyclically related to ensure accuracy.

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

Abstract

L'invention concerne un dispositif de détection électronique de la fréquence cardiaque dans un stéthoscope utilisé pour l'examen des caractéristiques propres aux ondes sonores engendrées par le battement du coeur. Le dispositif comprend: une composante de forme d'onde produisant une forme d'onde qui poursuit la forme d'onde sonore résultant de la fréquence cardiaque, telle qu'obtenue au contact du stéthoscope sur le patient dans la région du coeur; un dispositif de détermination de seuil destiné à établir un seuil de forme d'onde au-delà duquel les complexes de référence cycliques apparaissent et sont identifiés; un dispositif de chronométrage qui permet d'évaluer le temps écoulé entre des moments analogues sur des complexes de référence adjacents, fournissant une indication de la fréquence cardiaque; et un moyen de conversion destiné à convertir la mesure du temps écoulé en une indication de fréquence cardiaque.
PCT/CA1996/000408 1995-06-16 1996-06-17 Stethoscope Ceased WO1997000045A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU61186/96A AU6118696A (en) 1995-06-16 1996-06-17 Stethoscope

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA 2151966 CA2151966A1 (fr) 1995-06-16 1995-06-16 Stethoscope
CA2,151,966 1995-06-16

Publications (1)

Publication Number Publication Date
WO1997000045A1 true WO1997000045A1 (fr) 1997-01-03

Family

ID=4156060

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CA1996/000408 Ceased WO1997000045A1 (fr) 1995-06-16 1996-06-17 Stethoscope

Country Status (3)

Country Link
AU (1) AU6118696A (fr)
CA (1) CA2151966A1 (fr)
WO (1) WO1997000045A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999052435A1 (fr) * 1998-04-08 1999-10-21 Bang & Olufsen Technology A/S Technique et appareil permettant d'estimer le rythme de signaux d'auscultation
US8870791B2 (en) 2006-03-23 2014-10-28 Michael E. Sabatino Apparatus for acquiring, processing and transmitting physiological sounds

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1143014A (fr) * 1980-04-24 1983-03-15 Her Majesty The Queen, In Right Of Canada, As Represented By The Minister Of National Defence Appareil portatif numerique pour mesurer la frequence cardiaque et servant aussi de stethoscope
US4549551A (en) * 1982-11-24 1985-10-29 Her Majesty The Queen In Right Of Canada, As Represented By The Minister Of National Defense Heart rate detector

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1143014A (fr) * 1980-04-24 1983-03-15 Her Majesty The Queen, In Right Of Canada, As Represented By The Minister Of National Defence Appareil portatif numerique pour mesurer la frequence cardiaque et servant aussi de stethoscope
US4549551A (en) * 1982-11-24 1985-10-29 Her Majesty The Queen In Right Of Canada, As Represented By The Minister Of National Defense Heart rate detector

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999052435A1 (fr) * 1998-04-08 1999-10-21 Bang & Olufsen Technology A/S Technique et appareil permettant d'estimer le rythme de signaux d'auscultation
US7130429B1 (en) 1998-04-08 2006-10-31 Bang & Olufsen Technology A/S Method and an apparatus for processing auscultation signals
US8870791B2 (en) 2006-03-23 2014-10-28 Michael E. Sabatino Apparatus for acquiring, processing and transmitting physiological sounds
US8920343B2 (en) 2006-03-23 2014-12-30 Michael Edward Sabatino Apparatus for acquiring and processing of physiological auditory signals
US11357471B2 (en) 2006-03-23 2022-06-14 Michael E. Sabatino Acquiring and processing acoustic energy emitted by at least one organ in a biological system

Also Published As

Publication number Publication date
CA2151966A1 (fr) 1996-12-17
AU6118696A (en) 1997-01-15

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