Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/316—Modalities, i.e. specific diagnostic methods
  • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
  • A61B5/33—Heart-related electrical modalities, e.g. electrocardiography [ECG] specially adapted for cooperation with other devices
• • 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
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/316—Modalities, i.e. specific diagnostic methods
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/316—Modalities, i.e. specific diagnostic methods
  • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
  • A61B5/346—Analysis of electrocardiograms
  • A61B5/349—Detecting specific parameters of the electrocardiograph cycle
  • A61B5/363—Detecting tachycardia or bradycardia

Definitions

• This invention relates to cardiac monitors, in particular for long-term monitoring of patients, for example in intensive care or coronary care units, operating theatres, and pace maker clinics.
• an alarm is generated if the patient goes into rate alarm, usually an audible alarm.
• the bleep commonly produced by a monitor in step with the heart beats is replaced by a continuous tone when the monitor detects cardiac arrest.
• a cardiac monitor is fitted with timing means arranged to provide an indication of the time that has elapsed from the beginning of a rate alarm.
• the time indication can for example be presented on a CRT screen of the monitor, instead of or in addition to the conventional display of heart beat and numerical pulse rate, or alternatively a separate time display can be provided.
• the timing means is preferably arranged so that it can be reset to zero either manually, or automatically when the patient is in normal heart rhythm, for example after a certain length of time in normal rhythm or after a certain number of beats in normal rhythm.
• the timing means is so arranged that if the patient is resuscitated but relapses into rate alarm soon after resuscitation, the timing means will measure and display the total time spent in the successive episodes of rate alarm. Accordingly, re-setting of the timing means may be rendered ineffective for a predetermined delay after normal heart rhythm has been restored.
• Cardiac monitors commonly include a rate meter for determining the heart beat rate, controls for setting beat rates at which alarms are given, and a comparator which triggers the alarm when the measured rate reaches a predetermined value. Conveniently, this comparator also triggers the operation of the timing means, both to initiate timing and for automatic resetting when normal heart rhythm has been restored.
• Figure 1 is a block diagram of a cardiac monitor incorporating timing means, according to the present invention
• Figure 2 is a block diagram of a particular cardiac monitor to which the invention is applicable.
• the monitor has an ECG amplifier 2 connected to suitable ECG electrodes 1 and providing an output to a QRS detector 3 which detects successive beats of the patient's heart.
• the QRS detector provides outputs to a heart rate meter 4, and also to display control circuitry 5.
• the rate meter 4 provides an output voltage proportional to the mean heart rate, which is also supplied to the display control circuitry.
• the monitor also includes control logic 6, providing timing signals and other controlling signals for the display control circuitry, such that the latter controls the display on a built-in CRT display unit 7.
• the display may for example comprise upper and lower traces showing the heart beat wave form as a cascaded rolling display.
• the lower trace can be frozen, or the upper trace can be transferred to the lower trace and held frozen, to permit close examination of an. event appearing on either trace.
• a three-digit display of the heart rate determined by the rate meter appears above the upper trace, together with symbols indicating that a QRS has been detected, or a lead or electrode fault, or the presence of heart pacemaker pulses.
• the monitor may also include means for synchronous defibrillation in conjunction with a defibrillator.
• the features described above are known, for example in the "Cardiorater CR7" monitor made by Cardiac Recorders Ltd.
• the monitor also includes a loudspeaker or other sound source 11, connected to the QRS detector so as to produce a bleep each time a QRS (heartbeat) is detected.
• the rate meter 4 is connected to an alarm comparator 8 in which the signal representing the heart rate is compared with upper and lower alarm levels manually set by controls indicated generally by the reference numeral 9, for example slide potentiometer controls provided with scales calibrated in beats per minute on the front panel of the monitor. If the measured heart rate falls outside the range between the upper and lower set levels, the comparator 8 provides an output signal to the sound source 11 so that the latter produces a continuous alarm tone.
• the alarm is delayed from the onset of the alarm condit ion , f or example by seven seconds, and if the alarm state ceases within this delay no alarm is given. The alarm ceases when the alarm state ceases.
• the alarm can be turned off, by moving the "low" alarm control to its lowest position.
• the signal from the alarm comparator is also applied to a timer 10 of any convenient type, so that the latter starts timing from the onset of an alarm condition.
• the timer provides an output signal which is used to generate a display of elapsed time, either on the CRT display unit 7, or on a separate timer display. This provides a direct indication of the length of time for which the patient has been in a state of rate alarm. Since the patient must be resuscitated within about four minutes to avoid brain damage, knowledge of the duration of the rate alarm is extremely important to those attempting resuscitation.
• the timer When the state of rate alarm has ended, the timer will stop and its display may remain on the screen for a limited time.
• the recorded time is held in the timer long enough to ensure that if the patient's heart stops again after a short time, the timer will resume counting from the previously recorded time so that it will display the total time for which the heart has been stopped in two or more successive episodes.
• the timer is reset to zero manually or automatically when the heartbeat has been restored to a normal rhythm for a predetermined time or a predetermined number of beats.
• the monitor may be provided with a reset button providing a reset input to the timer, this input also being connected to the comparator 8 to reset the timer when the comparator no longer provides an alarm signal.
• a reset delay 12 may be included in the reset signal path.
• Figure 2 shows a block diagram of the above-mentioned, "cardiorater CR7" monitor, together with the cardiac arrest timer according to the present invention.
• This block diagram is believed to be self-explanatory and therefore is no described in detail.
• the alarm can be turned off manually. Staff may well forget to turn it on again when the patient has been resuscitated.
• the monitor may be provided with means for restoring the alarm circuitry to its previous operating condition automatically when the heartbeat has returned to a normal rhythm, either after a predetermined time or after a predetermined number, for example ten to twenty, of R waves.

Landscapes

• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Cardiology (AREA)
• Biomedical Technology (AREA)
• Medical Informatics (AREA)
• Biophysics (AREA)
• Pathology (AREA)
• Engineering & Computer Science (AREA)
• Veterinary Medicine (AREA)
• Heart & Thoracic Surgery (AREA)
• Physics & Mathematics (AREA)
• Molecular Biology (AREA)
• Surgery (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Physiology (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)

Applications Claiming Priority (2)

Publications (1)

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• 1984
  • 1984-03-20 GB GB08407155A patent/GB2156124B/en not_active Expired
• 1985
  • 1985-03-19 JP JP60501155A patent/JPS61501493A/ja active Pending
  • 1985-03-19 EP EP85901485A patent/EP0175734A1/en active Pending
  • 1985-03-19 WO PCT/GB1985/000106 patent/WO1985004087A1/en not_active Application Discontinuation
  • 1985-11-18 DK DK531485A patent/DK531485A/da not_active Application Discontinuation

Non-Patent Citations (1)

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