Apparatus and method for recording and playing back electrocardial signals
First Claim
1. A tape recorder for use in ambulatory monitoring of a cardiac patient, said tape recorder having recording head means for recording on a single track in a tape an ECG signal obtained continuously from a patient, and recording on the same single track several intermittent signals including blood pressure signal received intermittently from a portable blood pressure measuring device affixed to the patient, an event marker signal generated in response to actuation of an event marker control from time to time by the patient, and a periodic time of day signal, said tape recorder comprising in combination:
- recording means operatively associated with the tape and responsive to an applied electrical signal for recording the applied electrical signal on a single track in the magnetic tape;
multiplexer means connected to said recording means and providing to said recording means the applied electrical signal to be recorded, the latter including an ECG signal and an intermittent signal selected by said multiplexer means under control of an applied MX control signal from a set of signals including an encoded time of day signal, an encoded blood pressure signal, and an encoded event marker signal;
time of day encoder means for generating and storing an encoded time of day signal representing the time of day, said time of day encoder means connected to said multiplexer means and providing said encoded time of day signal to said multiplexer means under control of an applied T control signal;
blood pressure encoder means to which the blood pressure signals received intermittently from the blood pressure measuring device are applied for converting the blood pressure signals into a form suitable for storage, for storing the converted blood pressure signals, and in response to an applied BP control signal to read out the stored converted blood pressure signals and to encode them into a predetermined format, said blood pressure encoder means connected to said multiplexer means and providing said encoded blood pressure signals to said multiplexer means;
event marker signal generator means for generating an encoded event marker signal having a predetermined format in response to an EM control signal applied after the patient has actuated the event marker control, said event marker signal generator means connected to said multiplexer means and providing said encoded event marker signal to said multiplexer means;
control logic means connected to said time of day encoder means for generating and providing to said time of day encoder means said applied T control signals, connected to said blood pressure encoder means for generating and providing thereto said applied blood pressure control signals, connected to said event marker signal generator means for generating and providing thereto said applied EM control signal, and connected to said multiplexer means and generating and providing to said multiplexer means said applied MX control signal for controlling the selection by said multiplexer means from said set of signals of an intermittent signal to be recorded.
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Accused Products
Abstract
A system for encoding, recording, playing back, decoding, validating, and displaying cardiac signals obtained from a patient during ambulatory monitoring. The system permits the recording on a single track in a magnetic tape of a channel of ECG signals interrupted intermittently by blood pressure signals, time of day signals, and event marker signals. The ECG signal is recorded in analog form, but the other signals are recorded as pulse coded signals each having its own format. In the playback apparatus, decoders identify and verify each of the signals when they occur, and the played back information is plotted on a chart. If the time of day signal was not recorded on the tape, timing information can be produced by the playback apparatus from the cumulative tape travel. Fiducial signals introduced in the recording, playback, and charting operations are used in a method for identification and measurement of recording tape speed error, playback tape error, and plotter speed error.
43 Citations
42 Claims
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1. A tape recorder for use in ambulatory monitoring of a cardiac patient, said tape recorder having recording head means for recording on a single track in a tape an ECG signal obtained continuously from a patient, and recording on the same single track several intermittent signals including blood pressure signal received intermittently from a portable blood pressure measuring device affixed to the patient, an event marker signal generated in response to actuation of an event marker control from time to time by the patient, and a periodic time of day signal, said tape recorder comprising in combination:
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recording means operatively associated with the tape and responsive to an applied electrical signal for recording the applied electrical signal on a single track in the magnetic tape; multiplexer means connected to said recording means and providing to said recording means the applied electrical signal to be recorded, the latter including an ECG signal and an intermittent signal selected by said multiplexer means under control of an applied MX control signal from a set of signals including an encoded time of day signal, an encoded blood pressure signal, and an encoded event marker signal; time of day encoder means for generating and storing an encoded time of day signal representing the time of day, said time of day encoder means connected to said multiplexer means and providing said encoded time of day signal to said multiplexer means under control of an applied T control signal; blood pressure encoder means to which the blood pressure signals received intermittently from the blood pressure measuring device are applied for converting the blood pressure signals into a form suitable for storage, for storing the converted blood pressure signals, and in response to an applied BP control signal to read out the stored converted blood pressure signals and to encode them into a predetermined format, said blood pressure encoder means connected to said multiplexer means and providing said encoded blood pressure signals to said multiplexer means; event marker signal generator means for generating an encoded event marker signal having a predetermined format in response to an EM control signal applied after the patient has actuated the event marker control, said event marker signal generator means connected to said multiplexer means and providing said encoded event marker signal to said multiplexer means; control logic means connected to said time of day encoder means for generating and providing to said time of day encoder means said applied T control signals, connected to said blood pressure encoder means for generating and providing thereto said applied blood pressure control signals, connected to said event marker signal generator means for generating and providing thereto said applied EM control signal, and connected to said multiplexer means and generating and providing to said multiplexer means said applied MX control signal for controlling the selection by said multiplexer means from said set of signals of an intermittent signal to be recorded. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A decoder system for use in analyzing tapes recorded during ambulatory monitoring of cardiac patients, wherein several types of non-concurrent pulse coded signals are recorded along with a continuous ECG signal on a single track in the tape, said decoder system identifying the pulse coded signals on the basis of their formats and comprising in combination;
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playback means for converting the signals recorded on a single track of a tape into an electrical played-back signal which may include any of several types of non-concurrent pulse coded signals along with a continuous ECG signal, said pulse coded signals including, singly or in any combination, a blood pressure signal, an event marker signal and a time of day signal; blood pressure signal decoder means, connected to said playback means to receive said played-back signal and to produce a verified blood pressure signal corresponding to a segment of said played-back signal only when said blood pressure signal decoder means has determined that said segment satisfies predetermined blood pressure signal criteria; event marker signal decoder means, connected to said playback means to receive said played-back signal and to produce a verified event marker signal corresponding to a segment of said played-back signal only when said event marker signal decoder means has determined that said segment satisfies predetermined event marker signal criteria; time of day signal decoder means connected to said playback means to receive said played-back signal and to produce a verified time of day signal corresponding to a segment of said played-back signal only when said time of day signal decoder means has determined that said segment satisifies predetermined time of day signal criteria; tachometer means actuated by the tape when the tape moves and producing an electrical tachometer output signal indicative of the amount of motion of the tape; and
,time of day storage means for storing an applied time of day signal and for updating the stored time of day signal in response to an applied increment/decrement signal, connected to said tachometer means for receiving said electrical tachometer output signal as the applied increment/decrement signal, connected to said time of day signal decoder means for receiving said verified time of day signal, and operative to store said verified time of day signal when that signal is produced, and operative to increment and to decrement said stored time of day signal in response to said electrical tachometer output signal. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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28. A decoder system for use in analyzing tapes recorded during ambulatory monitoring of cardiac patients, wherein several types of non-concurrent pulse coded signals and a continuous ECG signal are recorded on a single track in the tape, said decoder system identifying the pulse coded signals on the basis of their formats and comprising in combination:
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playback means for converting the signals recorded on a single track of a tape into an electrical played-back signal which may include any of several types of non-current pulse coded signals and a continuous ECG signal, said pulse coded signals including, singly or in any combination, a blood pressure signal, an event marker signal and a time of day signal; blood pressure signal decoder means, connected to said playback means to receive said played-back signal and to produce a verified blood pressure signal corresponding to a segment of said played-back signal only when said blood pressure signal decoder means has determined that said segment satisfies predetermined blood pressure signal criteria; event marker signal decoder means, connected to said playback means to receive said played-back signal and to produce a verified event marker signal corresponding to a segment of said played-back signal only when said event marker signal decoder means has determined that said segment satisfies predetermined event marker signal criteria; time of day signal decoder means connected to said playback means to receive said played-back signal and to produce a verified time of day signal corresponding to a segment of said played-back signal only when said time of day signal decoder means has determined that said segment satisfies predetermined time of day signal criteria; wherein said time of day signal decoder means further comprise a decoder connected to said playback means for receiving the played-back signal and responsive thereto to produce a decoded time of day signal; and
,wherein said time of day signal decoder means further comprise tape speed error detector means connected to said decoder to receive from it said decoded time of day signal and operative to determine the amount by which the pulse repetition frequency of the decoded time of day signal deviates from a predetermined pulse repetition frequency criterion and to generate a tape speed error signal when the amount of the deviation exceeds a predetermined limit. - View Dependent Claims (29, 30, 31)
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32. A decoder system for use in analyzing tapes recorded during ambulatory monitoring of cardiac patients, wherein several types of non-concurrent pulse coded signals are recorded along with a continuous ECG signal on a single track in the tape, said decoder system identifying the pulse coded signals on the basis of their formats and comprising in combination:
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playback means for converting the signals recorded on a single track of a tape into an electrical played-back signal which may include any of several types of non-concurrent pulse coded signals along with a continuous ECG signal, said pulse coded signals including, singly or in any combination, a blood pressure signal, an event marker signal and a time of day signal; blood pressure signal decoder means, connected to said playback means to receive said played-back signal and to produce a verified blood pressure signal corresponding to a segment of said played-back signal only when said blood pressure signal decoder means has determined that said segment satisfies predetermined blood pressure signal criteria; event marker signal decoder means, connected to said playback means to receive said played-back signal and to produce a verified event marker signal corresponding to a segment of said played-back signal only when said event marker signal decoder means has determined that said segment satisfies predetermined event marker signal criteria; and
,time of day signal decoder means connected to said playback means to receive said played-back signal and to produce a verified time of day signal corresponding to a segment of said played-back signal only when said time of day signal decoder means has determined that said segment satisfies predetermined time of day signal criteria. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39)
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40. In a system in which a data signal is recorded on a tape, then later played back and applied to a plotter to produce a chart on which the data signal is plotted versus time and on which a specific distance along the time axis is intended to represent a corresponding specific time interval, a method for determining recorder speed error, playback speed error and plotter speed error, said method comprising the steps of:
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(a) recording on the tape time of day signals known to be generated at precisely determined intervals of time; (b) playing back and plotting on the chart the recorded time of day signals; (c) generating a tachometer signal as the tape is played back each time the tape has moved a predetermined distance plotter andd plotted versus time on the chart; (d) producing a plot on the chart of the tachometer signals versus time by applying the tachometer signals to the plotter; (e) generating a tape speed error signal as the tape is played back when the time between successive played back time of day signals deviates by more than a specified amount from the precisely determined intervals of time at which the time of day signals were generated, said tape speed error signals being indicative of a net error in the recordiing and playback tape speeds and consisting of a signal generated with a known duration, applied to the plotter and plotted versus time on the chart; (f) determining the plotter speed error, when said tape speed error signal is not being generated, from the distance between successive plotted time of day signals; (g) determining the plotter speed error, when said tape speed error signal is being generated, from the distance between the beginning and end of the tape speed error signal; (h) determining the playback speed error from the spacing between successive tachometer signals plotted on the chart and the plotter speed error; (i) determining the recorder speed error from the spacing on the chart between successive time of day signals plotted on the chart and the playback speed error determined in step (h). - View Dependent Claims (41, 42)
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Specification