Del Mar Avionics, Inc.

W David Squires

Stephen K Shu

Isaac R Cherry

Donald L Anderson

Apparatus is disclosed for long-term ambulatory monitoring of blood pressure by an auscultation method, employing a pressurizable cuff and requiring no intervention by the patient. Heartbeats are sensed by ECG electrodes, and a microphone is used to sense the Korotkow sounds as the pressure in the cuff is varied. The presence or absence of a Korotkow sound within a preset interval following each heartbeat is used in determining when the cuff pressure equals the systolic and diastolic pressures. Those pressures are determined in each cycle of operation and are recorded on a continuously-running portable tape recorder, along with the ECG signals. In each cycle of operation, the initial pressure to which the cuff is inflated is based on the systolic pressure measured in the immediately preceding cycle. The pressure in the inflated cuff is thereafter stepped downward in small discrete decrements triggered by successive heartbeats during the measurement phase of each cycle. After both the systolic and diastolic pressures have been determined, the remaining cuff pressure is vented through the same valve that was used to produce the stepwise pressure reduction. After a number of cycles of operation, the magnetic tape is removed from the portable recorder and inserted into an analyzer for high-speed playback and automated plotting of the heart rate and accompanying blood pressure readings on a common chart.

Blood pressure monitoring system

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.

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Huntington Beach, CA, United States of America

W David Squires