Cardiac compression wave measuring system and method

DETAILED DESCRIPTION The present invention relates to a method and an apparatus generally designated as a "seismocardiography.
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" The seismocardiograph.
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utilizes a transducer having a usable frequency response in the range of about 0.
025 Hz to about 800 Hz for detecting compression waves generated by heart muscle function.
Accelerometers of various types may be used to illustrate the features of the invention.
The accelerometer may use strain gauge type transducers, piezoelectric type or others, provided the transducers provide the sensitivity necessary to the function of the apparatus.
An example of a strain gauge transducer is produced by PCB Pieziotronic, Inc.
Piezoelectric crystal may also be used in an accelerometer with success.
Other types of transducers may be used, provided the transducer has at least a sensitivity to movement of one (1) microinch at a frequency of one (1) Hz.
A preferred embodiment of this invention utilizes a piezoelectric crystal and therefore the invention will be described with reference to such a transducer.
A commercially available transducer suitable for practicing this is available from PCB Piezotronics as the Model 393C Seismic Accelerometer.
A piezoelectric crystal is selected which has a usable response in the frequency range of about 0.
025 Hz to about 800 Hz for detecting compression waves normal to the outside surface of the human body where the transducer is placed for detection of the compression waves generated by heart wall muscle function.
The full-cycle functioning of the heart wall muscle is detected by detection of heart muscle-generated compression waves using a piezoelectric transducer.
The transducer generates an analog signal in which frequencies of the compression waves above about 50 Hz are eliminated.
The resulting analog signal is a band limited signal which can then be converted to a digital signal for further processing and analysis.
Selected single-cycle portions of the converted digital signal may be selected and averaged to provide an averaged compression signal representing a full cycle of the patient's heartbeat