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BACKGROUND OF THE INVENTION
In general, this case relates to a method and apparatus for detecting and
indicating when heart sounds emanating from particular physical areas of a
person are indicative of a known heart disorder. More particularly, the
invention intends to provide a means and method of detecting and comparing
audio signals emanating from the classical four physical areas of
auscultation with corresponding prerecorded audio signals representing
various known heart disorders.
In U.S. Pat. No. 3,665,087, assigned to the assignee of the present
invention, a manikin audio system was described in which proper placement
of a synthetoscope on one of the four classical areas to be examined
caused one of four audio signals stored on a continuous tape to be coupled
to the ears of the examiner. This system has proven to be an extremely
effective teaching tool, and although the audio signals do not emanate
directly from the physical area under auscultation, the proper sounds in
each of the four areas are coupled to the examiner at the time the
particular region of the manikin is explored. There are 50 different heart
disorders or diseases presently available for selection from the tape
library, each tape representing one disease and having four audio tracks
corresponding to the four areas. This enables the examiner to listen to
the sounds for each disorder and learn at an individual pace the
variations between sounds in the four areas.
The four classical sounds are related to the construction of the interior
of the heart which is divided into four chambers, namely, the right
antrum, right ventricle, left ventricle and left antrum. The right and
left ventricles consist of several layers of muscle which serve as the
primary pumps of the heart, and the left and right antrums serve as the
receptacles for blood returning to the heart. Each of the four chambers
produces a unique heart sound frequency spectrum that can be analyzed to
indicate a disorder or malfunction of an associated chamber.
The manikin audio system is particularly adapted to be utilized as a
teaching tool, and its use has been limited to medical students and those
specializing in heart disorders. Therefore, a large library of information
containing some fifty known heart disorders has not been available for use
by a large majority due to limited access and availability at only a few
teaching institutions. In addition, students, other than heart
specialists, once they have left the teaching institutions and have been
in practice for a number of years, soon lose the discrimination required
for the various sounds for a given disease when exploring particular
regions of the heart. Accordingly, a real need exists for a portable
device, namely, a heart detective, which could utilize this known
information during a physical examination and give an indication of a
disorder to physicians or other trained personnel in this country, as well
as in underdeveloped countries where doctors and heart specialists are in
great demand. The device is not intended to be a definitive diagnosis, but
rather to indicate a connection between a known disorder and the
particular person being examined. Once a problem has been detected, a more
thorough examination may be undertaken by a skilled heart diagnostician
utilizing some of the more advanced electronic and computer analysis
equipment. The device of the invention is particularly suited for use in
remote areas and locations that do not have ready access to heart
specialists and expensive analysis equipment.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and
means for indicating heart disorders.
Another object of the invention is to provide a portable device which may
be used to detect and display when heart sounds emanating from areas of
auscultation are indicative of a known heart disorder.
A still further object of the invention is to provide a means and method
for comparing audio signals emanating in real time from the classical four
physical areas of auscultation with prerecorded audio signals representing
the same areas for a known disorder.
According to the broader aspects of the invention, a portable heart
detective device is provided comprising means for simultaneously
ascultating a plurality of areas and temporarily storing the detected
heart sounds, means for comparing prerecorded heart sounds from said areas
with the detected sounds, and means for displaying an indication of the
correlation between the detected and recorded sounds.
A feature of the invention is that the portable device includes means to
receive a transducer to detect heartbeat pulses and means to display the
pulse rate.
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages and features of the invention will be readily appreciated
by reading the following description in connection with the drawings, in
which:
FIGS. 1A and 1B are a perspective illustration of a portable heart
detective device according to the invention;
FIG. 2 shows, in block diagram form, a preferred embodiment constructed in
accordance with the principles of the invention; and
FIG. 3 shows, in block diagram form, a signal comparator for use in the
embodiment of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The audio heart detective according to the present invention, is intended
to be used with prerecorded tapes as disclosed in U.S. Pat. Nos. 3,789,159
and 3,769,526. One tape normally represents one disease and contains four
tracks recorded in predetermined synchronism to represent the four
classical areas of auscultation which are examined for determining whether
or not a problem exists. A track or channel on the tape contains
synchronization information and the information is in the form of either a
foil strip or a 5 kHz synchronizing pulse. The synchronization information
is located 5 seconds apart and corresponds to a breath cycle of
approximately five heart sounds per cycle. Each of the four tracks or
channels contains this information which has been recorded as in the above
patents.
The device of the invention is designed to detect the heart sounds in real
time from the four classical areas so that they may be compared channel by
channel with the stored information on a tape and determine if there is
any correlation between the detected signals and the recorded signals. The
energy spectrum of the human heart varies, but normally can be plotted as
intensity versus time in the range of 20 to 600 Hz. The device and method
of the invention is designed to utilize this vast store of recorded
acoustical information for each heart sound for some 50 diseases by
feeding the detected audio signals to a signal comparator which is able to
compare channel by channel the information on a given tape track to the
information obtained and stored in real time.
Referring now to FIGS. 1A and 1B, the portable device according to the
information will be described. The heart detective 10 is a portable device
having on one side four directional microphones 11, 12, 13, 14 positioned
within a styrofoam or other isolating material 16 which may be covered by
a vinyl coating. The microphones are positioned according to the four
classical areas of examination of the human heart. The portable device is
approximately the size of a tape recorder and may be handheld against the
chest of the person under examination. A jack receptacle 18 is provided
for insertion of a connector for an auxiliary pulse detecting transducer.
The device will display pulse rate when it is set in a pulse monitoring
mode. The device contains a receptacle 20 for coupling AC power and DC
battery location 22 to enable battery operation of the device for areas
where AC connection is not possible or impractical.
As illustrated in FIG. 1B, the side opposite the microphones has the means
24 for receiving and reading a tape cartridge having recorded thereon the
reference signals for a particular disorder. Below the tape insertion area
is a display panel 26 which may be an LED display. The display 26 will
provide four discrete indications corresponding to the four detected audio
signals. Each channel display numbered 1, 2, 3, 4 provides an indication
of the correlation of a predetermined number of specific spectral
quantities. The display may be numerical, indicating a number which can
then be used with a reference table, or provide a "yes," "no," "go,"
"no-go" indication for each of the detected acoustical sounds. Below the
display 26 is an on-off switch 27, a DC-AC mode switch 28, a heart or
pulse mode switch 29, and clear button 30. When switch 29 is in the pulse
mode, the display 26 will indicate pulse rate. The pulse rate, of course,
will only be displayed when a pressure sensitive transducer has been
coupled to the device.
FIG. 2 shows, in block diagram form, an embodiment of the invention. A
single continuous prerecorded tape 32 is shown, each track t.sub.1,
t.sub.2, t.sub.3, t.sub.4 of each tape carrying the audio signals a.sub.1
to a.sub.4 corresponding to the audio sounds for the four classical areas
of auscultation for one heart disorder. The 5 kHz synchronizing pulses
s.sub.1 to s.sub.4 are indicated for each cycle. For a small portable
device according to this embodiment, each tape 32 or tape cassette will
contain audio reference signals for one disease, and it should be
understood in more elaborate schemes that a plurality of prerecorded
diseases may be included with larger tapes and tape drive, including the
appropriate clocking and disease select means. However, it must be
understood that the device is designed for portable field use to provide
an indication of a problem and one or more of the major heart diseases are
easily handled by changing cassettes.
Each of the prerecorded audio signals a.sub.1 to a.sub.4 include the
spectral reference frequencies f.sub.1 ' to f.sub.n ' which are to be used
by the signal comparator to determine a correlation between the detected
and the recorded signals. The plurality of reading heads R.sub.1 to
R.sub.4 selectably read the signals a.sub.1 to a.sub.4 and couple them to
driver amplifier 34 and through bandpass filter 36 having a band spectrum
f.sub.1 ' to f.sub.n ' corresponding to the specific spectral lines to be
used as a reference. The output from the filter 36 is coupled to the
signal comparator 40 as to be further described in connection with FIG. 3.
With a cassette in position, the power supply 38 turned on, and the device
placed in the H or heart mode, the components are initialized. Clock 42
will switch means 44 to a first operative condition to latch one of the
contact means 43a to 43d and one corresponding contact 45a to 45d to the
closed condition. Although the switch means 44 is shown connected by
dashed lines to contacts 43 and 45, it should be appreciated that the
implementation will be with transistor switching circuits. Switch 44 when
clocked will sequentially switch contacts 45a - 45d to enable the real
time audio signals from channels C1 to C4 to be coupled to the signal
comparator 40. The comparator 40 will correlate the acoustical sounds
received in real time from the microphones M1 to M4 and sounds a.sub.1 to
a.sub.4 recorded on an associated track t.sub.1 - t.sub.4 of the tape 32.
The reference and detected audio signals will be selectively coupled to
the signal comparator 40 according to the clocking of switch 44, so that
the associated input channels and references are coupled to the signal
comparator. Coupled to each directive microphone M1 - M4 is an audio
channel containing a preamplifier 50, a filter 52 having a bandpass
corresponding to the reference spectrum, the output of the filter being
coupled to an amplifier 54 with gain control means 56 to standardize the
level of signal intensity, and an acoustic delay line memory 58. The
acoustic delay memory may, for example, be a magnetostrictive delay line
in the form of a closed loop which is adapted to temporarily store the
acoustic real time signals for each channel and couple them to the signal
comparator 40.
One type of signal comparator 40 is described in connection with FIG. 3 and
will produce a correlation output which is coupled to the decoder 60 which
decodes the output into a display sequence to indicate for each channel
the correlation figure. Displays 1, 2, 3, 4 will then indicate the
correlation between channels C1 to C4 and reference tracks t.sub.1 -
t.sub.4. A zero may represent insufficient correlation or a reference
table may be used with a correlation number from 0 - 9 for each channel.
The components are cleared by activating the clear button on the device.
The output from the decoder 60 also enables synchronization detector 41
which detects a synchronization signal s.sub.1 and activates the clock to
a second output to clock switch means 44, to switch channels so that the
four channels may be sequentially compared.
The heartbeat pulses may be checked by switching the device to the pulse
mode P. In this mode, the audio components are disconnected and the pulse
rate components are connected to the decoder and display. A pressure
sensitive transducer 70 is coupled by connector cable 71 and detects the R
waves. The detected pulses are coupled to an amplifier and shaper 72 whose
output is counted and accumulated in accumulator 73. The accumulator feeds
a memory 74 under the control of a clock 75. The accumulator 73 is
normally cycled in one minute as is the clocked memory which couples the
pulse count to the decoder 60 for display in positions 2, 3 and 4. The
readout is the pulse rate per minute. In each ensuing minute, the memory
will retain the previous accumulated count until a new count is coupled to
the memory and which, in turn, couples the subsequent counts to the
decoder for display.
Referring now to FIG. 3, one type correlator for use as the signal
comparator of FIG. 2 is illustrated. It should be noted that sounds
emanating from the heart generally fall within two ranges, those sounds
which are below 20 cycles and are attributable to gross movements of the
chest wall and those sounds in the range of 20 to 600 Hz which are audible
and generally associated with cardiac auscultation. It has further been
found that 95% of the heart sound energy lies below 100 Hz so that the
bandpass filters may be limited, if desired, and cover 95% of all the
heart sounds. It is recognized that certain disorders have frequency
spectral lines above 100 Hz and these may be included if within desired
size and weight parameters for the comparator. The signal comparator
proposed in the preferred embodiment of the invention is a spectrum
analyzer which makes use of cross-correlation filters to effect narrow
banding, the cross-correlation filters acting to establish the presence of
a particular frequency f .+-. .DELTA.f frequency and, in addition, the
amplitude of the specific spectral line. One such analyzer utilizing the
correlation detectors which is proposed for utilization in the instant
invention, is described in U.S. Pat. No. 3,416,081, issued Dec. 10, 1968
and assigned to the assignee of the instant invention. Insofar as this
patent is necessary for an understanding of the instant invention, it is
hereby incorporated by reference. The spectrum analyzer of FIG. 3 is used
to analyze the frequency spectrum of the complex detected heart signal and
to do so under very poor signal-to-noise ratios. The analyzer is adaptable
to any desired degree of resolution which can be obtained by suitable
adjustment of the parameters of the analyzer.
The reference signals f.sub.1 ' to f.sub.n ' from each track of the tape
recorder will be coupled to a plurality of bandpass filters 401, each
filter passing one of the reference parameters f.sub.1 ', f.sub.2 ',
f.sub.n '. For example, if it is desired to analyze the frequencies from
20 Hz to 100 Hz, nine bandpass filters 401 may be utilized with each
filter centered at 10 Hz intervals. The input signal selectively coupled
from channels C1 - C4 contains the real time audio heart signal having a
frequency spectrum f.sub.1 to f.sub.n. The signal is coupled with the
outputs from filters f.sub.1 ', f.sub.2 ', f.sub.n ' to the correlation
detectors 402. The correlation detectors 402 will produce an amplitude and
frequency indication which is a measure of the amplitude and frequency
f.sub.1 ' .+-. .DELTA. f, f.sub.2 ' .+-. .DELTA. f and f.sub.n ' .+-.
.DELTA. f. By simply monitoring with a correlation counter 403, the
outputs from the detectors 402 can easily count the number of amplitudes
and frequencies within .+-..DELTA.f of the input spectrum. The correlation
count is then coupled to the decoder of FIG. 2 and the number of
correlations displayed in appropriate locations. The output from the
decoder will then trigger the synchronization detector 41 to enable
switching another real time signal to the comparator while simultaneously
coupling the associated reference signal to the comparator. The
cross-correlation is then made as to the audio heart sounds for this
second channel and the indication displayed. This cycle is repeated for
each of the four channels so that for one heart disease, the four channel
correlation count will indicate to the operator directly or with reference
to a chart, whether or not a sufficient correlation has been made to
indicate a known disorder in the examined individual.
The disclosed method of detecting sounds from a human heart for the four
classical areas generally associated with cardiac auscultation, comparing
them with the frequency spectrum for known diseases, and correlating the
two sounds to produce a correlation indication will, within acceptable
tolerances, identify a cardiac problem in the examined person.
The heart detective device of the instant application will find ready use
by most physicians, both in urban and rural areas, to check their
diagnosis and to determine whether or not any of their suspicions as to
particular type malfunctions can be confirmed by obtaining a correlation
indication with this portable device. The operation of this apparatus has
been sufficiently simplified to enable semi-skilled technicians to utilize
the device and with appropriate charts to determine if the correlation
indication is sufficiently high as to warrant further investigation by a
trained heart specialist with or without more complicated analysis
equipment. The incorporation in this equipment of a pulse rate indicator
will help to highlight problem areas since the pulse rate count
characteristically varies with certain abnormalities of the heart and the
appropriate comparison between the correlation indication and the pulse
rate count can be meaningfully made.
While I have described above the principles of my invention in connection
with specific apparatus, it is to be clearly understood that this
description is made only by way of example and not as a limitation to the
scope of my invention as set forth in the objects thereof and in the
accompanying claims.
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