SE452376B - Monitor for cardiac and respiratory activity - Google Patents

Abstract

The signal processor (3-15) re-transmits data which is then received (16) and transmitted (17) to a receiver which evaluates them. The processor (3-15) only passes information to the transmitter (16) with aerial (17) concerning cardiac activity during the time that respiratory sound is be recorded by the specially adapted microphone (2), and correspondingly only transmits respiratory activity data during the time that cardiac sound is being recorded. A two-position control (11,12) ensures that this occurs. The processor (3-15) comprises a parallel coupling of two band pass filters (4,5) which only allow to pass signals for cardiac and respiratory sound characteristic frequencies. To each filter is connected a DC convertor ,7) and an AND grid (10). A monostable rocker (15) is connected between the grid (10) output (14) and the transmitter input.

Description

452 376 It is also important to be able to control the heart functions in children at the same time, the same wishes and requirements naturally also apply to adult patients with heart and respiratory problems. For this purpose, it is possible to attach electrodes to the person's body and measure the electrical impulses of the heart muscles, so-called ECG (Electro Cardio Gram).

However, it is very inconvenient for the patient to have a number of electrodes attached to the chest, and the cords from these can either be torn off with a false cardiac arrest alarm as a result or cause entanglement of body parts therein and consequent inconveniences.

Electronic stethoscopes are now mainly used to control the two above-mentioned functions of persons requiring such control. These stethoscopes constitute the state of the art in the field of the invention and correspond to the preamble of claim 1.

The receiver for evaluating the information here consists of the person standing next to the person in question and by means of the stethoscope listening to heart or breathing sounds. It is a given that this type of monitoring is extremely inconvenient and even unreliable. First, you can only listen to and check either your breathing or your heart function at a time. It is also only possible to check these functions when the controller is in the vicinity of the person to be checked.

This requires a constant running around and listening to body sounds, even during the night hours. A combined median apnea mattress would of course be conceivable, but the control would still be too unreliable.

BRIEF DESCRIPTION OF THE INVENTION The object of the present invention is to far reduce the above-mentioned disadvantages of the prior art devices for monitoring cardiac and respiratory activity. . nu ... 1. ........ «, ...« ..-.-, ... ^ - .a-nnmszm = uns .. r "" '452 376 viteten hos en person, so that a device is obtained which can simultaneously monitor the cardiac and respiratory activity and this in a very reliable manner, in order to enable alarm sounding as soon as any disturbances in these activities occur.

This object is achieved according to the invention by providing a device of the above-mentioned type with the features stated in the characterizing part of claim 1.

By the inventive design of such a device, it is thus possible to simultaneously control both cardiac and respiratory activity.

By, as stated in requirement (a) the recipient only holds information about the heart activity and only during the time that breathing sounds are generated by the person, while controlling the frequency and appearance of the heartbeat, one can directly get an indication of incipient irregularities in breathing or pauses. An alarm can thus be triggered if the information from the heart either indicates a lack of heart function or because it appears in a certain temporal way and thus indicates breathing problems.

By, as stated in claim underb) the receiver only receives information about the respiratory activity and only during the time that heart sounds are generated by the person, analogously the nature of the breathing sounds can be examined and a short cessation of cardiac activity or an arrhythmia directly detected by an interruption in transmission of breathing sounds and alarms can be sounded.

The device according to the invention thus combines two functions in a single one, by controlling the cardiac activity, the respiratory activity is automatically controlled and vice versa. It thereby reduces the risk of injuries due to late detection of 452,376 heart and breathing difficulties to a minimum. By indirectly obtaining both types of information through a single measurement procedure, the device according to the invention becomes very energy-efficient, which is mainly important when it comprises its own internal power supply source, a battery, and is not connected by wires to any external power supply unit.

BRIEF DESCRIPTION OF THE DRAWING An exemplary preferred embodiment of the device according to the invention is described below with reference to the accompanying drawing, in which Fig. 1 is a schematic view of a lying person with the device according to the invention attached to the neck, and Fig. 2 is a block diagram rough features show the structure of said device and its mode of operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 1 shows a person lying on a bed, on the neck of which the device 1 according to the invention is fastened, for example by means of an adhesive. The person carrying the device 1 does not necessarily have to be bedridden, but can carry the device during all kinds of activities.

The device can also be arranged on the person's chest or other suitable body part.

The device 1 is arranged in a housing which has the shape of a disc with the appearance of a thick single crown, but can of course have another desired shape. The disc has no wire connections to the environment, for example for the device's energy supply, but contains a battery for this purpose. 452 376 Fig. 2 schematically shows the main components of the device, which are next described at the same time as the function of the device is explained. A microphone 2 simultaneously picks up breathing and heart sounds from the human body and converts these into electrical signals. These signals are conducted to an amplifier 3, arranged to amplify them to a desired strength. Through a line branch, these signals are routed to two parallel-connected bandpass filters 4, 5. The bandpass filter 4 is arranged to pass only signals with a characteristic characteristic of heart sound, and thus filter out breathing sounds and various noise, while the bandpass filter 5 is arranged to only pass signals originating from breathing sound. Tests have shown that heart sounds and breathing sounds are far apart on the frequency scale, which is why such a separation can take place without excessive problems.

The filtered signals are passed on to AC / DC converters 6, 7, which convert them to direct current signals. These DC signals are then routed to each input 8, 9 of an exchanger Q0 acting as an AND gate. The exchanger receives a control signal from a unit 11 which can be set via a switch 12 to transmit either a logic "one" or a ditto "zero". If the control signal arrived at the input 13 of the exchanger 10 is a logic "one", then the input signal originating from the heart sounds is released through the exchanger and out at its output 14 - if the control signal is a logical "zero" then the breathing audio signal is passed through the exchanger.

At the output 14 a logical "one" is consequently obtained, i.e. a signal, if both inputs 8, 9 have a signal, and otherwise a logical "zero". ie no signal.

Whether the output signal consists of the respiratory or cardiac signal is thus determined by the control signal from the unit 11. The signal from the exchanger 10 is passed on to a monostable flip-flop 15, which is triggered to deliver a signal at its output, the duration of which also depends on the control signal 452 376. 11. For example, a logic "one" as a control signal gives a long pulse at the output of the flip-flop, and a "zero" gives a shorter pulse. The signal or pulse from the flip-flop 15 is routed to a transmitter 16 which has an antenna 17, via which the transmitter can transmit a carrier to a suitable receiver (not shown) when the transmitter is reached by an input signal.

The receiver does not belong to the device 1 itself, and may be arranged to evaluate the signal emitted by the antenna 17, and to draw conclusions which may lead to measures such as alarm triggers.

Through the pulse length of the signal sent to the receiver, the receiver can identify the signal and tell if it originates from heart or breathing sound. However, in the case of a direct current signal, only the intensity of the said sound in relation to a reference value can be determined and assessments concerning the person's condition can be made on this basis.

It is not possible to determine the shapes of the actual amplitude curves of the breathing and heart sounds. However, this could be achieved by connecting the output of the filters 4 and 5 to a unit inserted between the flip-flop 15 and the transmitter 16 which transmits the heart signal from the filter 4 on to the transmitter if the pulse coming from the flip-flop is long, and the breathing signal from the filter 5 if the pulse is shorter.

The advantage of this type of device for monitoring the heart and respiratory activity of a person is, in addition to the above already mentioned, that the energy consumption is minimal, as measurements only take place when both heart and respiratory sounds occur and a single measurement delivers statements about both activities. As a result, a battery located inside the housing of the device can be a considerable time. Likewise, round-the-clock monitoring of the person can take place without any problems if the receiver is an electronic device that evaluates the signals from the transmitter 16 and, if necessary, sends alarms to authorized personnel. The invention is of course not limited to the exemplary embodiment described above, but a number of modification possibilities thereof will be obvious to a person skilled in the art without departing from the inventive concept.

It would of course be possible to send the signals from the transmitter to a receiver via wires, which, however, should preferably be avoided. The same applies to the energy supply.

The wiring diagram shown in Fig. 2 could also be modified in various ways without changing its basic function.

The respiratory signal can, of course, be made longer than the cardiac signal, and a "zero" as a control signal controls the latter and so on.

Claims (8)

452 376 nu ... __ .. Patent claim A device for monitoring the cardiac and respiratory activity of a person, in particular a hospital patient in a dormant state, the device (1) comprising first means (2) for recording respiratory and cardiac sounds and converting them into electrical signals , a device (3-15) for processing these signals and transmitting information and other means (16, 17) for receiving and transmitting this information to a receiver intended to evaluate said information, characterized in that said device (3-15) is either a) arranged to provide to said second means (16, 17) only information about the cardiac activity and only during the time that breathing sound is registered by said first means (2) or is b) arranged to provide to said second means (16, 17) only information about the respiratory activity and only during the time that heart sounds are registered by said first means (2). Device according to claim 1, characterized in that the device comprises in two positions adjustable means (11, 12) arranged to influence the device to function a) in one position and to function b) in the other position. Device according to claim 1 or 2, characterized in that the device is provided with its own, energy source built into it for its energy supply, and that the transmission of signals from said second means (16, 17) to the receiver is arranged to be done in a wireless way. Device according to any one of the preceding claims, characterized in that said first means (2) consists of a microphone of suitable design. 452 376 Device according to any one of the preceding claims, characterized in that said second means consists of a transmitter (16) with antenna (17), via which it transmits a carrier to the receiver. Device according to one of the preceding claims, characterized in that the device (3-15) comprises a parallel connection of two bandpass filters (4, 5) which only transmit signals with frequencies characteristic of cardiac sound and respiratory sound, respectively, a direct current converter (6, 7) connected to each filter and a switch (10) acting as an AND gate, each filter being connected via respective transducers to each input (8, 9) of the switch (10), that the first means ( 2) is arranged to feed both branches of the parallel connection with the signals from the registered sounds, and that the exchange is arranged to send information to said second means (16, 17) only if signals are present at both inputs of the exchange (8, 9) at the same time. 7. Device according to claims 2 and 6, characterized in that the means (11, 12) for setting function a) or b) is connected to said gear (10) and arranged to provide in its one position a logic "one" and in its second position give a logical "zero" on a control input (13) of the exchange and thus control the exchange to send only either heart sound or breathing sound signals to said transmitter (16, 17). Device according to claim 7, characterized in that a monostable switch (15) is connected between the output (14) of the switch and the input of the transmitter, that said means (11, 12) is connected to the switch while supplying the same signal thereto to the switch (10), and that the temporal length of the signal from the device (3-15) to the transmitter (16, 17) depends on the character ("one" or "zero") of that from the means (11, 12) to the signal (15) applied to the signal. ..._. ~ ...