WO1994020818A1

WO1994020818A1 - Monitoring equipment

Info

Publication number: WO1994020818A1
Application number: PCT/FI1994/000085
Authority: WO
Inventors: Juhani Kupiainen; Raimo Sepponen
Original assignee: MILESTONE Oy
Current assignee: MILESTONE Oy
Priority date: 1993-03-09
Filing date: 1994-03-09
Publication date: 1994-09-15
Anticipated expiration: 1995-09-09
Also published as: FI931050A0; AU6208994A; FI931050A7

Abstract

The invention relates to equipment for monitoring periodic or nonperiodic movements that are caused by activity of an object such as human body or a motor, for example monitoring respiratory movements and heart beat in a human body. The equipment has a measuring volume (TV), which has at least two substances, which have different weights by volume, and to which energy is conducted. The interaction between the energy and the substances in the measuring volume is observed with the observing means (RD) of the equipment and their output signal is used for monitoring the mentioned movements.

Description

MONITORING EQUIPMENT

The invention relates to an equipment for monitoring periodic or nonperiodic movements that are caused by activity of an object or conducted form internal or external source to the object's construction, the object being for example human or animal body, or device such as motor or paper machine, or mass or its part such as earth shell, and for example from the human body monitoring respiratory movements and heart beat.

Movement is generally one important feature in the function of a device. When a motor is spinning the unbalance of masses cause trembling, the character of which changes when the motor parts wear or fail. It is often difficult to recognize the service need when the repair requirement is still small, because it is difficult to notice small changes in the trembling. There are equipment available for measuring and monitoring the trembling, but they are typically expensive and require installing electrical cables from the measuring unit to the sensor.

One special case of need for monitoring movement is patient monitoring (patient means here widely healthy or ill person or animal). The monitored patient is often in laying position and it would be desirable to monitor at least respiratory rate, RR and heart beat rate, HR. There are many known techniques: the heart rate can be monitored with eg. EKG by registering the time between QRS complexes. The respiration can be monitored so that the patient lies on a mattress, which registers the movements caused by respi¬ ration and heart function. This kind of solutions are described in eg. references: US 4,474,185, US 4,320,766, US 4,383,771, US 3,760,794, DE 3421045A. In this kind of solu¬ tions the respiratory movements of the patient are rela¬ tively easy to be registered, but registering the heart function is unreliable. The bed cloth layers between the patient and the registering mattress even make the reliability worse.

With help of the invention it is possible to accomplish a monitoring equipment where the disadvantages of the known technology are eliminated. The monitoring equipment according to invention is simple and inexpensive, its function does not require galvanic connection to the patient or to the monitored device. What is characteristic for the invention is described in claim 1 and the following claims.

The invention is illustrated with the attached drawings, where

Fig 1 describes the principle of the monitoring equipment.

Fig 2 describes an alternative solution to accomplish the sensor of the monitoring equipment.

Fig 3 describes one possible block diagram of the central unit of the equipment.

The sensor of the monitoring equipment includes a measuring volume TV, which contains two substances Ml and M2 of different weights by volume. "Substance" can mean here also vacuum. Energy is conducted via transfer means MTS to the measuring volume TV and to interaction with Ml and M2.

The energy source is ES. The energy, which has been in interaction with Ml and M2 is conducted from TV via transfer means TMD to observation means RD, whose output signal is processed in measuring electronics CP. The energy movement in the measuring volume TV is illustrated with dashed line in the figures. The energy movement can also be controlled by reflecting means R. The equipment may also have several above mentioned means.

A monitoring equipment according to invention for monitoring patient's movements, respiratory movements and heart function can be accomplished for example in a following way:

TV is made of transparent material, such as glass or plastic. TV being approximately ball-shaped its suitable inside diameter is 3 - 6 mm. Ml is gas like for example air. M2 on liquid, like for example water or mixture of water and alcohol or water and some substance that varies the surface tension such as soap solution. Also oil based solutions as well as other organic substances are possible.

The properties of the substances affect the sensitivity and frequency responce and temperature behaviour of the sensor.

Also the inner diameter of TV, and the wall material, and the adhesion between the substances and TV wall affect the properties of the sensor.

When using light energy it has been experimentally found advantageous to choose the TV material, inner diameter and liquid properties so that the gas forms a curved surface volume, that is a bubble. Curve liquid/gas surface, while moving, affects the light movement stronger than a straight plain surface.

A suitable energy source RS is in this application a light source such as incandescent lamp, fluorescent lamp, light emitting diode or for example a piece of light emitting substance. From the energy source RS the light can be conducted via a fibre to volume TV and accordingly the penetrated light can be conducted with a fibre to the obrervation means RD.

The sensor that is attached to the patient must be of small size, so it is often advantageous to conduct the light transmitted by RS via optical fibre to the sensor that is attached to the patient. The same way the light that is penetrated through TV can be led via fibre from the sensor to RD, which can be for example a light sensitive semiconductor. In this case TMS and TMD are at least partly optical fibre. To increase the transfer ratio it is possible to add interface components to both ends of TMD and TMS such as lenses, matching liquid etc. Suitable components are manufactured eg. by Hewlett Packard, California, U.S.A..

The function of the device is following: TV's movement causes acceleration forces mainly to M2, which moves and at the same time the border surface between Ml and M2 moves. In the example case the gas/liquid border surface, which as known causes a strong refracting of light, moves, and this movement causes changes in the amount of light that has passed through TV and observed by PD.

One possible block diagram of CP is described in figure 3: The figure shows that it is advantageous to include into CP's construction RS and RD, to which TMS and TMD are connected with connectors CS and CD. The output signal of RD is amplified with the amplifier A and is filtered with the filter F before the conversion into digital form with the AD-converter ADC. The digital signal is led to the central unit CPU, which can be connected to a local network LAN. Memory means SCM and mass storage media (tape, hard disc etc. ) DSU are connected to the CPU. The user controls the equipment with the control means KB, which can be for example a keyboard, and the monitoring entities, such as the processed output signal of RD are shown with the display means DDU. The equipment can also include alarm means AU, which detect existence of some abnormal condition or condition that requires attention. The equipment receives its operating voltage from the power supply PSU, which can be connected to mains or contains an accumulator, battery, light cell etc.

CP can, as described in figure 3, contain eg. an amplifier for amplifying the signal of RD, the precircuits required by the function of RD and filters for filtering the disturbing components from the signal of RD. Regarding the function of respiration and heart the interesting frequency band is 0.05 - 30 Hz. It is possible to separate the respiratory signal and signal connected to the heart function from the acquired signal by using purely analog technics. It is however most advantageous to convert the amplified signal to digital form by an AD-converter and to process the signal for example in such a way that from the frequency peaks of the signal spectrum a respiratory component (which is on the area 0.05 - 0.5 Hz) and component caused by heart function (which is on the area 0.5 - 30 Hz, and the basic component equalling the heart function is on the area 0.5 - 4 Hz) are separated. It is advantageous to calculate the spectrum for example by using the generally known FFT algorithm. The achieved results can be storaged, and set alarm limits can be associated with them and they can be displayed by means that are included or connected to CP.

The required A/D converters are manufactured by eg. Motorola Inc. and Linear Technology Corp., USA and suitable microprocessors are manufactured by eg. Intel Corp., USA. The storage media can be for example semiconductor memory, or magnetic, optical or magneto-optical disc, magnetic tape or so called smart card or even punch card or tape. A suitable device that is compatible with so called IBM PC devices is manufactured by eg. Dover Electronics Manufacturing West, USA. The type of the device is ESP8680 and suitable interface means are available. Another manufacturer is National Instruments Corp., Austin, Texas, U.S.A., whose delivery program include interface boards and program packages, such as LabView ja LabWindows program packages and suitable interface boards such as AT-A2150.

Naturally for mass production an own device solution must be designed, which is productionwise economical.

Generally known signal processing technology and computer technology that can be used are not explained here in more detail but is referred to eg. the following references: Spectral calculation and related matters are handled in numerous publications, of which is mentioned here only Proakis J.G. ja Manolakis D.G.: Introduction to digital signal processing, Macmillan Publishing Company, New York, 1988 and Oppenheim A.V. and Schafer R.W. : Discrete-Time Signal Processing, Prentice-Hall International Inc., Englewood Cliffs, New Jersey, 1989. It is also possible to use so called autoregressive algorithmes (autoregressive algorithmes and other analysing methods that are suitable when the number of samples taken from the signal is small are described eg. in reference: Kay et al: Proceedings of IEEE, vol. 69, no. 11, 1981).

In the equipment it is possible to apply many known solutions, the main principles of which are described for example in publications Tompkins W.J. and Webster J.G.: Design of microcomputer-based medical instrumentation, Prentice-Hall Inc, Englewood Cliffs, New Jersey, 1981 ja Webster J.G.: Biomedical instrumentation, 2nd Edition, Prentice-Hall Inc, Englewood Cliffs, New Jersey, 1991.

In another way to accomplish the sensor, RD observes changes of light in TV or in a reflector outside of TV, which light is transmitted from RD. MT can then be a common cable that can consist of several fibres that are divided between RS and RD.

The invention can be applied by using eg. ultra sound as energy. One application is to use TV as part of resonator, where connected to a piezoelectric element a sensitive movement sensor is achieved, whose oscillating frequency depends on the mutual motion of Ml and M2.

TV can also be a part of radio frequency resonance circuit, where it is possible to monitor mutual movement of its Ml and M2 with an external coil arrangement. The resonance frequency of the resonance circuit that is connected to TV depends on the movement of Ml and M2. In this case M2 can be mercury or other liquid that conducts electricity and Ml can be gas or liquid, whose electrical properties differ from M2. Naturally it is possible to measure the resonance frequency of the resonance circuit that is connected to TV also in other ways, for example by arranging the TV to be a part of oscillator. In this case the oscillation frequency of the oscillator depends on the movement of TV and this can be tranferred eg. wirelessly to the CP, which then has the required receiving means.

The sensor means can be attached to the monitored object or to a piece that is in mechanical connection with the object, for example clothing, with attachment means such as glue, tape or belt. They may also have disposable parts that are changed always when starting the measurement of a new object. The sensor means include at least a measuring volume (TV) with the substances (Ml and M2) inside it.

The equipment according to invention can be used for eg. detecting movements of people or animals. Movements include in this case eg. respiratory movement and beat caused by the heart function. Heart beat can be researched from eg. the surface of the chest and on the surface of the arteries. By using sensors that are placed to many different places it is possible to tutkia eg. the advance of the blood pressure pulse in the body caused by the heart function. By analysing signals from several sensors with eg. correllation calculation it is possible to get information from eg. advance of oscillations in the building frame, bridge construction or even aeroplane frame.

CP can also be arranged to alarm in the case of abnormal movement of the object. This is advantageous for example in patient monitoring in connection with magnetic resonance imaging. The imaging incident lasts for several minutes and the patient must be almost still for the whole time. If the patient starts to move during the imaging, it is reasonable to stop the imaging, because the images as a result would be often not usable. The problems connected to this are discussed eg. in the above mentioned reference DE 3421045A, compared to the solution that is described there the invention offers a significantly more sensitive and reliable solution. In addition, since the sensor with its interface means can be made from non-conducting and non- magnetic materials, the equipment according to the invention is well suited to this purpose. The mentioned abnormal situations also include too low or too high respiratory rates and heart rates. For monitoring them the CP can include means for setting limits and means for following exceeding or going under these set values. From the abnormalities CP can announce via alarm means such as signal light or sound generator.

For monitoring movements and other associated entities there can be registering means connected to CP such as plotter, oscilloscope, tape station, electrical memory, hard disk, magnetic disk station.

With the sensor it is possible to measure except the amount of movement/acceleration also the direction of the movement/acceleration, or the orientation of the sensor. In this case it is advantageous to measure interaction of substances Ml and M2 with energies that travel two or several routes. The monitoring equipment can then include several energy sources RS, energy transfer means TMS, observation means RD and/or energy transfer means TMD. In this case several signals are received from observing means, and the mutual intensity ratios correllate with interaction energies travelling different routes with Ml and M2. By defining the typical effect of sensor orientation or movement/acceleration on interaction of energies travelling different routes it is possible to derive from the strength of signals the sensor orientation and direction of sensor movement/acceleration relative to the direction of the gravitation.

When measuring energies that travel several routes it can further be advantageous to use different wave lengths of energy, thus being possible to separate from each other energies that have travelled different via routes with for example filters or by using observing means, whose sensitivity to different wave lengths is different.

The equipment according to the invention can be used also for measuring the mutual movement of two or more points by installing the sensors to these points. In this case it is advantageous to form a differential signal from the signals achieved from the observing means so that signal changes caused by the movement/acceleration of same direction are eliminated.

To the sensor construction it is possible to combine also other sensors to an essentially one mechanical whole, such as optical temperature sensor, movement sensor of under skin blood circulation, oxidation sensor.

The equipment according to invention can be used in addition to above described exaples eg. as a part of a burglar alarm system or as a part of a system for detecting the oscillations of the earth shell used for eg. prediction of earthquakes.

Above only some embodiments according to invention are described. It is possible to realize several modifications of the invention within the inventional idea that is specified in the following claims.

Claims

PATENT CLAIMS

1. Monitoring equipment for monitoring movements of an object such as motor or human body characterized in that the sensor of the equipment includes a measuring volume (TV), which contains at least two different substances (Ml and M2), which have different weights by volume, and with which the energy that is conducted from the energy source (RS) to measuring volume (TV) is in interaction, which is observed with observing means (RD) that are included in the equipment.

2. An equipment according to claim 1 characterized in that the equipment has means (TMS) for conducting the energy from the energy source (RS) to the measuring volume ( V).

3. An equipment according to claim 1 or 2 characterized in that the equipment has means (TMD) for conducting the energy from the measuring volume (TV) to the observation means (RD).

4. An equipment according to claims 2 and 3 characterized in that the means (TMD) and (TMS) are structurally combined.

5. An equipment according to any preceding claim characterized in that the energy source (RS) is a light source, such as lamp, fuorescent lamp, piece of light emitting substance or light emitting diode.

6. An equipment according to any preceding claim characterized in that the measuring volume (TV) is at least partly of light transparent material, such as glass or plastic.

7. An equipment according to any preceding claim characterized in that the means for conducting the energy (TMS, TMD and MT) are light conducting such as optical fibre.

8. An equipment according to any preceding claim characterized in that at least one of the substances (Ml and M2) is liquid, such as water, water solution, oil or alcohol solution.

9. An equipment according to any preceding claim characterized in that at least one of the substances (Ml and M2) is gas, such as air.

10. An equipment according to claim 9 characterized in that the measures of the measuring volume (TV) and the properties of the liquid being one substance are chosen in such a way that the gas being the second substance forms a so called bubble.

11. An equipment according to any preceding claim characterized in that it has means for creating a frequency spectrum of the signal that is derived from the output signal of observation means (RD).

12. An equipment according to any preceding claim characterized in that at least one substance (Ml, M2) in the measuring volume (TV) differs by its some electrical property such as conductivity, dielectric constant, permeability or magnetism from other substances that are in the measuring volume.

13. An equipment according to any preceding claim characterized in that the measuring volume (TV) is a part of resonance circuit such as electrical or acoustic resonance circuit.

14. An equipment according to any preceding claim characterized in that the measuring volume (TV) is a part of sensor means, which also include attachment means attaching the sensor means to the monitored object, for example to device or human body or to a piece that is mechanically connected to them such as clothing.

15. An equipment according to any preceding claim characterized in that it is used for observation of person's or animal's movements such as respiratory movements and beat caused by the function of the heart.

16. An equipment according to any preceding claim characterized in that essentially as a united structure connected to the sensor means there are other sensors for registering other entities, such as temperature or blood oxidation.

17. An equipment according to any preceding claim characterized in that the observation means (RD) are used for measuring energies that have travelled via two or several routes.

18. An equipment according to claim 17 characterized in that the energies that travel via different routes have different wave lengths, and from the observation means signals are received, where energies with different wave lengths have different strength coefficients.

19. An equipment according to any preceding claim characterized in that the signals that are received from the observation means RD are used for defining the direction of movement and/or the orientation relative to the direction of gravity.

20. An equipment according to any preceding claim characterized in that the equipment includes two or several measuring volumes, where by observing the interaction between energy and masses, information is received on the mutual movement of the measuring volumes.

21. An equipment according to claim 20 characterized in that for observing the mutual movement of the measuring volumes a differencial signal is created from the signals that are received from the observation means that are connected to different measuring volumes.