ES2436541T3 - Autonomous assistance system in a situation to save a life - Google Patents

Abstract

System for monitoring parameters during cardiopulmonary resuscitation, comprising - compression measurement means (9), - ventilation measurement means (11), - processing means (12) connected to the compression measurement means and to the ventilation measurement means, adapted to compare the values from the compression and ventilation measurement means with respective reference intervals and, if at least one of the measured values deviates from the respective reference interval, provide an indication of the deviation, characterized in that, in the event that more than one measured value deviates from the respective reference intervals, the processing means (12) are adapted to provide a sequence of indications of the deviations in order of priority.

Description

Autonomous system for assistance in a situation to save a life.

This invention relates to a system designed for measurement, recording and feedback on cardiopulmonary resuscitation performance (CPR) as applied to victims of cardiac arrest or to a dummy for training purposes.

Background of the invention

Cardiopulmonary resuscitation (CPR) is a procedure performed as first aid to save a life in case of sudden cardiac arrest. The procedure includes chest compressions and ventilation. Recent publications have pointed out numerous problems with how CPR is being carried out today by professionals:

Aufderheide et al. showed in their publication "Hyperventilation-Induced Hypotension During Cardiopulmonary Resuscitation", Circulation. 2004; 109 that trained personnel of the Emergency Medical Services (SMU) had trouble producing proper ventilation. Even after its formative recycling, the ventilation rate was still too high compared to the “Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care” published by the American Heart Association, in collaboration with the International Consensus Committee on Resuscitation, called hereinafter "the Guidelines".

van Alem, Sanou and Koster noted another problem with CPR performed in “Interruption of Cardiopulmonary Resuscitation With the Use of the Automated External Defibrillator in Out-of-Hospital Cardiac Arrest”, Annals of emergency medicine 42: 4 (October 2003); Even trained SMU personnel performing CPR carried out compressions or ventilations less than 50% of the time on the scene, that is, the non-intervention time / idle time was too high.

Two articles in the Journal of American Medical Association (JAMA) published on January 19, 2005, Vol. 293, No. 3, "Quality of Cardiopulmonary Resuscitation During In-Hospital Cardiac Arrest" by Abella et al. and "Quality of Cardiopulmonary Resuscitation During Out-of-Hospital Cardiac Arrest" by Wik et al., conclude that the non-intervention time was too high, the correct compression depth was not reached, the compression rate was either too low. or too high and hyperventilation frequently occurred.

Many assistive devices for CPR are known. US Patent No. 6,306,107, Myklebust et al., "System for Measuring and Using Parameters During Check Compression in a Life-Saving Situation or a Practice Situation and Also Application Thereof", describe such a device. This device does not consider ventilation, ventilation inactivity or compression inactivity.

Another description of a device for CPR is described by Halperin et al. in US Patent No. 6,390,996, "CPR Check Compression Monitor". This device only considers compression. Other simpler CPR assistive devices base their feedback on strength and time. Such a device is CRPEzy from Medteq Innovations Pty. Ltd.

Some CPR assist devices are part of an automatic external defibrillator (AED) or a defibrillator. Such a device is part of AEDPlus of Zoll Medical Corporation. That device only considers compressions. The acquisition of a new defibrillator with a CPR assist device may not be an option for emergency medical systems (SMUs) that already have a well-functioning DEA / defibrillator system. Such SMUs would consider rather an autonomous solution for the measurement and feedback of CPR.

EP 1 491 175 discloses a system according to the preamble of claim 1. Describes a cardiopulmonary resuscitation device with feedback from the measurement of the pulse and / or blood oxygenation.

There are no prior art systems or devices that provide feedback on both the compression and ventilation activity as well as the inactivity through the complete CPR procedure. It is believed that these issues are very important in increasing CPR performance and therefore in survival rates.

Another problem related to known systems, such as Zoll's AEDplus, is that they are relatively expensive, large and complicated; so that lay rescuers will not have them at all times. Devices manufactured for lay resuscitators are described in EP 1 578 340, which describes force-sensitive devices that provide sound signals for resuscitator assistance, and more particularly a device to be placed between the hands of a person performing chest compression and he

chest of a patient. Even more particularly, the device that is the object of EP 1 578 340 is designed to emit a sound when thoracic compression is performed with a force that exceeds a predefined value and optionally also to emit a sound indicating the desirable rate of thoracic compression . This is obtained in a cheap and compact device that can be independent of batteries and therefore is always ready for use, or in the embodiment that uses a battery, which has a very low energy consumption.

Practice has shown that sound signals can be difficult to hear in some cases, especially in some urgent situations. In addition, in some cases there is a need for a more precise basis for user feedback. If, for example, the force applied is too intense, there is a risk of hurting the patient. Therefore, in such cases there is a need for an energy efficient and compact device to provide quality CPR feedback, in which the feedback is provided in a manner that is reliable and likely to be received by the resuscitator in all possible situations.

Summary of the invention

The objective of the present invention is to provide a system for monitoring parameters during CPR, to allow a person to perform CPR in a correct and efficient manner by guiding them through CPR based on the measurement and feedback of chosen parameters related to CPR treatment, thus providing the patient with better treatment and greater chances of survival.

A further objective of the invention is to provide a device for providing feedback to the resuscitator in order to improve CPR treatment, the device being small, versatile, reliable and affordable.

The object of the invention is also to overcome the limitations of the prior art to which reference has been made.

Orientation is defined herein as corrective and directive feedback, and feedback may be in the form of tonal, verbal, tactile, vibration, light and / or graphic messages. Directive feedback can be reminders about how to perform specific stages of CPR.

The feedback is provided in one embodiment by means of indications to the resuscitator by means of tactile feedback at the hand of the resuscitator provided in an energy efficient manner, for example to prolong the life of the battery and therefore the reliability of the device when stored without charging.

Important parameters on which feedback can be provided based on the monitored signals of the system according to the invention are, but are not limited to, compression depth, compression rate, compression inactivity, incomplete compression release, compression rate. ventilation, current ventilation volume, ventilation inflation time and ventilation inactivity.

The present invention can be parked wherever many people meet, for example: airports, sports stadiums, shopping centers, subway, buses, etc. The invention is suitable for use by both legal persons and by trained persons. It can also be placed in SMU vehicles, police and / or firefighters, or distributed as a personal device for people who provide basic life support (SVB).

The information measured by the present invention can also be registered to report and / or transmit it later to an emergency medical (communication) center and / or hospital. The transferred data could be used to further adapt the hospital treatment as long as the patient is admitted to the hospital.

The object of the invention is obtained by a system as specified in the appended claims.

According to the invention, the system for monitoring parameters during cardiopulmonary resuscitation comprises compression measurement means, ventilation measurement means, processing means connected to compression measurement means and ventilation measurement means, adapted to compare the values of the compression and ventilation measuring means with respective reference intervals and, if at least one of the measured values deviates from the respective reference range, they provide an indication of the deviation, in which in the case that More than one measured value deviates from the respective reference intervals, the processing means are adapted to provide a sequence of indications of the deviations in order of priority.

According to one embodiment, the system according to the invention comprises a feedback unit that provides the indication of a deviation in the form of an auditory, visual and / or tactile output.

According to one embodiment, the feedback unit comprises a coil wound around a central hole and a magnetic core disposed movably in the central hole of the coil, the coil being connected

to a power supply that turns on and off in order to induce movement of the magnetic core.

According to a further embodiment, the ventilation measurement means measures the ventilation rate, the tidal volume and / or the inflation time.

According to a further embodiment, the compression measurement means measures the compression rate and / or the compression depth.

According to a further embodiment, the compression measurement means and / or the ventilation measurement means and the processing means are integrated in a housing.

According to still a further embodiment, the compression measurement means, the feedback unit and the processing means are integrated in a housing.

In a further embodiment, the prioritization of the indication signals is performed by comparing the respective measurands corresponding to the measured values that deviate with a priority list stored in the processing means.

Compression measurement means measure the compression rate.

Brief description of the drawings

The invention will be explained in more detail below, with reference to the accompanying drawings illustrating the

invention by way of examples, in which

Figure 1 schematically shows a person with a compression unit for the implementation of the

invention.

Figure 2 schematically shows a person with a compression adapter and airway for

implementation of the invention Figure 3 schematically shows a person with an additional compression and ventilation unit with electrodes for the implementation of the invention.

Figure 4 shows a generalized flow of information in the processing means.

Figure 5 schematically shows the system components for the device.

Figure 6 shows alternative embodiments of the device.

Figure 7 shows a typical signal flow diagram.

Figure 8 shows a typical accelerometer signal flow diagram.

Figure 9 shows a perspective drawing of a tactile feedback device according to the invention.

Figure 10a, b, c illustrates the feedback unit of the touch feedback device in Figure 9.

Figure 11 illustrates the position of the feedback unit inside the device of Figure 9.

Figure 12a, b schematically illustrates the feedback unit according to an embodiment of the invention.

Figure 13a, b illustrates the principle of the feedback unit according to the invention.

Figure 14 illustrates an example of the circuitry of the feedback unit.

Figure 15 illustrates the circuitry of the feedback unit according to a preferred embodiment of

the invention.

Detailed description

Figure 1 shows a patient 1 with a compression unit 2 attached to his chest. This unit can be fixed using adhesive tape. When a resuscitator compresses the patient's chest, the resuscitator puts his hand on top of unit 2. The unit will therefore travel the same distance as the chest is compressed. A motion sensor, which includes or connected to calculation means, inside the compression unit

will detect distance / depth. This motion sensor can be an accelerometer, but other solutions such as the use of a gyroscope or distance measurements from a reference point or by triangulation can be used. In the case of an accelerometer, in order to find the depth, the signal from the sensor must be filtered and subjected to double integration, as is well known in the art. An additional force-sensitive unit, in its simplest form simply a force-activated switch, will also be part of the unit. This force-sensitive unit will be activated each time the resuscitator performs a compression, and will therefore define the compression / integration time window / interval. This reduces the incidence of detection of false compression positives. Having a force sensor instead of a force-activated switch can facilitate possible future changes in the CPR protocol / guidelines for the measurement of depth to force compression, or a combination thereof. In one embodiment, the compression unit may be arranged with a force transducer instead of a motion sensor. According to an embodiment of the invention, the compression unit 2 comprises a tactile feedback unit to provide tactile indications concerning distance / depth measurement.

Figure 2 shows a patient 1 with the compression unit 2 fixed to his chest. In addition to what has been described about the compression unit in Figure 1, the compression unit is connected through either a flexible tube or an electric cable 3 to an airway adapter 4 that is placed between a mask or ET 5 tube and a ventilation bag or fan 6.

In one embodiment, the airway adapter has some kind of ventilation measurement means. One solution is to arrange a restriction in the airways, and measure the decrease in pressure along this restriction. The pressure sensor (s) can in this case be placed in the compression unit 2 or in / through the airway adapter 4. Then the flow can be calculated since it is to provide the square root of the pressure decrease. By integrating the flow is the ventilation volume.

Alternative ventilation measurement means may be constituted by means other than differential pressure monitoring, such as monitoring of airway temperature fluctuations, indicating whether air enters or leaves the person, a single transducer pressure, which measures the pressure of the airways inside the airway adapter 4, thus allowing the detection of ventilation events and associated pressure profiles, or small turbines, all located in the airways.

Alternatively, or in addition, chest impedance measurements can be used to indicate the volume of air in the lungs, as described in the next section.

Another system configuration may also be viable. The ventilation measuring means may be integrated, for example, in the mask, and there may or may not be a ventilation bag. Instead, the resuscitator can use his mouth to ventilate the patient.

In addition or instead of flow measurements, final expiratory CO2 (CO2EF) measurements can also be implemented. CO2EF can be used as an indicator of how good the treatment is, and therefore if CPR can be improved.

Advanced life support staff (SVA) can intubate a victim of cardiac arrest and perform compressions and ventilations at the same time. As compressions will compress the lungs, thereby pushing air out of them, compressions can influence ventilation measurements. Therefore, low pass filtering or adaptive filtering of ventilation measurements may be necessary. Adaptive filtering can use any or a combination of force, acceleration, speed and / or depth as additional inputs, since all of them are related to the compression activity. An expert in the field of signal processing knows how to do this.

Figure 3 shows a patient 1 with the compression unit 2 which in addition to the functionality mentioned above also has electrodes 7 fixed to each side of the unit. These can be used to measure the chest impedance of patients. The chest impedance is usually measured by supplying an approximately constant alternating current between the electrodes and at the same time measuring the alternating voltage between the electrodes. It is also possible to apply an approximately constant alternating voltage between the electrodes and at the same time measure the alternating current flowing between the electrodes. It may be necessary to place the electrodes in close proximity to the compression unit as well as being small in size since defibrillation electrodes could also be placed in the patient. Due to the close proximity of the electrodes and the relatively small electrodes, the preferred frequency for measuring the impedance could be greater than that normally used; frequencies between 0.1 kHz and 500 kHz or even higher may be used depending on the electrode size. When the lungs are inflated, the impedance of the chest increases (the path between electrodes increases), which allows the unit to detect if air is really entering the lungs. Impedance measurements per se are known from other similar applications or applications and will not be discussed in more detail herein. Filtering can also be applied (to eliminate compression activity), as described in relation to Figure 2.

The system according to the invention comprises some kind of processing means for example a microprocessor, microcontroller or some type of programmable logic unit (CPLD or FPGA). The processing means may be integrated in the compression unit 2 or in the ventilation measurement means, or they may be in a separate unit. The processing means are preferably provided with rewritable means, such as flash memory, for updating the program and the predetermined set of preferred activities from which the deviations are found. The ability to update the means of processing will be an advantage since "the Guidelines" are updated regularly.

The processing means will be responsible for collecting information from sensors / measuring means, processing the individual signals and deciding what type of feedback will be provided to the resuscitator. This process is summarized in Figure 4. If it is necessary to correct more than one parameter, the processing means includes a priority process so that it selects to provide feedback on the most critical parameter (s) first based in a priority list. A priority list is stored in the processing means, and it can be a conventional list, for example one mentioned in "the Guidelines", or it can be defined by the user or the manufacturer according to the specific use of the system.

The system according to the invention is further provided with some type of feedback actuator 13, for example comprised in the compression unit 2. Since the resuscitator usually already has enough things in the head, feedback can preferably be provided by means of voice messages. This may depend, however, on the intended use of the equipment, since voice messages in some cases, such as in areas with many people, can be misunderstood by passersby or can drown in noise. In such cases, tonal, visual, tactile or vibration feedback signals (for example pagers, flashing LEDs, solenoids or vibration motors) can be used. Different configurations can be used. In one example, a pager is used to provide the compression rate feedback, in the form of either a corrective metronome indicating the correct rate when the resuscitator is outside the correct window / rate range and which remains silent when the resuscitator is within the correct rate window / range, or a directing metronome that indicates the desired rate continuously, device vibration or a touch on the hand occurs when the compression depth is sufficient and an LED flashes to provide directive feedback on the ventilation rate. In another example, an LED stack is used to show the compression depth, each LED being illuminated when a certain depth is reached. Therefore, one embodiment may use a combination of verbal, tonal, visual, vibration and / or tactile feedback. The compression unit 2, the ventilation measurement means and / or the processing means can also be connected to an independent feedback unit, which can be part of any other visual presentation / feedback equipment for use in that location.

In addition, a recording possibility may be available in which the measured information, for example unprocessed sensor events and / or data and the feedback provided can be stored for later retrieval. The measured information can be stored in the processing means 12 or in a separate storage device, for example a flash memory 14 (card). The registration function can be used to tailor training according to the need of each rescuer, and can be part of a continuous quality improvement (MCC) program. The registration function can be implemented in the device or transferred to a computer or other devices, for example by radio communication. One possibility is that the device is adapted to communicate with a defibrillator, thus constituting part of a larger set of life-saving equipment. In such a situation, part of the user feedback can be provided from the AED / defibrillator, even if it is measured by the compression unit 2. Such communication could be in the form of wireless or cable communication.

In an embodiment of the system according to the invention, all components are implemented in the compression unit 2 comprising sufficient power supply and processing power to be used alone, preferably with input means and / or connection means for receiving data. of ventilation, either electronically as measurement signals, or as pressure transferred through one or more suitable tubes or other suitable physical transfer of physical properties for direct measurement in the compression unit 2. In addition, the compression unit 2 may comprise electrodes, or electrode connection / coupling, for impedance measurements.

This is shown in Figure 5. Most of the components are inside the housing 8, such as the processing means 12, a motion sensor 9 and a ventilation measurement means 11 (these can alternatively be arranged outside from the housing and transfer the signal to the electronic components inside the housing 8). The force-sensitive unit 10 is shown outside the housing, but other solutions may also be vials. Another solution is to present a housing that flexes; that is, the distance between the outer shell decreases slightly when a force is applied. Therefore, it will be possible to measure the force from inside the housing. The feedback actuator 13 can be arranged outside the housing, with a connection to the processing means 12 through the walls of the housing. In case of voice feedback through a loudspeaker, the loudspeaker can be placed inside the compression unit, the compression unit being provided with a slot in the housing 8 to allow the sound of the device to be output. In the case of

tactile feedback, the feedback actuator will preferably be integrated in the housing.

Two alternative embodiments of the system are presented in Figure 6. These alternative embodiments comprise two modules; one 61 for a single use (disposable) and another 60 for multiple uses. The reason for this two module approach is that parts that are in contact with the patient should be discarded for hygienic reasons. It will also work as a way to renew the energy supply. There could be both electrical and mechanical interconnections between these modules. Normally the disposable module 61 contains the power supply, feedback means and connections to the external flow measurement means. The multipurpose module 60 normally contains the processing means, the motion sensor and the force-sensitive unit.

Figure 7 shows a flow chart illustrating a possible signal flow in a preferred embodiment of the invention. This embodiment comprises means for measuring compression and ventilation, means that may be necessary to provide different signals related to each necessary feedback. At certain intervals all the signals of interest are collected / sampled, in this case the acceleration signal as well as the force sensor to monitor the compression and the pressure signal to monitor the ventilation, and then treated separately to produce parameters of interest, such as compression depth, compression rate, compression inactivity, incomplete release, ventilation rate, tidal volume, inflation time and ventilation inactivity.

In the illustrated example, the acceleration data is converted to linear displacement (depth). The force-sensitive unit is used to validate the depth, that is, the depth is not considered when the force is below a certain threshold. From the validated depth, statistical data are extracted, such as rise / fall time, compression rate etc., while the sampled pressure signals are converted into flow and then into ventilation volume, and statistical data such as rise / fall time, ventilation rate, etc. If any of the statistical data is outside the predetermined limits, the data for user feedback is marked.

The predetermined limits are stored values that can be based on statistical models or previous recorded samples of the previous use, for example, corresponding to known deviations from preferred CPR procedures as described in "the Guidelines" as mentioned above.

Therefore, each main loop (compression or ventilation) then decides if any feedback on a parameter is necessary, mark this as the feedback to be provided. A common (by voice) feedback module then decides on which parameter feedback should be provided, based on a priority list. The priority list is stored in this case in the feedback module.

In one embodiment, the feedback module is a program module integrated in the processing means 12.

These loops continue to operate until the device or system according to the invention is turned off, or possibly provided that the force sensor or switch detects activity above a certain level.

There are cases in which only one of these loops may be suitable, for example a simpler device for use by legal persons. The system described in Figure 7 is, however, preferable both for its flexibility in different situations and for the quality of the output. Furthermore, it is possible to base these loops on other parameters, combining the parameters or adding more loops, for example of the force sensor, within the scope of this invention.

Figure 8 shows more details about a possible flow of acceleration signal processing. Most of this signal processing can be done either in the analog domain (before scanning) or in the digital domain, however, only all processing performed in the digital domain will be discussed here. First of all, it is necessary to eliminate its DC component from the acceleration signals. This can be achieved using a high pass filter that is a type of filter either IIR or FIR. A notch filter can also be used. The use of a FIR filter of length M results in

where a is the unprocessed acceleration signal and afilt the filtered acceleration signal. The filtered acceleration signal is then integrated numerically,

where C is half of the sampling interval (T / 2). This unprocessed integrated signal is then filtered low pass, with a filter that can be similar to the first filter,

This filtered signal is integrated numerically again,

where s is then used as depth. A possible solution to keep the drift in the depth signal to a minimum is to keep the integration variables at zero whenever the force sensor, or a switch or a real force sensor is not activated. Another solution is to equalize integrations to zero (both Vsin process and s) each time the depth has an inflection point (first derivative approximately zero (positive to negative), second negative derivative) near zero depth. After this, other parameters can be extracted from s. For example, the compression depth (checking the maximum value between two reboots) and the compression rate (time between two maximum values).

When a CPR error is detected, it is forwarded to a feedback software module using a slightly modified last input, first output (LIFO) buffer, that is, it is always the most recent CPR error that is considered for feedback . The errors in the buffer of more than A seconds ago will be eliminated. After verbal feedback has been provided, the following feedback is usually considered after B seconds. A and B are configurable parameters, usually in the range of 2-6 seconds.

One way to prioritize feedback is to classify all the CPR errors that occurred in a certain period of time according to their priority, and placing only the CPR error with the highest priority in the LIFO buffer. In this way, the feedback software module only has to verify that no other feedback message is provided before executing the feedback warning. This ensures that the most critical error for feedback is considered first.

Another procedure is to place each CPR error in the LIFO buffer, and perform the prioritization in the feedback software module. This allows for more tailor-made adaptation, that is, different errors may remain in the LIFO buffer for longer periods of time, depending on the criticality of the error.

Details of an embodiment of a touch unit included in the device 2 illustrated in Figures 1 and 2 are shown in Figures 9 to 15. The resuscitator places his hand on the device 2 and performs CPR. According to a preferred embodiment of the device according to the invention illustrated in Figure 9, the device provides feedback to direct the resuscitator to provide a desired compression depth, for example by providing a small touch on the hand of the resuscitators when the compression has reached sufficient depth in each compression performed correctly.

Referring to Figures 9, 10 and 11, the feedback unit comprises a coil 22 that is located inside the device 2, preferably off-center / in an end section of the device, the coil having a central hole 21 adapted for insertion of a core 23 of a magnetic material located in the center (figure 10a). The direction of the magnetic field of the core and the coil when a current is applied is chosen so that the core moves out of the central hole 21 (Figure 10b). This will be described in more detail below.

As can be seen from Figures 10a and 10b, a cable is wound around a coil body 26 creating a coil 22 that also maintains the central position of the coil.

The core 23 may be equipped with a rounded end section 27 of a material chosen to make contact with the user more tactile and easy to detect. This can be any desired material.

The manufacture of at least one end section of the iron core 23 provides the additional advantage that the field lines of the magnet are changed to a radial distribution in the iron. This concentrates the magnetic field in a smaller region outside the core magnet, gives the field lines a more preferred direction / distribution in the end sections, and therefore provides a more energetic interaction with the electromagnetic field of the coil. This will therefore increase efficiency. A further improvement of this concept is illustrated in Figure 10c, in which a piece of iron 27a, 27b is added at both ends of the magnet. In Figure 10c, an additional coil 22b is also added, which can be controlled separately or simultaneously to the

first coil 22a, to make a more uniform magnetic field interact with the magnetic core. The current flowing in the two coils 22a, 22b can, for example, have opposite directions to impose attraction to one end of the core, and repulsion from the other end.

As is evident from Figure 9, the feedback actuator is preferably placed off-center in the sensor, since tests have shown that it is unpleasant to receive the blow in the center of the hand when CPR is performed for long periods of time.

The upper cover of the device 2 is composed in the embodiment illustrated by a soft and / or flexible material, and a recess in the cover is provided in an area around the point of impact of the feedback actuator so that this area is hollow (figure eleven). When the magnet core collides with the cover, only a limited part of the cover moves, thus making the stroke more effective. Alternatively, part of the material may be removed at the point of impact, but this may result in an unpleasant and hard blow to the hand. The device 2 preferably has a rubber liner 25 or the like that covers the hole 21 and the magnetic core 23, so that the core 23 makes a tactile touch through the liner 25 when activated.

The principle of this circuit set is widely known as the principle of, for example, an electromagnetic gun and the tactile feedback unit will be explained schematically with reference to Figures 12a, b and 13a, b, while the associated circuit set is described in Figures 14 and 15. The main feature of this solution is the simple structure and efficiency of the feedback compared to the energy consumption related to it, since it provides a large moment to the core in response to an impulse of relatively low energy In the illustrated example, the coil has a winding direction that is counterclockwise (as seen from the above) and the core 23 of magnetic material placed with the positive pole down towards the bottom of the device, and the pole negative pointing up. When the device is not active, the core rests in a lowered position on the housing 24 of the device (see Figure 13b).

In Figure 12a, the feedback unit uses the magnetic forces of an electric coil 22 and a powerful permanent magnet 23 that constitutes the core located in the center. The feedback unit will expel the magnet 23 from the coil hole 21 when a magnetic field is created in this coil hole. The magnetic field is created by a current through the windings of the coil.

The function of the coil and the core is described in detail with reference to Figures 12a, b and 13a, b. When a current is applied to the coil 22, a magnetic field is created that has the same direction as the magnet 23. This causes the magnet to accelerate and move out of the magnetic field as seen in Figure 13b upwards. The hand of the rescuers.

The function of the feedback unit is that if the permanent magnet 23 and the coil 22 are oriented as shown in Figures 13a and 13b and the current through the coil generates a field of the direction shown by N and S for the coil; The magnet will "fire" out of the coil. The direction depends on how the permanent magnet is displaced before the application of the current. In fact, if it were possible to perfectly center the magnet, it would remain motionless. However, this cannot be achieved in practice, and in this case it is convenient to provide a support 24 for the slightly eccentric magnet 23 in an upward direction, so that the direction of movement of the magnet is predetermined. The force on the magnet will remain fairly stable from about halfway to the coil, until the magnet leaves the gap (if the field created by the coil remains constant) Above the gap, the forces decrease rapidly and the magnetic forces They tend to apply rotation to the magnet.

Since the magnet accelerates out of the coil, it is energy efficient to apply a field in the coil only for a short time, just enough to provide the magnet with enough time to make the tactile movement perceptible through the liner 25 of the device .

In the preferred embodiment, the device is designed to be used in an orientation in which the direction with respect to the resuscitator's hands is ascending, so that the core does not need any spring or the like to return to its site after moving. Gravity will simply drive it back to its initial position on the support 24, defined by the device housing, before the next compression and possible emission of an electronic pulse. Other solutions, such as springs, may be contemplated under certain conditions, but which result in a more complicated touch unit.

In addition, in an embodiment without the coating on the hole 21, protruding or similar features may be provided on the magnet or the coil housing to prevent the magnet from falling out of the device.

Different coils can be designed in terms of dimensions, design and wire. The following parameters are important in the coil design

• Size

•

 Electric power

•

 Complexity

•

 Price

•

 Reliability

A coil with low resistance and high inductance is desirable for many applications. High inductance is desirable since high inductance is synonymous with high field strength (Φ). To obtain a higher inductance, more windings are necessary. To obtain a lower resistance, the wire must have a greater cross-sectional area. This will make the coil larger with respect to the inductance. The coil body should be made as large as possible (20x13 mm is a practical dimension for use in a CPR sensor), and the choice of the number of windings and the cable dimension should be made based on the size of the coil body . This means that the coil is as optimal as possible due to the limitations set by the design. The excitation circuit presented in Figure 15 will allow more flexibility with respect to the choice of wire gauge and the number of windings.

In an exemplary embodiment, the coil body 26 (see Figure 10b) has a total height of 13 mm. The cable is only wound in a 6 mm high section of the coil body, the rest of the coil body is used as a guide for the magnet.

The lower end of the coil can be closed by a cover (not shown). The centerpiece of the lid is 8 mm in diameter in a practical embodiment and protrudes in the coil air gap that forms the support 24 for the magnet 23. A 1 mm thick rubber is fixed above the centerpiece. The rubber will ensure that when the permanent magnet returns to its initial position, it will not make an audible noise. The centerpiece will also provide the displacement of the magnet necessary to obtain "ejection forces" as described above. The wire used to wind the coil in this exemplary embodiment is an insulated copper wire with conventional lacquer, 0.15-0.18 mm thick.

The permanent magnet that has been used in the exemplary embodiment is a powerful rare earth magnet, neodymium (N35). Magnets of this type have been widely used in various devices, such as speakers in mobile phones. These magnets have a powerful field compared to mass, but they are mechanically fragile and lose their magnetism at temperatures above 80 ° C. Other magnets may be used depending on the required specifications.

Above the magnet 23 there is preferably a dome to make the stroke more "centered", as shown in the upper part of the magnet illustrated in Figure 2b. The magnet is preferably made of one piece, but certain features, such as the dome, can be performed separately, depending on the required features as shown in 27 and 27a where the dome is made of iron.

In Figures 14 and 15 the set of electronic circuits coupled to the coil 22 is described. The circuitry and therefore the operation of the feedback actuator is controlled by the processing means.

Electronic components with reference to Figures 14 and 15. A capacitor charging circuit 35 will charge the capacitor 32 efficiently from batteries. The batteries will normally have a low voltage (3-5 V), but the capacitor should be charged at a higher voltage (20-50 V normally). This will produce a more powerful field in the coil 22 and therefore accelerate the magnet 23 located therein more vigorously when the feedback device is activated. The current switch 34 will turn on the current through the coil 22 at the correct time. When the magnet 23 has accelerated beyond the recess of the coil, the current switch will turn off.

A more sophisticated circuit is illustrated in Figure 15, in which some components have been added to improve the energy efficiency of the circuit.

In Fig. 15 the capacitor 32 is charged by the capacitor charging circuit 35. At the correct moment, switches Q1 and Q3 are turned on (switch Q2 is turned off). Current will build up in the coil. When the current reaches the maximum current; which is synonymous with maximum field strength in the recess of the coil; Q1 and Q3 turn off. Immediately after this, switch Q2 is turned on. Now the current will continue to flow through the coil and Q2. The current will decrease as energy is consumed either by the resistivity of the coil or by energy transfer to the permanent magnet 23 when accelerated by the field in the coil 22. When the permanent magnet has moved out of the coil 22 , switch Q2 will turn off; The remaining energy in the coil will flow back to the capacitor through D2 and D3. Diode D1 is adapted to prevent transients during the switching process.

The key benefits of this circuit are:

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Only power is taken from the capacitor until the maximum field is set.

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If the coil exhibits low resistance, the coil energy will be transferred to mechanical movement of the magnet.

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The remaining energy in the coil is supplied back to the capacitor.

The capacitor charging circuit 35 will be designed to fully charge the capacitor 32 between each compression of the chest. At the same time, the charging circuit will be designed to take current from the batteries at an almost constant rate to avoid loss of battery power due to high peak currents.

Claims (8)

1. System for monitoring parameters during cardiopulmonary resuscitation, which includes 5 -a compression measurement means (9),

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ventilation measuring means (11),

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processing means (12) connected to the compression measuring means and the means for

10 ventilation measurement, adapted to compare the values from the compression and ventilation measurement means with respective reference intervals and, if at least one of the measured values deviates from the respective reference range, they provide an indication of the deviation , characterized in that, in the event that more than one measured value deviates from the respective reference ranges 15, the processing means (12) are adapted to provide a sequence of indications of the deviations in order of priority. 2. System according to claim 1, characterized in that it comprises a feedback unit (13) which provides the indication of a deviation in the form of an auditory, visual and / or tactile output. twenty System according to claim 2, characterized in that the feedback unit (13) comprises a coil (22) wound around a central hole (21) and a magnetic core (23) disposed movably in the central hole of the coil , the coil being connected to a power source that turns on and off in order to induce movement of the magnetic core. System according to any of the preceding claims, characterized in that the ventilation measuring means (11) measure the ventilation rate, the tidal volume and / or the inflation time. System according to any one of the preceding claims, characterized in that the compression measuring means (9) measure the compression rate and / or the compression depth. System according to any of the preceding claims, characterized in that the compression measuring means and / or the ventilation measuring means and the processing means are integrated in a housing (8).

7.

System according to any of claims 2 to 6, characterized in that the compression measuring means, the feedback unit and the processing means are integrated in a housing (8).

8.

System according to any of the preceding claims, characterized in that the prioritization of

40 the indication signals comparing the respective measurands corresponding to the measured values that deviate with a priority list stored in the processing means.