DE102009028257A1 - Device for recording and monitoring the thoracic bioimpedance, which allows the determination of urgent thoracic conditions - Google Patents

Abstract

The recording and monitoring apparatus has a generator (G) of harmonic alternating current, where three application electrodes (AE) are provided for application of current on the chest. Three recording electrodes (SE) are provided for voltage recording on the chest, where an amplifier (Z) and an analog-digital converter are provided. Independent claims are included for the following: (1) a computer program for analysis and evaluation of the measured bio-impedance values; and (2) a method for differential diagnosis of urgent thorax conditions.

Description

Field of engineering

The Emergency medicine is part of the preclinical Care and in the central reception centers of the hospitals with conditions caused by acute deterioration of health are characterized, and serious injuries. Part of the Emergency medicine is also the implementation of the Cardiopulmonary resuscitation in patients with acute cardiac arrest. All of these conditions are diagnostic methods invaluable, easy to perform and non-invasive, and at the same time unique information deliver. In this area can also be the capture and monitoring of pneumothorax, pulmonary artery embolism and cardiac tamponade using thoracic bioimpedance, which allows the new device according to the invention.

Previous state of the art

A the serious acute complications of health is for example pneumothorax. It is a pathological Presence of air in the pleural cavity, which is between the lung skin and pleura. In this room exists under normal conditions slight negative pressure, which is the maximum Expansion of the lungs ensures and thus their correct Function. The presence of air in this cave leads to a partial or total collapse of the lungs, which is not can breathe and also allows no exchange of respiratory gases. A life-threatening variant of pneumothorax is the so-called stress or over-pressure pneumothorax, which controls the pressure in the pleural cavity increased, it comes to the oppression of the vena cava and the heart with subsequent deterioration of the filling the right-sided parts of the heart and reducing the cardiac output, which in the further consequence to a collapse of the circulation and to the Death leads. Just influencing the activity The right heart is used for diagnostics with the help of the device used according to the presented invention.

A specific complication is pneumothorax in a patient with polytrauma, typically after traffic accidents with Craniocerebral injury and contusion of the rib cage. The patient is typically unconscious and very difficult to study. It follows from the above that the pneumothorax also in the Today's medicine is very often a problem, especially in preclinical Maintenance.

In urgent situations, such as extensive injuries, one needs to have rapid diagnostic methods available. Especially in the case of an acute cardiac arrest, when the resuscitation team proceeds according to the internationally valid instructions ( Baskett P, Nolan J: European Council for Resuscitation. Pocket Edition of the Resuscitation Guidelines 2005 , Czech Council for Resuscitation 2006 ), for example, it is always necessary to exclude the following, so-called reversible causes of acute cardiac arrest: hypothermia, hypovolemia, hypoxia, hypo- or hyperkalaemia and metabolic breakdown, furthermore tension pneumothorax, cardiac tamponade, toxic substances, coronary thrombosis and pulmonary thromboembolism. However, the guidelines do not define a procedure for eliminating these causes, and it is then only a question of the experience and the education of the medical staff as to whether the diagnosis is recognized.

HOW TO USE DIAGNOSTIC METHODS

pneumothorax

The The basis is the physical examination, especially one careful auscultation, in which it is established that the affected side is not breathing. The physical examination auscultation is subjective, and in the context of hospital care, z. As in injuries, very difficult to perform. In preclinical care, in a moving ambulance, The auscultation proves to be impracticable, which also for the accident site applies, where they often by the existing Noise is difficult or impossible. The golden standard The diagnosis is the radiographic examination of the Lungs (perhaps a computer tomography), even existence Small amounts of air in the pleural cavity discovered and quantified. An X-ray examination in the context of preclinical Care is not, and probably will never be available. in the Hospital always means delay, and often transportation of Patients in the radiographic workstation, d. H. another threat to the patient and another delay. In addition, some patients are examined while lying down Types of pneumothorax are not detected, and for that reason will That's why in a polytrauma computed tomography is golden Standard, which also provides more information about a possible impairment of other organs or systems supplies.

pulmonary embolism

A massive pulmonary embolism can lead to syncope, hypotension, the Development of cardiogenic shock to acute cardiac arrest to lead. It is accompanied by acute cor pulmonale, the yourself as shortness of breath and the presence of signs of an acute Failure of the right ventricle manifested - tachycardia, acute dilatation of the right ventricle, tachypnea and increased (central) venous pressure. In particular, the development is specific a precapillary pulmonary hypertension increase the mean pressure in the pulmonary artery about 20 mmHg in normal pulmonary artery occlusion pressure (PCWP) and elevated transpulmonary gradient. This condition does not develop with a Herzbeuteltamponade, still with a Pneumo- or a Haematothorax, and not in cardiac contusion, and this fact (ie the influence of an acutely developing precapillary pulmonary hypertension on the values of bioimpedance) is used in diagnostics with the help of the device after used invention.

cardiac tamponade

Cardiac tamponade is a complication that acutely threatens the patient's life. Normally the pressure in the pericardial sac is negative. A rapidly increasing volume of the pericardial fluid leads to an increase in intrapericardial pressure, and at the same time the diastolic filling pressure of the right ventricle and the mean pressure in the right atrium increase, while at the same time the pressure difference between the left and right atria decreases. In the initial phase, the function of the left heart is relatively unaffected, and it first shows a failure of the right-sided heart parts, for which physiologically a low pressure is characteristic. Gradually, she shows a restriction of the filling of both chambers of the heart, and in the final stage, the heart chambers fill only in the atrial systole. There is a rapid decrease in the systolic volume of the chambers and the cardiac output, followed by a fall in arterial pressure. An early sign of the tamponade is an extension of the pre-ejection time of the left ventricle ( Brubakk O, Kalber T, Acta Med Scand 200, 465-67, 1976 ). This parameter is usually not used, but is one of the parameters that are detected and evaluated using the apparatus according to the present invention.

a Contribution to diagnostics by means of physical examination supplies the so - called Beck 's Triassic (increased filling of the Jugular veins, hypotonia and soft heart sounds), and further also, which is essential for the presented invention, a pulsus paradoxus, d. H. a dependence of the pulse pressure breath, where the measured difference usually greater than 10 mmHg. The presented invention Uses, among other things, this phenomenon, the influence respiration on the bioimpedance curve.

bioimpedance

The Beginnings of the development of the method of thorax bioimpedance measurement fall into the sixties of the last century, if this Method used by NASA to monitor astronauts in spacecraft was used. The development of electronic data processing brought a clarification of the method up to the clinical Monitors that are produced today (eg, BioZ, Vasamed - USA, Niccomo, Cardioscreen - Germany, TaskForce - Austria, PhysioFlow - France and others). These devices use the thoracic impedance to get some hemodynamic parameters to calculate. The method of measuring thoracic bioimpedance is solved in several patent documents.

After the patent US 4,450,527 For example, an alternating current of defined frequency is applied by means of electrodes placed laterally on the neck and in the lower part of the thorax, typically in the region just below the sternum. Between these application electrodes measuring electrodes are mounted, which absorb the electrical voltage and subsequently evaluate. As an alternative according to the patent US 3,340,867 The electrodes are attached to the forehead or circular around the neck and chest.

In another arrangement, the electrodes are inserted into the esophagus as in the patent US 4,836,214 or the electrodes of an implanted cardiac pacemaker are used.

The processing of the measurement signal can be solved by different means and in different ways. For example, the signal conducted from the sensing electrodes via active filters may be demodulated in rectifiers and subsequently amplified in a differential amplifier. Further processing of the signal is analogue until DC voltage is obtained, which is proportional to the basal thoracic impedance Z and the time change of the impedance dZ in synchronism with the heart activity. Both of these signals are for subsequent processing digitized.

The clinical application is z. In the documents WO 84/00227 . US 4,450,527 , where the baseline impedance data and the deviations from it, which depend on cardiac activity, are processed and from which signals various hemodynamic parameters are calculated - e.g. Cardiac output, vascular resistance, ejection fraction and others, using as a basis mathematical models describing the propagation of electrical current in the thorax.

In summary It can be said that the absolute value of the impedance is the most through the level of fluid in the thorax is affected and their time changes, in sync with the ECG, provide information about individual ejection volumes.

The in the document WO 95/02991 described solution works in the calculation not with the basal impedance, but only with the impedance change, dZ. There are also methods that determine other heart diseases due to the impedance measurement, the z. In WO 90/09757 are described.

commercial Thorax impedance monitors use application electrodes to supply AC power, which are switched so that a group in the cervical region, while the other group is placed in the lower half of the thorax is. The location of the application electrodes may vary, depending on the Recommendations of individual manufacturers. The situation where the application electrodes For example, attached to the neck can be associated with recommendations be, the electrodes in front of various devices, laterally over the carotid artery or at the back of the neck to attach. In similar Way become on the body of the patient receiving electrodes attached, record the thoracic impedance. The result of the measurement the basal impedance is always a value for bioimpedance of the entire thorax, and not separately for the right and left half, as is the case in our invention is. For the calculation of hemodynamic parameters will be various adjustments and modifications of the mathematical Model uses the passage of electric current through describe the thorax, or calculate how this current passage is influenced by the pulsating heart activity.

In the document WO 2007/002992 For example, the thoracic bioimpedance signal is measured in at least two body segments, one segment always being the thorax, and the other, for example, the extremity. From the thoracic bioimpedance, an index is calculated which is compared to the index from the second segment, in this case a limb, and thus the degree of pulmonary edema is quantified. This above invention finds a solution for stepwise measurement of the impedances of individual extremities, and even for a thoracic impedance measurement from right to left and from left to right, the specific being that the measurement is made diagonally, over the whole thorax, and not separately for individual pages, as the present invention provides.

A complicated system described in the publication of Zlochiver S et al., IEEE Transactions on medical imaging, 22, 12 pp. 1550-60, 2003 , uses up to 32 electrodes, and uses simulation algorithms to calculate the content of fluid in different parts of the lung. However, it does not take into account the possibility that air may be present in the thoracic cavity, and this system therefore appears unsuitable for the study of pneumothorax.

Some inventions, eg. For example, in the document WO 2007/031951 , find a solution for the analysis of pulmonary edema using the electrodes of an implanted cardiac pacemaker, and then calculate the characteristics of both lungs from the different distribution of current in the thorax. The use of a cardiac pacemaker with several electrodes is assumed, whereby the configuration of the thorax is recalculated depending on the position of the electrodes.

Impedance and pneumothorax

The most important parameter from the point of view of pneumothorax diagnostics, with regard to the presented invention, is the so-called index of thoracic fluid content. This can be determined by analysis of the basal impedance, which is the time-averaged inverse of the basal impedance, ie the index does not follow the temporal evolution of the impedance as a function of cardiac activity. Its significance relates to the amount of fluid in the lungs, ie it provides quantitative information about any pulmonary edema that may be present. Pneumothorax was already monitored with the help of impedance, z. B. in the Publication Noack G, Freyschuss, Acta Pediatr Scan 66, pp. 677-80, 1977 , However, the impedance was measured with a commercially available device, summarily over the whole Thorax, as recommended for the measurement of thoracic fluid content, and no thoracic side analysis was performed, and no DP analysis was performed in pneumothorax diagnostics. The device in the sense of the cited publication and its application therefore differs significantly from the presented invention.

Impedance and embolism and tamponade

The basic knowledge regarding diagnostics and monitoring embolization of the pulmonary artery and cardiac tamponade, and the assessment of tension in pneumothorax were in the following Documents described.

In WO 2007/144776 the interpretation of the bioimpedance measurement is described, consisting in the determination of the velocity change curve of the blood flow on the bioimpedance, in determining whether this curve contains two peaks, in the determination of the time interval between these peaks and based on this analysis then the interventricular asynchrony is assessed and The decision to implant a pacemaker is patented. The cited invention also deals with the interval between these two peaks and the subsequent interpretation. This interval corresponds to the time between the maximum right ventricular ejection and the maximum left ventricular ejection, which is essential from the point of view of pacemaker implantation. Unlike the solution according to the present invention, the solution is concerned WO 2007/144776 not with the part of the curve before a possible first peak, no ECG is registered simultaneously, and no analysis of the temporal relationship between the ECG and the rate of change curve is made. It is precisely this part of the curve which, inter alia, contains information on the effects of the right ventricle, and this is essential to the solution according to the present invention.

In the document WO 97/37591 the calculation of the ejection volume is described on the basis of the specification of the duration of the systole left ventricle, where from the bioimpedance curve the so-called effective ejection time of the left ventricle is read. This time begins with the time of the opening of the aortic valve, which is one of the symptoms used in the solution according to the present invention, but where this point in time limits the end of the tracked interval. Another difference is the use of this parameter - it does not serve to diagnose some conditions, but is used to specify the calculation of hemodynamic parameters.

All above mentioned documents solve the registration of the impedance in only one direction, vertical direction, and direct from the measured signal only the parameters of the left-sided heart parts. In the solution according to the present invention, the registration becomes performed in at least two directions, which is possible makes a separate analysis and evaluation of the right-sided and to perform the left-sided parts, which is not yet was possible. It has not been a compact and mobile Device available that meets the requirements of Would correspond to emergency medicine and that it is possible would do an analysis and almost immediate diagnosis the reversible causes of acute cardiac arrest, such as tension pneumothorax, cardiac tamponade and pulmonary embolism, perform in situ.

The essence of the invention

Device for measuring chest impedance

The apparatus for measuring and monitoring the bioimpedance and subsequent determination of urgent (acute) conditions in the thorax in a preferred embodiment is shown schematically in FIG 1 shown.

The generator G generates harmonic alternating currents which are conducted into the application electrodes AE placed on the thorax. The signal propagates between the electrodes as in 2 shown. The pickup electrodes SE are placed "parallel" with the application electrodes, separately for both chest halves in the vertical direction, and separated for the horizontal direction (see 2 ). The device requires for its proper functioning at least 3 application electrodes AE and at least 3 receiving electrodes SE . The measured signals are amplified in the amplifier Z , digitized in transducers A / D and then introduced into the operation unit DSP for control, data processing and analysis (hereinafter, operation unit only) which is a part of the control unit R. The control unit can, for. B. be realized by a device analogous to the computer of the PC type or a commercial computer.

Component of the device are further a unit for receiving an electrocardiogram EK and possibly a unit with microphone SO to register the heart sounds.

The Control unit also contains a display device, z. As a monitor or a display. The advantage is that the Control unit also a device for may contain the archiving of the measured values, and possibly also for the registration of the calculated parameters, eg. B. in the form of a device of the "Holter" type. It is also possible that the unit with a device equipped that enables data communication, z. With a computer or other parent Unit, z. B. a device for IR communication or a "Bluetooth", whereby also a communication by means of a computer network is possible. Another Possibility is that the unit with a communication device equipped, the telemetric monitoring and data transfer allows.

The unit for control, data processing and analysis contains an algorithm implemented for the processing and evaluation of the measured data and for the determination of the required values, and in particular the symptoms (see the description below). 4 and 5 ), in the form of a computer program (software).

The control unit R , by means of implemented software, ensures automated measurement of basal impedance values, separate for both thoracic halves, and subsequent analysis of the impedance change curve in synchrony with cardiac activity (see below).

All measured data are evaluated by the control unit R , the symptoms are determined, and on monitor M the values of the basal impedance and the curves of the impedance change are mapped, whereby it is also possible to map all detected symptoms.

The control unit R or the software implemented in it, further analyzes all data and evaluates information about the probabilities of the diagnoses. The decision algorithm of the control unit operates on the basis of matrices of the temporal relationships of the symptoms under physiological circumstances and in the above diagnoses, and compares these with the current state. By analyzing the symptoms, as determined by the bioimpedance measurement and the ECG, and comparing them to normal values, the algorithm determines the relationships in the right and left side cardiac parts and determines the probabilities of the above diagnoses. Respiration is monitored by the indication of basal impedance. The respiratory cycle information is used in the decision algorithm for further analysis of the intervals between the symptoms and for determining the significance of the influence of the respiration on these intervals, as is the case, for example, with cardiac tamponade. It is advantageous if the information about the type of ventilation of the patient is entered into the control algorithm, ie whether it is breathing spontaneously or is ventilated. At the same time the blood pressure values are determined and monitored.

The means that the evaluation is done in principle so will that data and certain symptoms for comparing the current patient with values and symptoms, in healthy people and patients with pneumothorax without overpressure, with tension pneumothorax, pulmonary embolism or cardiac tamponade were found. These data were determined experimentally (see details in Table 1), and may be further clarified become.

you can also assume that the way of processing and evaluation of the measured data and the determination of the impedance values, and especially the symptoms of the invention, in the form of a computer program (Software), also implemented as a self-contained part can be, for. On a disk (such as flash memory, CD-ROM or DVD) and / or there is the possibility of an implementation in any computer, which then evaluate the measured data and analyze, regardless of the measuring part of the device according to the invention.

The The preferred solution described above processes the signals digital. However, it is also possible to have an analog solution which is to filter the measured signal, amplified and processed analogously until a voltage which corresponds to the basal impedance and a voltage which corresponds to the impedance change. Only this data can subsequently digitized and processed, similar as in the case of the digital solution.

That is, the presented invention also relates to a novel method of differential diagnosis of urgent thoracic conditions, such as pneumothorax without overpressure, tension pneumothorax, Pulmonary embolism or cardiac tamponade, which is possible by the use of the device according to the invention.

Application of the device according to the invention

Around To gain symptoms (described below) are) that enable the required differential diagnosis, the attached electrodes must be arranged specifically be.

The placement of the electrodes must allow the thoracic impedance to be recorded in two fundamental directions: in the horizontal, transverse, and vertical directions, ie, in the axis of the patient's body. These two directions correspond to the orientation of the application or current electrodes AE (FIG. 1 ), in which alternating current with a defined frequency is supplied. The recording or voltage electrodes SE ( 1 ) are also arranged in these two directions for the purpose of registration, the vertical direction being additionally recorded separately for the right and left thorax half. 2 shows two possible basic arrangements of the electrodes.

ever Three electrodes of both types represent the minimum number of Electrodes necessary for correct function the device according to the invention. The expert can easily introduce a modification of the device, eg. B. with four, and possibly even more electrodes of both types.

• A) Die basale Impedanz (Z₀) in allen drei aufgenommenen Richtungen ermöglicht eine getrennte Aufnahme aus beiden Thoraxhälften (in vertikaler Richtung), was wichtig ist für die Ermittlung separater basaler Impedanzen für beide Thoraxhälften. Die basale Impedanz in horizontaler Richtung – über beide Thoraxhälften – dient der Registrierung der Atmung des Patienten und der Registrierung der totalen basalen Thoraximpedanz.
• B) Die Registrierung in zwei Richtungen ermöglicht die Verfolgung pathophysiologischer Vorgänge im Brustkorb auf eine neuartige Weise: die horizontale Richtung registriert insbesondere die Impedanzänderungen ausgelöst durch die Strömung des Blutes in Pulmonalarterie und gibt deshalb Aufschluss über die Verhältnisse im rechten Herzen. Die vertikale Richtung verfolgt besonders die Impedanzänderungen, die durch den Blutfluss durch die Aorta bedingt, und gibt deshalb Aufschluss über die Verhältnisse im linken Herzen.

The obtained signal of the thoracic impedance is then analyzed. A) the basal, average value of the impedance in all directions and B) the impedance change synchronously with the action of the heart in two directions are determined:

• A) The basal impedance (Z ₀ ) in all three sensed directions allows separate acquisition from both halves of the thorax (in the vertical direction), which is important for determining separate basal impedances for both halves of the thorax. The basal impedance in the horizontal direction - across both halves of the thorax - is used to register the patient's breathing and register the total basal chest impedance.
• B) The registration in two directions allows the pursuit of pathophysiological processes in the thorax in a novel way: the horizontal direction registers in particular the impedance changes triggered by the flow of blood in the pulmonary artery and therefore provides information about the conditions in the right heart. The vertical direction particularly tracks the impedance changes caused by the blood flow through the aorta and therefore provides information about the conditions in the left heart.

The Processing of the impedance signal in synchronization with the heart activity exists concretely in a morphological and temporal analysis the curves (that is, the time dependencies). It will be any individual heart action analyzed separately, in the case of a Inferior signal (see below) ends the analysis of this signal and the device will do the next Heart action continues. In case it becomes impossible to separate Actions can be analyzed by the device in the so-called averaging regime work with set number of heart actions.

Principle of the analysis of the impedance curves

The Bioimpedance curves (i.e., the bioimpedance dependency from time) and ECG curves are analyzed and provided simultaneously after processing with the algorithm according to the invention the values the required symptoms.

The principle of analyzing an action shows 3 in which the curve H (the first from above) corresponds to the time course of the ECG recorded from the surface of the thorax. Curve A is the negated (inverted) shape of the impedance curve through the left-sided heart parts -Z _L , which corresponds to the blood volume in the left-hand part. Curve B is the negated shape of the impedance curve through the right-hand heart parts -Z _P , which corresponds to the blood volume in the right-hand heart part. Curve C represents the sum of curves A and B which can be obtained after processing in the measurement of the thorax bio-impedance -Z. Curves A and B can not be obtained independently by the measurement. Curve D corresponds to the derivative of curve A after time -dZ _L / dt. It is the dependence of the change of the flow. Curve E is the derivative of curve B after time -dZ _P / dt. It is the dependence of the change of the flow. Curve F is the derivative of the curve C after the time -dZ / dt. It is the dependence of the change of the flow. Curve G is the second derivative of curve C after time -d ² Z / dt ² . Their course makes it clear that they can be used very well to identify the symptoms PO and AO since these points lie in the local inflection points of this curve.

The device according to the present invention measures on the thorax surface at least two impedance curves C for the horizontal direction (C _H ) and for the vertical direction (C _V ) and the curve H. Curves F and G are calculated.

The shapes of the curves in 3 , in particular the curve C and the curves F and G derived therefrom, are typical for the vertical tracking of the impedance, which registers the change of the flow through the aorta the most. Conversely, in the horizontal direction recording analysis, the shape of the curve C is most affected by the curve B, while the influence of the curve A is suppressed here. The comparison of the horizontal and vertical recording curves C, F and G thus makes it possible to specify the timing of the symptoms PO and AO by comparing the results of the analysis in both directions, and then making the difference larger is considered a set limit, the analysis is excluded and the device goes to the next record.

On curves it is possible to read times of the following characteristic events - symptoms:
The ECG trace provides point P, which corresponds to the depolarization of the atria, point Q, which signals the beginning of the ventricular depolarization, and the QRS complex, which contains information about the course of depolarization of the ventricles.

The Analysis of the impedance curves provides the point PO, d. H. the time the opening of the pulmonary valve, and the point AO, d. H. the timing of the opening of the aortic valve. The algorithm seek these points (see below) with the help of the analysis of local inflection points of curve G.

Point MC, d. H. the time of closure of the mitral and Tricuspid valve, and point AC, d. H. the time of closing the aortic and pulmonary valve, are beneficial with the help of a Analysis of the recording of the heart sounds with a to the Thorax wall applied microphone found. If no microphone connected is, one can determine the point AC by means of the analysis of the curve C, by finding their local inflection point, the point MC in this case not measured, but arbitrarily as one third of the distance between points R and S of the QRS complex is determined.

The Time interval between points MC and AO corresponds to the arterial Prejection time, and the time between points MC and PO corresponds to the pulmonary pre-ejection time.

The whole procedure for finding the symptoms is illustrated with a flowchart in 4 shown schematically.

The procedure for Processing the measured data and determining the symptoms

The algorithm according to the invention (in the form of software implemented in the device according to the invention, which implementation can also be done in an independent computer or other control unit) performs an analysis of the measured temporal ones for the purpose of determining the symptoms described above Traces of bioimpedance and ECG, and possibly an analysis of the heart sounds to determine symptoms (see 5 ), which in the further course allow a differentiation of the diagnosis for individual diseases.

As already mentioned, it is an essential feature of the device according to the invention that it allows registration in two different, mutually perpendicular directions (vertical and horizontal), which results in curves E and D by solving a system of two equations can be identified separately with two unknowns, and in this way the curves of flow change can be found separately for the right and left part of the heart. The impedance measured in both directions can be described by the equations: C H (t) = a * LK (t) + PK (t) (1) C V (t) = LK (t) + b * PK (t) (2) where C _H (t) is the time course of the impedance in the horizontal direction and C _V (t) is the course in the vertical direction. LK (t) and PK (t) are the time courses of the curves E and D. The parameters a, b are coefficients the projection of the influences LK (t) and PK (t) in the individual recording directions.

The coefficients a, b are found by the algorithm as follows: the curve LK (t) has a constant course in the zero line in the time interval between symptoms PO and AO, while the curve PK (t) increases, which is a consequence of the fact that the pulmonary valve opens before the aortic valve. It is therefore possible to determine the coefficient b in the interval PO - AO. Finding the coefficient a implies that the rate of blood ejection from the right ventricle into the pulmonary artery from PO is constant until the time of AO and the interval is twice longer (ie, until the time AO + AO - PO). The justification of this assumption is based on the fact that the conditions in the pulmonary circulation are characterized by low resistance and low pressure, as is the case, for example. In Aschermann, M et al .: Cardiology, Galén 2004 , is specified. Given this requirement, the influence of the right-hand parts on the registration of the impedance in both directions is known, and one can determine the coefficient b by calculation.

After this the values of both coefficients a, b are known, the curves become found as solutions of the system of equations.

In thus obtained by calculation, curves E and D then become the following symptoms were found: on curve E its maximum value (ML), the time to reach this maximum value (TL) and the Time to reach the zero value (NL).

The Symptom TL is the time of the maximum acceleration of the outflow from the left ventricle, symptom ML is the index value of this acceleration and symptom NL is the time of maximum outflow velocity the left ventricle.

By The analysis of the curve D can be similar to the symptoms for find the right-sided part of the heart where symptom TP is the time the maximum acceleration of outflow from the right ventricle, Symptom MP is the index value of this acceleration and symptom NP is the time of maximum outflow velocity of the right ventricle.

By the analysis of curve F similarly becomes total symptoms For the whole heart, so the symptoms TS, MS and NS. These symptoms are for control, for comparison with symptoms separate heart parts.

The application of the procedures, the z. In WO 84/00227 . WO 90/00367 or WO 2005/089056 for the analysis of the curves E and F found by means of the device according to the invention, it is possible to quantify the hemodynamic parameters separately for the right and left heart parts, which was hitherto impossible.

Further Analysis of all specific symptoms considers the influence of breathing on these symptoms. All the symptoms determined in time recorded in memory, along with the value of the basal impedance in a horizontal direction. After a few respiratory cycles (detected from the basal impedance) becomes a group of three heart actions at the summit of inhalation with a group of three actions at the summit compared to the exhalation. In case the values of the this same symptoms will differ by more than 10 percent Fact pictured by the control unit and it becomes another symptom calculated as the ratio of these values respiration index.

The display unit M of the device shows all measured and determined curves and all symptoms found.

The Control unit is further with an algorithm for interpretation equipped with the acquired symptoms so that they have a differential diagnosis allows, as described above.

Since the measured symptoms or the measured vectors of the symptoms actually represent a contextually dependent data sequence, a contextually dependent classifier is used for the classification. Its function is based on hidden Markov models, which is a technique of stochastic modeling known from artificial intelligence (described, for example, in Duda, OD et al., Pattern Classification, John Wiley & Sons, Inc. (2001), ISBN 0-471-05669-3 ).

• • Basale Impedanz Z₀ in vertikaler Richtung rechts/links
• • Intervall MC-PO
• • Intervall AO-TL
• • Intervall PO-TP
• • Verhältnis ML/Z₀
• • Verhältnis MP/Z₀
• • Verhältnis MS/Z₀
• • Respirationsindex

The algorithm uses the following symptoms when identifying:

• • Basal impedance Z ₀ in vertical direction right / left
• • Interval MC-PO
• • Interval AO-TL
• • Interval PO-TP
• • Ratio ML / Z ₀
• • Ratio MP / Z ₀
• • Ratio MS / Z ₀
• • Respiratory Index

• • Normaler Patient
• • Pneumothorax ohne Überdruck
• • Spannungspneumothorax
• • Lunbenembolisierung
• • Herzbeuteltamponade

Symptoms, or vectors of symptoms, are called "images" in classifier theory because they "map" classified objects and phenomena into a set of numbers. In our case, then the images (ie the measured symptoms arranged in vectors) represent the diagnosed patient. The classifier then places the images that get into its input into one of the pre-selected classes, with the classes directly linked to individual diagnoses. In the case of the presented invention are the following classes (diagnoses):

• • Normal patient
• • Pneumothorax without overpressure
• • tension pneumothorax
• • Lunebeam embolization
• • Heart bag tamponade

The Classification of images in the classes is by a group of Guaranteed images for the right diagnosis is known (so-called training amount of images). The classifier will be using this training amount even before its installation into the on-line diagnostic process. The Symptoms for the above-mentioned individual classes (diagnoses) are given in Example 1 in Table 1. This table shows how individual symptoms affect individual diseases become. The factual classification is then mentioned by the Classifier performed.

Description of the pictures

1 shows a schematic representation of the device according to the invention. G is the generator of harmonic alternating currents, AE are application electrodes (full wheels), SE are recording electrodes (empty wheels). Z are amplifiers of the measured signals, A / D are analog-digital converters. DSP is the control, data processing and analysis operation unit that is a part of the control unit R that further includes the display device M.

2 shows a preferred arrangement of the application electrodes (full wheels) and the receiving electrodes (empty wheels). The full line shows the direction of current propagation, the dashed line marks the measured voltage.

3 schematically shows the time course of the measured ECG and bioimpedance values and further the dependencies calculated from these.

Curve H (the first one from the top) is the recording of the ECG derived from the thorax surface.

Curve A is the negated (inverted) shape of the impedance curve through the left-side heart parts Z _L , which corresponds to the blood volume in the left-hand part.

Curve B is the negated shape of the impedance curve through the right-hand heart parts Z _P , which corresponds to the blood volume in the right-hand part.

Curve C is the sum of the curves A and B, which are obtained after processing when measuring the thorax impedance Z can win. Curves A and B can can not be obtained directly as such by measurements.

Curve D is the derivative of curve A after time -dZ _L / dt. It is the flow rate graph.

Curve E is the derivative of curve B after time -dZ _P / dt. It is the flow rate graph.

Curve F is the derivative of the curve C after the time -dZ / dt. This corresponds to the graph of flow change.

Curve G is the second derivative of curve C after time -d ² Z / dt ² . It is clear from its history that it can be used well to identify the symptoms of PO and AO, as these points lie in the local inflection points of this curve.

4 FIG. 10 is a flowchart showing the thorax bioimpedance detection and monitoring algorithm using the apparatus of the invention. FIG.

5 Fig. 10 is a flow chart illustrating the algorithm for finding the time course of bioimpedance in the vertical and horizontal directions.

embodiments the invention

Example 1: Symptoms for Differential Diagnosis

In healthy volunteers, patients with appropriate diagnosis or by means of a model, the values of the basal impedance Z _{0 were} determined, the basic symptoms (MC-PO, AO-TL, PO-TP, ML / Z ₀ , MP / Z ₀ , MS / Z ₀ ) and the respiratory index calculated according to the diagnoses followed (control - normal patient, pneumothorax without overpressure, tension pneumothorax, pulmonary embolization, cardiac tamponade). All values are summarized in the following Table 1.

Example 2: Experimental Device

In order to practically test the principle of measurement and analysis of the data described in the present application, an experimental apparatus has been constructed which is essentially the same as the apparatus 1 equivalent. Recording of bioimpedance in two directions on the thorax and their synchronized recording were made using a device constructed in ÚPT AVČR (Institute of Device Engineering of the Academy of Sciences of the Czech Republic) Brno and a special one advantageous embodiment of the device according to the invention. It is a device with two channels, where in each channel a measuring current in the range of 0 to 1 mA and a frequency of 10 to 100 kHz is independently adjustable. Optimum measurement results are obtained with current values of approximately 0.7 mA and a frequency of approximately 50 kHz, with the measurement voltage obtained in this setting varying in the range of 15 to 40 mV. The electrodes used are ordinary self-adhesive ECG electrodes, e.g. B. Type TYCO h92sg electrodes.

The recording of the ECG was carried out with the help of the device "GE Patient monitor DASH 4000", which is well known to the specialists. Registration of the phonocardiogram was carried out with the device phonocardiograph (ÚPT AVČR Brno), which is in principle an acoustic battery powered amplifier with a microphone adapted to measure heart sounds. The signals from said devices were recorded and fed into a computer using a DAQ Card-6036E + BNC-2110 data acquisition card. The processing of the data was realized by means of the program MATLAB for PC, which is known to those skilled in the art. The evaluation of data and determination of symptoms were performed with a program containing algorithms according to the invention described in the present application (see also US Pat 4 and 5 ).

Example 3: Device for commercial use (prototype)

This is an embodiment of the device, which is essentially the scheme of 1 equivalent. The data acquisition and data processing unit DSP is realized on a printed circuit board comprising a patient interface with current sources and amplifiers of the registered signals, a galvanic separation for safety, further digital-analog and analog-digital converters, circuits for generation, processing and evaluation of the Contains signals and circuits for communication with higher-level device. The unit forms a module that can be plugged into the patient monitor and communicates with the patient monitor through the monitor interface. Part of the unit is the software for processing and evaluating the measured signals based on the algorithms described in the application submitted (see also 4 and 5 ), and to communicate with the patient monitor. The patient monitor is software adapted for communication with the mentioned unit and for visualization of the measured parameters on its display.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 4450527 [0010, 0013]
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Claims (9)

Device for detecting and monitoring the thorax impedance and subsequent determination of urgent thoracic conditions, characterized in that it comprises a generator (G) of harmonic alternating currents, at least three application electrodes (AE) for application of the currents to the thorax and at least three receiving electrodes (SE) for voltage absorption the thorax, possibly amplifiers (Z) and analog-to-digital converters (A / D), an electrocardiogram (EK) unit and possibly also a heart sound recorder (SO) unit, further includes an operation unit (DSP) for control , Data processing and analysis, which together with the display unit (M) is part of the control unit (R), wherein the operating unit or the control unit has an implemented algorithm for analyzing and evaluating the measured bioimpedance values, the ECG and possibly the heart sounds, and for determining of symptoms that the diagnostic determination dr and possibly the device may further include a data archiving unit, a data communication unit with a remote computer, another control unit or a computer network, or a telemetry communication unit. The device according to claim 1, characterized that the operation unit (DSP) or the control unit (R) with Help of the implemented algorithm measuring the values of the basal impedance separately for both thoracic halves and a subsequent analysis of temporal relationships Impedance in synchrony with cardiac activity is ensured. The device according to claim 1 or 2, characterized characterized in that the implemented algorithm is an evaluation Impedance measurement, recording of the electrocardiogram and possibly also the heart sounds and their analysis, and the determination the curves of the impedance curves separately for the right side and left side of the heart part allows. The device according to one of claims 1 to 3, characterized in that the implemented algorithm makes it possible to evaluate the measurement of the impedance in horizontal and vertical direction, to record the electrocardiogram and possibly also the heart sounds, and the values of the basal impedance Z ₀ in the vertical direction to the right / left determined and further the following symptoms: Interval MC-PO, interval AO-TL, interval PO-TP, ratio ML / Z ₀ , ratio MP / Z ₀ , ratio MS / Z ₀ and respiration index. The device according to one of the claims 1 to 4, characterized in that the implemented algorithm further allows the hemodynamic parameters separately for the right and left side of the heart to calculate. The device according to one of the claims 1 to 5, characterized in that the implemented algorithm Allows to set the values and symptoms in one the following clusters, the normal state or urgent thoracic states characterize: normal condition, pneumothorax without overpressure, tension pneumothorax, Pulmonary embolization or cardiac tamponade. The device according to one of the claims 1 to 6, characterized in that it is an instruction manual with the indication of an advantageous arrangement of at least three Application and three receiving electrodes on the chest contains. Computer program for analyzing and evaluating the measured bioimpedance values, the ECG and possibly the heart sounds, and for determining the symptoms for the diagnostic determination of urgent thoracic conditions, and for use in the device essentially according to any one of the preceding claims, characterized in that it has algorithms for determining the Values and symptoms such as the basal impedance Z ₀ in the vertical direction right / left, the interval MC-PO, the interval AO-TL, the interval PO-TP, the ratio ML / Z ₀ , the ratio MP / Z ₀ , the ratio MS / Z ₀ and the respiratory index, and algorithms for classifying the values and symptoms found into one of the following clusters characterizing normal or urgent thoracic conditions: normal, pneumothorax without overpressure, tension pneumothorax, pulmonary embolization or cardiac tamponade. Method for differential diagnosis of urgent thoracic conditions, characterized in that it contains the steps in which, from the measurement of the chronological progression of the thoracic bioimpedance in the horizontal direction and in the vertical direction, symptoms are determined for the right and left thorax parts, which then enter into one of the following clusters, which characterize the normal condition or urgent conditions: normal condition, pneumothorax without overpressure, tension pneumothorax, pulmonary embolism tion or cardiac tamponade.